Örebro Universitet Examensarbete
Institutionen för naturvetenskap och teknik 2014-01-29
Apiculture and bee health in Central Sweden
Date:
Course: Självständigt arbete, Biologi C, BI3007 Author: Olof Larne
Supervisor: Jana Jass Examinor: Alf Ekblad
Apiculture and bee health in Central Sweden
Abstract
Pollination necessary for the agricultural crop production affects the functions of the ecosystems on earth. In landscapes where wild pollinators are decreasing, honey bees promote the maintenance of plant species, therefore honey bee losses are of great concern. Current honey bee colony losses (Apis mellifera) worldwide are caused by Colony collapse disorder, the mite Varroa destructor and pesticides. This results in the honey bees weakened immune defenses making them susceptible to different diseases. Studies show that long-term natural selection for coexistence, or resistance to Varroa mites by honey bees is possible, but further developments are needed for this application in managed beekeeping. Furthermore, lactic acid bacteria found in honey bees can play a crucial role by improving its immune response. At places where apicultural practices have led to decreased amounts of lactic acid bacteria in the bees, supplementary feeding is a possible treatment solution. The beekeepers' observations of mite reproduction dynamics and the overwintering of strong and healthy honey bees are needed to decrease Varroa treatment with synthetic chemicals. Based on this knowledge, a small survey of beekeepers in Örebro County, Sweden, was conducted in an attempt to determine the status of their bees during the last 5 years. The largest colony loss over the past 5 winters was predominantly in 2012-2013. Varroa mite infestations with disease symptoms were primarily found in the central region. Since the survey was small and time was limited it was only possible to make general conclusions. Deeper understanding of lactic acid bacteria in honey bee societies and their inhibition of different diseases are important for future research.
Contents
1. Introduction………...……….4
2. Entomology...5
2.1 The honey bee colony...………...………...5
2.2 Maintenance of the honey bee health...6
2.3 Honey bee-parasite interaction………...……...8
2.4 Interactions between the honey bee, the Varroa mite and pathogens...…………...10
2.5 The natural selection process of host-parasite interactions………...…...11
2.6 Long-term selection process of two distinct European honey bee populations...12
2.7 Future honey bee threats and treatment of bee pathogens...13
3. Benefits of LAB on bee health and apiculture...16
3.1 Colony defense...16
3.2 LAB symbionts in human and animal microbiota………...16
3.3 Honey bee commensal bacteria ………...………...17
3.4 Benefits of honey bee LAB for human health………...18
3.5 Enhanced immune response in honey bee colonies...………...18
4. Survey of beekeepers in Örebro County...19
4.1 Conclusions from survey...23
5. Summary and future challenges for apiculture..………...25
1. Introduction
Approximately 1/3 of the edible crops globally are dependent on pollinating insects, primarily honey bees (Jordbruksverket, 2013a). Swedish plants of economic importance requiring honey bee pollination are primarily oilseeds, apples and strawberries (Pedersen et al., 2009). The early spring pollination is an important nutrient resource for the growth of bee populations and the survival of species such as the flowering goat willow (Ehnström & Öberg, 2009). Honeybees and wild pollinators are essential contributors to the maintenance of plant biodiversity, but changes in the agricultural landscape have vastly decreased their number (Wide, 2009). Together with honey bees, bumble bees are important for pollinating plants in colder climates, and are more effective in
pollinating leguminous plant flowers (Nätterlund, 2007). For example clover, which is a leguminous plant, almost totally depend on insect pollination, and the broad bean - primarily dependent on wild bees and many species of bumble bees for pollination because of their long tongues (Käck et al., 2012). While honey bees have also been shown to pollinate the broad bean flower, hives placed in such fields can complement wild pollinators. Thus, the placement of bee hives in landscapes where wild pollinators are on the decline is important for agriculture (Pedersen, 2012). Some Swedish beekeepers rent their hives to farmers, enabling them to pollinate agricultural crops (Eriksson, 2012). This is more common in the USA. In California, about 85% of all national bee hives are gathered for increasing the almond yield every year. This operation unfortunately often results in diseased and dead bees. A discouraging scenario is the insufficient pollination on chinese apple farms, which was solved by human hand pollination (Sahlberg, 2008). Large pesticide operations in the Maoxian county in the northwestern Sichuan Province of China made it risky to have honey bees, and instead of relying on the natural pollinators, the economic interests demanded that the fruit farming continues. To reduce the large human and economic input, plums and other self-pollinating species were used to phase out apple trees in 2011 (Partap & Ya, 2012). Intercropping of vegetables has been adopted to improve the farmers income. Changes to a colder climate also demands more frequent hand pollination and consequently a higher economic input. Overall, the honey bees promote pollination services and maintain species interactions in nature, highlighting the importance of observing apiculture (the bees managed by human) together with its environment, to maintain food production and natures diversity. Defined as an ecosystem service, pollination has a great impact on the regulating functions of the ecosystems on earth.
This review aims to present the benefits from a long-term natural selection process of the European honey bee (Apis mellifera) for improving managed bee keeping in Sweden and the benefits of
newly discovered lactic acid bacteria (LAB) for maintaining honey bee health and apiculture. The information available raises questions about the bee colonies in Örebro County, therefore, a survey was conducted on how Swedish beekeepers maintain healthy colonies and this is compared to the current research. The objectives are; 1) how the long-term selection process of two distinct
European bee populations (A. mellifera) have helped to improve bee health; 2) the effect of recently found LAB on honey bees and human health; and 3) how Swedish beekeepers prevent bee losses and their general opinions regarding bee health.
2. Entomology
2.1 The honey bee colony
The inhabitants of a honey bee colony can be divided into three types of bees - a queen, 100-1000 male drones and 15000-50000 female worker bees (Sveriges biodlares riksförbund, 2013a; Locke, 2012) (Figure 1). Honey bees are defined as eusocial insects, meaning that reproduction is limited to a small number of individuals in the colony and that there is a division of labour (Gullan & Cranston, 2000). All three types of bees are developed from egg to larva, pupa and adult within the wax comb of the nest, in small compartments called 'cells' (Sveriges biodlares riksförbund, 2013b). The queen is the only fully developed female bee that prevents the reproduction of the worker bees by sending out chemical signals (pheromones). She starts to lay eggs in the middle of the society, which develops outward in increasing circles. The egg-laying in neighbouring wax comb 'brood cells' results in the shape of a globe. After the eggs hatch larvae appear. The bees close the cells with wax caps and the larvae develop into pupae which finally become adult bees, leaving the cells. The larva and pupa are called brood. The larvae will receive different food quality, depending on if it is to become a worker or a queen bee, while the drones are developed from unfertilised eggs. The task of the drone is to mate with a virgin queen which is recognised by the pheromones released. The ones who manage to mate with the queen will die. Before the overwintering of the society, all the drones are killed. The worker bees feed the larvae, pack the pollen, receive and deal with the nectar, build the wax combs, regulate the warmth, clean and guard the hive. They also deliver nectar, pollen, water and propolis (an antibiotic substance from trees) from the outside. The nurse bees (young worker bees) spend their first three weeks inside the hive, while the last two weeks of their lives they start foraging on the outside of the hive. They can become 5-6 weeks old during the summer and the worker bees born at the end of the summer will overwinter with the queen. The nectar is concentrated into honey, which serves as food during the winter. The honey bee colony
groups in a cluster during the winter, maintaining the right temperature by changing place with each other (Harry, 2013).
Figure 1. The three types of individuals found in a honey bee society from left to right are: the queen, the drone and the worker bee (Authors interpratation of picture by Lang in Mattson & Lang, 1994).
The queen is responsible for colony growth and reproductive fitness (Locke, 2012). If the queen is considered too old to produce new eggs, or the colony needs more space, swarming emerges (Sveriges biodlares riksförbund, 2013b). The colony moves to a new location, and when the queen’s ability to reproduce is decreasing she is replaced with a new one. The rest of the worker bees stay in the hive where a number of new queens will appear from the swarm wax comb cells. Consequently, reproduction takes place both on the individual and the colony level. Selective fitness can have an effect on both levels (Locke, 2012).
2.2 Maintenance of the honey bee health
As previouly mentioned, the ecosystem services are largely dependant on the honey bee. The decline of wild honey bees and other wild pollinators have increased the importance of domesticated bees as pollinators (Pedersen et al., 2009). The decreased genetic variation in domesticated honey bees, partially caused by the low number of wild honey bees for the bees to mate with, reduces the ability to resist diseases. The loss of honey bee colonies and dispaired bee health in recent years suggests multiple factors, including the Varroa mite, different viruses and pesticides (Potts et al. 2010; Neumann & Carreck, 2010). Worldwide, the Varrroa mite parasitises most managed honey bee colonies (A. Mellifera), which impacts colony mortality together with different viruses and pesticides. The mechanisms of this parasitism will be more thoroughly described in the next sections. National and regional variations of colony mortality has promoted the establishment of the global network called, Prevention of honeybee colony losses” (COLOSS) that is important when comparing international research data. A survey covering 11% of the US beekeepers aimed to compare national with international loss estimates (vanEngelsdorp et al.,
2012). Winter colony losses from 2006-2010 were on average about 30% per year. The following winter, 2010-2011, showed a similar result. During these five years, higher total colony losses were reported by beekeepers that observed “no dead bees in the hive or apiary”. This symptom is a characteristic of Colony collapse disorder (CCD) and is more likely related to larger beekeeping operations. CCD exhibited by the honey bees in the USA has been speculated by media to be the reason to large colony losses also in other countries, but so far, a coupling between CCD and large colony losses has not been verified to occur ooutside the USA. Neumann & Carreck (2010)
compares this to “The Isle of Wight Disease”. In 1906 colonies on the Isle of Wight died without an explanation. Within some years, all British colony losses seemed to have the same reason, which resulted in considerable media attention and was considered the “Isle of Wight Disease” (Neumann & Carreck, 2010). Many decades later an infection by chronic bee paralysis virus accompanied by poor weather conditions and too many colonies on limited forage area were the determined reason, as described by Bailey and Ball (1991) and Bailey (2002) (cited in Neumann & Carreck, 2010). However, there is no clear explanation for the recent CCD, although it has been linked to certain bee viruses and is more common among honey bees after the introduction of the Varroa mite (Rosenkranz, 2010).
The Varroa destructor is a parasitic mite on A. mellifera, which damages its host by feeding on blood, and vectoring different viruses, thus a worldwide threat for apiculture (Rosenkranz, 2010). The mites reproduces inside the closed wax comb cells on developing bee brood and attaches to the bodies of the fully developed bees to reach new bees or wax comb cells. The increased virus
infections caused by the Varroa mite transmission in honey bee colonies leads to colony death within 1 to 3 years if no treatment is used (Locke, 2012). The adaptation to survive the mite
infestation among unmanaged, feral honey bees in Gotland and Avignon occurred through inherited natural selection and this was due to lowering of the mites reproductive success (Locke, 2012). The coexisting of honey bees and mites for several years is believed to give an answer on how to improve honey bee health, and to reduce chemical apicultural treatment (Locke et al., 2012b). The build-up of chemicals in the wax combs after treatment of Varroa mites can poison or weaken the honey bee society (Pedersen et al., 2009b). A relationship between the bee mass death and
neonicotinoids has also been observed - neonicotinoids are commonly used to reduce insects in crop fields. These chemicals have shown to block specific acetylcholine receptors (AChR) impacting the synapse nerve transmission of bees, but are not consistent with the main reasons of some large honey bee colony losses (Pedersen et al., 2009b). However, specific neonicotinoids used as seed tretment have resulted in bee mass death. In 2013, three neonicotinoids were banned by the EFSA
(European Food Safety Agency) (Anonymous, 2013), but there are uncertainties and the risk assessment for bees is still under development (EFSA, 2013). However, decreased navigation ability of honey bees induced by sub-lethal doses of the neonicotinoid imidacloprid, was suggested by Bortolotti et al. (2003). Studies by Kimura-Kuroda et al. (2012) revealed that imidacloprid and another neonicotinoid, acetamiprid, stimulated the nicotine acetylcholine receptor (nAChR) of neurons in mammalians, which suggested possible developmental toxicity in the human brain. The results indicate the importance of further investigations, since the effects of these neonicotinoids to the nAChR of mammalians is not clearly known. Analysing the problems caused by the Varroa mite seems relevant for understanding their impact on honey production as well as beekeeping
husbandry.
2.3 Honey bee-parasite interaction
The Varroa mite’s natural host is the Asian honey bee (Apis cerana), which is resistant to the mites from a long history of natural selection (Locke, 2012). The worker pupae that are infested by mites are removed by the bee, limiting the mite reproduction to a few drone pupae of the colony. The infested drone pupae become too weak to open the cocoon cap themselves and die, which results in trapping of the mites, which subsequently also dies. The grooming behavior towards phoretic mites (life stage of the mite) is also limiting the mite reproductive success. Other honey bee species adapted to different levels of resistance to the mite include African and 'Africanized' honey bees.
In the 1970s, a host shift for the Varroa mite occurred from A. cerana to A. mellifera in Europe (Locke, 2012). Honey bee viruses that were previously non-virulent in A. cerana were virulent in A. mellifera when transferred via the mite parasitation on A. mellifera colonies. Honey bee importation spread it worldwide. There are two haplotypes of the Varroa mite that parasitise A. mellifera
colonies, the Japanese/Thailand haplotype and the Korean haplotype. Of these, the Korean is considered the most virulent and is found among honey bee colonies worldwide.
The Varroa mite feeds on the bee hemolymph (blood) by puncturing and parasitising the bee's body. It has two distinct life stages: the phoretic phase on the adult bees, travelling within or between colonies; and the reproductive phase, taking place in the closed brood cells during honey bee pupal development (Figure 2). To reach a new brood for reproduction, female mites prefer travelling on nurse bees, as explained by Locke and others (2012). The female mites enter the brood cell just before it is closed by the wax cap, attracted by volatile chemicals released from the larval cuticle. Mites infest the drone brood more often than worker brood (Fuchs, 1990). Locke (2012) describes
three possible explanations for this: first it could allow the maturation of more mite offspring; second, the nurse bees more frequently visits drone larvae, and third, the drone larvae production of compounds attractive to the mites is both higher and lasts longer. Inside the cell, the oogenesis of the Varroa mite is triggered by volatile substances of the host larvae and the first egg appears 60-70 hours after cell capping (Locke, 2012). Normally the unfertilised egg develops into a male mite (this process is referred to a haplodiploid system) that fertilises subsequent eggs laid by the mother mite, resulting in female offspring. The bodies of the nymphal mites are too soft to pierce the pupa cuticle to feed and rely on the mother mite during their development. Adult brothers and sisters mate within the brood cell, however only mature adult female mites survive when the bee emerges. The reproductive success of the Varroa mite population is defined as the ability of the mother mite to produce at least one viable, fertilised female mite before the adult bee finally emerges.
Grooming behavior exists in A. mellifera colonies to a lower extent than in A. cerana, but the growth of the mite population is too fast to control in this way (Locke, 2012). Hygiene behavior is defined as the detection and removal of dead or diseased brood, and exists to a variable degree in A. mellifera colonies. However, the mite doesn’t always die and most mites escape during this
process.
Figure 2. Reproductive and phoretic phase of the Varroa mite. The reproductive phase includes: (A) the mite enters into the brood cell before capping and (B) reproduction and mating within the closed cell. The phoretic phase (C) is when the mite is spread by attaching to the adult bee (Authors
2.4 Interactions between the honey bee, Varroa mite and pathogens
The mite causes damage when piercing the honey bee body and the hemolymph is consumed. This results in reduced weight in adult bees, shorter lifespan and poor navigation when foraging (Locke, 2012). The colony-level fitness is affected by a reduced ability of the drones to mate and to swarm. The serious colony-level effect of the Varroa mite infestation is the development of overt viral infections, causing the colony to collapse (Locke, 2012). Viruses carried by the Varroa mite include Kashmir bee virus, Sacbrood virus, Acute bee paralysis virus, Israeli acute paralysis virus and Deformed wing virus (Table 1) (Rosenkranz, 2010). Before the introduction of Varroa mites viruses were not a big problem for honey bees. If not reduced by treatment, the viral infections can kill a colony within 1-3 years. This has nearly led to an elimination of wild and feral honey bees in Europe and Northern America. Reduced honey bee colony growth and honey production can be signs of Varroa infestation, even when no clinical symptoms are found by the beekeeper.
Table 1. Viruses carried by the Varroa mite and their effects, symptoms and occurrence in honey bee (A. mellifera) colonies (de Miranda et al., 2012).
Virus Effects Symptoms Occurence
Kashmir bee virus Rapid mortality of individuals and colony.
Undefined. Worldwide. Not Sweden.
Sacbrood virus Mortality of brood individuals.
The pupa looks like a sac. Worldwide. Common in Sweden.
Acute bee paralysis virus
Rapid mortality of individuals and colony.
Undefined alternatively harmed wings, paralysis and death outside the bee hive.
Worldwide. Minor findings in southern Sweden.
Israeli acute paralysis virus
Rapid mortality of individuals and colony.
Undefined alternatively harmed wings, paralysis and death outside the bee hive.
Worldwide. Not Sweden.
Deformed wing virus Colony mortality. Deformed wings and body, reduced immune response.
Worldwide. Common in Sweden.
The mite primarily transmits and replicates the Deformed wing virus (DWV) while feeding on the bee hemolymph. This virus often exists in a colony with no visible symptoms when the infestation is low or absent. The growth of the mite population increases the risk of overt infection and
elimination by the colony. Symptoms of the DWV on adult bees are deformed wings, shortened body and poorly functioning immune system. Observations also show that the DWV symptoms might be related to the replication of the virus in the infesting mite during the pupal stage of bee development (Yue & Genersch, 2005; Yue et al., 2007).
2.5 The natural selection process of host-parasite interactions
The virulence of a pathogen decreases the survival or reproduction of a host and results in increased pathogen fitness (Locke, 2012). The transmission route of a pathogen determines the evolution of pathogen virulence (Lipsitch et al., 1996; de Miranda, personal communication). This affects the natural selective process of host-parasite interactions towards disease resistance or tolerance. In healthy honey bee colonies, pathogens referred to as viruses, usually persist as covert infections (de Miranda et al., 2012). Environmental stresses, such as parasites, co-infections with other pathogens, harsh weather, lacking food stores and toxicity of pesticides used in the hive as disease treatment or outside the hive on chemical treated crops, contributes to development of overt infections. These are characterised by increased virion production in the titers of a colony, which can result in disease symptoms and even colony mortality (see section 2.4). Horizontal virus transmission between individual honey bees as well as between colonies of the same generation, can occur by direct (oral, contact, air and veneral transmission) and indirect (vector-borne transmission) means. Vertical virus transmission in the honey bee is possible through bee reproduction, either at the colony level or at the individual level. Different viruses have distinct effects on individuals and colonies of the honey bees. A pathogen may spread even after the death of the infected brood or adult bee, especially when the bee dies outside the hive, while carrying mites and viruses (Locke, 2012; de Miranda, personal communication).
Locke (2012) and others pointed out that the treatment methods for Varroa reduction in bee colonies have removed the selective pressure for honey bees to adapt by developing tolerance or resistance to mites. Build up of chemical residues in the wax comb may harm the bees since they are sensitive to many chemical insecticides and there are little knowledge of how the pesticides interact with the bees or bee pathogens (Locke, 2012). The mites can also develop resistance to acaricides, i.e.
synthetic chemicals, which can make the treatment ineffective and even damage the bees (Locke et al, 2012b).
2.6 Long-term selection process of two distinct European honey bee
populations
In 1999, several honey bee colonies from different parts of Sweden were introduced to Gotland island. These were infested by Varroa mites to determine whether an isolated population of bees would survive under Nordic conditions. They did not receive any mite control treatment, which resulted in a decrease in bee colonies from 150 to 21 within three years. Despite this, more than ten years after the start of the experiment, a small number of colonies (hybrid sub-populations)
remained (Locke & Fries, 2011). Compared to other colonies treated with regular mite control beekeeping methods, the hybrid sub-population on Gotland were found to have developed mite resistant traits (Fries & Bommarco, 2007). The exact mechanisms behind these traits were not defined, but the reduced brood production of the surviving colonies was limiting the mite
population growth by reduced opportunities, or success of the mites reproduction (Locke & Fries, 2011).
In Avignon, France, feral and abandoned managed colonies that didn't receive any mite control for over 7 years showed no significant difference in colony mortality compared to control colonies (Le Conte et al., 2007). This showed that natural selective pressure had resulted in the adaption of the bee, the mite, or both in order to coexist. The mechanisms behind this host-parasite relationship were unclear, but similar to the Gotland experiment, it showed that honey bees can develop tolerance to the mites. However, it doesn’t offer a solution for beekeepers risking both the lives of their colonies and the decrease of pollination services, as expressed by Fries (2010). Studies in Italy and North America (DeJong & Soares, 1997; Seeley 2007) report the survival of feral and
unmanaged European honey bee strains after several years without any treatment against the mites. The genetic variation among bees is optimally maintained by promoting the variation of interacting organisms in its local surrounding (Pedersen et al., 2009). The basis for disease resistance is that they adapt to their local environment with natural opportunities to reproduce with other local adapted colonies.
Swedish Bee breeding (Svensk Biavel) commissioned Ingemar Fries and the bee health consultant (bihälsokonsulent) Preben Kristiansen to explore the possibility of breeding for Varroa mite
tolerance in Swedish honey bees (Fries, 2010). They concluded that the resistance to mites is likely a combination of many properties, and influenced by geographic differences and bee varieties. The best approach is to find a strategy to see which colonies are the more resistant. To compare the rate of mite growth in bee colonies with differing genetic background, with the rate of growth of the Varroa population in each colony, is a possible way to observe where the growth is the fastest. Fries (2010) proposes that overwintered healthy bees not yet parasitised by mites as a key to apiculture in the Swedish climate. The presence of the mites in the honey bee colonies during the spring and the beginning of the summer is not a problem for a good honey harvest and overwintering of the bees. During these seasons the growth of the mites must be observed, to limit the mite infestation rate, before the bees are overwintered.
2.7 Future honey bee threats and treatment of bee pathogens
Fabricius-Kristiansen (2013) describes the Tracheal mite as the most alarming future threat for honey bees in Sweden, as it has been found in the colonies of neighbouring countries and the Swedish restrictions for bee importations exist to avoid its arrival. The Tracheal mite (Acarapis woodi) is a microscopic spider that infests the inside of the breathing tubes of the bee
(Jordbruksverket, 2013b). The disease symptoms are often seen early in the springtime when bees are unable to fly and are found on the ground in front of the bee hive. Since thers are similar
symptoms of other bee pathogens, the disease needs to be identified in the laboratory. The spread of the Asian predatory wasp (Vespa Velutina) in recent years poses a low risk for southern Sweden but it has occurred in France, Spain and Belgium. It causes colony losses by eating the bees. The wasp resembles the European hornet (Vespa crabro), but has not been observed in Sweden (Fabricius-Kristiansen, 2013). The small hive beetle, another predator of the bees, thrives in warmer climates (southern Africa, North America and Australia) and presents a low risk for establishment in Sweden. The larvae of the small hive beetle eats everything in the honey bee colony, resulting in colony death.
A group of harmful organisms, suggested to cause Colony collapse disorder and other mass deaths in bee populations include the Varroa mite and associated viruses, Israeli acute bee paralysis virus, Deformed wing virus, Acute bee paralysis virus, Kashmir bee virus and Nosema ceranae (Pedersen et al., 2009b). The Israeli acute bee paralysis virus has been associated with the Colony collapse disorder. Acute bee paralysis virus and Kashmir bee virus were found in danish bee colonies after large winter losses in 2007-2008. The microsporidians Nosema ceranae and Nosema apis both
nutrient uptake in the intestine which leads to a shortened life in bees and worsens the ability to feed the brood (Mattson & Lang, 1994). Weak colonies often develop this disease, such as those infected by viruses and due to stress (Jordbruksverket, 2009; Pedersen et al., 2009b). Exchange of wax combs is a way to prevent the disease, because the spores survive there. Microscopic analysis is used to determine the disease and heavily infested colonies need to be killed. Two brood diseases that will be briefly described here are the Sac brood and the Chalk brood diseases. Sac brood virus is similar to the American foulbrood causing death to the developing pupa in the closed wax comb cell (Jordbruksverket, 2009). The dead brood looks like a sac and can be removed from the comb. The disease normally clears from the colony after a shorter period. Chalk brood is caused by a mold (Ascophaera apis), that after ingestion with their food converts the developing larvae in the closed cells into hard white mummies. The bees clean out smaller outbreaks of the disease, which is facilitated by the beekeeper spraying a sugar solution on the wax combs. Heavily diseased colonies are moved to a new clean wax comb.
Honey bee diseases that are considered so serious that they are regulated by Swedish laws, include the American foulbrood (Paenibacillus larvae), Varroa mites (V. destructor) and Tracheal mites (Acarapis woodi) (Jordbruksverket, 2013a). The two first mentioned have comprised the main part of this report. The American foulbrood disease occurs in Sweden and is a worldwide problem for apiculture. Smaller levels of infection can be swept away by the larva itself (Jordbruksverket, 2013b), however mortality of an entire colony occurs if the bacteria Paenibacillus larvae increase. These bacteria produce spores that germinate during the pupal development stage in the closed wax comb cell allowing the growth of the bacteria. A colony with clinical symptoms of American foulbrood (AFB) must be eliminated because of the severity of this disease. The spread of AFB in wild bee colonies in Sweden has demanded that the authorities remove infected colonies. The AFB together with the Varroa mite spread has severely impacted the wild bee populations (Pedersen et al., 2009). Biotechnical and biological methods against Varroa mites, generally advised by the Jordbruksverket, are the removal of drone brood, and the ‘trapping comb technique’. Comb foundations with smaller cell size (4,9 mm - 5,1 mm) are also used, but less often (Rosenkranz, 2010). The smaller cell size in some honey bee species is likely affecting the rate of Varroa mite invasion and reproduction, but this needs to be further studied. Acaricides are chemical substances used for mite control. Formic, lactic and oxalic acids, are organic substances occurring in the honey bee colony, and are applied as acaricide treatments by the beekeeper (Rosenkranz, 2010). Before applying these organic acids, the number of mites that drop onto a board under the hive are counted (Kristiansen, 2001). This is done in June, and the result show if, and when treatment is needed. The
acaricides are applied from August to October, before the winter bees are born, depending on the extent of the mite population. Formic acid is used in an early stage, since its vapours kill mites in the brood cells, as well as those attached to the adult bees. Closer to the winter period when the bee society is free from brood, oxalic acid or lactic acid is applied since these work directly on mites attached to the bees. Thymol is another natural substance used for mite control, by which vapours can reduce the mites by 90% (Rosenkranz, 2010). Synthetic acaricides needs special competence to apply safely. For example Apistan has an efficacy against mite infestation close to 100% (Locke et al., 2012b). However, this chemical acts negatively on the physiology of the bee. Aditionally, Apistan and similar synthetic chemicals are likely causing acaricide resistance, since mites in the sealed cells may be affected by wax residues (Rosenkranz, 2010).
Table 2. Various bee diseases, their first incidence in Sweden, symptoms, treatment, and severity (Pedersen et al., 2009b; Mattson & Lang, 1994; Jordbruksverket, 2009).
Disease First incidence in Sweden
Symptoms Treatment Severity
Nosema ceranae/ Nosema apis N. ceranae in 2006. Laboratory diagnosis. Decreases protein uptake in bees, resulting in weakened bees.
Exchange of wax combs to prevent spores. Acetic acid is used to remove the infectious agent from the comb. Heavily infested colonies are eliminated.
High. Shortened life, increased disease by other stressors.
Chalkbrood 1950s Mumified brood. Sometimes characterised by grey-green spores.
Heavily infested wax combs are burned, after moving the bees to new wax combs.
High, but most often cleaned out by the bees themselves. American
foulbrood
1950s Dark cell caps. Small holes in cell caps and a pronounced sour odor.
If the second symptom is defined, the colony must be eliminated.
High, but smaller infestation levels can be cleaned out by the bees themselves.
3. Benefits of lactic acid bacteria on bee health and apiculture
3.1 Colony defense
A Swedish research team (Olofsson & Vásquez, 2011) has discovered a new group of commensal lactic acid bacteria (LAB) inside the honey crop (the stomach) of honey bees. The relationship between these LAB and the most recent ancestor to the honey bee is thought to be more than 80 million years (Vásquez et al., 2012). They have found that these LAB protect the bee colony from pathogens and microorganisms that spoil the nectar, picked-up from other animals that have interacted with the flowers before the bees visits (Olofsson & Vásquez, 2011).
3.2 Lactic acid bacteria symbionts in human and animal microbiota
LABs are recognised as beneficial microbes in healthy humans (Vásquez et al., 2012) and are also found within other animals and insects, according to Hammes (2006) (cited in Vásquez et al., 2012). The symbiotic relationship between the LAB and the human intestine is defined as
commensal and mutualistic, and they are referred to as symbionts (Jass, personal communication). One result of this symbiosis is improved immune response. The antimicrobial effect of LAB is likely improving the gastrointestinal defense in mammalians (Servin, 2004).
About 20% of all insects are estimated to support symbionts in a mutually beneficial way, describes Madigan et al. (2012). These symbionts attach either outside or inside the insects bodies, providing them with nutritional advantages or protection. The mechanisms of LAB in the gut of honey bees are less known than in humans and other vertebrate animals (Vásquez et al., 2012). However, Vásquez et al. (2012) believe that these mechanisms in the honey bee gut have functions similar to the human gut, and thus play an important role in the bees immune defense. The LAB antimicrobial mechanisms are likely evolved to defend the bees against harmful microbes, and maybe even pathogens. A similar kind of defense has been shown in the normal flora of the fruit fly gut, where the growth of pathogens was inhibited (Silverman & Paquette, 2008). This insect has a very limited microbial gut diversity which demonstrates that a normal flora is very critical to sustain health. Like other social insects, the honey bee gut microflora contains a diversity of beneficial symbionts (Evans, 2006). Honey bees and bumble bees easily exchanges symbionts between its members, since they live in very dense societies (Martinson et al., 2011). This facilitates each individual to maintain a consistent gut microbiota, a microbiota which is not yet clearly investigated.
3.3 Honey bee commensal bacteria
Recently, 13 species within the genera Lactobacillus and Bifidobacterium were identified in the microbiota of the honey bee crop (Olofsson & Vásquez, 2008). This microbiota is transferred to the sterile crops of newly emerging bees when interacting with the other bees of the colony (Vásquez et al., 2012). More precisely, the bees store gathered nectar in their honey crop and transfers the nectar mouth-to-mouth to bees in the hive (Olofsson & Vásquez, 2008). These in turn bring it to the honey comb 'cells', where most liquid evaporates. The bees add enzymes to the nectar, which is ripened and sealed in the cells with a wax cap. This ripened nectar is what we call honey. Olofsson & Vásquez (2008) proposes that the nectar sugars probably promotes the LAB present in the honey crop to increase in numbers. Nectar from different flower species also results in different amounts of LAB in the bees.
Forsgren et al. (2010) found that the spore forming bacteria P. larvae, the cause of American foulbrood disease (AFB), was inhibited by the LAB microbiota of the honey bee crop. In an inhibition assay 11 of the LAB phylotypes applied together, showed no visible growth of P. larvae. A mixture of these LAB phylotypes added to bee larval food showed a significant reduction of AFB infected larvae in exposure bioassays. These experiments demonstrate that the honey bee specific LAB microbiota are beneficial to the bee health. Other experiments have shown that the LAB also decreases broods infected with the similar disease, the European foulbrood (Vásquez et al., 2012). This is common in Switzerland and England where the density of colonies is high (Fries &
Kristiansen, 2012). LAB also protect the nectar, pollen, bee bread and honey from microorganisms, and protect the foraging bees (Vásquez et al., 2012). Absence of LAB in the bee food endangers the health of bees, for example those that are fed with substitutes for honey and pollen (Vásquez et al., 2012). Even pathogens as the Varroa mite and N. apis are inhibited by the antimicrobial organic acids produced by the LAB in the honey bee colony (Olofsson & Vásquez, 2008). This is important since the function of LAB might be an alternative to organic acids treatment in apiculture.
Yeasts (Saccharomyces species) can also promote the spoilage of honey. Lactobacillus kunkeei, previously known to inhibit the alcoholic fermentation of yeasts (Saccharomyces species) in wine production (Olofsson & Vásquez, 2008 and others) appeared to dominate the microbiota of the honey crop. L. kunkeei, also seems to be left on damaged grapes visited by bees. Since the nectar collected by the bees has a water content that decreases over several days until reaching the safe
level of 18%, Olofsson & Vásquez (2008) believe that L. kunkeei inhibits the yeasts from spoiling the honey.
3.4 Benefits of honey bee LAB for human health
Antibiotics inhibit pathogens in the gastrointestinal tract, but also the growth of the normal
microflora, which leads to the loss of antibiotic-susceptible microorganisms (Madigan et al., 2012). This enables the establishment of antibiotic-resistant microorganisms which can cause disease or disturbance to the intestinal tract. Probiotics, such as Lactobacillus and Bifidobacteria, are live microbes that can help the recolonisation of the normal competitive microflora and may enhance the immune response (Montville, 2008). These bacteria have traditionally been used in food
fermentation to prevent dairy, meat and vegetable products from spoilage.
The newly found honey bee LAB species, consisting of nine Lactobacillus, and four
Bifidobacterias, were characterised and combined with honey at a high (26%) water content (Olofsson & Vásquez, 2013). A high water content prevents the LAB from getting destructed. Contrary to the normal honey sold in shops, these newly found LAB resulted in a probiotic product that conserves LAB. The maximum number of LAB in wild fresh honey is 100 million per gram. Similar numbers of LAB in this new natural health product are ingested with the intention to cure sore throat, decreased immune response and to recover after heavy physical training. The LAB defend against harmful bacteria and produces antimicrobial substances, which is the reason why honey has been used as a folk medicine since long ago (Olofsson & Vásquez, 2013). Honey hunters likely have obtained similar health benefits after harvests of wild bee nests.
3.5 Enhanced immune response in honey bee colonies
Studies shows that the genes involved in innate immunity in honey bees are reduced to one third, compared to other insects (The Honey Bee Genome Sequencing Consortium, 2006). Therefore the LAB ingested by honey bee broods may act as an additional defense. Strong colonies more
effectively remove broods that have been parasitised by P. larvae (Fries et al., 2005). The variability of this hygienic behavior among bees suggests that it is even more important to enhance the
immune response, for example by strategies of maintaining the LAB symbionts of the bee. Such a strategy is the supplementary feeding of LAB to bees, a possibility to improve bee health in beekeeping husbandry, as suggested by Vásquez et al. (2012). Their development of a probiotic product for honey bee colonies is promising (Symbeeotic, 2014). This strategy seems to be of extraordinary importance in the USA, where antibiotics are used more widely and the beekeepers uses synthetic sugar solutions as substitutes to the bees' natural food storage (Vásquez et al., 2012).
4. Survey of beekeepers in Örebro County
In 2009 The EFSA, European Food Safety Agency, determined that there are no organised statistics of national honey bee colony losses within the EU (Jordbruksverket, 2013c). Two years later, 17 countries chose to participate in an organised statistical recording where Jordbruksverket decided to record the colony losses during winter and active seasons, the extent of the Varroa onset, occurrence of Acute bee paralysis virus, Deformed wing virus, American foulbrood, European foulbrood, Sac brood, Nosema and Tracheal mites in Sweden between 2012 and 2013. This background together with the large winter declines of honey bee colonies (Pedersen et al., 2009), Varroa mites in all parts of Örebro County and the absence of AFB (Jordbruksverket, 2012) has prompted the survey of the beekeepers in Örebro County about their opinions regarding their bee colony health.
A small survey was prepared to determine the status of the bee colonies in Örebro County
(Appendix 1). This included the general statistics of their bee colonies, the spread of Varroa, AFB and other honey bee diseases, treatment methods, winter colony loss, and the general opinions of the bee health in their colonies over last 5 years. The common spread of the Varroa mite and the absence of AFB, as mentioned above, made it relevant to ask the local beekeepers how their colonies are fairing. The survey was sent in December 2013 to 60 beekeepers evenly distributed over 12 municipalities of Örebro County (Figure 3). Of these, 45 responded (75%), however, 1 stopped keeping bees and was therefore excluded from the analyses. The county was divided into northern (A), central (B) and southern (C) regions. The majority of the responses originated from the central region of Örebro County (Table 3). From the survey, most beekeepers had between 1 and 10 colonies, while there were a few with over 100 colonies within the County. The average winter colony loss from 2009 to 2013 was quite evenly distributed, with about 4,3 per beekeeper in the whole County. The majority of the beekeepers indicated a low average loss. The higher level of colony loss was in the central and southern regions, with those that had more than 100 colonies (Table 4). The winter 2012-2013 had the greatest colony loss over the entire County, however in the southern region both the winter of 2009-2010 and the winter of 2010-2011 had equally high losses. The disease spread showed that most of the bee colonies had Varroa mites and that the majority of them were within the central region. Interestingly, some reported to have bees with deformed wings or body from the central region. Nosema and AFB are other serious diseases that were reported. AFB was indicated by one beekeeper in the northern region, while one had Nosema in the central
region, and chalkbrood was found in both the northern and southern regions at low levels. Related Nosema symptoms observed by one beekeeper were “many bees were weakened and dead” and “the hives very dirty”. One beekeeper had seen “grooming of undeveloped brood”. Mice reported by one beekeeper, though not a symptom, is normally a threat for honey bee colonies.
Full responses to the question regarding treatment methods was not received, therefore
interpretation of this needs to be done cautiously. Apparently, every beekeeper was removing drone brood from their colonies, a treatment for Varroa mites, in combination with a chemical treatment (Table 5). Only one used smaller sizes of the cells in the wax combs as a treatment option (see section 2.7). Organic acids were the most common chemical treatment and synthetic chemicals were used by 20% of the beekeepers. Oxalic acid was the most common used organic acid (27% of the beekeepers). One tested the synthetic chemical Baiticol once, but did not continue to use it. Two of the beekeepers using chemical treatment used two different organic acids. However, only one beekeeper bred bees for Varroa resistance.
The beekeepers had varying opinions when asked if they were concerned about any future honey bee diseases in Sweden. Equal amount (32%) were concerned about diseases as those not
concerned. Six beekeepers were worried about the Tracheal mites. Two beekeepers were concerned about unknown and resistant diseases and two were concerned about the use of pesticides. Of this last group, one beekeeper was worried about 'The small hive beetle' and Tracheal mites, especially as the climate becomes warmer. A considerable group of beekeepers consider the threat of
agriculture on apiculture. More research on chemical agents that are used in plant cultivation was suggested by one beekeeper. The toxicity of the pesticides along with worsened habitats for the bees, were suggested to contribute to the problems of resistant bee diseases.The importance of breeding or resistance against Varroa mites among bees, was mentioned by three beekeepers. Many agreed that good beekeeper education was important. Mixed treatment methods was advised against resistance in the colonies. The need for Varroa treatment was also stated; where one beekeeper highlighted that synthetic chemical treatment can lead to resistant mites, while other beekeepers mentioned that Apistan is sometimes useful. One beekeeper explained he was breeding for natural selection in his colonies. This was done by replacing the queens in the worst Varroa infested
colonies. He observed that an increasing number of colonies didn't need any treatment, in others the chemical treatment was decreased. The importance of hygiene in the apiary was also mentioned by three beekeepers, of whom two added the importance of wax exchange. Overwintering of strong
colonies was another important issue that two beekeepers noted. It is clear that the beekeepers used different strategies to maintain the health of their bees with varying success.
Örebro County
(A) Northern region, 3558 km².
(B) Central region, 2892 km².
(C) Southern region, 2055 km².
Figure 3. The division of Örebro County into regions included in the survey (authors rendition of Google maps).
Table 3. Survey responses in the three regions of the Örebro county.
Region A Region B Region C Örebro County
No. Responses 11 19 14 44
% responses per region 69% 68% 88% 73%
Table 4. Winter colony losses, diseases and symptoms of bees in Örebro County over the past five winters, 2009-2013. Data collected in a survey of beekeepers in Örebro County, December 2013.
Region A Region B Region C Örebro County (Number of colonies) Colonies lost over 5 years
Average 2,4 4,1 4,9 4,3
Range 1-6 0-25 1-20 -
Winter colony losses
2012-2013 8 10 4 22 2011-2012 3 4 4 11 2010-2011 2 5 5 12 2009-2010 5 5 5 15 2008-2009 3 5 3 11 Diseases/infestations Varroa mites 7 14 12 33 American foulbrood disease 1 0 0 1 Nosema 0 2 0 2 Chalk brood 1 0 1 2 Other 0 0 1 1 Disease symptoms Deformed wings 2 6 4 12 Deformed body 1 3 2 6
Deformed wings and body 0 2 1 3
Weak colonies 2 2 1 5
Grooming of undeveloped brood
0 0 1 1
Mice, starvation, frost 0 0 1 1
Other 0 0 2 2
Table 5. The beekeepers applying various methods to prevent or treat diseases in Örebro County. Results from a survey of beekeepers in Örebro County in December 2013.
Region A Region B Region C Örebro County (Number of beekeepers
using the method) Biological methods
Drone brood removal 3 6 3 12
Small cells 0 0 1 1
Chemical methods
Organic acids and
essential oils 6 4 6 18
Synthetic 1 8 0 9
Synthetic and
organic acid 1 1 0 2
Chemical and
drone brood removal 3 6 3 12
Other
Breeding 0 1 0 1
4.1 Conclusions from survey
Honey bee colonies infested by Varroa mites, does not mean that they have a disease. As indicated in the survey, it can weaken the immune defense of the bee, leading to viral transmission and death. Some responders have observed deformed wings and body, the signs of DWV, which might suggest that from the colonies affected by the mites, some have disease. Since these symptoms, including the Varroa infestations, were slightly higher in the central region, a possible reason might be the higher density of colonies in this region. It was surprising that one beekeeper suggested that his
bees had AFB, since the previous observations reported in Örebro County showed none
(Jordbruksverket, 2012). This requires further investigation to confirm these conclusions. Nosema often manifests as dirty hives since the bees leave feces in the hive because of intestinal problems. Interestingly one beekeeper has seen “grooming of undeveloped brood”, which may indicate the hygienic behaviour of the bees against Varroa mites. The use of the synthetic chemical Apistan seems to be common because it easily reduces the number of mites (Rosenkranz, 2010). Apistan kills the mites by emitting a tau-fluvalinate substance, applied by a plastic strip in the bee hive. It is mentioned among the beekeepers that they need to avoid using one chemical too long, because the bees or mites may develop resistance. This is also reported by Rosenkranz and others (2010).
Therefore some beekeepers mix Apistan with other methods such as drone brood removal. Similarly the active substance in Baiticol, or Bayticol, is a pyrethroid chemical that acts against the Varroa mites by targeting their nerve functions.
Breeding for Varroa resistant bees as mentioned is of course positive for people that have high beekeeper skills and the one reported here is hopefully promoting the genetic diversity of his bees. The suggestion to select the colonies that suffer the most from Varroa infestation and replacing the queen is an interesting strategy that appears to work. On the contrary, the change of natural habitat for the queen seems rather strange. This beekeeper was also treating his bees with Thymol, whose active substance is naturally occuring in thyme, for fighting the mite. To summarise, beekeepers in this survey seem conscious to find suitable solutions for disease prevention. Education is a step towards future challenges, and the National honey program (Nationella honungsprogrammet) established by the Swedish government for such strategy may contribute to future improvements. In general there are concerns about future diseases as indicated by some beekeepers, such as Tracheal mites, unknown and resistant diseases, and also the impact of pesticides on bees. Recent news about the damage of some neonicotinoids on bee health is obviously being noticed. The worsened habitat circumstances for the bees, as one beekeeper express himself, refers to the landscape change because of agricultural practices that are established (Wide, 2009). The same beekeeper thinks that this, in concert with pesticides and wrong environmental planning from the municipality, leads to effects that underly missing bacteria in the bees gut followed by resistant bee diseases. This is similar to the research on LAB as previously mentioned, and may thus be a novel solution to some of these concerns. An increased value of managed beekeeping in Sweden may be to estimate the importance of the products that honey bees provide, as mentioned by Eriksson (2012). In Sweden honey is the dominating product being sold, and the bees are often fed sugar solutions during the winter for increasing yields (by taking from the bees winter stored honey).
Eriksson (2012) reasons that wax, pollen and propolis could be sold more, and that the dependence on selling honey might decrease. He also suggests that the important role bees play in increasing plant biodiversity must be considered. A development for promoting honey bee pollination is the placement of hives in crop fields through The Pollination Pool (Pollineringspoolen), which helps farmers find local beekeepers that rent their hives (Biodlingsföretagarna, 2014).
5. Summary and future challenges for apiculture
The pollination services that honey bees (A. mellifera) provide supports agricultural crop production and biodiversity. Placement of bee hives in fields and promoting flowering plants preferred by threatened pollinators, can benefit the diversity of several species. Worldwide decline of honey bee colonies are caused by Colony collapse disorder, the mite V. destructor, and pesticides in crop production. This affects the bees' life by impaired immune defenses and different diseases. The hygienic behaviour of the bee is the ability to detect and remove dead or diseased brood. However, this trait varies in different bees. The Varroa mite damages the bee's physiology and transmits lethal viruses. Resistance against synthetic acaricides among mites is common, but sometimes the
beekeepers have no alternative treatments. These synthetic acaricides also remove the natural
selective pressure, needed for evolution of mite tolerant, or the development of resistant honey bees. Studies show that long-term natural selection for such honey bee traits is possible, but not yet a sustainable solution for apiculture. This is an important area that needs scientific development and research. Beekeepers' observations of mite reproduction dynamics during the warmer seasons is essential for overwintering strong honey bees and, consequently, decreases chemical treatment. It has also been shown that species of LAB in the honey bee act by improving the immune response. Active LAB microbiota produces antimicrobial organic acids, normally inherent in a honey bee colony, protecting bees from pathogens such as Varroa and American foulbrood disease. Since beekeepers uses organic acids as treatment for this disease, the LABs plays an important role as a probiotic. Where apicultural practices have led to decreased amounts of LAB in the bees,
supplementary feeding of bee colonies is a possible solution. This strategy is highly promising for future apiculture, and commercial ventures to develop LAB supplementary feeding are in progress. A small survey of beekeepers in Örebro County, Sweden, showed a Varroa mite infestation in their colonies with symptoms similar to Varroa disease primarily found in the central region. This may possibly reflect a higher density in colonies in this region. Organic acids were the most common treatment method used, and drone brood removal was occasionally combined with this. Of the last
five years, the winter with the highest colony loss in Örebro County was predominantly 2012-2013. Mixed treatment methods to avoid resistance in colonies, was suggested the best control strategy by some beekeepers. There is however a major concern about pesticides, such as neonicotinoids, and Tracheal mites, similar to possible future honey bee threats, described by the Swedish agricultural board (Jordbruksverket). Furthermore, no beekeepers used the LAB supplementary feeding of their colonies. Finding that the bees natural defense benefits from LAB might interest these beekeepers to evaluate this as an alternative treatment method.
Acknowledgements
Thanks to Dr. Jana Jass for your patience as a supervisor; Hans Ekström, Länsstyrelsen i Örebro län for assistance in survey preparations; the participants of the survey; Joachim de Miranda for
information about bee viruses; Illona Larsson for help with pictures, and Dr. Olivia Larne for proof reading assistance.
References
Anonymous (2013). Sverige stödjer förbud av neonikotinoider. Lantbrukets affärstidning. Accessed 2014-01-20. http://www.atl.nu/lantbruk/sverige-st-djer-f-rbud-av-neonikotinoider
Biodlingsföretagarna (2014). Pollineringspoolen. Accessed 2014-01-28. http://www.biodlingsforetagarna.nu/pollineringspoolen/
Bortolotti, L.; Montanari, R.; Marcelino, J.; Medrzycki, P.; Maini S. & Porrini, S. (2003). Effects of sub-lethal imidacloprid doses on the homing rate and foraging activity of honey bees. Bologna University. Bulletin of Insectology, 56: 63-67.
De Jong, D. & Soares, A. E. E. (1997). An isolated population of Italian bees that has survived Varroa jacobsoni infestation without treatment for over 12 years. American Bee Journal, 137: 742-745.
de Miranda, J. R.; Gauthier, L.; Ribière, M. & Chen, Y.-P. (2012). Honey bee viruses and their effect on bee and colony health. Honey Bee Colony Health: Challenges and Sustainable Solutions (eds. Sammataro, D. & Yoder, J. A.); Chapter 8, pp 71-102. Oxford: Taylor & Francis Group Ltd.
EFSA (2013). News and events - EFSA identifies risks to bees from neonicotinoids. Press release, 16 january 2013. Accessed 2014-02-17. http://www.efsa.europa.eu/en/press/news/130116.htm
Ehnström, B. & Öberg, T. (2009). Sälgen behövs. (Jordbruksinformation 3). Jönköping: Jordbruksverket.
Eriksson, J. (2012). Landsbygdsdepartementet Remiss 2012-07-05 L 2012/1449
Landsbygdsprogram 2014-2020, samt behov av nya mål och åtgärder för ekologisk produktion i landsbygdsprogrammet. Accessed 2013-12-19.
http://www.biodlarna.se/website1/1.0.1.0/1055/121011%20Remissvar-Yttrande%20L%202012-1449%20%20Ekotj%C3%A4nster.pdf
Evans, J. & Armstrong, T.-N. (2006). Antagonistic interactions between honey bee bacterial symbionts and implications for disease. BMC Ecology, 6: 1-9.
Fabricius-Kristiansen, L. (2013). Beredskapsplan 2014, exotiska sjukdomar, parasiter och skadegörare på honungsbin. Jordbruksverket. Accessed 2014-02-11.
http://www.jordbruksverket.se/download/18.58f2066813fc03d6a203a/1373350585017/Beredskapsp lan+mot+exotiska+skadeg%C3%B6rare.pdf
Forsgren, E.; Olofsson, T.; Vásquez, A. & Fries, I. (2010). Novel lactic acid bacteria inhibiting Paenibacillus larvae in honey bee larvae. Apidologie, 41: 99-108.
Fries, I. (2010). Avel för tolerans mot varroakvalster hos honungsbin – en förstudie. Uppsala: Ekologiska institutionen, SLU.
Fries, I.; Kristiansen, P.; Lindström, A. & Forsgren, E. (2005). Amerikansk yngelröta – biologi diagnos och bekämpning. (Jordbruksinformation 16). Jordbruksverket.
Fries, I. & Kristiansen, P. (2012). Studieplan till boken sjukdomar, parasiter och skadegörare. Studieförbundet vuxenskolan.
Fries, I. & Bommarco, R. (2007). Possible host-parasite adaptions in honey bees infested by Varroa destructor mites. Apidologie, 38: 525-533.
Fuchs, S. (1990). Preference for drone brood cells by Varroa jacobsoni Oud in colonies of Apis mellifera carnica. Apidologie, 21: 193–199.
Gullan, P. J. & Cranston, P. S. (2000). The insects, an outline of entomology. Second edition. California: Blackwell Science Ltd.
Hammes, W. & Hertel, C. (2006). The genera Lactobacillus and Carnobacterium. The Prokaryotes: Bacteria: Firmicutes, Cyanobacteria (eds. Dworkin, M.; Falkow, S; Rosenberg, E.; Schleifer, K.-H. & Stackebrandt, E.), 4: 320-403.
Harry, T. (2013). Sociala bin. Accessed 2013-11-23. http://www.sef.nu/smakrypsguiden/guide-till-insektsgrupperna/egentliga-insekter-insecta/steklar-hymenoptera/aculeata/apoidea/
Jordbruksverket (2009). Handledning för bitillsynsmän. Accessed 2014-02-11.
http://lansstyrelsen.se/skane/SiteCollectionDocuments/Sv/djur-och-natur/djurskydd/djurslag/ovriga-djurslag/biodling/Handledningmaj2009.pdf
Jordbruksverket (2012). Myndigheternas roller I smittbekämpningen - Statistik från bitillsynen 2012, enheten för häst, fjäderfä och vilt. Accessed 2014-01-09. http://www.jordbruksverket.se/amn esomraden/djur/olikaslagsdjur/binochhumlor/myndigheternasrollerismittbekampningen.4.1a4c164c 11dcdaebe12800054.html
Jordbruksverket (2013a). Biodlingens roll. Accessed 2013-11-12.
http://www.jordbruksverket.se/amnesomraden/djur/olikaslagsdjur/binochhumlor/biodlingensroll.4.1 a4c164c11dcdaebe12800044.html
Jordbruksverket (2013b). Beskrivning av bisjukdomar. Accessed 2014-01-26 from:
http://www.jordbruksverket.se/amnesomraden/djur/olikaslagsdjur/binochhumlor/beskrivningavbisju kdomar.4.1a4c164c11dcdaebe12800064.html
Jordbruksverket (2013c). Pilotprojekt för övervakningssystem. Accessed 2014-01-09.
http://www.jordbruksverket.se/amnesomraden/djur/olikaslagsdjur/binochhumlor/biodlingsprojekt/pi lotprojektforovervakningssystem.4.362991bd13f31cadcc2cff.html
Kimura-Kuroda, J.; Komuta, Y.; Kuroda Y.; Hayashi, M. & Kawano, H. (2012) Nicotine-Like Effects of the Neonicotinoid Insecticides Acetamiprid and Imidacloprid on Cerebellar Neurons from Neonatal Rats. Accessed 2014-02-09. PLoS ONE, 7: e32432. doi:10.1371/journal.pone.0032432.
Kristiansen, P. (2001). Varroabekämpning med ekologiska metoder. (Jordbruksinformation 10). Jönköping: Jordbruksverket.
Käck, Å.; Olrog, L. & Christensson, E. (2012). Försök med utplacering av bisamhällen i fält med åkerböna. Hushållningssällskapet Väst.
Le Conte, Y.; De Vaublanc, G.; Crauser, D.; Jeanne, F; Rouselle J.-C. & Becard, J.-M. (2007). Honey bee colonies that have survived Varroa destructor. Apidologie, 38: 566-572.
Lipsitch, M., Siller, S. & Nowak, M. A. (1996). The evolution of virulence in pathogens with vertical and horizontal transmission. Evolution, 50: 1729–1741.
Locke, B. (2012). Host-Parasite Adaptations and Interactions Between Honey
Bees, Varroa mites and Viruses. Uppsala: Swedish University of Agricultural Sciences.
Locke, B. & Fries, I. (2011). Characteristics of honey bee colonies (Apis mellifera) in Sweden surviving Varroa destructor mite infestation. Apidologie, 42: 533-542.
Locke, B.; Le Conte, Y.; Crauser, D. & Fries, I. (2012a). Host adaptions reduce the reproductive success of Varroa destructor in two distinct European honey bee populations. Ecology and Evolution, 2: 1144-1150.
Locke, B.; Forsgren, E.; Fries, I. & de Miranda, J. R. (2012b). Acaricide Treatment Affects Viral Dynamics in Varroa destructor-Infested Honey Bee Colonies via Both Host Physiology and Mite Control. Applied and environmental Microbiology, 78: 227-235.
Madigan, M. T.; Martinko, J. M.; Stahl, D.; Clark, D. (2012). Brock Biology of Microorganisms. 13th edition. Sanfransisco, CA: Pearson education.
Martinson, V. G.; Danforth, B. N.; Minckley, R. L.; Rueppel, O. V.; Tingek, S. & Moran, N. A. (2011). A simple and distinctive microbiota associated with honey bees and bumble bees. Molecular Ecology, 20: 619-628.
Mattson, C.-O. & Lang, J. (1994). Bin till nytta och nöje. Stockholm: LTs förlag.
Montville, T. & Matthews, K. R. (2008). Food microbiology – an introduction. Second edition. Washington, DC : ASM Press.
Neumann, P. & Carreck, N. L. (2010). Honey bee colony losses. Journal of Apicultural Research, 49: 1-6.
Nätterlund, H. (2007). Öka Skörden med honungsbin och jordhumlor. (Jordbruksinformation 21). Jönköping: Jordbruksverket.
Olofsson, T. & Vásquez, A. (2011). The holy grail when the antibiotics fail? Microbiology today, 38: 226-229.
Olofsson & Vásquez (2008). Detection and Identification of a novel lactic acid bacterial flora within the honey stomach of the honey bee Apis mellifera. Current microbiology, 57: 356-363.
Olofsson & Vásquez (2013). Naturally healthy with H13. Accessed 2013-11-23. http://doktorhonung.se/en/what
Partap, U. & Ya, T. (2012). The Human Pollinators of Fruit Crops in Maoxian County, Sichuan, China. Mountain Research and Development, 32: 176-186.
Pedersen, T. R. (2012). Värdet av honungsbins pollinering av grödor i Sverige 2011. Jönköping: Jordbruksverket.
Pedersen, T. R.; Bommarco, R.; Ebbersten, K.; Falk, A.; Fries, I.; Kristiansen, P.; Kryger, P.; Nätterlund, H. & Rundlöf, M. (2009). Massdöd av bin - samhällsekonomiska konsekvenser och möjliga åtgärder (Rapport 2009:24, kortversion). Jönköping: Jordbruksverket
Pedersen, T. R.; Bommarco, R.; Ebbersten, K.; Falk, A.; Fries, I.; Kristiansen, P.; Kryger, P.; Nätterlund, H. & Rundlöf, M. (2009b). Massdöd av bin - samhällsekonomiska konsekvenser och möjliga åtgärder (Rapport 2009:24). Jönköping: Jordbruksverket
Potts, S. G.; Roberts, S. P. M.; Dean, R.; Marris, G.; Brown, M. A.; Jones, R.; Neumann, P. & Settele, J. (2010). Declines of managed honey bees and beekeepers in Europe. Journal of Apicultural Research, 49: 15-22.
Rosenkranz, P.; Aumeier, P. & Ziegelmann, B. (2010). Biology and control of Varroa destructor. Journal of Invertebrate Pathology, 103: S96-S119
Sahlberg, H. (2008). Bina är borta – nu gör människorna jobbet. Sveriges radio P1, Vetenskap och miljö. Accessed 2013-11-23. http://sverigesradio.se/sida/artikel.aspx programid=406&artikel=1881 250
Seeley, T. D. (2007). Honey bees of the Arnot forest: a population of feral colonies persisting with Varroa destructor in the northeastern United States. Apidologie, 38: 19-29.
Servin, A. L. (2004). Antagonistic activities of lactobacilli and bifidobacteria against microbial pathogens. FEMS Microbiology Reviews, 28: 405-440.
Silvermann, N. & Paquette N. (2008). The right resident bugs. Science, 319: 734-735.
Sveriges Biodlares Riksförbund (2013a). Binas biologi - Drönaren. Accessed 2013-11-23. http://www.biodlarna.se/website1/1.0.1.0/15/1/
Sveriges Biodlares Riksförbund (2013b). Bisamhället. Accessed 2013-11-23. http://www.biodlarna.se/website1/1.0.1.0/14/1/
Sveriges biodlares riksförbund (2014). Bisjukdomar och parasiter – Nosema. Accessed 2014-02-11. http://www.biodlarna.se/website1/1.0.1.0/38/1/.
Symbeeotic (2014). SymBeeotic – Their natural defense. Sweden: Apicellae Ltd. Accessed 2014-02-18. http://symbeeotic.apicellae.se/
The Honey Bee Genome Sequencing Consortium (2006). Insights into social insects from the genome of the honeybee Apis Mellifera. Nature (London), 443: 931-949.
vanEngelsdorp, D.; Caron, D.; Hayes, J.; Underwood, R.; Henson, M.; Rennich, K.; Spleen, A.; Andree, M.; Snyder, R.; Lee, K.; Roccasecca, K.; Wilson, M.; Wilkes, J.; Lengerich, E. & Pettis, J. (2012). A national survey of managed honey bee 2010-11 winter colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research, 51: 115-124.
Vásquez, A.; Forsgren, E.; Fries, I; Paxton, R. J.; Flaberg, E.; Szekely, L. & Olofsson, T. (2012). Symbionts as major modulators of insect health: Lactic acid bacteria and honeybees. Plos one, 7: 1-9.
Wide, C. (2009). Guidehandledning - Guida i odlingslandskapet. Naturskyddsföreningen. Yue, C. & Genersch E. (2005). RT-PCR analysis of Deformed wing virus in honey bees (Apis mellifera) and mites (Varroa destructor). Journal of General Virology, 86: 3419-3424.
Yue, C., Schroeder, M., Gisder, S. & Genersch E. (2007). Vertical transmission routes for deformed wing virus of honeybees (Apis mellifera). Journal of General Virology, 88: 2329–2336.
Appendix 1
Bee health of apiaries within Örebro County
Örebro, November 2013 Survey number _____ Hi!
My name is Olof Larne and I am a Måltidsekolog student at the University of Örebro. I’m interested to learn more about the health of honey bees, treatment methods of bee diseases and the opinions about treatment methods, in Örebro County. Research
promoting the honey bee natural defense against pathogens, and their improved immune response has been the background for this survey. The answers to the questions will be used in a thesis about apiculture and bee health within the subject biology. It would be very interesting to hear about your opinions. When you have finished the survey, use the
response envelope. Your answers will need to be posted before December 20. The survey will be treated anonymously. For any questions about this survey please send an e-mail to ololah101@studentmail.oru.se
Olof Larne
************************************************************************************************* 1. How many colonies do you have?
1-5 6-10 11-50 51-100 over 100
2. On average, how many colonies have you lost during the past 5 years? _______ 3. Which of the following winters have you lost most of your colonies?
2012-2013 2011-2012 2010-2011 2009-2010 2008-2009
4. Have your colonies had any disease(s)? Yes No If yes, which ones?
Affected by American foulbrood
5. What symptoms have been observed, in that case? Deformed wings Deformed body Other
6. What method(s) or treatment(s) do you use for disease prevention? Biological method Chemical treatment Other
7. Are you concerned about future diseases that have not reached Sweden yet? ___________________________________________________________________ ___________________________________________________________________
8. Other comments to improve bee health, or comments referring to any treatment methods: ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________
9. Are you interested in the result of this survey? Yes No Please write your address:
_____________________ _____________________ _____________________
