Mechanisms+Influencing+Colony+Collapse+Disorder+in+the+United+States


 * Introduction **

toc The Western European honey bee, //Apis mellifera,// is highly valued in America for its natural pollination services and production of honey. Contributing to an estimation of $12 billion dollars of crop value, apiculture has influenced the agricultural economy greatly [14]. Researcher labs and funding agencies have become increasingly interested in honey bees as their species is now being threatened by the syndrome referred to as Colony Collapse Disorder (CCD). While disappearances have been documented in the past, CCD is characterized for its unanticipated desertion of adult worker bees that result in colony failure. This phenomenon is responsible for annual honey bee mortality rates reaching an average of ³ 30% in the United States alone [14]. Although CCD has yet to be traced to one definitive cause, there are multiple contributing agents that have been investigated and are prevalent today.

=** Background **=

** Contributing Factors **
Due to the undetermined nature of CCD syndrome, there is extensive possible causes that have been theorized. The primary four mechanisms that have been frequently tested to contribute to CCD are: The variability of each factor and their data proves inconsistent across the geographic range of losses [8]. Colony losses can be associated with each of these factors, but often the synergy between multiple factors can prove the most harmful.
 * ** [|Varroa Mites] **
 * ** [|Pathogens and Diseases] **
 * ** Agricultural demand and resources **
 * ** [|Pesticides] **

=** Effects **=

** Varroa Mites **
Originally recognized as the parasitic mite associated with the Asian honey bee, //Apis cerana;// these ectoparasites migrated to the United States around the 1950’s [13]. Now identified as //Varroa destructor//, these mites are responsible for increased annual colony losses and are a contributing factor to CCD. The effects of this ectoparasite have now reached //Apis mellifera// worldwide.


 * ** Effects ** : In addition to attaching themselves onto adult bees, they typically feed on the host and their pupae which can lead to nutritional deficits and brood death. Although varroa mites are harmful to the colony, they do not have a direct effect on CCD alone [13]. //Varroa destructor// is increasingly harmful when carrying different pathogens. When synergized with pathogens and diseases, it disrupts the productivity and colony greatly. “For several of the about 18 known honey bee viruses, interactions with //Varroa destructor// are known, either through virus transmission by mite, or through other means of action” [13]. More commonly, the toxic protein carried in varroa saliva can cause the onset of deformed-wing virus in adult honey bees and irregular brood development [16]. Parasitic mites can comprise the health and immunity of the honey bee which leaves it more susceptible to the different pathogens they are exposed to.

** Pathogens and Diseases **
There are a variety of different pathogens that can be connected to //Apis mellifera,// but only few have been suggested to be a factor in CCD. Much like varroa mites, pathogens and diseases prove to be more harmful when combined with other stressors. Different variables, such as weather conditions, blooming seasons, exposure to pesticides, and pollen availability can affect honey bee mortality rates as well.


 * ** Effects: **
 * 1) // Nosema: // //Nosema apis// is a microsporidian fungus that is transmitted by sexual contact or through pores found in feces and pollen. Similar to //N. apis, Nosema Cerenae// is said to be a “new //Nosema//” that can be found at high frequencies in healthy and declining colonies [6]. //N. cerenae// can affect the queen and even result in colony collapse. When exposed to certain fungicides or pathogens, //Nosema// prevalence can often be more than doubled in honey bees than the pathogen independently [7].
 * 2) Black Queen Cell Virus (BQCV): BQCV is characterized by the death and deformation of the colonies brood. Exposure to certain adjuvants in pesticides and exogenous viruses can result in higher mortality rates and an increase in BQVC titers. A recent study showed that the synergistic relationship between BQVC and a common “inert” adjuvant resulted in a 17.89% increase in mortality over the independent virus [5]
 * 3) “Pathogen Pollution”: Due to the high demand of honey bees on today’s agriculture; managed colonies are often transported to areas with high bloom demands. This Global transportation and trade can leave colonies vulnerable to exotic pathogens, e.g., //Nosema Cerenae.// [8]
 * 4) Deformed-winged virus (DWV): DWV is a RNA virus commonly transmitted through //Varroa destructor// mites. The saliva in the varroa mites contains a toxic protein that increases DWV titers that initiate deformed wings in //Apis mellifera// adults [16].
 * 5) Other: Israeli Acute Paralysis Virus and Sacbrood Virus can result in colony failure. Both viruses are commonly found present in the colonies hive and in popular foraging environments.

** Agricultural Demand and Resources **
“While the number of colonies has increased 45% globally since 1961, the proportion of pollinator-dependent crops has risen by 300%” [8]. As honey bee colonies continue to be effected by CCD, the agricultural demand for apiculture does not diminish. The annual California almond blooms demand for pollination services grows as its acreage does. This bloom spans over a time of 6 weeks and requires 60% of the countries managed honey bee colonies to be moved to the almond orchards in CA. Almond production, among other crops, is dependent on the pollination production provided by honey bees [3, 5]. The average acreage is growing exponentially and the demand for pollination is forecasted to only increase each year. As CCD poses a threat to the supply of the increasing demand, there has been raised concern as to how these pressures may negatively impact the honey bee colonies [3].

** Pesticides **
Honey bees are regularly exposed to pesticides from residues that persist in plant pollen and nectar. Newly systemic insecticides, called [|neonicotinoids], have become an interest of study to researchers who believe it compromises the immunity of honey bees and can induce colony failure [5]. Neonicotinoids are approved and regulated through the [|Environmental Protection Agency] (EPA). The use of neonicotinoids is heavily disputed as the correlation between these pesticides and CCD is called into question.


 * ** Effects: ** There is a general consensus that CCD is not caused by one factor, but rather a marriage of different parameters acting on one another. Pesticides is thought to be one of the considered stressors that may interact with CCD. “ Recent work has shown that pesticides can negatively impact honey bee immunity, resulting in increased viral replication ” [5]. This synergistic relationship between pathogens and pesticides has proven to be harmful to the honey bee colonies brood [5, 8, 9]. Even more, pesticides have the capability of infecting the whole colony. Foraging honey bees that come into direct contact with insecticides can expose the whole colony to it [10]

= = =** Restoration **=
 * ** Controversy: ** Although studies have been tested to show there are sublethal effects of pesticides on honey bees, these effects have yet to be observed in field studies with realistic dosages and environmental factors [9]. There is insufficient evidence, at this time, to support beekeepers’ claims that pesticides have a long-term progressive impact. The EPA issued a response that they will be dismissing calls for suspension on neonicotinoids because there is “no evidence directly linking pesticides to CCD” and that “natural conditions” could be the cause of the reported, harmful effects [9,10]

Although there is not a definitive explanation to the phenomenon behind CCD, there are efforts being implemented. Due to the abruptness and the magnitude of colony losses, CCD has gained public awareness [14]. Public outreach campaigns were able to educate people about the threat of honey bees and provide support in searching for a solution. In 2015, the Obama Administration assigned a “Pollinator Health Task Force” to tackle and reduce the impact stressors have on honey bees [15]. In their report, //National Strategy to Promote the Health of Honey Bees and Other Pollinators,// they concentrate on reducing honey bee colony losses through outreach and investigation. This relief effort “calls for more than $82 million in federal funding to address pollinator health’ [14].

=** Conclusion **=

Colony Collapse Disorder poses a tangible threat to the Western European honey bee. The United States agriculture has become dependent on honeybee pollination and could be at risk of losing familiar crops that are important to our diet and economy. Although there is speculation behind the mechanisms driving CCD, understanding each parameter provides framework into understanding colony losses. As synergistic relationships become better understood and more appropriate field studies are conducted, CCD syndrome will eventually be diagnosed. Despite there being multiple stressors influencing colony failure, restoration efforts are gaining momentum and necessary precautions will continue to be made to improve honey bee health.

=** Cited References: **=

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[4] De Vere N, Jones L, Gilmore T, Moscrop J, Lowe A, et al. 2017. Using DNA metabarcoding to investigate honey bee foraging reveals limited flower use despite high floral availability. Scientific Reports. 7:1-11

[5] Fine JD, Cox-Foster DL, Mullin CA. 2017. An Inert Pesticide Adjuvant Synergizes Viral Pathogenicity and Mortality in Honey Bee Larvae. Scientific Reports 7:1–9.

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[8] Smith K, Loh E, Rostal M, Zambrana-Torrelio C, Mendiola L, Daszak P, et al. 2013. Pathogens, Pests, and Economics: Drivers of Honey Bee Colony Declines and Losses. EcoHealth. 10(4):434-445.

[9] Suryanarayanan S. 2013. Balancing Control and Complexity in Field Studies of  Neonicotinoids and Honey Bee Heath. Insects. 4(1):153-167

[10] Suryanarayanan S, Kleinman D. 2013. Be(e)coming experts: The controversy over insecticides in the honey bee colony collapse disorder. Social Studies of Science. 43(2):215-240

[11] Thom M, Eberle C, Forcella F, Gesch R, Weyers S. 2017. Specialty oilseed crops provide an abundant source of pollen for pollinators and beneficial insects. Journal of Applied Entomology. 142(1-2):211-222.

[12] vanEngelsdorp D, Evans J, Saegerman C, Mullin C, Haubruge E, Nguyen B, Frazier M, Frazier J, Cox-Foster D, Chen Y, et al. 2009. Colony Collapse Disorder: A Descriptive Study. PLoS ONE. 4(8):e6481

[13] vanEngelsdorp D, Meixner M. 2010. A historical review of managed honey bee populations in Europe and the United States and the factors that may affect them. Journal of Invertebrate Pathology. 103:S80-S95.

[14] Watson K, Stallins J. 2016. Honey Bees and Colony Collapse Disorder: A Pluralistic Reframing. Geography Compass. 10(5):222-236

[15] White House 2015. National Strategy to Promote the Health of Honey Bees and Other Pollinators. Washington, D.C. Pollinator Health Task Force.

[16] Zhang Y, Han R. 2018. A Saliva Protein of Varroa Mites Contributes to the Toxicity toward //Apis cerana// and the DWV Elevation in //A. mellifera.// Scientific Reports. 8:1-9.

[17] California Department of Food and Agriculture. 2018. 2017 California Almond Acreage Report. Sacramento (CA): cdfa.

[18] “Colony Collapse Disorder.” //Wikipedia,// May 7, 2018. []

[19] Macleod D. 2009. Green Pencil for Haagen-Dazs Help The Honey Bees Campaign. Inspiration Room. [2009 May 7; accessed 2018 May 7] []