Description
CAA: Chronic Bee Paralysis Virus (CBPV), Ascosphaera apis (Aapis), Acarapis woodi (Awoodi)
CBPV affects adult honey bees and causes a contagious case of chronic paralysis which can easily spread to other members of a colony (National Bee Unit, 2019). Symptoms have been categorized into two syndromes: Syndrome 1 includes trembling of wings and body, paralysis, loss of flight with bees found crawling on the ground, bloated abdomens, dysentery, and death within days of the symptoms; Syndrome 2 consist of bees that are hairless, dark colored almost black, having a shiny, greasy appearance and rejection by healthy members of the colony (National Bee Unit, 2019). Colonies may carry CBPV without showing symptoms and it is not until the colony is put under stress that the symptoms start to show. The virus appears to infect older bees more frequently and foragers are often found to have a higher virus burden. Unlike other honey bee viruses, CBPV has so far not been associated with the Varroa destructor mite (National Bee Unit, 2019). CBPV appears to survive in colonies at low levels throughout the year with peak outbreaks occurring in spring and summer (de Miranda et al., 2011). It is thought that a combination of large population sizes and periods of confinement in the colony, due to bad weather, causing crowded conditions that exacerbate the spread of infection through bodily contact between bees. CBPV can be spread through queens during trophallactic exchange of food and through feces of infected bees. Beekeepers can reduce the pressure on a colony from overcrowding by giving the bees more room, adding brood chambers or supers, and prevent undue stress when food limited. Good husbandry and hygiene are crucial and should not be underestimated. Beekeepers should try to ensure dead material is cleaned up and safely destroyed (National Bee Unit, 2019).
The pathogenic fungi, Ascosphaera apis (Aapis), is the predominant causal agent of chalkbrood in honey bees (Apis mellifera). The fungal spores are ingested in the larval food. These spores then germinate in the digestive tract of bees and begin mycelial formation during the larval development. This mycelial growth is responsible for the chalky appearance. Infected individuals are highly infectious and often reinfect the colony via food supply or direct transfer from adult bees to larvae.
The honey bee tracheal mite Acarapis woodi is an internal parasite of adult honey bees (Apis mellifera). Heavy tracheal mite infestation causes diminished brood area, smaller bee populations, looser winter clusters, increased honey consumption, lower honey yields and ultimately, colony losses (Kojima et al., 2011). The small size of the mites (~120–190 μm) and their location within the bee’s trachea create a challenge for diagnostic identification, leading to misdiagnosis (Quintana et al., 2019). The use of molecular tools in the identification of these mites can aid in the surveillance and management of these pests in honey bee colonies.
References
de Miranda, J., Gauthier, L., Ribière, M. & Chen, Y. P. 2011. Honey Bee Viruses and Their Effect on Bee and Colony Health. Honey Bee Colony Health: Challenges and Sustainable Solutions, 71-102.
National Bee Unit. 2019. Chronic Bee Paralysis Virus [Online]. APHA, National Agri-Food Innovation Campus. Available: https://www.nationalbeeunit.com/downloadDocument.cfm?id=1158.
Bee Health. 2019. What is the basic life cycle of the fungus, Ascosphaera apis that causes chalkbrood disease in honey bee colonies? Available:
https://bee-health.extension.org/what-is-the-basic-life-cycle-of-the-fungus-ascosphaera-apis-that-causes-chalkbrood-disease-in-honey-bee-colonies/
Aronstein and Colby. 2015. A multiplex PCR assay for determination of mating type in isolates of the honey bee fungal pathogen, Ascosphaera apis. Journal of Apicultural Research, 54(2), 105-107.
Quintana, et al. (2019). Comparison of qPCR and Morphological Methods For Detection of Acarapis woodi in Honey Bee Samples. Journal of Apicultural Science, 63, 125 – 129.
Kojima, Y., Yoshiyama, M., Kimura, K., & Kadowaki, T. (2011). PCR-based detection of a tracheal mite of the honey bee Acarapis woodi. J Invertebr Pathol, 108(2), 135-137.
