DCV: Deformed Wing Virus (DWV), Chronic Bee Paralysis Virus (CBPV), Varroa Destructor Virus-1 (VDV1)
DWV seems to be especially tied to mite parasitism. The virus can be found everywhere, it is like the “herpesvirus of bees”. DWV shows annual peaks in late summer or fall, with lows in January through March or April. Prevalence of DWV continues to remain high with between 80 – 90% of hives infected (Traynor et al., 2016). DWV is not always a problem due to the noticeable increase of incidence within the US, but if the bees become stressed (lack of food, pesticide exposure, and transportation) could lead to sickness and death. DWV replicates in the Varroa mite, making it a biological as well as physical vector. Winter colony mortality is strongly associated with DWV presence (de Miranda et al., 2011). Varroa infection should be reduced in a colony far in advance of producing overwintering bees, to ensure reduction in DWV viral load (de Miranda et al., 2011). DWV is genetically closely related to Varroa destructor virus – 1, which together form the Deformed Wing Virus Complex (Moore et al., 2011).
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).
Varroa destructor virus-1 (VDV-1) was discovered by scientists in search for pathogens of the Varroa mite (Ongus et al., 2004). VDV-1 is a species of RNA viruses under the genus Iflavirus. Other Iflaviruses include Sacbrood virus, Slow Bee Paralysis virus and its closest relative, Deformed Wing Virus (Ongus et al., 2004). VDV-1 has been known to cause high rates of overwintering colony losses in Europe, but the correlation has not been made yet in the US. VDV-1 and the closely related Deformed Wing Virus are the most widespread and the most prevalent viruses in honey bees, but are also likely the most significant in terms of their impact on honey bee colony health (Ryabov et al., 2017).
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.
Moore, J., Jironkin, A., Chandler, D., Burroughs, N., Evans, D. J. & Ryabov, E. V. 2011. Recombinants between Deformed wing virus and Varroa destructor virus-1 may prevail in Varroa destructor-infested honeybee colonies. J Gen Virol, 92, 156-61.
National Bee Unit. 2019. Chronic Bee Paralysis Virus [Online]. APHA, National Agri-Food Innovation Campus. Available: https://www.nationalbeeunit.com/downloadDocument.cfm?id=1158.
Ongus, J. R., Peters, D., Bonmatin, J. M., Bengsch, E., Vlak, J. M. & van Oers, M. M. 2004. Complete sequence of a picorna-like virus of the genus Iflavirus replicating in the mite Varroa destructor. J Gen Virol, 85, 3747-3755.
Ryabov, E. V., Childers, A. K., Chen, Y., Madella, S., Nessa, A., vanEngelsdorp, D. & Evans, J. D. 2017. Recent spread of Varroa destructor virus-1, a honey bee pathogen, in the United States. Scientific Reports, 7, 17447.
Traynor, K. S., Rennich, K., Forsgren, E., Rose, R., Pettis, J., Kunkel, G., Madella, S., Evans, J., Lopez, D. & vanEngelsdorp, D. 2016. Multiyear survey targeting disease incidence in US honey bees. Apidologie, 47, 325-347.