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Honey Bee Viruses

Viruses can attack at different developing stages and castes of honey bees, including eggs, larvae, pupae, adult worker bees, adult drones, and queens. Although bee viruses usually persist as inapparent infections and cause no overt signs of disease, they can dramatically affect honey bee health and shorten the lives of infected bees under certain conditions.  For example significant infestations of colonies with the Varroa mite (Varroa destructor) and its association with Deformed wing virus (DWV) can seriously harm the health and productivity of honey bees. Of the 18 or so viruses identified as infecting honey bees, six viruses, namely, Deformed wing virus (DWV), Black queen cell virus (BQCV), Sacbrood virus (SBV), Kashmir bee virus (KBV), Acute bee paralysis virus (ABPV), and Chronic bee paralysis virus (CBPV) are the most commonly recorded around the world (not necessarily the UK). Note that for the UK, KBV incidence is very low and Israeli Acute Paralysis virus (IAPV) has not been detected despite the completion of very large scale apiary surveys.

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Chronic Bee Paralysis Virus

The photograph on the right is a typical example of a CBPV infected bee, all "shiny and black". These bees in infected hives are often found isolated, motionless and/or shaking on the top bars. When the colony is smoked they do not tend to move down between the frames as the other "normal" bees do. Abdomens may also be distended and the wings dislocated. They can't fly and so can also be seen crawling in front of the hives.

CBPV was identified as a cause of adult bee paralysis after long suspicion that the tracheal mite, Acarapis woodi, was the culprit of the paralysis. CBPV was extracted from naturally paralyzed bees as one of the first viruses isolated from honey bees and has since been detected in adult bees of A. mellifera from almost every continent. 

CBPV mainly attacks adult bees and causes two forms of ‘‘paralysis’’ symptoms in bees. The most common one is characterized by an abnormal trembling of the body and wings, crawling on the ground due to the inability to fly, bloated abdomens, and dislocated wings. The other form is identified by the presence of hairless, shiny, and black-appearing bees that are attacked and rejected from returning to the colonies at the entrance of the hives by guard bees. Both forms of symptoms can be seen in bees from the same colony. The variation in the disease symptoms may reflect differences among individual bees in inherited susceptibility to the multiplication of the virus.

The close contact of overcrowded bees breaks hairs from the cuticle, allowing CBPV to spread from diseased bees to healthy bees via their exposed epidermal cytoplasm. It is likely that any factors that result in decreased foraging activities and crowded conditions in the bee colonies may lead to disease outbreaks of CBPV. It has been reported that CBPV is very widespread in Britain and infects most bees and can cause mortality in bee colonies particularly during long periods of confinement.

Treating CBPV

In crowded conditions, CBPV will spread more rapidly because bees will be in greater contact with each other – increasing the chances that bees will rub up against one another thereby pulling out hairs from their abdomens. This would leave an open wound on the bee where the virus is free to enter and worsen or cause infection in healthy bees. As a result we recommend that in strong colonies showing signs of CBPV, beekeepers ensure there is plenty of room by adding supers or an extra brood box and also that colonies are well fed. CBPV can cause severe problems and if a colony cannot combat the virus through its
own means then the recommended method of control is to re-queen a colony with a queen from a less susceptible strain.

Last updated on 29/06/2018