British Columbia bees face growing threat from deadly virus carried by mite

All over the world, colonies of bees are being devastated by a mite, smaller than your little fingernail, carrying a deadly virus.

The deformed wing virus (DWV), first detected in 1982 and transmitted by varroa mites, deforms the wings of a bee so that it cannot leave its colony to feed. The virus can spread rapidly through colonies, often leading to mass starvation as fewer bees are able to leave and return with food.

A recent study on the spread of the highly transmissible variant of DWV-B suggests that the growth of infections worldwide has led to increased colony loss rates in temperate regions.

Professor Leonard Foster, senior academic bee researcher at the University of British Columbia’s BeeHIVE research group, said the virus has been prevalent in Canada since bee mortality nearly tripled in 2007.

“Since DWV-B spread across the country, we’ve seen higher than historical bee losses in all provinces, including British Columbia,” Foster said.

Although DWV is not the only virus transmitted by varroa mites, Foster said DWV variants A and B are certainly the most common.

“The two main variants of deformed wing virus are probably the biggest bee health problem that is also linked to varroa mites,” he said.

According to Foster, the most dangerous type of transmission from a mite to a bee occurs when the mite attaches itself to an egg or larva.

“If an adult is infected, basically there’s no effect on the bee,” Foster said. “But if an egg or a larva is infected, then the virus causes a malfunction in the development of the wings.”

Symptoms can range from a slightly deformed wing, to a residual or non-functional wing, to no wing at all, Foster explained.

Beekeepers lose bees and money

The ever-increasing spread of the virus in British Columbia is not only killing bees, but also collapsing beekeepers’ livelihoods. Foster said while beekeepers have been able to stay afloat in recent years, the continued spread of DWV and other viruses is making it increasingly difficult to earn a living.

“As more and more beekeepers decide to retire from the business because there are too many of these threats to bee health for them to maintain a viable business, that will mean less and less ‘bees,’ he said.

Professor Robert Paxton, co-author of the recent study into the spread of the DWV-B variant, said in an emailed statement that beekeepers are likely to experience greater colony losses this year than in the past.

Paxton wrote that beekeepers need to become increasingly vigilant to control the spread of Varroa, especially during the winter months.

Preventive measures

So how do beekeepers fight to keep DWV out of their colonies? It depends on time, resources and ethics, Foster said.

“There is no equivalent of a vaccine in bees against viruses,” he said. “The only mechanism beekeepers have is to control varroa mites, the vector that moves the virus between colonies.”

While the most effective preventative measures include constant monitoring and the use of chemicals, Foster said some beekeepers prefer not to use chemicals and will use alternative measures.

These alternative measures may include freezing male bee larvae, which are considered more palatable to mites than female larvae, to kill the mites, and dousing the bees in icing sugar, which forces the mites to detach. bees.

Despite growing concern about DWV and the global spread of its B variant, Foster said it’s important to remember that bee health is much more complex than just this virus.

“This DWV-B is certainly not the only problem bees face.”