Bloodsucking Parasite Threatens Honeybee Populations with Devastating Virus

It's not new news that honey bees across the globe are in danger due to threats that range from pesticides to disease. Now, though, researchers have uncovered a new challenge for these important insects; it turns out that a bloodsucking parasite may be responsible for Deformed Wing Virus (DWV), which may just have become one of the biggest threats for bees in the UK.

Honeybees are key for pollination. In fact, they add about $40 billion globally to crop value with their efforts. Yet in recent years, the spread of parasites and viruses have resulted in massive population losses.

DWV is actually one of the most common viruses infecting European honeybees. It causes developmental deformities in wings which makes it difficult for bees to forage which, in turn, can reduce their lifespans. Yet DWV is only common when a certain parasite, called Varroa destructor, is also present.

Intrigued by this, scientists decided to take a bit of a closer look. The researchers found that when Varroa feeds on honeybee blood, called haemolymph, specific virulent strains of the virus are transmitted and amplified in bees. This, in particular, explains why colonies infested with the mite suffer from DWV most severely.

"We found that a harmful variant of the virus only multiplies rapidly if it is directly injected into honeybee haemolymph by Varroa," said David Evans, the leader of the new study, in a news release. "Once injected, the variant takes over. In mite-exposed bees, levels of this single virulent form can be 10,000 times higher than in the absence of Varroa. Although exposure to Varroa caused disruption to a number of genes involved in the bee's immune response, it is the route of transmission which has caused this severe strain of DWV to become widespread."

This mite is actually globally distributed, which means that these findings may not just have implications for Europe. It could help researchers across the globe.

"Our results strongly suggest that DWV is widespread in UK honeybees-event where Varroa is absent," said Evans. "However, the identification of a single virulent form of the virus is an important step in developing strategies to boost honeybee health, to prevent colony losses and to safeguard this important pollinator."

The findings are published in the journal PLOS Pathogens.