Moku?

It will never end. But at least this one has a cute name: The Moku virus. Science Daily had a piece, A New Threat to Bees Worldwide, which gives us yet another bee story that may go viral. The Moku virus was found on non-native invasive wasps which are attacking honey bees on Hawaii’s big island.

Moku virus is named for a Hawaiian district which was recently invaded by a major pest, Vespula pensylvanica, the western yellowjacket. The wasp is native to northern temperate zones of western North America. The wasp’s populations tank in cold weather, but in Hawaii’s tropical paradise, there is no break in its reproduction cycle and the wasp’s numbers have exploded.

Nasty and mean

The western yellowjacket, like most wasps, is nasty and mean. It hunts insects for meat and gets carbohydrates from plant nectar – or from honey stolen from a hive. The wasp can capture a bee and carry it to a quiet vertical surface where the bee’s legs and wings are chewed off. With captured drones, the head is often removed first. Then the rest of the victim is eaten at leisure. In Hawaii, yellowjackets stealthily enter honey bee colonies, usually facing no real opposition when they make off with a bee. Not only is the wasp a brutish pest, but it is also the carrier of a virus which may spread to honey bees when the wasp enters a hive looking for fresh meat.

The Moku virus was identified at the labs of Earlham Institute (formerly The Genome Analysis Centre) in Plymouth, England. There, Dr Gideon Mordecai reported, “The use of next generation gene sequencing techniques has led to a rapid increase in virus discovery, and is a powerful tool for investigating the enormous diversity of viruses out there.” The Moku virus was identified when 8 yellowjackets from Moku were DNA-sequenced and the new virus was found in the mix. This is amazing:

“Complementary DNA (cDNA) sequencing was performed at Earlham Institute on the Illumina HiSeq, from which the novel viral genome of 10,056bp (base pairs) [Humans have ~3 billion bp – RM] was sequenced and assembled from eight wasp individuals, whose closest relative was found to be the Slow bee paralysis virus.

“Purnima Pachori at EI performed the QC and assembly of viral samples from honey bees, V. pensylvanic and the varroa mite. Crucially, she was able to clean up the insect and mite-specific RNAs to leave only viral sequence for analysis, which allowed for the identification of the novel Moku virus – led by Gideon Mordecai of the Marine Biological Association, Plymouth.”

     – from Earlham Institute’s news release

The discover of the new virus alarmed researchers who suggested that the virus might jump to honey bees – a likely event given the intimate relationships the wasps have with their lunch.

I haven’t heard if honey bees have actually been infected, though cross-species migration of the virus is possible. I suspect that the warning – which was published in the esteemed Nature network of journals – is premature and slightly alarmist. However, Moku evolved in V. pensylvanica, its host for perhaps thousands of generations. Hosts usually develop coping strategies over time. Jumping to a new host – one unfamiliar with the virus – can have devastating results as we’ve seen with swine and avian flu.   How bad could a new honey bee virus be? Many researchers think that  colony collapse disorder was caused by a virus. However, it’s instructive to note that there has been no CCD in over five years, indicating that a new host might quickly develop resistance.

…and many, many more

The list of viruses known to affect honey bees is significant – nearly twenty honey bee viruses have been discovered. These include chronic bee paralysis, acute bee paralysis, Israel acute paralysis, Kashmir bee virus, cloudy-wing, deformed wing, picornavirus, bee virus X, bee virus Y, Arkansas bee virus, and the black queen cell virus. We know of others and many more will eventually be found.

Viruses mutate quickly and their incredibly tiny size allows easy access to hosts. The size of a virus compared to a human body is less than the size of the human body to the entire Earth. The rate of viral evolution makes it impossible to fight all the possible viruses with anti-viral medication. But just as with humans, bees that are the healthiest, strongest, and most resilient are usually most able to fight a virus attack.

Research scientist Gideon Mordecai also said, “future challenges will be assessing the biological relevance of these novel pathogens and the role they play in the ecology of their hosts.” Indeed it will. Rather than attempting to battle each new virus as it arises (remember there are already at least 20 known to affect honey bees), our best strategy is keep colonies free of varroa (a virus vector) and stocked with healthy young queens. Of course, weak colonies with large varroa populations are doomed to fail, with or without viruses.