Bees have a fairly weak immune system, so they have to rely on behavioural changes to try to defeat viruses. This involves changes in social activity, so scientists decided to monitor the effect. First, they infected about 100 “volunteer” bees with the highly deadly Israeli Acute Paralysis Virus (IAPV). Then they monitored the bees’ trophallaxis. Trophallaxis is part of a healthy honey bee’s social life, where bees make contact with other bees by touching antennae and sharing regurgitated food.
And it turns out the bees infected with IAPV were shunned by their healthy mates and were only fed half as much as healthy bees, despite being more active in looking for food.
This shows that bees use an equivalent to social distancing to combat viruses, which was interesting news for the scientists, but not so good for the volunteer bees, as shivering, paralysis and death from IAPV soon followed.
But scientists also noticed a more worrying effect of IAPV. Bees normally stick to their own hives and are prevented from entering other hives by guard bees. The guard bees use their antennae to recognise specific chemicals on incoming bees and if they don’t match, then they are refused entry.
As an aside, guard bees also check the health of incoming bees, and are particularly intolerant of any bees who might have been snacking on tree sap. Tree sap can intoxicate bees so they often have difficulty trying to land back at the hive. But even if they do manage to find the hive and to land successfully, they are met by the guard bees, who fail to see the funny side and will often chew off the legs of the intoxicated bees, which seems a bit harsh.
But when the IAPV-infected bees tried to enter a neighbouring hive, scientists noticed that they were able to sneak past the guards twice as many times as healthy bees. This suggests the virus was somehow impacting the guard’s ability to identify foreign bees.
The virus seems to have adapted to be specifically able to hide its identity until it’s too late, which allows the virus to pass quickly between the hives in a colony and each hive ends up fighting its own virus breakout.
But the good news is that even though some viruses have shown some pretty innovative mutations, honey bees have so far always managed to adapt and have survived for over 100 million years.
