Too many fly bites can lead to death by bug-spit poisoning

It seems every day there are new revelations about horrible ways we can die. Today? Simuliotoxicosis. That's just toxic shock syndrome, which could be associated with anything. But lately, it has been especially associated with mass attacks of black flies. They can bite an animal - or human - so much that their saliva causes death.

In Louisiana, in 2010, twenty birds were brought into a zoological medical department with hundreds of tiny little hemorrhages under their skin. About half of them died. The staff diagnosed an acute outbreak of black flies in the area. It's not actually surprising that one of the plagues of Egypt was flies. Black flies live in most rivers, and plant parasites that live in the human body, devastating it over time. Untreated, the parasites can cause pains, organ failure, and blindness over the life of the sufferer. But they can dish out an even more horrible death.

Black flies latch on when they eat, and can't be removed until they're done. Of course, they can be swatted, but that's not so easy when there are hundreds of them. Even if they don't exsanguinate animals outright, or shoot them up with debilitating larvae parasites, they are injecting something into their food source. Black flies' saliva contains a cocktail of drugs. They have an anticoagulant component, a compound that keeps the area from swelling up, and a special compound that dilates the capillaries in the area to let blood flow more quickly. None of these should hurt a normal animal experiencing a single bite. It's a different story when we're talking about hundreds of bites over a couple of hours. Eventually the skin does swell up in response to a storm of white blood cells. The capillaries do the same, swelling until they're destroyed. Hemorrhaging begins under the skin, and at last the heart gives out. Although the hundreds of tiny wounds, and the attendant exposure to infection, can't help - overall the body is responding to the massive amount of tiny doses of drugs. An animal, or even a person, can die of bug spit poisoning.


Black fly epidemics are getting less common, especially since humans - one of the carriers of their young parasites - are increasingly getting more effective drugs to kill off the parasites inside them. Still, there are hundreds of thousands of people who suffer from this kind of parasitism all their lives, and some river basins still lie empty, because too many black flies swarm there.

Image: USDA

Via NCBI, The Naked Scientists, NCBI.

Correction: This post originally stated that black flies shoot larvae into animals' bodies. That is incorrect; they transmit the nematode parasite Onchocerca volvulus. Thank you to vox_vulpes and Morgan Jackson at Biodiversity in Focus for bringing this to our attention.


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