Toxoplasmosis and Traffic Fatalities

Not entirely applicable to biking, but interesting and at least tangentially related.
Toxoplama Gondii is a parasitic protozoa and the third leading cause of death attributed to foodbourne illness in the United States.

More than 60 million men, women, and children in the U.S. carry the Toxoplasma parasite, but very few have symptoms because the immune system usually keeps the parasite from causing illness.

The normal lifecycle of Toxoplasma is that it's excreted by cats, eaten by rats and mice (as well as other mammals and birds) and then the infected rats and mice are eaten by the cats. The really interesting thing is that the parasite changes the behavior of rats and mice.

making them drawn to rather than fearful of the scent of cats. This effect is advantageous to the parasite, which will be able to sexually reproduce if its host is eaten by a cat.The infection is almost surgical in its precision, as it does not affect a rat's other fears such as the fear of open spaces or of unfamiliar smelling food.

So what?
As noted above humans can get it too and in human populations it's known that changes human behavior as well, by mpairing reaction times in infected subjects,

which results, for example, in a higher risk of traffic accidents in subjects with this life-long infection.

Those who are RhD-positive (so O+ or A+ bloodtypes), especially RhD heterozygotes, are protected against latent toxoplasmosis-induced impairment of reaction times. But a recent study showed,

that RhD-negative subjects with high titers of anti-Toxoplasma antibodies have a probability of a traffic accident of about 16.7%, i.e. a more than six times higher rate than Toxoplasma-free or RhD-positive subjects.

Presently only immunodeficient people and pregnant women get treatment for the disease, but it seems the auto insurance and health insurance companies could improve their bottom lines by encouraging testing and treatment of this parasite in all RhD-negative subjects. The rest of us would then be free riders on safer roads.