Vector biologist Brian Foy has published a case study that claims to be the first documented evidence of an insect-borne illness being spread between people through sexual contact.
Unfortunately for Foy, the research methods were a bit more intimate than most people would prefer. In fall of 2008, Foy returned from a trip to Senegal where he was collecting mosquitoes for malaria research. About five days later, he got sick with what later turned out to be Zika virus—a rare, mosquito-transmitted disease. And, not long afterwards, so did his wife. The catch: Joy Chilson Foy hadn’t been to Senegal.
There is no direct evidence that Foy’s wife was infected through sexual contact, but the circumstantial evidence is strong. It’s very unlikely that she was infected by a bite by a mosquito that first bit her husband; the three tropical Aedes mosquito species known to transmit Zika don’t live in northern Colorado, and moreover, the virus has to complete a 2-week life cycle within the insect before it can infect the next human; Foy’s wife fell ill just 9 days after his return. And yes, as the paper puts it, “patients 1 and 3 reported having vaginal sexual intercourse in the days after patient 1 returned home but before the onset of his clinical illness.” (“My wife wasn’t happy with what happened afterwards,” Foy adds.)
Foy and his co-authors believe sexual transmission of a mosquito-borne virus has never been reported before, although there were hints from the literature that it might be possible. Boars experimentally infected with the Japanese encephalitis virus, for instance, shed the virus in their semen, and female pigs artificially inseminated with it become infected.
Scientists already knew that many insect-borne pathogens can be transmitted orally as well, says medical entomologist Paul Reiter of the Pasteur Institute in Paris. So even if it hasn’t been documented before, it’s not a big surprise that infected semen deposited inside the vagina could cause an infection, he says.
Science Now: Sex after a field trip yields scientific first
Via Maryn McKenna
Image: Some rights reserved by dr_relling