The West Nile virus spreads not only through mosquito bites between infected birds and from female mosquitoes to their offspring, but also through a previously unknown route of transmission: mosquito feces. A team of French researchers recently wrote this in a article published on bioRxiv. This is a pre-print that still needs to be assessed by independent scientists.
The West Nile virus mainly affects birds, but sometimes also spreads to humans. “After a first infection in 2020, no new cases in humans have been reported in the Netherlands,” says Reina Sikkema, veterinarian and researcher of zoonotic viruses at Erasmus MC, who was not involved in the recent study but was involved in other studies into the virus. . “But more people may have been infected unnoticed, as only 20 percent of infected people show flu-like symptoms and only 1 percent develop serious neurological complaints.”
The house mosquito of the genus Culex is the main spreader of the virus. These mosquitoes become infected when they bite an infected bird. The virus travels from the mosquito's stomach, via the blood, to the salivary glands. During a subsequent bite, the virus can then be transmitted to another bird, which acts as a reservoir host in which the virus can multiply and survive. In addition to this form of transmission, a female mosquito can also infect her offspring.
Wetland habitats
The new research reveals another way of spread: through mosquito feces. Although the presence of viral genetic material in the feces of infected mosquitoes was already known, it remained unknown whether the feces are also infectious.
CulexMosquitoes lay their larvae in wetland habitats and standing water. Not only do the larvae develop into pupae there; the mosquitoes also leave their poop there. The researchers therefore wanted to know whether young mosquitoes could become infected with the virus without being infected directly by the mother.
To test this, the research team started working with a highly virulent strain of West Nile virus, which they fed to their research mosquitoes via a blood meal. They dissolved the infected mosquito droppings that they harvested in culture water. This contaminated water was used to culture pupae and test the contagiousness of the virus-rich feces. It turned out that 17 percent of the emerged adult mosquitoes were infected.
“This research shows that the virus in the feces is actually infectious and can infect mosquito pupae,” Sikkema explains. “Although the experiments so far have only been conducted in controlled environments in the lab and still require confirmation in the field, this study points to a potentially important factor in the spread of the virus.”
“If the results of this research are reproduced in the field, it emphasizes the importance of preventing water reservoirs, such as buckets and rain barrels, by closing them properly,” says Sikkema.
#Mosquitoes #infect #West #Nile #virus #feces