West Nile virus is a disease spread by infected mosquitoes. When the infectious virus enters the blood stream of a person it targets the central nervous system. The majority of infected people show no symptoms; however, one fifth of those bitten by an infected mosquito develop a fever. This can be accompanied by headache, aching, joint pains, vomiting, and diarrhea.
West Nile virus cases are rising in the U.S., since the first case was reported in 1999, and some research groups are keen to know the reason. Possibilities include changes to weather and changes to the breeding grounds of the carrier mosquito.
A new study into the “dry” water retention basins in Illinois found the problems associated with mosquitoes that carry the virus took a turn for the worse once authorities started mowing down the grass and other vegetation in the basins. There was a notable rise in the numbers of Culex pipiens mosquitoes, which are the main vector for the virus.
The reason is because the process of mowing cut downs large numbers of cattail and phragmite grasses. These are two invasive plants found in stormwater basins. The cutting process leads to an accumulation of plant debris to the water. This, in turn, results in a build-up of bacteria. Where bacterial populations are high, mosquitoes tend to lay eggs because the bacteria are a food source for the resultant larvae.
The increase in numbers of mosquitoes, which can potentially carry the West Nile virus, then presents a risk to near-by human populations. The advice is: don’t mow.
The findings have been posted to the journal Ecological Applications. The research is titled “Cascade of ecological consequences for West Nile virus transmission when aquatic macrophytes invade stormwater habitats.”
