West Nile Threat: Controlling Some Outbreaks is a Double-Edged Sword

A strategy that could help contain some mosquito-borne illnesses has now been discovered to make West Nile virus more prevalent among local swarms - an incredibly important discovery in the midst of growing concerns about this year's outbreaks.

You likely have heard the latest bad news from the Caribbean. Two new and dangerous mosquito-borne illnesses are sweeping across the Americas and headed for Florida. The non-fatal chikungunya virus has even shown up in a number of imported and isolated cases in the United States.

Still, even in the wake of these alarming reports, malaria and West Nile virus have not been forgotten. Public health officials have already made a call for caution this summer season, asking citizens across the world to "cover and dump" still and shallow water - the ideal breeding habitat for mosquitoes - in the interest of controlling populations.

Researchers have even proposed  introducing bacteria strains or genetic modification that could eradicate populations of mosquitoes entirely.

Experts have used a natural bacterium that affects insects specifically, called Wolbachia, to target mosquito swarms in trial runs in the United States - as approved by the Environmental Protection Agency.  The trials, conducted in 2013, showed that infecting mosquitoes with the bacteria prevented them from contracting and spreading dengue fever, which is approaching epidemic levels in the Americas.

However, new research detailed in the Journal PLOS Neglected Tropical Diseases, reveals that if this strategy is used, it may result in rampant spread of West Nile among remaining populations.

"We were surprised to find that Wolbachia infection did not block West Nile virus in this mosquito," study author Jason Rasgon told Entomology Today. "Instead, these mosquitoes had significantly higher West Nile virus infection rates seven days after we fed them infected blood. In other words, Wolbachia infection allowed the mosquitoes to become infected with West Nile virus faster than our controls."

"Our results point to a previously unforeseen complication," Rasgon added. According to the researcher, Wolbachia could still be used in dire situations, but only after careful consideration of the potential consequences.

The study was published in PLOS Neglected Tropical Diseases on July 10.