West Nile Virus Vector Identified in U.K.

According to a statement from the British Equine Veterinary Association (BEVA), Culex modestus—a type of mosquito capable of transmitting West Nile virus (WNV)—has been found in marshes in southeast England. West Nile—while often identified in African, Eastern European, and West Asian horses, among other populations—has never been found in the U.K. in any species, the release said.

"Cx. modestus has not been seen in the U.K. since 1945, when only a handful were recorded," the statement said, adding that the mosquitoes were found and identified by Centre for Ecology & Hydrology (CEH) and University of Oxford post-graduate student, Nick Golding. Golding found the mosquitoes living in marshes north of Kent and south of Essex, the statement said.

Golding said, in the statement, that it's not clear how long the mosquitoes have been living and breeding in the U.K., however he believes the species "arrived fairly recently."

"No one knows for certain how these mosquitoes got to the U.K.," the BEVA statement relayed. "They can't fly far so probably didn't travel from mainland Europe under their own steam. It's more likely they were accidentally transported by ship, especially given the number of international shipping terminals in the area where Cx. modestus now seems to be established."

The BEVA statement indicated that researchers are currently working to establish how widespread the Cx. modestus population is and if there is any disease risk for area people, horses, or other animals.

First confirmed in the United States' horse population in 1999, WNV infection is responsible for equine clinical signs including flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia, or hypersensitivity to touch and sound; changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%. The USDA Animal and Plant Health Inspection Service reported 83 cases of WNV in U.S. horses in 2011.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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