West Nile Virus Update

The National Veterinary Services Laboratory recently confirmed two additional equine clinical cases of West Nile virus (WNV), one in New Jersey and the other in New York. Both horses began showing signs of the disease last October. The New Jersey case involved a 4-month-old colt, the youngest horse ever known to have developed clinical illness due to WNV in the U.S.

In all, 59 cases of clinical WNV were confirmed in this country in 2000, according to the United States Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS). Thirty-six of the horses survived, and 23 (39%) died or were euthanized. They were located in seven different states: Connecticut, Delaware, Massachusetts, New York, New Jersey, Pennsylvania, and Rhode Island.

Eleven additional cases of WNV were reported in New Jersey and New York in 2000, but these cases, as of late January of this year, had not been classified as confirmed or probable WNV infections by USDA-APHIS for various reasons.

WNV appeared for the first time in this country in 1999. Until then, for the most part, the disease had been confined to Africa, the Middle East, and Southwest Asia. However, sporadic outbreaks had been reported in Southern Europe.

Horses get WNV when mosquitoes bite them. The disease also has caused death in humans and birds.