West Nile virus Epidemic in Horses, Tuscany Region, Italy

摘要

During the late summer of 1998, veterinary authorities in Tuscany, Italy, received reports of cases of neuro-logic disease among horses residing in a large wetland area located in the provinces of Florence and Pis-toia. West Nile virus was isolated from two of the six horses that died or were euthanized. A retrospectiveepidemiologic study identified 14 clinical neurologic cases that occurred from August 20 to October 6(attack rate of 2.8%). A serologic survey conducted over a 700-km2area in stables with and without appar-ent clinical cases confirmed a wider spread of the infection, with an overall seroprevalence rate of 38% inthe affected area. No significant differences in age-specific prevalence were observed, suggesting that thehorses residing in the area had not been exposed previously to West Nile virus and supporting the hypoth-esis of its introduction in the wetland area during the first half of 1998