CULICOIDES-VARIIPENNIS AND BLUETONGUE-VIRUS EPIDEMIOLOGY IN THE UNITED-STATES

The bluetongue viruses are transmitted to ruminants in North America b y Culicoides variipennis. US annual losses of approximately $125 milli on are due to restrictions on the movement of livestock and germplasm to bluetongue-free countries. Bluetongue is the most economically impo rtant arthropod-borne animal disease in the United States. Bluetongue is absent in the northeastern United States because of the inefficient vector ability there of C. variipennis for bluetongue. The vector of bluetongue virus elsewhere in the United States is C. variipennis sono rensis. The three C. variipennis subspecies differ in vector competenc e for bluetongue virus in the laboratory. Understanding C. variipennis genetic variation controlling bluetongue transmission will help ident ify geographic regions at risk for bluetongue and provide opportunitie s to prevent virus transmission. Information on C. variipennis and blu etongue epidemiology will improve trade and provide information to pro tect US livestock from domestic and foreign arthropod-borne pathogens.