Isolation of arboviruses from Culicoides midges (Diptera: Ceratopogonidae) in Colorado during an epizootic of vesicular stomatitis New Jersey.

An arbovirus survey was conducted in Colorado and Utah during an epizootic of vesicular stomatitis New Jersey (VSNJ) that occurred in the western United States in 1982-1983. From 120,422 insect specimens assayed, 106 viruses were isolated. Four were rhabdoviruses (VSNJ), three were orbiviruses (bluetongue serotype-11), 92 were Bunyamwera group (65 Main Drain and 27 Lokern), and seven were Simbu group (Buttonwillow) bunyaviruses. Culicoides spp. accounted for 105 viral isolates (C. (Selfia) spp., C. variipennis (Coquillett), C. stellifer (Coquillett), and C. cockerellii (Coquillett], and one was from Simulium bivittatum Malloch. C. (Selfia) spp. accounted for 59% of all pooled specimens and was the source of 89.6% (95) of the isolates. Insects from two sites accounted for 44% (52,802) of all pooled specimens and 67% (71) of the viral isolates. The isolations of VSNJ, Main Drain, Lokern, and Buttonwillow viruses from C. (Selfia) spp. are the first arbovirus isolations reported for this subgenus; this is the first time these viruses have been isolated from Culicoides species other than C. variipennis.

Epizootic vesicular stomatitis in Colorado, 1982: some observations on the possible role of wildlife populations in an enzootic maintenance cycle.

Sera obtained from wild ungulates, carnivores, and rodents in Colorado were tested for neutralizing (N) antibody against vesicular stomatitis, New Jersey serotype (VSNJ), virus to determine their involvement in the 1982 Colorado VSNJ epizootic in domestic animals. Viremic and N antibody responses of two local rodent species to a 1982 Colorado isolate of VSNJ were determined in the laboratory. The rodents produced only weak viremias, but all developed N antibody. N antibody prevalences for VSNJ in sera from wild ungulates was sufficiently high to indicate their involvement during the epizootic. In addition, the demonstration of N antibody in elk (Cervus elaphus) and mule deer (Odocoileus hemionus) prior to the epizootic in cattle and horses suggests that an enzootic cycle may exist in Colorado.

Epizootic vesicular stomatitis in Colorado, 1982: epidemiologic and entomologic studies.

An epizootic of vesicular stomatitis (VS) caused by the New Jersey serotype of VS virus affected livestock and humans in 14 western states in 1982-1983. Epidemiological observations were made on at least 10% of the cattle in 4 dairy herds that were located in the vicinity of Grand Junction, Colorado. High rates of neutralizing antibody to the New Jersey serotype were seen in all cattle regardless of whether livestock in the dairy had clinical VS or a decrease in mild production. Antibody titers remained high in these cattle for as long as 2 years after the epizootic. No virus isolations were made from 32 humans with clinical signs compatible with viral disease. Entomological information was obtained during the epizootic from 23 premises in northwestern Colorado. Insect collections yielded 4 isolates from Culicoides spp. midges, 2 from C. variipennis, and 1 each from C. stellifer and C. (Selfia) spp. This is the first report of VS virus isolations from field-collected Culicoides.

Epizootic vesicular stomatitis in Colorado, 1982: epidemiologic studies along the northern Colorado front range.

Epidemiologic evaluations were made of farm personnel on vesicular stomatitis-affected premises along the front range of the Rocky Mountains in Colorado during the 1982 epizootic. A similar antibody prevalence was noted to that of veterinarians and research and regulatory personnel who were involved with the same epizootic. Risk of infection resulted from intimate physical contact with infected horses or cows. Incidence and infection rates in horses were 45%; rates in cows were much lower, only 5%. Some epidemiologic clues were gained by a detailed study of an equine ranch. The pasture was incriminated as the area of highest risk, where 100% infection rates were noted. Horses in open pens and barns were at lower risk. Severe clinical disease in horses resulted in higher neutralizing antibody titers than inapparent or mild infection. Maternal antibody was detected in foals up to 4 months of age, and the level of antibody in the foal was a reflection of the dam's antibody level.