The occurrence and effects of the local strains of the California encephalitis group of viruses in domestic mammals of Florida

William E. Parkin Department of Epidemiology and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15213

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A quantitative micro-plaque reduction test using Keystone (KEY) virus disclosed the presence of neutralizing antibodies in the sera of 57/111 horses, 34/104 cattle, 22/119 dogs, and 0/9 swine collected in Florida in 1970. Similar results for neutralizing antibodies to California group viruses were obtained using the weanling mouse neutralization test with KEY, Trivittatus (TVT), LaCrosse, and California encephalitis (CE) viruses. Only 8 of 111 equine sera tested by the hemagglutination-inhibition test with CE virus exhibited this type of antibody. Viremia was not observed in any of 6 horses or 8 dogs inoculated with either KEY or TVT virus although 4 horses developed a persistent increase in neutralizing antibodies, as did 1 dog inoculated with TVT. Two dogs inoculated with KEY 28 days after TVT inoculation possessed KEY and/or TVT neutralizing antibodies 35 days after the second inoculation. Horses and cattle may be useful as monitors of KEY and TVT activity in Florida.

Author Notes

Present address: William E. Parkin, Chief, Epidemiology Section, Box 90, Department of Health, Harrisburg, Pennsylvania 17120.