A 5-year (1959–1963) virologic and serologic survey in Kern County, California, revealed that wild mammals had been infected with several arboviruses. Seven strains of virus were recovered from 1,889 blood samples: 2 strains of western equine encephalomyelitis (WEE) virus from 1 Ammospermophilus nelsoni and 1 Mus musculus, 4 strains of a Simbu group virus from 3 Sylvilagus auduboni and 1 Lepus californicus, and 1 strain of an adenovirus from Peromyscus maniculatus. No virus was isolated from ticks or fleas. Based on hemagglutination-inhibition tests, antibodies to WEE virus were frequent in L. californicus but rare in other species. Antibodies to St. Louis encephalitis (SLE), Powassan, and/or Modoc virus, but not Rio Bravo virus, were widespread. The yearly prevalence of antibodies to any one group B arbovirus varied. Antibody to SLE virus decreased and antibody to Powassan virus increased over the 5-year period. WEE viral antibody rates in L. californicus paralleled viral infection rates in Culex tarsalis and immunity conversion rates in sentinel chickens. No such relationship was found for WEE and SLE viral antibodies in rodents.
Postdoctoral fellow supported in part by a U.S. Public Health Service Postdoctoral Fellowship No. 5 F2 AI-9015 from the National Institute of Allergy and Infectious Diseases.