This report describes the isolation and partial characterization of a virus from soft ticks which had been collected on Bush Key, Dry Tortugas, Florida, and provisionally identified as Ornithodoros capensis Neumann, 1901. Another virus which appears to be similar or identical to the Dry Tortugas isolate was recovered from a pool of ticks of the same species collected under rocks near nesting gulls and terns on Raza Island, Gulf of Baja California, Mexico.
Infection was produced in Swiss mice, house mice, hamsters, guinea pigs, a rhesus monkey, and chick embryos by at least one route of inoculation. In all mice and suckling hamsters, significant histopathologic changes were present only in the central nervous system.
The Dry Tortugas agent has been passed through filters of various pore sizes and appears to be about 100 mµ in diameter. It is sensitive to both ethyl-ether and sodium desoxycholate.
Mouse brain and serum antigens were tested for ability to hemagglutinate and the results were negative. These same antigens failed to react in either complement-fixation or neutralization tests with any of the antisera that were available, including that prepared against several other tick isolates. Therefore, this agent probably represents an undescribed virus.
U. S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Montana.
Entomology Section, Division of Plant Industry, Florida Department of Agriculture, Gainesville, Florida.