Experimental Infections of Rickettsia Prowazeki among Domestic Livestock and Ticks

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  • 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, Naval Medical Research Unit No. 3, Department of the Navy, Hamilton, Montana 59840

Verification of infections in young sheep, goats, camels, and donkeys after inoculation with Rickettsia prowazeki was unsuccessful. Rickettsiae could not be isolated from peripheral blood or other tissues of the domestic animals, although similar isolation in guinea pigs and Microtus was successful. Antibody response in sheep and goats varied with the size of the inoculum. Injection of similar quantities of live or dead R. prowazeki into young sheep produced similar agglutinin and complement-fixing serum antibody responses. Thus, antibody response alone is not certain evidence of infection in domestic animals. Infection of the ticks Dermacentor andersoni, Hyalomma dromedarii, Hyalomma anatolicum excavatum, Rhipicephalus simus, Ornithodoros moubata, Ornithodoros turicata, and Ornithodoros lahorensis by feeding on rickettsemic Microtus, guinea pigs, and gerbils was unsuccessful, although intracoelomic inoculation produced generalized infections in D. andersoni and H. dromedarii but not in H. a. excavatum. Failure to produce rickettsemia in domestic animals and to infect ticks by feeding on rickettsemic Microtus suggests that neither domestic animals nor ticks are importantly involved in the epidemiological cycle of epidemic typhus.

Author Notes

Present address: Armed Forces Institute of Pathology, Walter Reed Medical Center, Washington, D. C.