HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Burgdorfer, W. Articles by Hoogstraal, H. Search for Related Content PubMed PubMed Citation Articles by Burgdorfer, W. Articles by Hoogstraal, H.

Ticks as Vectors of Rickettsia Prowazeki—A Controversial Issue^*

The possibility that ticks are involved as vectors of the typhus rickettsia, Rickettsia prowazeki, in an extra-human cycle has been evaluated experimentally. Although adult Dermacentor andersoni and Amblyomma variegatum could readily be infected by intracelomic injection of infectious yolk-sac suspensions, all attempts failed to initiate generalized and prolonged infections by feeding larval and/or nymphal D. andersoni, A. variegatum, A. cohaerens, Rhipicephalus simus, R. evertsi, and Hyalomma dromedarii on rickettsemic guinea pigs and/or voles (Microtus pennsylvanicus). Testing of ticks by injection of tissue suspensions into normal guinea pigs and voles, immediately after infectious feeding and at varying intervals thereafter, indicated that R. prowazeki was ingested by all of the designated species of ticks except A. cohaerens; in some instances, the rickettsia was maintained transstadially into the next developmental stage. However, fluorescent antibody microscopy of tick tissues revealed that rickettsial infections, wherever detectable (i.e. in D. andersoni and H. dromedarii), were atypical and limited to the tissues of the midgut. These results, as well as those of other workers, suggest that the minimum dose requirement for successful infection of ticks with R. prowazeki is considerably higher than that provided by concentrations of rickettsiae circulating in the blood of infected laboratory animals used so far. Until animals are found in nature that meet this minimum dose requirement, incrimination of ticks as vectors of R. prowazeki does not appear justified.

Accepted for publication May 8, 1972.

^* From Research Project MR041-09.01-0037A, Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C.

The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy or of the naval service at large.