Resistance of leopard tortoises and helmeted guineafowl to Cowdria ruminantium infection (heartwater)

Experimental infection trials were conducted to investigate susceptibility of leopard tortoises (Geochelone pardalis) and helmeted guineafowl (Numida meleagris) to infection with Cowdria ruminantium, the causative agent of he artwater, a tickborne disease of domestic and wild ruminants. Ten guineafow l were inoculated intravenously with a virulent dose of C. ruminantium deri ved from bovine endothelial cell cultures, and four leopard tortoises were exposed to C. ruminantium infection by the feeding of infected Amblyomma he braeum ticks. Uninfected A. hebraeum ticks ton both tortoises and guineafow l) and Amblyomma marmoreum ticks ton tortoises only) were fed on the animal s during weeks 2 and 3 post-exposure in an attempt to detect infection. The se ticks were analyzed for C. ruminantium infection by xenodiagnosis and wi th the C. ruminantium-specific pCS20 polymerase chain reaction (PCR) assay. Attempts to detect infection in ticks fed on either species were negative by both tests. These results suggest that leopard tortoises and helmeted gu ineafowl are refractory to C. ruminantium infection and, therefore, are unl ikely to be capable of introducing heartwater directly into new areas. Howe ver, leopard tortoises are efficient hosts of A. marmoreum and A. hebraeum and are like ly to be important epidemiologically in the transport and main tenance of these tick vector species. (C) 2001 Elsevier Science B.V. All ri ghts reserved.