High prevalence of Rickettsia gravesii sp. nov. in Amblyomma triguttatum collected from feral pigs

A survey of ectoparasites on feral pigs identified two commonly occurring ixodid tick species; Amblyomma triguttatum triguttatum and Ixodes australiensis. Molecular screening of A. t. triguttatum and I. australiensis for the presence of Rickettsia species detected the presence of rickettsiae belonging to the Spotted Fever Group (SFG) in 78.4% of screened A. t. triguttatum. None of the screened I. australiensis were positive for rickettsiae. Sequence analysis of the gltA and ompA loci of positive Rickettsia isolates were 100% homologous to the newly described species Rickettsia gravesii sp. nov. BWI-1. Serological screening of feral pigs detected antibodies to SFG Rickettsia in 50% of serum samples tested. These findings suggest that A. t. triguttatum is a vector/reservoir for R. gravesii sp. nov.