The role of dogs in the eco-epidemiology of Rickettsia typhi, etiological agent of Murine typhus.

Rickettsia typhi, etiological agent of Murine typhus (MT), is transmitted to humans from an animal reservoir through two cycles: a classic rat-flea-rat cycle, and a peridomestic animal cycle. There are not many studies concerning which animals are involved in the peridomestic cycle, and most of them are focused on cats. The aim of this study was to determine the presence of R. typhi in dogs, not only by serological methods but also by direct methods such as culture and molecular detection. Two hundred and one dog blood samples were collected from Veterinary clinics, kennels, and shelters in Northeastern Spain (2006-2008). Age, sex, municipality, living place, healthy status, contact with animals, and ectoparasite infestations were surveyed. IgG was measured by IFA. Titers ≥ 1/64 were considered positive. Cultures were carried out using samples of dogs with titers ≥ 1/128. The molecular detection was performed by real-time PCR. Nine dogs (4.5%) were positive according to IFA (5: 1/64; 3: 1/128; 1: 1/512). There were no significant differences in the rates of antibodies related to any of the variables. Rickettsial DNA was detected in two cultures. Sequences obtained were identical to those of R. typhi. The results show direct and indirect evidences of the presence of R. typhi infection in dogs.