Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/20/2004
Publication Date: 10/1/2005
Citation: Greenlee, J.J., Alt, D.P., Bolin, C.A., Zuerner, R.L., Andreasen, C.B. 2005. Experimental canine Leptospirosis caused by Leptospira interrogans serovars Pomona and Bratislava. American Journal of Veterinary Research. 66(10):1816-1822. Interpretive Summary: An critical step in testing new vaccines is development of an infection challenge model. No infection model for dogs using Leptospira interrogans serovars Pomona and Bratislava was available. The goal of this study was to develop an method to study Leptospira infections in dogs with serovars Pomona and Bratislava. Dogs challenged with L. interrogans serovar Pomona readily developed infections, while all attempts to infect dogs with L. interrogans serovar Bratislava were unsuccessful. These results show serovar Pomona is an effective pathogen in dogs, but bring into question the importance of serovar Bratislava in canine leptospirosis. Successful development of an infection model for serovar Pomona infection of dogs provides a means to test the efficacy of different vaccine formulations to prevent infections. This study was the result of a cooperative research project between ARS, the Biotechnology Research and Development Corporation, and Iowa State University, aimed at developing better Leptospira vaccines for dogs.
Technical Abstract: The goal of this study was to develop an experimental infection model to study canine leptospirosis as a result of challenge with Leptospira interrogans serovars Pomona and Bratislava. Eight-week-old female beagle dogs were randomly assigned to challenge or control groups. Challenge groups were inoculated on three successive days by conjunctival instillation of 5x107 cells of either L. interrogans serovar Pomona (n=12) or serovar Bratislava (n=12); control dogs (n=4) were inoculated with sterile leptospiral culture media. Clinical signs were recorded and clinical pathology assays and necropsies (7/timepoint) were done at 7, 10, 14, and 20 days post-inoculation (PI). Infection could not be confirmed in any serovar Bratislava inoculated dog, and control dogs remained healthy throughout the experiment. Positive culture and fluorescent antibody test results were confirmed in 92% (11/12) of serovar Pomona inoculated dogs. Fever and lethargy starting at day 7 PI were the most common clinical signs in serovar Pomona infected dogs. On day 10, gross lesions included multifocal renal and pulmonary hemorrhage and perirenal edema. Serovar Pomona inoculated dogs had histopathologic lesions including hepatitis, interstitial nephritis, and pneumonia at 7, 10, 14, and 20 days PI. Elevations in BUN, anion gap, and bilirubin occurred on days 10, 14, and 20 PI. Platelet counts from culture positive dogs were decreased from baseline values on days 10, 12, and 14 PI. Conjunctival inoculation with L. interrogans serovar Pomona resulted in a high rate of infection with concomitant hemorrhagic and inflammatory lesions of the kidneys, liver, and lungs.