Agglutinating antibodies against pathogenic Leptospira in healthy dogs and horses indicate common exposure and regular occurrence of subclinical infections

In order to get insight in the level of exposure to pathogenic Leptospira under the moderate sea climate conditions in the Netherlands, healthy dogs and horses were tested for antibodies using the Microscopic Agglutination Test (MAT). 55% of 198 dogs tested had agglutinating antibodies against one or more pathogenic serovars with serovar Copenhageni, the common cause of Weil's disease in dogs and humans, being predominant. Of a total 112 horses tested 79% had agglutinating antibodies against one or more pathogenic serovars, again with serovar Copenhageni predominating. Some dogs may have been vaccinated, but the low prevalence of anti-serovar Canicola antibodies and the results of an unvaccinated group suggest that this did not really influence the outcome. Horses, however, are never vaccinated. Results demonstrate that exposure to, and subclinical infections with, serovar Copenhageni and other pathogenic serovars commonly occur in dogs and horses in the Netherlands. Humans share part of their biotope with these species and are therefore also exposed, although probably to a lesser extent as a result of their less intimate contact with the environment.