Increasing incidence of canine leptospirosis in Switzerland

Abstract

A marked increase in canine leptospirosis was observed in Switzerland over 10 years with a peak incidence of 28.1 diagnosed cases/100,000 dogs/year in the most affected canton. With 95% affected dogs living at altitudes <800 m, the disease presented a seasonal pattern associated with temperature (r2 0.73) and rainfall (r2 0.39), >90% cases being diagnosed between May and October. The increasing yearly incidence however was only weakly correlated with climatic data including number of summer (r2 0.25) or rainy days (r2 0.38). Serovars Australis and Bratislava showed the highest seropositivity rates with 70.5% and 69.1%, respectively. Main clinical manifestations included renal (99.6%), pulmonary (76.7%), hepatic (26.0%), and hemorrhagic syndromes (18.2%), leading to a high mortality rate (43.3%). Similar to the human disease, liver involvement had the strongest association with negative outcome (OR 16.3). Based on these data, canine leptospirosis presents similar features and severity as the human infection for which it therefore can be considered a model. Its re-emergence in a temperate country with very high incidence rates in canines should thus be viewed as a warning and emphasize the need for increased awareness in other species.

Figure 1

Age distribution of 298 dogs diagnosed with leptospirosis in Switzerland.

Figure 2

MAT seropositivity for 11 serovars tested in 259 dogs diagnosed with leptospirosis in Switzerland.

Figure 3

Geographic representation of the origin of 298 dogs diagnosed with leptospirosis (2003–2012) and their localization in the three main bioregions of Switzerland.

Figure 4

Geographic representation of the origin of 298 dogs diagnosed with leptospirosis (2003–2012) and their relationship to the altitude.

Figure 5

Annual number of cases of canine leptospirosis diagnosed at the University of Bern from 2003–2012 and association with country-wide average annual temperature and number of rainy days.

Figure 6

Seasonal distribution of 298 cases of canine leptospirosis in Switzerland and corresponding average monthly temperature and rainfall.

Figure 7

Distribution of 256 cases of leptospirosis by quarters for the 10 mainly affected cantons (2003–2012) and corresponding temperature and rainfall curves.