Seasonal occurrence of canine babesiosis is influenced by local climate conditions

Abstract

Global warming and its effect on local climate conditions is one of the presumed underlying causes for changes in temporal and spatial distribution of vector-borne diseases. In Europe, canine babesiosis is transmitted by Dermacentor reticulatus. This hard tick species is observed to spread to new endemic areas. Within these new areas, specific local climate conditions may be responsible for sudden seasonal onset and termination of occurrence of this disease in dogs. From 2000 to 2006, 343 confirmed cases of canine babesiosis were documented at the Veterinary University of Vienna and in the Laboratory for Veterinary Diagnostic (INVITRO, Vienna). Estimated week of infection was analysed for mean air and soil temperature, relative humidity, and precipitation for each case. For seasonal start in spring, a sudden rise of air temperature up to 12 °C and defrosting of soil were essential. In autumn, the seasonal start was associated with a drop of temperature below 17 °C. Termination of occurrence of canine babesiosis, independent of season, correlated either with a sudden drop of temperature (Δ T>9 °C) with concurrent heavy rain, persistent drought, or with air temperature above 20 °C (spring/summer) or below 5 °C (autumn/winter). Relative humidity and precipitation did not have a major influence on the incidence of canine babesiosis at all. Global climate changes and adaptation of ticks to new environmental conditions introduce vector-borne diseases into new areas.