Serological survey for antibodies to Leptospira in dogs and raccoons in Washington State.

A high number of reported canine leptospirosis cases occurred in Washington State from 2004 to 2006. This prompted a serosurvey of healthy dogs from around the state to determine the distribution of exposure risk and to provide insight into serovar epidemiology in the region. In addition, a convenience sample of sera from injured raccoons was also tested, and clinical serological data from the Washington Animal Disease Diagnostic Laboratory were examined. The proportion of dogs with an antibody titre (>or=1:100) to any serovar was 27/158 (17.1%, 95% CI 11.6-23.9), and that proportion among raccoons was 22/115 (19.1%, 95% CI 12.4-27.5) suggesting that the potential for exposure in Washington state is not uncommon. The most frequently detected serovars in healthy dogs were Autumnalis, Icterohemorrhagiae and Canicola, in clinical canine samples Autumnalis, Bratislava and Pomona were more frequent and in sick or injured raccoons Autumnalis, and Pomona were most frequently detected. Clinical canine serology demonstrated a late summer-fall seasonality that was consistent with other reports. An outbreak of canine leptospirosis occurred during 2004-2006 and was located primarily in western Washington counties, as were three reported human cases in 2005. Canine leptospirosis surveillance is an important tool for detecting human risk of exposure and may provide insights into which serovars are currently of clinical importance.