CPB 69700 RESEARCH SEMINAR

DEPARTMENT OF COMPARATIVE PATHOBIOLOGY

Raju Gautam, BVSc & AH

CPB Graduate Student in Clinical Epidemiology

“Seroprevalence And Spatial Clustering Of Canine Leptospirosis

In The U.S. During 2000-2007”

Thurs., March 12, 2009

VPTH 112

3:30 pm

.

ABSTRACT: Canine leptospirosis is a re-emerging infectious disease in the United States (U.S). Increasing prevalence of canine leptospirosis with newer serovars has been reported in the recent past. A study was carried out to determine the seroprevalence and potential spatial clustering of canine leptospirosis using serological test results from a nationwide database of a commercial veterinary diagnostic laboratory. Electronic records of Leptospira microscopic agglutination test (MAT) results for dogs from 2000-2007 were obtained from IDEXX Laboratories Inc. A titer of ≥1:1600 to at least one of seven serovars was defined as a positive test. Spatial scan statistic for population rate data (Poisson distribution) was used to identify statistically significant clusters using a spatial window of 0-20% of the total population at risk and a temporal window of 0-6 months. An overall seropositivity of 8.1% (95% CI=7.8-8.4) was observed from 33,119 submissions. The lowest seropositivity (4.8%; 95% CI=4-5.7) was recorded for the year 2001 and the highest (10.2%; 95% CI=9.5-10.9) for 2007. One significant spatial cluster (739 km radius) was identified consisting of several states in the Midwest. Six significant space-time clusters were identified (29-1,343 km radius; P=0.001) that covered different geographic locations for different time points. Significant serovar specific space-time clusters were also identified for six important clinical serovars. Two clusters of Icterohaemorrhagiae, 3 each of Autumnalis and Canicola, 4 of Bratislava and 5 each of Gryppotyphosa and Pomona were identified. Leptospirosis in dogs potentially clusters in space. Serovar specific clusters in different geographic regions indicates potential role of specific reservoir hosts, environmental risk factors or difference in practice of preventative measures. Further investigation is required to identify the risk factors for serovar specific clustering of leptospirosis in dogs in specific cluster locations.