Detection of Leptospira in Urban Swedish Rats: Pest Control Interventions as a Promising Source of Rats Used for Surveillance

Rat carcasses obtained from pest control interventions can potentially be used for an efficient surveillance of zoonotic diseases such as leptospirosis. To evaluate the performance of different laboratory methods for detection of pathogenic Leptospira spp., heart and kidney samples from wild Norway rats were analyzed by microscopic agglutination test (MAT, the gold standard), a commercial IgG enzyme-linked immunosorbent assay, and by an optimized quantitative PCR (secY qPCR, followed by sequencing). We found secY qPCR to be as sensitive as MAT for screening of Leptospira infection in pest control rats and selected secY qPCR for a larger screening of rats from urban and rural areas in central and southern Sweden. We identified secY qPCR positive rats from the cities Stockholm, Gothenburg, and Malmo, which were further confirmed by sequencing.