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Risk factors for positive canine leptospirosis PCR test results

  • November 22, 2019 1:33 PM EST

    Drs. Jason Stull and Michelle Evason presented a webinar on The Increasing Threat of Canine Leptospirosis - Keys to Diagnosis, Therapy and Prevention.

    As a follow up, they have a recently published research article
     and we are pleased to share this abstract and provide a link to the full open access article:

    A cross-sectional study of environmental, dog, and human-related risk factors for positive canine leptospirosis PCR test results in the United States, 2009 to 2016

    Smith, A.M., Arruda, A.G., Evason, M.D. et al.  BMC Vet Res 15, 412 (2019) doi:10.1186/s12917-019-2148-6


    Canine leptospirosis is a reemerging zoonotic disease concern in North America, and a better understanding of its epidemiology is needed. Wide-scale use and subsequent analyses of polymerase chain reaction (PCR) testing may provide additional insight into leptospirosis. This study aimed to describe temporal trends, to descriptively map, and to identify environmental, dog, and human-level factors associated with positive canine leptospirosis PCR test results in the United States.


    Data obtained from IDEXX Laboratories, Inc. on 40,118 canine leptospirosis PCR tests run in the United States between 2009 and 2016 were evaluated. Climate and socioeconomic (e.g. urban influence, income) data were obtained from public databases. Choropleth maps were created to identify high test-positive proportion areas and a cross-sectional analysis was completed with generalized (univariable, followed by multivariable) mixed logistic regression models accounting for county within state to identify significant predictors for a positive test. Overall test-positive proportion was 5.4% across the United States, with the regional point estimate highest in the southwest (8.1%). In the final multivariable model, the odds of a positive test were greater for male dogs (Odds Ratio [OR] = 1.28) and dogs 0–4 years of age (ORs ranged from 0.35–0.71 for the other age groups). The odds of a positive test were greater for dogs living in areas with wet environmental conditions (OR = 1.24). Season and temperature, as well as the interaction between them, were significant predictors of a positive test. Dogs had a greater probability of testing positive during cool temperatures (< 4 °C) compared to the other temperature categories in the fall season.


    These findings based on PCR testing allow for an improved understanding of factors influencing a positive canine leptospirosis PCR test and will assist targeted education and prevention efforts.

    This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (