A comparison of risk factors for canine leptospirosis and seropositivity in New South Wales, Australia.

This study aimed to identify and compare risk factors associated with canine leptospirosis and Leptospira seropositivity in New South Wales, Australia. Seventy-nine canine cases of confirmed leptospirosis (clinical cases) and 16 healthy dogs seropositive to Leptospira (seropositive cases) were included in the study; these were separately compared to 394 healthy dogs seronegative to Leptospira (controls) in at-risk areas. A questionnaire investigated rat contact, stagnant water, dog park access and household number of dogs and cats. Associations between these factors, signalment and risk of leptospirosis or Leptospira seropositivity were screened using Pearson Chi-Square test and logistic regression was used to estimate odds ratios of association. Significantly associated with both leptospirosis risk and seropositivity risk was rat contact (P < 0.01) which increased the risk 4.3- and 4.5-fold, respectively. Other factors significantly associated with leptospirosis risk were breed (P < 0.01) and age (P < 0.01). Being a herding dog or Terrier increased leptospirosis risk 27.2-fold and 8-fold, respectively and being a young adult dog increased leptospirosis risk 3.9-fold. Frequenting dog parks decreased leptospirosis risk (OR 0.12). In contrast, no other significant risk factors were identified for seropositivity risk. Exposure to Leptospira through contact with reservoir hosts resulted in seropositivity as well as clinical leptospirosis. However, host factors like breed and age seem to be important factors in determining if exposure results in clinical disease. Increased urbanisation and landscape fragmentation could result in increased exposure to reservoir hosts. Environmental sampling is needed to identify sources of infection. Risk mitigation includes reducing contact with reservoir hosts and contaminated environments and increased pest control.