In this VetGirl blog, we review the basics about leptospirosis, a thin, motile spirochete with a hook-shaped end that results in zoonotic disease in veterinary medicine. With canine leptospirosis, infection with certain serovars are thought to be associated with certain types and severities of clinical disease, although this is not definitive (Goldstein et al). L. pomona appears to result in more severe renal disease and worse outcome (50% as compared to 78-81%) as compared to other serogroups (Goldstein et al).
The prevalence of leptospirosis is higher in warm, tropical locations with high rainfall (Skyes et al). The top geographical locations where humans are diagnosed with leptospirosis include the Caribbean, Latin America, India, Southeast Asia, Oceania, and Eastern Europe (Skyes et al). In North America, Hawaii is the state with the highest human cases. In the United States, high antibody prevalence (>1,600) has been seen in dogs from the following regions: Hawaii, West coast states (e.g., northern California, Oregon, Washington), the upper Midwest (e.g., Minnesota, etc.), the Northeast, the mid-Atlantic coastal regions, and other regions (e.g., Texas, Colorado) (Skyes et al).
While canine leptospirosis used to be considered more prominent in large breed, male, working dogs that free roam in rural environments, more recent studies have found that urban areas have a growing prevalence, with smaller dogs < 15 pounds being one of the fastest growing populations of canine leptospirosis. Of increased concern are studies showing that >20% of dogs may be chronic healthy carriers (based on studies in Michigan) (Stokes et al).
Additional risk factors for leptospirosis include exposure to slow-moving or stagnant water, conditions where higher rainfall has occurred, late autumn, exposure to urbanized wild animals, or rodent exposure. One hypothesis is that global warming has contributed to the growing prevalence of leptospirosis due to the creation of warmer, wetter (e.g., flooding) weather conditions. Likewise, urban sprawl – the invasion of humans into the environment of wildlife - has increased the prevalence of canine leptospirosis.
Skyes JE, Hartmann K, Lunn KF, et al. 2010 ACVIM Small Animal Consensus Statement on Leptospirosis: Diagnosis, Epidemiology, Treatment, and Prevention. J Vet Intern Med 2011;25:1-13.
Goldstein RE, Lin RC, Langston CE. Influence of infecting Serogroup on clinical features of leptospirosis in dogs. J Vet Intern Med 2006;20:489-494.
Stokes JE, Kaneene KB, Schall WD, et al. Prevalence of serum antibodies against six Leptospira serovars in healthy dogs. J Am Vet Med Assoc 2007;230(11):1657-1664.