Which animal is a major vector of leptospirosis in the US?

Updated: Jul 08, 2021
  • Author: Sandra G Gompf, MD, FACP, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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These reported cases starkly contrast with the prevalence rates found under active surveillance. [25] Using active surveillance measures, Hawaiian researchers projected the state's true local incidence at approximately 128 cases per 100,000 persons. Major risk factors identified in Hawaii include the use of water catchment systems, wild pig hunting, and the presence of skin wounds.

An estimated 100-200 cases are identified annually in the United States, with about 50% of cases occurring in Hawaii. Endemic canine leptospirosis is becoming more common in the United States, and California has seen a re-emergence of disease since 2000. Over the past 20 years, epidemiology has begun to shift from primarily recreational water exposures to an increasing number of occupational exposures related to farm and agricultural activities. [26]

Although less dramatic and often unrecognized, people with no obvious risk factor have significantly higher background infection rates than reports often indicate. Approximately 30% of children in urban Detroit [27] and 16% of adults in Baltimore [28] demonstrated serologic evidence of past infection. The Detroit study also showed correlation between degree of rat infestation and seropositivity rates. This finding suggests rats are major, if not the most important, vectors for human leptospirosis in the mainland United States.

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