Leptospirosis infections in cats: an underestimated One Health issue?

Cats have long been considered relatively resistant to leptospirosis, but a review suggests that this view is increasingly difficult to maintain. Evidence of antibodies, urinary shedding, viable leptospires and occasional clinical disease indicates that cats can become infected and may contribute to environmental contamination, even if their epidemiological role remains much less important than that of rodents, livestock or dogs.

Published in Pathogens, the review brings together historical and recent data on feline leptospirosis, a field that remains much less developed than canine leptospirosis. Cats are frequently exposed to rodents, the main maintenance hosts of pathogenic Leptospira, yet clinical disease in felines has traditionally been considered rare.

Exposure may be more common than clinical disease suggests

Serological surveys indicate that feline exposure is not exceptional. A recent meta-analysis cited in the review estimated seroprevalence at 40.6% in Australia, 15.0% in Europe, 11.4% in Asia, 7.2% in North America and 5.1% in South America. European studies range widely, from around 9% in the UK and Czech Republic to 48.5% in one French dataset, although differences in testing methods make direct comparison difficult.

PCR studies also show that some cats shed leptospiral DNA in urine. Reported prevalences include 4.5% in Hong Kong, 4.9% in Malaysia, 3.3% in Germany, 1.9% in Croatia, 1.7% in Spain and 3.4% in Canada. Much higher figures have occasionally been reported, but the authors stress that PCR positivity does not necessarily prove persistent renal infection.

Cats can become renal carriers

After entry through damaged skin, mucous membranes or ingestion of infected prey, leptospires can disseminate via the bloodstream to the kidneys, liver and other organs. In cats, leptospiraemia appears to be short-lived and often subclinical.

Renal colonisation is particularly relevant epidemiologically. Experimental studies suggest that urinary shedding may begin around two weeks after infection and persist for 60–80 days. Some infected cats may shed bacteria despite weak or undetectable antibody responses.

Clinical leptospirosis is rare but can be severe

Most feline infections appear asymptomatic, but natural clinical cases are increasingly recognised. Reported signs include fever, vomiting, diarrhoea, polyuria-polydipsia, haematuria, jaundice, uveitis, anorexia, weight loss and lethargy. Acute kidney injury is among the most important clinical findings, while hepatic abnormalities are usually milder than those observed in dogs.

The review notes that fatal outcomes have been reported in clinical case series, although the available evidence remains sparse and based largely on isolated cases rather than large prospective studies.

No feline vaccine is currently available

Treatment generally follows principles used in dogs. Penicillin derivatives such as ampicillin or amoxicillin may be used during the acute phase, while oral doxycycline is considered important for eliminating renal carriage. Supportive treatment is directed mainly at renal, gastrointestinal and electrolyte abnormalities.

There is currently no licensed leptospirosis vaccine for cats. Prevention therefore relies on reducing exposure to rodents, contaminated water and other high-risk environments. The review also notes that feline-specific vaccination remains a research gap, particularly because immune responses and vaccine safety cannot simply be extrapolated from dogs.

A possible sentinel rather than a major reservoir

The One Health implications require careful interpretation. Current evidence does not provide definitive molecularly confirmed examples of transmission from cats to humans or other animals. Compared with recognised maintenance hosts such as rodents, livestock and dogs, cats probably play a smaller role in maintaining Leptospira circulation.

Their importance may instead lie in their ability to act as sentinels of environmental exposure, particularly outdoor cats that hunt rodents or enter contaminated habitats. Such animals show higher probabilities of seropositivity and urinary shedding.

The review therefore shifts the discussion away from whether cats are a major leptospirosis reservoir. The more relevant question is whether their exposure and occasional shedding can provide useful information about Leptospira circulation at the interface between wildlife, domestic animals, the environment and humans.