Leptospirosis is caused by a bacterium (Leptospira interrogans) About Leptospirosis | Leptospirosis | CDC. Once thought to be contained, it has emerged as one of the most widespread zoonotic diseases in the world. Leptospira spp. are found in over 160 mammals worldwide, including dogs, cats, ruminants, horses and sea lions Leptospirosis- Disease Fact Sheet_2025.pdf. Leptospirosis is estimated to infect millions of humans annually with case fatality rates ranging from 5 to 25%. The highest occupational risk for contracting the disease are veterinarians, farmers, slaughterhouse workers, butchers and sewer workers Leptospirosis: Causes, Symptoms, Treatment, Prevention. Routes of infection are through direct contact (urine or body fluids) or indirect contact (contaminated water or soil), through the mucous membranes and conjunctiva. Many outbreaks have been related to floods caused by high rainfall events. 

Leptospirosis is found in every continent, except for the earth’s polar regions. Outbreaks of leptospirosis increase in warmer temperatures following periods of heavy rainfall and when flooding occurs. Animals can become chronic carriers of leptospires once they have recovered from the acute phase of the infection Leptospirosis - Infectious Diseases - Merck Manual Professional Edition. This allows the disease to perpetuate in nature, posing a risk to humans and other animals. Leptospirosis in humans mimics the flu and the presentation of the disease in humans ranges from asymptomatic to severe. Typically, symptoms begin within a few days after exposure but can take up to four weeks to occur. Human leptospirosis is treated using antibiotics such as penicillin, erythromycin or doxycycline, and most effective when given early in the course of the disease. Even though the acute disease can be self-limiting, 5-10% of cases lead to severe illness. In humans, prevention is through early identification and monitoring of outbreaks, hygienic practices in the workplace, avoidance of wading or swimming in water contaminated by animal urine will also help decrease the occurrence of leptospirosis. 

Infections in animals vary Leptospirosis in Animals | Leptospirosis | CDC. In ruminants, incidental infections occur more often by indirect transmission by contaminated surfaces, feed and water Leptospirosis in Animals - Overview - Infectious Diseases - Merck Veterinary Manual. Most infections in ruminants tend to be subclinical (no symptoms) although abortions can occur. Vaccines are available for bovines (worldwide) and small ruminants in some countries, such as Australia, but not licensed for use in the United States (US). 

Leptospirosis in swine occurs worldwide, with reproductive losses in adults and in young animals, signs such as jaundice, renal failure, hematuria and hemorrhage from acute infection occurs and can be fatal. There is a vaccine for swine in the US. In dogs the classic presentation is vomiting, diarrhea, fever, jaundice, uremia secondary to renal failure, disseminated intravascular coagulation (DIC), hemorrhage and death Leptospirosis in dogs | American Veterinary Medical Association. The incidence of canine leptospirosis in the US has increased over the past 25 years. The increase in cases could be due to decreased vaccination rate for leptospirosis in dogs. Penicillin, amoxicillin and doxycycline are the drugs of choice for treating leptospirosis in dogs. 

Horses can also be infected with Leptospira Leptospirosis in Horses - Infectious Diseases - Merck Veterinary Manual. In North America, the transmission of Leptospira to horses is believed to be mainly through contact with wildlife; however, contact with contaminated feed, water and/or soil infected with Leptospira does occur. In horses, leptospirosis has several clinical syndromes. In pregnant mares abortion, stillbirth or premature foaling is common. In yearlings recurrent uveitis (Moon Blindness) and renal failure are frequent. Other rare systemic clinical manifestations seen in horses are fever, anorexia, lethargy, respiratory distress, encephalitis, jaundice and liver failure. 

In Kentucky, the occurrence of leptospirosis in horses has been well documented and has caused millions of dollars of losses for the equine industry UKVDL Records Rise in Equine Leptospirosis Cases | Equine Programs. The advent of an equine vaccine in 2015 has shown a decrease in the number of abortions in the state of Kentucky Zero confirmed equine lepto abortions, A 30-year first, demonstrates power of research leading to a successful vaccine | Equine Programs. Clinical leptospirosis occurs infrequently in cats. Prevention in animals includes wildlife control, avoiding feed contamination, clean water, vaccination, isolation of sick animals and proper farm management practices.