Leptospirosis in Sheep: Kidney Infection, Fever, and Abortion Risks

Leptospirosis is an infectious disease caused by Leptospira bacteria. These bacteria survive well in wet environments and are spread mainly through urine from infected animals. Sheep can become infected after exposure to contaminated standing water, muddy pens, wet pasture, feed areas, or shared environments with rodents, wildlife, cattle, pigs, dogs, or other livestock.

In sheep, leptospirosis is often discussed as a reproductive disease because it can lead to abortion, stillbirth, weak lambs, and reduced flock productivity. Some animals may also develop a more acute illness with fever, depression, and organ damage, especially involving the kidneys and sometimes the liver. In other cases, infection is mild or silent, which makes flock-level disease harder to recognize early.

This is also a public health concern. Leptospirosis is zoonotic, meaning people can become infected through contact with contaminated urine, birth fluids, placentas, or wet environments where the bacteria are present. If abortion losses or sudden illness are happening in your flock, your vet can help protect both animal health and human safety while working toward a diagnosis.

Leptospirosis is caused by pathogenic Leptospira bacteria. In ruminants, some strains are more adapted to livestock, while others are incidental strains picked up from the environment or from other species. Merck Veterinary Manual notes that incidental infections are often associated with outbreaks and more obvious clinical disease, while host-adapted strains may be harder to detect and can contribute to ongoing reproductive losses.

Sheep are usually infected when bacteria enter through the mouth, nose, eyes, or broken skin after contact with urine-contaminated water, mud, pasture, bedding, or feed. Wet, shaded, and poorly drained areas increase risk because the organism survives longer there. Rodents and wildlife can contaminate the environment, and mixed-species farms may have added exposure if sheep share pasture or water with cattle or pigs.

Management factors matter. Crowding, standing water, poor drainage, feed contamination, and delayed cleanup after abortions or lambing can all increase exposure. If your flock has abortion losses, your vet may also consider other important causes such as chlamydial abortion, campylobacteriosis, toxoplasmosis, listeriosis, salmonellosis, and Q fever, because several diseases can look similar at first.

Diagnosis usually starts with flock history and a careful exam. Your vet will ask about recent abortions, weak lambs, fever, access to ponds or puddles, rodent pressure, wildlife exposure, and whether sheep share space with cattle, pigs, or dogs. Because leptospirosis can mimic other abortion diseases, history alone is not enough.

Testing often combines serology and direct detection. In ruminants, the microscopic agglutination test, or MAT, looks for antibodies, while PCR can detect bacterial DNA in blood, urine, placenta, or fetal tissues. Merck Veterinary Manual notes that culture is considered the reference method, but it is used less often because it is technically difficult and more costly. In acute infections, high MAT titers can support the diagnosis, but chronic or subclinical infections may be missed if serology is used by itself.

If a ewe aborts, your vet may recommend submitting the placenta and fetal tissues to a diagnostic laboratory. Cornell's sheep abortion guidance emphasizes that placenta, fetal tissues, and blood from the dam improve the chance of finding the cause. Fresh placenta, fetal kidney, liver, lung, stomach contents, and maternal blood are often the most useful samples. Quick, clean sample handling matters, so call your vet before discarding any materials.

Prevention focuses on reducing exposure and working with your vet on flock-level risk management. Keep sheep away from stagnant water, chronically muddy areas, and poorly drained lots when possible. Clean water sources, good drainage, elevated feeders, and prompt removal of wet bedding all help lower environmental contamination. Rodent control also matters because rodents can shed Leptospira in urine.

If abortions occur, isolate affected ewes and remove placentas, fetuses, and heavily contaminated bedding right away using gloves and protective clothing. Cornell's sheep abortion guidance recommends isolating aborting females and disposing of abortion materials completely. This protects the rest of the flock and reduces risk to people handling the area.

Vaccination may be part of prevention, but it should be tailored to your region, flock history, and product availability. In ruminants, Merck Veterinary Manual describes vaccination as an important control tool, often used alongside management changes and antimicrobials, while also noting that vaccine performance can vary and may not fully prevent kidney colonization. That means vaccination is helpful in many settings, but it works best as one part of a broader plan rather than the only step.

Because leptospirosis is zoonotic, prevention also includes human safety. Wear gloves when assisting lambing, handling urine-soaked bedding, or cleaning up after abortions. Wash hands well, disinfect equipment, and keep food and drink out of animal care areas. If anyone on the farm develops flu-like illness after exposure to sick sheep or abortion materials, they should contact a physician and mention possible livestock exposure.