Leptospirosis in Pigs: Reproductive Losses, Fever, and Zoonotic Risk
- Leptospirosis is a bacterial infection that often shows up in pigs as infertility, sporadic abortion, stillbirths, or weak piglets rather than dramatic illness.
- Some pigs, especially nonpregnant adults, may look normal while still shedding bacteria in urine and exposing other pigs and people.
- Fever, poor appetite, and weakness can occur, but reproductive losses are often the first clue in a breeding herd.
- Diagnosis usually involves your vet collecting blood, urine, or fetal tissues for PCR and/or serology, because signs can overlap with PRRS, parvovirus, and other causes of pregnancy loss.
- This is a zoonotic disease. Anyone handling urine, aborted fetuses, placentas, or contaminated water should use gloves, dedicated boots, and careful hand hygiene.
What Is Leptospirosis in Pigs?
Leptospirosis is an infection caused by Leptospira bacteria. In pigs, it is best known for causing reproductive losses such as infertility, abortion, stillbirths, and weak piglets. In many herds, especially with adult pigs, the infection can be quiet enough that the first obvious problem is a sow or gilt losing a litter.
Pigs can also become renal carriers, meaning the bacteria may persist in the kidneys and be shed in urine for a long time. That matters for herd health and for human safety. Moist environments, contaminated water, and contact with infected urine help the bacteria spread.
This disease also has a zoonotic risk, which means people can become infected. Pet parents, farm workers, veterinarians, and anyone handling urine, placentas, or aborted tissues should treat suspected cases carefully and involve your vet early.
In pigs, serovar Pomona has historically been especially important for reproductive disease and zoonotic risk, while Bratislava is also associated with reproductive problems. Not every infected pig looks sick, so herd history and testing are often more useful than appearance alone.
Symptoms of Leptospirosis in Pigs
- Sporadic abortion, often 2-4 weeks before term
- Stillbirths or weak newborn piglets
- Infertility or reduced conception rates
- Mummified or macerated fetuses
- Fever
- Poor appetite, depression, or lethargy
- No obvious signs at all
Call your vet promptly if you see abortion, stillbirths, weak piglets, or a sudden drop in breeding performance. Those signs deserve attention even if the sow otherwise looks fairly normal. Leptospirosis can be easy to miss because many pigs have mild or no visible illness.
Use extra caution if anyone has handled urine, placentas, or aborted tissues without protection. Wear gloves, avoid splashing contaminated fluids, and keep children and immunocompromised people away from suspect materials until your vet guides you.
What Causes Leptospirosis in Pigs?
Leptospirosis in pigs is caused by infection with Leptospira interrogans and related pathogenic leptospires. In swine, Pomona and Bratislava are especially important. Pomona has long been linked to reproductive losses and human exposure risk, while Bratislava is also associated with infertility and sporadic abortion.
The bacteria spread mainly through urine from infected animals. Pigs can pick up infection from contaminated water, wet bedding, mud, wallows, feed areas, or surfaces where urine collects. Transmission is more likely in moist environments, because leptospires do not survive well when dried out.
Risk tends to rise in systems where pigs have more opportunity for urine exposure, including outdoor housing, wallows, solid-floor pens, contaminated drinkers, open gutters, and recycled lagoon water used for flushing. Rodents and other wildlife can also help maintain or introduce leptospires on a property.
Venereal transmission is also suspected with some serovars, especially Bratislava. Because several other diseases can also cause abortion in pigs, your vet may need to investigate the whole herd picture rather than assuming one cause.
How Is Leptospirosis in Pigs Diagnosed?
Diagnosis starts with history and pattern recognition. Your vet will want to know whether the problem involves one sow or multiple animals, when abortions occurred, whether fetuses were mummified or autolyzed, and whether there has been exposure to standing water, rodents, wildlife, or new pigs.
Testing often includes PCR and serology. In abortion cases, fetal tissues and stomach contents are especially useful. PCR is generally more sensitive and specific than older tissue staining methods, particularly when fetuses are already autolyzed. Blood testing with the microscopic agglutination test, or MAT, may help, but interpretation can be tricky in pigs because titers may be low even in infected herds.
Your vet may also recommend testing urine, placental tissues, or multiple affected animals to improve the odds of finding the cause. Because leptospirosis can look like PRRS, parvovirus, brucellosis, or porcine circovirus-related reproductive loss, a broader abortion workup is often the most practical path.
If there is a human exposure concern, tell your vet right away. That helps the clinic advise on safer sample handling and on-farm precautions while results are pending.
Treatment Options for Leptospirosis in Pigs
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or herd-health consultation with your vet
- Isolation of affected breeding animals when practical
- Basic PPE guidance for anyone handling urine, placentas, or aborted tissues
- Submission of selected fetal tissues or one to two PCR/serology tests
- Immediate sanitation, water-source review, and rodent control steps
- Targeted medication plan only if your vet believes it is appropriate and legal for the situation
Recommended Standard Treatment
- Full veterinary reproductive-loss workup
- PCR testing on fetal tissues, stomach contents, urine, and/or blood as indicated
- Serology on affected and in-contact animals when useful
- Herd-level review of water hygiene, pen design, urine exposure, and biosecurity
- Medication plan directed by your vet for outbreak control where appropriate
- Vaccination review and booster planning for the breeding herd
- Written zoonotic-risk instructions for staff and family members
Advanced / Critical Care
- Expanded herd investigation with multiple animals and repeated sampling
- Necropsy and pathology on fetuses or piglets when needed
- Broader differential testing for PRRS, parvovirus, circovirus, brucellosis, and other reproductive pathogens
- Intensive outbreak-control planning with movement restrictions and pen-by-pen management changes
- Large-scale vaccination and monitoring program for the breeding herd
- Detailed occupational-safety planning for workers, family members, and visitors
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Leptospirosis in Pigs
Bring these questions to your vet appointment to get the most out of your visit.
- Based on the pattern in this sow or herd, how likely is leptospirosis compared with PRRS, parvovirus, or other causes of abortion?
- Which samples give us the best chance of diagnosis right now: fetal tissues, stomach contents, urine, blood, or placenta?
- Should we test only the affected pig, or do we need herd-level testing to look for carriers?
- What biosecurity steps should we start today to reduce urine contamination of water, feed, and housing areas?
- Is vaccination appropriate for this herd, and if so, which leptospiral serovars should the vaccine cover in our region?
- Are there medication options that are appropriate and legal for these pigs, and what are the withdrawal considerations for food animals?
- What personal protective equipment should family members or staff use when handling aborted tissues or cleaning pens?
- How will we know whether the outbreak is controlled, and when should we recheck breeding performance or repeat testing?
How to Prevent Leptospirosis in Pigs
Prevention usually works best as a herd plan, not a single step. Vaccination with a multivalent bacterin is widely used in breeding herds and can reduce abortions and the overall prevalence of infection. Your vet can help decide whether vaccination fits your pigs, your region, and your management style. Because immunity is serovar-specific, vaccine choice matters.
Housing and sanitation also make a real difference. Try to reduce urine contamination of water and feed, fix drinkers that leak or can be fouled, improve drainage, and limit standing water, mud, and pooled waste. Outdoor systems and solid-floor pens need especially careful moisture management.
Strong rodent and wildlife control is another key layer. Store feed securely, remove attractants, and reduce access by small mammals that may carry leptospires. Quarantine and evaluate new breeding animals before mixing them with the herd, especially if they come from a source with unknown vaccination or reproductive history.
Because leptospirosis can infect people, prevention also includes human safety. Wear gloves, dedicated boots, and protective clothing when handling urine, placentas, aborted fetuses, or contaminated bedding. Wash hands well, clean equipment carefully, and ask your vet what extra precautions make sense for your farm or home setup.