Cow Abortion: Causes, Infection Risks & What to Do

Abortion in cattle has many possible causes, and infection is high on the list. Important infectious causes include leptospirosis, infectious bovine rhinotracheitis (IBR/BHV-1), campylobacteriosis, trichomoniasis, listeriosis, and neosporosis. Merck notes that BHV-1 can cause abortion outbreaks in nonvaccinated herds, leptospirosis is a well-recognized reproductive disease of cattle, and Tritrichomonas foetus more often causes infertility but can also cause abortion in the first half of pregnancy. Listeria can infect the uterus at any stage of pregnancy and lead to placentitis, fetal death, abortion, stillbirths, and metritis.

Not every abortion is infectious. Cows may also lose a pregnancy because of twinning, heat stress, poor body condition, mineral or vitamin imbalances, toxic plants or molds, trauma, severe systemic illness, or fetal defects. In some herds, a single abortion is sporadic. In others, multiple losses over a short period can point to a herd-level problem that needs rapid investigation.

Timing can offer clues, but it does not give a diagnosis. For example, Cornell dairy reproduction materials note that Neospora caninum is often linked with abortions around 5 to 6 months, while IBR abortions are more often seen after 4 months. Your vet will use the stage of gestation, vaccination history, breeding method, feed changes, and herd pattern to narrow the list.

Some causes also matter for human health. Brucellosis, leptospirosis, listeriosis, Q fever-related coxiellosis, and some Campylobacter infections can infect people, especially through contact with aborted tissues, fluids, and contaminated bedding. Pregnant people and anyone immunocompromised should avoid handling these materials.

See your vet immediately if a cow aborts, especially if she is late in gestation, seems sick, has a retained placenta, or if more than one cow in the herd is affected. Rapid veterinary input matters because some abortion causes spread quickly among pregnant cattle, and early sample collection improves the odds of finding the cause.

Urgent signs in the cow include fever, weakness, poor appetite, foul-smelling uterine discharge, straining, dehydration, collapse, severe depression, or a placenta that is not passed in a timely way. These signs can go along with metritis or systemic illness. Merck also notes that retained placenta is often seen after some infectious abortions, including trichomoniasis-associated losses.

Home monitoring is only appropriate after you have spoken with your vet and the cow is bright, eating, drinking, and not showing signs of systemic illness. Even then, the focus at home is not waiting to see if it happens again. It is careful observation, isolation from pregnant cattle, and safe handling of tissues and contaminated materials.

If there is any chance of a zoonotic infection, treat the event as a biosecurity issue. Wear gloves, wash thoroughly, disinfect boots and equipment, and keep dogs, scavengers, and wildlife away from the fetus and placenta until your vet gives instructions.

Your vet will start with the cow, the pregnancy history, and the herd picture. Expect questions about breeding dates, vaccination status, natural service versus AI, recent feed or silage changes, new cattle introductions, water sources, and whether other cows have aborted or returned open. A physical exam may include temperature, hydration, uterine discharge assessment, and checking whether fetal membranes are retained.

Diagnostic work is often the most valuable step. Your vet may recommend submitting the fetus and placenta to a diagnostic lab, along with blood samples from the dam and sometimes herd mates. Merck emphasizes that placenta and fetal tissues are key samples for causes such as leptospirosis, listeriosis, and IBR. Fresh, cooled samples are usually preferred over frozen ones.

Treatment depends on the cow's condition and the suspected cause. Options may include supportive care, anti-inflammatory medication, treatment for metritis if present, fluid support, and herd-level control measures such as isolation, breeding management changes, vaccination review, or testing bulls for venereal disease. If an infectious cause is suspected, your vet may also advise movement restrictions and extra sanitation.

Your vet may coordinate with a state or university diagnostic laboratory. Current U.S. lab fees show that bovine abortion PCR or screening tests can start around $55 to $66, while more complete abortion screens or necropsy-based panels often run about $250 to $300, not including farm call, sample collection, shipping, or treatment.

Home care starts with biosecurity and observation. Move the cow to a clean, dry area away from pregnant cattle if your vet recommends it. Wear gloves when handling the cow, fetus, placenta, or contaminated bedding. Bag or contain tissues as directed by your vet, and keep diagnostic samples cool, not frozen, until they can be submitted.

Keep the cow comfortable with clean water, easy access to feed, shade or shelter, and low-stress handling. Watch her closely for appetite, temperature if your vet asks you to check it, milk production, attitude, and vaginal discharge. A foul odor, fever, weakness, or refusal to eat means the situation is no longer routine.

Do not pull on retained membranes or start medications on your own. That can worsen bleeding, contamination, or uterine injury. Instead, follow the treatment plan your vet gives you and ask exactly what changes should trigger a recheck.

Clean and disinfect boots, tools, and equipment after contact with the cow or abortion materials. Merck notes that abortion events linked to agents such as coxiellosis can heavily contaminate the environment around calving or abortion. Good cleanup protects other cattle and lowers risk for people on the farm.