Neosporosis in Sheep: Abortion and Protozoal Infection
- Neosporosis is a protozoal infection caused by Neospora caninum that can lead to abortion, stillbirth, mummified fetuses, or weak newborn lambs.
- Dogs and wild canids are the definitive hosts. Sheep are infected after exposure to feed, water, or pasture contaminated with infective oocysts shed in canid feces.
- Many ewes show few outward signs before pregnancy loss, so an abortion event may be the first clue that the flock has a reproductive disease problem.
- Diagnosis usually requires lab testing of the fetus and placenta, plus flock history and sometimes blood testing. Placenta is one of the most useful samples to submit.
- There is no single field treatment that reliably clears infection in sheep, so care often focuses on confirming the cause, protecting the rest of the flock, and improving biosecurity.
What Is Neosporosis in Sheep?
Neosporosis is an infection caused by the microscopic protozoan parasite Neospora caninum. In sheep, it is most important as a cause of reproductive loss, especially abortion, stillbirth, fetal mummification, or the birth of weak lambs. Dogs, coyotes, and other canids play a key role in the life cycle because they can shed infective stages of the parasite in their feces.
A ewe may look normal until she aborts, which can make this disease frustrating for pet parents and flock managers. Infection can happen after a ewe eats or drinks material contaminated by canid feces, and the parasite may then spread to the placenta and fetus. In some cases, infection during pregnancy is more likely to cause fetal damage than infection outside pregnancy.
Neosporosis is less commonly discussed in sheep than in cattle, but it is still a recognized cause of abortion in small ruminants. Because many other diseases can also cause abortion in ewes, your vet usually needs lab testing to tell neosporosis apart from toxoplasmosis, chlamydial abortion, campylobacteriosis, listeriosis, and other reproductive infections.
Symptoms of Neosporosis in Sheep
- Abortion, often with few warning signs
- Stillborn lambs
- Weak newborn lambs that struggle to stand or nurse
- Mummified or decomposed fetuses
- Retained placenta or abnormal vaginal discharge after abortion
- Repeat reproductive losses in the flock
- Occasionally no visible illness in the ewe before pregnancy loss
Call your vet promptly for any abortion, stillbirth, or weak lamb syndrome, even if only one ewe is affected. In sheep, one abortion can be the first sign of a flock-level infectious problem. See your vet immediately if multiple ewes abort, if a ewe is depressed or feverish, or if lambs are born alive but weak. Save the fetus and placenta if possible, keep them cool but not frozen unless your vet or lab instructs otherwise, and limit access by dogs, wildlife, and scavengers.
What Causes Neosporosis in Sheep?
Neosporosis in sheep is caused by Neospora caninum, a coccidian parasite. Dogs and wild canids are the definitive hosts, which means the parasite completes part of its life cycle in them and may be shed in feces. Sheep become infected when they consume contaminated feed, water, bedding, or pasture.
Once inside the ewe, the parasite can invade tissues and, during pregnancy, may infect the placenta and fetus. This can lead to fetal death, abortion, stillbirth, or a weak lamb at birth. Timing matters. Infection or reactivation during pregnancy may be more likely to cause reproductive loss, especially earlier in gestation.
Risk goes up when feed storage areas, lambing areas, or water sources are accessible to farm dogs, stray dogs, coyotes, or other canids. Feeding raw tissues, placentas, or aborted fetuses to dogs can also help maintain the parasite's life cycle on a farm. That is why prevention focuses heavily on biosecurity and canid control, not only on the affected ewe.
How Is Neosporosis in Sheep Diagnosed?
Your vet usually cannot diagnose neosporosis from signs alone. The most useful approach is a full abortion workup through a veterinary diagnostic lab. That often includes examination of the fetus and placenta, histopathology, and targeted testing such as PCR or immunohistochemistry when available. In sheep abortion cases, placenta is one of the most valuable samples to submit.
Blood testing may help show whether a ewe or flock has been exposed, but a positive antibody test by itself does not prove that neosporosis caused the abortion. Your vet will interpret lab results alongside gestation stage, flock history, number of affected ewes, and whether other common abortion causes have been ruled out.
If you find an aborted fetus or placenta, contact your vet right away about sample handling. In many cases, the best plan is to refrigerate the materials and submit them quickly. Good records also help: breeding dates, vaccination history, feed changes, dog access, and how many ewes are affected can all improve the odds of getting a clear answer.
Treatment Options for Neosporosis in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or herd health consultation
- Physical exam of affected ewe
- Basic supportive care for the ewe after abortion
- Isolation from lambing group if advised by your vet
- Collection and submission of the most useful available samples, often placenta and/or fetus
- Immediate biosecurity steps to keep dogs and scavengers away from tissues, feed, and water
Recommended Standard Treatment
- Complete veterinary reproductive exam and flock history review
- Diagnostic lab abortion panel with fetus and placenta when available
- Serology or additional flock screening if your vet recommends it
- Treatment of concurrent problems such as metritis, dehydration, or retained placenta if present
- Written flock biosecurity plan for feed storage, dog access, carcass disposal, and lambing area hygiene
- Follow-up discussion on breeding management and monitoring of exposed ewes
Advanced / Critical Care
- Expanded laboratory testing such as PCR, histopathology, and immunohistochemistry when available
- Multiple-animal flock investigation during an abortion cluster
- Necropsy and broader infectious disease rule-outs
- Intensive treatment for severely ill ewes or weak live-born lambs
- Detailed herd-level risk assessment with repeat monitoring and reproductive management planning
- Consultation with a veterinary diagnostic specialist or production medicine service
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Neosporosis in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- What samples should I save right now, and how should I store the fetus and placenta before submission?
- Based on this ewe's stage of pregnancy and the flock history, how likely is neosporosis compared with toxoplasmosis or other abortion causes?
- Which diagnostic tests are most useful for my flock, and what cost range should I expect for each option?
- Should we test only the affected ewe, or do you recommend flock-level screening or an abortion panel?
- What immediate steps should I take with dogs, feed storage, water sources, and carcass disposal?
- Is this ewe likely to recover well, and when would you consider breeding her again?
- Do any other ewes need closer monitoring during this lambing season?
- What signs would mean I should call you urgently after an abortion, such as fever, retained placenta, or weak lambs?
How to Prevent Neosporosis in Sheep
Prevention centers on breaking the parasite life cycle. Keep farm dogs, stray dogs, coyotes, and other canids away from stored feed, hay, grain, mineral tubs, water sources, and lambing areas. Clean up spilled feed promptly, and use storage methods that reduce contamination from feces.
Do not allow dogs to eat placentas, aborted fetuses, dead lambs, or raw tissues from sheep or wildlife. Dispose of reproductive tissues and carcasses quickly and safely according to your vet's advice and local rules. This step matters because infected tissues can help maintain the parasite on the farm.
Good abortion response is also prevention. Any aborted fetus or placenta should be handled as potentially infectious until your vet says otherwise. Isolate affected ewes when practical, wear gloves, disinfect equipment, and keep clear records of breeding dates and losses. If your flock has repeated abortions, ask your vet for a broader reproductive disease plan, because neosporosis is only one of several important causes of abortion in sheep.