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Bovine neosporosis
Neosporosis is a parasitic disease caused by a microscopic parasite, Neospora caninum, which settles in the tissues of the cow and crosses the placenta to reach the fetus. It does not make the adult cow visibly ill: its only manifestation,...
What is it?
Neosporosis is a parasitic disease caused by a microscopic parasite, Neospora caninum, which settles in the tissues of the cow and crosses the placenta to reach the fetus.
It does not make the adult cow visibly ill: its only manifestation, but it is major, is abortion. It is one of the leading causes of infectious abortion in cattle worldwide.
The dog plays a central role in the parasite cycle: it is in him that the parasite reproduces and it eliminates in its excrement the forms which will contaminate the cattle.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
In adult cows: no signs of disease. She eats, produces and behaves normally.
Abortion, most often in the middle of gestation, but possible over a long period. It may be an isolated case, repeated cases in the herd, or a wave of abortions over a few weeks.
The fetus is often expelled dead and partially decomposed; it can also be mummified or reabsorbed, the cow then simply appearing empty.
Calves born alive but infected: most are normal at birth and will remain so in appearance.
A minority of calves are born weak, with difficulty standing, a staggering gait, paralysis of one or more limbs, deformed limbs or eye abnormalities.
Growth retardation in some infected calves.
Cows that come into heat repeatedly, the embryo having been lost very early.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The infection is caused by the parasite Neospora caninum, which lodges in the cow's tissues and reactivates during pregnancy.
Reactivation of the parasite during gestation causes its passage to the fetus; it is this passage that causes abortion or the birth of an infected calf.
A first infection during gestation, from food contaminated by dog feces, also causes abortion, sometimes in waves within a herd.
Presence of dogs with access to food storage areas, silos and pastures.
Dogs or wild carnivores with access to placentas, runts and carcasses.
Purchasing animals without knowing their neosporosis status.
Conservation of heifers from infected mothers, which perpetuates the disease in the herd.
Food stored in the open air, unprotected silos, water points accessible to dogs.
Transmission
Two paths coexist and do not fight each other in the same way.
Transmission from mother to calf during pregnancy is by far the most common: an infected cow transmits the parasite to its fetus, often at each pregnancy. Females thus infected are born carriers and will in turn transmit: the disease then becomes established permanently in the lines of the herd.
Transmission through food comes from dogs: farm dogs, stray dogs or foxes consume placentas, aborts or infected raw meat, then eliminate the parasite in their excrement. These excrements contaminate the fodder, silage, ration or water, and the cows become infected while eating.
There is no direct transmission from one cow to another by simple contact, nor by the bull.
The parasite is not transmitted to humans: the consumption of milk and meat does not present a known risk of neosporosis for people.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Before any abortion, notify the veterinarian: the diagnostic process must be carried out by him, and the abortion is an event to be declared as part of the surveillance of reproductive diseases.
The diagnosis is based on blood tests looking for antibodies in the cow, and on examination of the fetus and its placenta in the laboratory.
Analyzing the runt is particularly useful: keep it cool, away from dogs and cats, until treatment.
At the same time, the veterinarian rules out other causes of abortion - some of which are transmissible to humans and require immediate precautions. This is yet another reason to never handle a runt with your bare hands.
In an affected herd, comprehensive blood screening makes it possible to identify infected lines and guide renewal decisions.
Treatment
There is no treatment to rid an infected cow of the parasite. A positive cow remains so all its life.
The care is therefore collective and based on herd management, not on medication.
On heavily affected farms, the veterinarian helps decide which cows to keep and which lines not to keep for renewal, taking into account the screening results.
Infected cows can sometimes be kept for milk production while avoiding keeping their daughters for reproduction.
A cow that has aborted must be isolated during examinations, because other causes of abortion are contagious.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is based above all on the separation between the dogs and the feeding of the herd.
Prevent all access of dogs to silos, fodder reserves, troughs and water troughs.
Collect and dispose of placentas, aborts and dead calves immediately. Never leave them accessible to dogs, cats or wild animals, and never feed them.
Never feed raw meat to farm dogs.
Limit the number of dogs present and avoid stray dogs wandering around the farm.
Do not keep females born to mothers known to be infected for breeding.
Check the status of purchased animals before their introduction into the herd.
No vaccine is available: hygiene and management of renewal are the only levers.
Possible complications
Repeated abortions in the same cow from one pregnancy to the next.
Significant economic losses: lost calves, lactations not started, lengthening of intervals between calving, culling.
Sustainable establishment of the infection in the herd by replacement females born infected.
Live infected calves showing nervous disorders or slowed growth.
When to see a veterinarian
Your cow has aborted: call the veterinarian, regardless of the gestation period.
Several abortions occur in the herd over a short period of time.
A calf is born weak, unable to get up, staggering or paralyzed.
Cows repeatedly come into heat after being confirmed pregnant.
Always handle an abortion with gloves and wash your hands thoroughly: other causes of abortion can be transmitted to humans.
Prognosis
An infected cow remains infected for life and risks aborting or transmitting the parasite with each pregnancy, without any treatment being able to rid it of it.
Many infected cows still carry full-term pregnancies and give birth to live calves, which are often infected in their turn.
At the herd level, the situation clearly improves when the two levers are applied together: avoiding contamination by dogs and not keeping the daughters of infected mothers.
Frequently asked questions
Should I get rid of my farm dog?
No. This involves preventing it from accessing the herd's food and denying it access to placentas, aborts and raw meat. A well-fed dog, kept away from silos and troughs, poses no particular risk.
Is milk and meat from an infected cow dangerous for my family?
Neosporosis is not known to be transmitted to humans. The usual hygiene and cooking precautions are of course still required, as with any animal product.
Is there a vaccine?
No, there is no vaccine available against bovine neosporosis. Prevention relies entirely on hygiene, dog management and selection of replacement animals.
My cow aborted once: will she abort at each pregnancy?
Not necessarily. Many infected cows go on to carry full-term pregnancies, but the calf born may be a carrier. This is why we avoid keeping our daughters for reproduction.
References
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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