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Sarcosporidiosis
Sarcosporidiosis is caused by microscopic parasites which settle permanently in the muscles of sheep and goats, forming small cysts. Like coenurosis and hydatid cyst, it is based on a two-animal cycle: the sheep becomes infested from the ex...
What is it?
Sarcosporidiosis is caused by microscopic parasites which settle permanently in the muscles of sheep and goats, forming small cysts. Like coenurosis and hydatid cyst, it is based on a two-animal cycle: the sheep becomes infested from the excrement of a carnivore, here the dog or the cat, and the carnivore becomes infested by eating raw sheep meat. In the vast majority of cases, the sheep shows nothing at all: the cysts are discovered upon inspection of the meat, sometimes visible to the naked eye in the form of small elongated white grains, particularly in the esophagus and the diaphragm. An acute form exists, however, when an animal swallows a large quantity of parasites all at once, generally from fodder or water massively soiled by dog excrement. It then causes fever, anemia, abortions and sometimes deaths. It is therefore a primarily economic disease, through the seizures and devaluation of carcasses, but which recalls the same lesson as the hydatid cyst: raw sheep meat should never be given to dogs and cats.
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:
Most often, no signs: the animal lives, grows and produces normally with its muscle cysts.
In the acute form, a few weeks after massive contamination: fever, marked depression, refusal to eat.
Pale mucous membranes reflecting anemia, animal that gasps at the slightest effort.
Muscle weakness, animal that has difficulty getting up, walks stiffly and remains lying down.
Rapid weight loss in animals that were in good condition.
Loss of wool in patches in some cases, a few weeks after the acute episode.
Abortions in pregnant ewes, lambs born weak or stillborn.
In chronic and heavy infestations: poor condition, slowed growth, animals that do not compare with the rest of the lot.
Deaths can occur in the most severe acute forms.
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 parasites complete their cycle between two species: the sheep, where they form cysts in the muscles, and a carnivore, dog or cat, where they reproduce in the intestine.
The carnivore becomes infected by eating raw sheep meat containing cysts: abandoned carcasses, slaughter waste, remains of raw meat given as rewards.
It then eliminates microscopic infesting forms in its excrement, in large quantities and for a long time, without appearing ill.
The sheep swallows them with fodder, stored food or water contaminated by these excrement.
The parasites pass into the blood, cross the vessels - it is this phase which causes fever, anemia and abortions in the acute form - then reach the muscles where they encyst.
Once the cysts are formed, they remain in place for the entire life of the animal and generally do not cause anything further.
Farm dogs and cats who sleep in sheds, on fodder reserves or near troughs are at the heart of the problem: they deposit their excrement directly on the herd's feed.
Dogs and cats having access to fodder reserves, silos, storage sheds, troughs and water troughs.
Habit of giving raw meat, offcuts or leftovers from sheep slaughter to dogs and cats.
Carcasses of dead animals left accessible to carnivores.
Farm slaughter without waste management, informal killings.
Storage of fodder on the ground, in premises open to animals.
Numerous stray dogs around the farm.
Young animals or animals in poor condition, more sensitive to acute forms.
Open-air water troughs accessible to dogs.
Transmission
There is no direct contagion from one sheep to another: without passage by a dog or a cat, the cycle stops.
Contamination of the herd occurs only by swallowing carnivore excrement present on fodder, in troughs, in water or on stored food.
The forms emitted are immediately infective and last a long time in dry fodder stored under cover.
A single dog installed on a pile of hay can massively contaminate a reserve intended for the entire herd: this explains the acute forms which affect several animals at the same time.
Stray dogs and uncontrolled farm cats maintain the cycle just like herding dogs.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
In living animals, there is no simple and common examination to confirm the disease: the cysts are not visible from the outside and the animal most often shows nothing.
In the acute form, the veterinarian relies on the clinical picture and the context - several animals affected at the same time, fever, anemia, abortions, after the distribution of a given batch of fodder - and rules out other causes of abortion and anemia in the herd, several of which are contagious or transmissible to humans and require immediate measures.
Blood tests may be done to evaluate for anemia and to look for other causes.
The diagnosis is most often confirmed after death or at the slaughterhouse, by examining the muscles, particularly the esophagus, diaphragm and heart.
Faced with a series of abortions in a flock, the veterinarian's priority approach is not to think about this parasite but to first rule out major abortive diseases in the ewes. Do not touch it without protection and seek advice on the samples to take.
A farmer who finds small white grains lying in the muscles of a slaughtered animal should speak to the veterinarian or veterinary services rather than deciding the fate of the carcass himself.
Treatment
There is no practical and effective treatment to remove cysts already established in a sheep's muscles.
In acute forms, treatment is symptomatic and decided by the veterinarian: support for the animal, rest, quality food, treatment of anemia and inflammation depending on the condition. Certain products can be used in a specific context, on prescription and on animals from an exposed batch, but this decision rests solely with the veterinarian.
No dose or product should be decided on your own initiative.
The useful response is not medication: it consists of immediately removing suspect fodder from distribution, protecting carnivore reserves and dealing with the issue of dogs and cats on the farm.
Animals affected by an acute form which recover keep their muscle cysts for life, without consequences for them, but these cysts can lead to a devaluation of the carcass at slaughter.
As with hydatid cyst and whirling disease, the real measure is to never give raw sheep meat to a dog or cat.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Never give raw sheep or goat meat, cutting scraps, or slaughter waste to dogs and cats. Meat intended for a dog must be cooked.
Protect fodder and food reserves: closed premises, raised storage, tarpaulins, doors kept closed, so that neither dogs nor cats can sleep or defecate there.
Cover or protect troughs and drinkers, and immediately clean any food soiled with feces rather than handing it out.
Collect dead animals quickly and have them disposed of according to regulations.
Limit the presence of stray dogs around the farm, sheds and water points.
Regularly deworm farm dogs on veterinary prescription: this measure does not directly target this parasite, but it is part of the same management of dogs which protects the herd and the family from hydatid cyst and whirling disease.
Supervise slaughter on the farm and plan in advance for the destruction of waste.
Monitor slaughterhouse returns: repeated observations on carcasses indicate an active cycle on the farm.
Possible complications
Abortions and losses of lambs during acute forms.
Severe anemia and mortality in the most affected animals.
Slow recovery and sustained loss of status in survivors of acute illness.
Devaluation or seizure of carcasses when muscle cysts are numerous and visible.
Slow growth and reduced production in heavy infestations.
Persistence of the problem from one year to the next as long as carnivores have access to forage.
When to see a veterinarian
Several ewes abort within a short period of time: this is always a situation to be examined without delay, several causes of abortion in the flock are serious and some are transmissible to humans.
Animals have fever, pale mucous membranes and marked weakness shortly after a change of forage.
An animal has difficulty getting up or remains lying down.
Patchy shedding of wool appears in several animals without obvious skin cause.
You discover small white grains lying in the muscles or esophagus of a slaughtered animal: seek advice rather than deciding the fate of the carcass alone.
Dogs or cats are sleeping on your feed reserves: talk to the veterinarian before a problem appears.
Prognosis
The silent forms, by far the most common, affect neither the health nor the longevity of the animal: only the carcass can be devalued.
Acute forms have a guarded prognosis: the most affected animals can die, pregnant ewes often abort, and survivors take time to recover.
At the herd level, the prognosis is excellent once carnivores no longer have access to fodder and no longer receive raw meat: contamination stops, and young generations are born in a sanitized environment.
Frequently asked questions
Can I eat meat from a sheep that has these small cysts?
The decision rests with the veterinarian or the meat inspector, who assess the importance of the damage: a severely affected carcass is discarded. The species of this parasite which affect sheep are not recognized as transmissible to humans, but the meat must in any case be well cooked, and a suspect carcass must be presented to a professional rather than consumed without advice.
Can I give leftover cutouts to my dog?
Not raw. It is exactly this action that maintains the cycle: the dog develops the parasite, sows infective forms in the fodder and recontaminates the herd. The same gesture also transmits the tapeworm responsible for the hydatid cyst, which is much more serious for the family. If you feed your dogs mutton, it must be cooked.
My sheep aborted, is it necessarily this parasite?
No, and we should definitely not stop at this hypothesis. Several diseases cause abortions in sheep, some of which are transmitted to humans and require immediate precautions for people handling abortion products. A series of abortions must always be subject to veterinary examination and sampling.
How do I prevent my dogs from contaminating feed?
By closing storage areas, raising or covering reserves, covering troughs and not letting dogs sleep in sheds. It is a simple measure, without medication costs, and which solves most of the problem.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
EFSA — Autorité européenne de sécurité des aliments
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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