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Sheep babesiosis
Babesiosis, which many breeders call piroplasmosis, is caused by a microscopic parasite that multiplies inside red blood cells until they burst. It is inoculated by the bite of a tick. Unlike other diseases transmitted by ticks, this one st...
What is it?
Babesiosis, which many breeders call piroplasmosis, is caused by a microscopic parasite that multiplies inside red blood cells until they burst.
It is inoculated by the bite of a tick. Unlike other diseases transmitted by ticks, this one starts quickly: a few days to two weeks after the bite, the animal can go from a normal state to a serious state in less than two days.
The destruction of red blood cells occurs directly in the vessels: the released hemoglobin passes into the urine, which takes on a red-brown color, compared by breeders to coffee or wine. This is the sign that gives the disease its popular name.
Key point
Babesiosis progresses within a few days. Fever and dark urine in a sheep during tick season warrant a call to the veterinarian the same day: a few hours change the prognosis.
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:
Sudden, high fever at the very beginning, before other signs. This is the time when the treatment works best, and it is also the time when the breeder does not yet see anything spectacular.
Urine dark, red-brown to almost black. This sign is very evocative but it is not always present immediately: do not wait for it to call.
Mucous membranes at first red and congested, then frankly pale as the blood is destroyed.
Yellow discoloration of the mucous membranes and the white of the eye, which sets in within one or two days.
Slaughtered, immobile animal, which no longer ruminates, refuses to eat and separates from the herd.
Rapid breathing, fast heartbeat, tremors.
Dehydration, animal that no longer drinks, scanty urine in severe forms: this is a sign that the kidneys are failing.
Lying animal that never gets up, then dies within a few days if nothing is done.
Discrete forms exist in animals from a region where the disease is constantly circulating: simple temporary fever and decline in condition, without colored urine.
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 parasite is inoculated by the saliva of the tick when it attaches and engorges. It reaches the blood and enters the red blood cells, where it divides until they rupture.
With each wave of rupture, the animal loses blood from the inside and releases hemoglobin, which explains both the anemia, the color of the urine and the yellow tint of the mucous membranes.
The kidneys filter this excess hemoglobin and become damaged. It is often damage to the kidneys, and not the parasite itself, which kills the animal.
Some ticks transmit the parasite to their offspring: a plot can therefore remain dangerous from one season to the next even without a carrying animal.
In areas where the disease circulates year-round, animals born there become immunized young and remain protected as long as they continue to be exposed. This explains a puzzling phenomenon: it is often animals purchased elsewhere, or those from a herd carefully treated against ticks and then brutally exposed, which produce fatal forms.
Tick season, spring and autumn, with an increase after the rains.
Bushy paths, forest edges, hedges, wastelands, edges of low walls and old sheepfolds.
Animals purchased in a tick-free zone and introduced into a tick-bearing zone: these are the most exposed to serious forms.
Adult animals that have never encountered the parasite, unlike young ones born there who become discreetly immunized.
Sudden interruption of a tick control program in a herd accustomed to being protected: the animals lose their immunity to exposure and become vulnerable.
Stress, transport, giving birth, undernutrition, other parasites: anything that weakens promotes a severe form.
Animals that have had their spleen removed or have another blood disease.
Transmission
Only by tick bite. There is no direct contagion between animals, neither through contact, nor through drinking water, nor through the air.
The tick must remain attached for a certain period of time before inoculating the parasite: removing ticks early and regularly really reduces the risk, even if it does not eliminate it.
Transmission by a dirty needle is possible but remains marginal compared to ticks.
The disease is not transmitted to humans under livestock conditions.
A herd can carry the parasite without causing visible cases: it is these animals which replenish the ticks.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian takes the temperature, examines the color of the mucous membranes and looks at the urine. A feverish sheep with red-brown urine in tick season is very orienting.
He looks for ticks on the animal: ears, under the tail, groin, armpits, udder and bursae are the places to examine as a priority. Not finding one doesn't rule anything out, as the tick responsible could have fallen off a long time ago.
A stained blood smear, examined under a microscope, shows the parasite inside the red blood cells and quickly confirms the diagnosis. It is a simple test that the veterinarian can perform early.
A blood test assesses the depth of the anemia and the condition of the kidneys, decisive information for the prognosis.
The veterinarian distinguishes babesiosis from other causes of dark urine in sheep, notably certain poisonings and certain deficiencies, and from other blood diseases transmitted by the same ticks, which are not treated in the same way.
The examination of a dead animal is very telling: enormous spleen, dark urine in the bladder, liver and kidneys of abnormal color. Do not make a dead animal disappear without talking to the veterinarian, this will protect the rest of the flock.
Treatment
There are blood-specific antiparasitics active against this parasite. They have nothing to do with the dewormers used against digestive worms and do not replace them: giving a dewormer to an animal suffering from babesiosis is of no use and wastes the hours that count.
The choice of product, route and timing is up to the veterinarian. These molecules are not harmless and no dose should be decided without it.
The deciding factor is the deadline. Treated from fever, an animal often does very well; treated once lying down with damaged kidneys, he can die despite an eliminated parasite.
Supportive care is a big part of the result: shade, absolute calm, clean water within immediate reach, palatable food. An infusion may be necessary to protect the kidneys; it is the veterinarian who puts it in place.
A blood transfusion may be considered for a valuable, very anemic animal.
Do not move, chase or charge an affected animal: the effort kills very anemic animals. Treat on site.
Remove the ticks present on the animal and examine the other animals in the group the same day: when a case occurs, others are often incubating.
The waiting periods for meat and milk are specific to each product and must be requested from the veterinarian before any slaughter or milking.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
The fight against ticks is the only truly effective prevention, and it protects at the same time against anaplasmosis, theileriosis and other agents inoculated by the same bite. Anti-tick products exist in several families and in several forms, for external application or injection: the schedule is discussed with the veterinarian according to the region and the season, not randomly.
Inspect the animals by hand, regularly during the season, paying particular attention to the ears, groin, underside of the tail, udder and bursae.
Remove the ticks carefully, unhooking them completely and without crushing them. Do not burn them, do not tear them off with your bare hand or put any product on them: an attacked tick regurgitates and increases the risk of inoculation. Wear gloves, as some ticks transmit serious diseases to humans unrelated to those of sheep.
Also treat buildings: cracks in walls, under feeders and old wood harbor ticks from one season to the next.
Clear brush around sheep pens, containment corridors and water points where animals stay.
Quarantine any purchased animal, rid it of ticks and monitor its temperature for the first few weeks.
Be particularly vigilant when changing your behavior: introducing animals from a tick-free zone, or suddenly stopping an anti-tick program, are two situations that produce crises.
Possible complications
Renal failure: this is the most feared complication. The animal may die even though the parasite has been eliminated.
Profound and prolonged anemia, with very slow recovery.
Abortion in pregnant ewes, weak lambs at birth.
Collapse of milk production.
Sudden death during exertion, sorting or transport in a very anemic animal.
In some cases, damage to the nervous system with animals staggering or convulsing.
Simultaneous occurrence of other diseases transmitted by the same tick, which confuses the picture and worsens the prognosis.
When to see a veterinarian
An animal urinates red-brown or almost black: call the veterinarian the same day, it is an emergency.
An animal has a fever, refuses to eat and no longer chews the cud during tick season.
The mucous membranes are pale or yellow.
An animal is down, isolated, breathing quickly or refusing to get up.
A recently purchased pet becomes ill within a few days of arriving on a tick trail.
Several animals from the same batch deteriorate within a few days after a period of high tick presence.
An animal dies suddenly on pasture during tick season: have the dead animal examined, this protects the rest of the herd.
Prognosis
Treated at the first signs, before the urine becomes dark, the animal most often heals well and recovers in a few weeks.
Treated late, with kidneys already affected, the prognosis becomes poor despite correct treatment.
Cured animals maintain protection for a certain time, provided they remain exposed to ticks: this is the paradox of this disease, regular exposure protects as much as it threatens.
At the herd level, everything depends on the fight against ticks and the speed of calling the veterinarian: the same disease causes very different damage depending on whether you call on the first or third day.
Frequently asked questions
My sheep is urinating red, is it blood?
Most often, it is not whole blood but the pigment from destroyed red blood cells, which gives a homogeneous red-brown urine. In a sheep in tick season, this primarily suggests babesiosis. In all cases, abnormally colored urine requires a call to the veterinarian the same day.
I didn't find any ticks on the animal: is this still possible?
Yes, absolutely. The responsible tick bit one to two weeks earlier and has long since detached itself. The absence of a tick at the time of examination never rules out the diagnosis.
Can a dewormer cure this disease?
No. The parasite is in the blood, not in the intestine: dewormers have no effect on it. You need a specific antiparasitic medication, prescribed by the veterinarian. Wasting two days trying a dewormer often costs the animal.
Should the entire herd be treated when one animal is affected?
It's up to the veterinarian to decide. What is certain is that one case indicates high tick pressure: the other animals must be examined the same day, their temperature monitored, and the question of tick control asked immediately for the entire herd.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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