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Animal trypanosomiasis
Animal trypanosomiasis is a blood disease caused by microscopic parasites that circulate in the blood and tissues. It is transmitted by biting flies. In sub-Saharan Africa, the tsetse fly is the main vector; elsewhere, including in North Af...
What is it?
Animal trypanosomiasis is a blood disease caused by microscopic parasites that circulate in the blood and tissues.
It is transmitted by biting flies. In sub-Saharan Africa, the tsetse fly is the main vector; elsewhere, including in North Africa and the Middle East, transmission occurs mainly mechanically through horseflies and stable flies which pass from one animal to another.
It affects cattle, but also camels, horses and donkeys, with sometimes very different forms depending on the species.
Key point
Chronic and debilitating disease, mandatory reporting in certain countries for some of its forms. The diagnosis must be made by the veterinarian before any treatment.
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:
Fever that comes and goes, rather than continuous fever: it often goes unnoticed.
Progressive anemia: mucous membranes of the eyes and gums becoming increasingly pale.
Continuous weight loss despite a correct diet, dull and pitted coat.
Despondency, animal that stays behind, fatigue with effort.
Enlarged lymph nodes, palpable under the skin.
Edema of the lower parts: limbs, under the stomach, pocket under the jaw.
Fall in milk production, abortions, difficulties in obtaining a pregnancy.
Tearing and clouding of the eye in some animals.
In advanced forms, extreme weakness and nervous signs, with an animal that ends up not getting up again.
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 culprits are microscopic parasites of the Trypanosoma genus, which live in blood and tissues.
Several species exist, with different severity depending on the region of the world and the animal species affected.
These parasites constantly change their appearance in relation to the animal's defenses, which allows them to evade the immune system. This is also the reason why no vaccine exists.
Anemia and weakening of defenses are the main consequences of their presence.
Areas with a high density of biting flies and horseflies, particularly around waterholes and wetlands in the warm season.
The introduction of animals from regions where the disease is circulating, without quarantine or screening.
Neighborhood or mixing with camels, often carriers.
Group interventions on the herd carried out without changing the needle.
Animals that are weakened, undernourished, or subjected to intense work.
Herd movements and transhumance.
Transmission
By the bite of insects: tsetse fly in its distribution area, horseflies and biting flies elsewhere.
In mechanical transmission, the insect simply transports infected blood from one animal to another: the closer the animals are and the more flies, the more the disease circulates.
By equipment soiled with blood, in particular needles reused from one animal to another: this is an avoidable and often underestimated route.
From mother to cub in some cases.
There is no contagion through simple contact or through milk.
Animal movements, particularly camels, play a major role in introducing the disease into a disease-free region.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Call the veterinarian if you experience any unexplained weight loss accompanied by pale mucous membranes, especially in an area where the disease is known.
Diagnosis is by examining the blood under a microscope, where the parasite can be seen, and measuring the degree of anemia.
The parasite is not always detectable at any given time: repeated examinations or more sensitive laboratory tests are sometimes necessary.
Serological and molecular tests exist in specialized laboratories, particularly to detect carrier animals.
Inform the veterinarian of the origin of the animals, recent movements and the presence of camels in the environment.
In several countries, certain forms of the disease must be declared to the veterinary services: find out more.
Treatment
Specific treatments, called trypanocides, exist. Their use is strictly the responsibility of the veterinarian.
Parasite resistance to these treatments is a proven problem, fueled by repeated, poorly targeted or incomplete uses. Treatment carried out without diagnosis or follow-up can do more harm than good in the long term.
Treatment must be accompanied by supportive care: rest, quality food, clean water, and management of other parasites that aggravate anemia.
A treated animal may relapse if it remains exposed to flies: treatment alone does not solve anything without vector control.
Waiting times for milk and meat must be respected; only the prescribing veterinarian can tell you these.
Never use a trypanocide on your own or leftover treatment: this is the best way to select resistant parasites in your area.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Fight against biting flies and horseflies: manure management, sanitation of wet areas around buildings, protection of animals during periods of high insect activity, on veterinary advice.
One needle per animal, and disinfection of equipment between animals.
Quarantine and screening of all introduced animals, particularly camels and animals coming from areas where the disease is circulating.
Monitoring body condition and color of mucous membranes during routine manipulations.
Correct feeding and watering: a healthy animal tolerates the infestation much better.
There is no vaccine, due to the parasite's ability to evade the body's defenses. Prevention therefore relies entirely on vectors, hygiene and control of animal movements.
Possible complications
Severe anemia and extreme weight loss, with an animal that ends up not getting up again.
Infertility, abortions, delayed reproduction.
Sustainable decline in milk production and the working capacity of draft animals.
Weakening of immune defenses, with secondary infections and a reduced response to vaccinations.
Nervous signs in advanced forms.
Mortality, especially in untreated or late treated animals.
When to see a veterinarian
An animal loses weight continuously without obvious cause, with a dull coat.
The mucous membranes of the eyes or gums are pale.
You observe swollen lymph nodes or edema of the limbs and under the stomach.
Milk production drops and abortions or pregnancy failures increase in the herd.
Several animals show the same signs after the introduction of animals from elsewhere.
An animal is very weak or can no longer get up: it is an emergency.
Prognosis
Diagnosed early and treated under veterinary supervision, the disease is cured in a good number of cases, but recovery takes time.
In a very emaciated and anemic animal, the prognosis is guarded.
Without fighting against biting flies, reinfestations are the rule and the herd remains permanently penalized.
The most serious consequences are often chronic: less milk, fewer calves, animals that do not finish.
Frequently asked questions
Is this disease the same as sleeping sickness in humans?
No. Human sleeping sickness is caused by different parasites present in equatorial Africa. The forms which affect cattle, camels and horses are animal diseases: they are not transmitted to the breeder through contact, milk or meat.
Can my camels contaminate my cows?
Yes, indirectly. Camels are often carriers, and biting flies carry the parasite from one animal to another, including between species. Sharing water points and enclosures increases the risk.
Why is there no vaccine?
Because the parasite constantly changes its appearance in relation to the animal's defenses: the acquired immunity no longer recognizes it. It is for this reason that prevention is based on the fight against flies, needle hygiene and the control of introduced animals.
Can I preventively treat my entire herd?
This is not a decision to make alone. Repeated and untargeted use of trypanocides selects for resistant parasites, a problem that is already very real. The strategy is defined with the veterinarian, depending on local pressure and screening.
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 09 August 2026
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