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bacterial disease Sheep, Goat Transmissible to humans

Ovine tuberculosis

Tuberculosis is a chronic bacterial disease that forms hard nodules, called tubercles, in the lungs, lymph nodes and sometimes other organs. In sheep, it is rare: it is a species naturally not very receptive, and most of the control efforts...

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Zoonosis Prognosis FAQ Sources Affected species

What is it?

Tuberculosis is a chronic bacterial disease that forms hard nodules, called tubercles, in the lungs, lymph nodes and sometimes other organs.

In sheep, it is rare: it is a species naturally not very receptive, and most of the control efforts focus on cattle and, in certain regions, on goats, which are much more sensitive.

But rare does not mean unimportant. Tuberculosis is transmitted to humans, and a flock of sheep living in contact with infected cattle or wild animals can harbor and maintain the bacteria, going completely unnoticed.

Key point

Tuberculosis remains rare in sheep, but it is transmitted to humans, mainly through raw milk, and children are particularly vulnerable. Never consume or sell raw milk, and report to the veterinarian any animal that is losing weight or coughing for a long time: the suspicion must be reported to the veterinary services.

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:

Cough Weight loss Difficulty breathing Swollen lymph nodes Shortness of breath on exertion Fatigue Fever Reduction Fall in milk production Dull coat

The progression is slow and the signs are very discreet for a long time: many infected animals show absolutely nothing.

Progressive weight loss, despite a correct diet and in the absence of parasitism: this is the most constant sign.

Dry, intermittent cough that returns with exercise, change of weather or when gathering in a building.

Abnormal shortness of breath upon exertion, animals remaining behind the herd.

Breathing more and more difficult in advanced forms.

Enlarged lymph nodes, particularly under the jaw and at the entrance to the chest, palpable by the veterinarian.

Irregular fever, dull coat and wool, animal losing its condition.

Decreased milk production in lactating females.

Chronic diarrhea in digestive forms.

Death after a long period of wasting away, or accidental discovery of lesions at the slaughterhouse in an animal that appeared healthy. This discovery at the slaughterhouse is, in practice, the most common way in which the disease is identified in sheep.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

Infection by mycobacteria of the tuberculosis complex, including that mainly responsible for bovine tuberculosis.

These bacteria are very resistant in the outdoor environment, particularly away from light, in damp litter and dark buildings, where they survive for a long time.

Contamination most often occurs through the air, by breathing droplets emitted by an infected animal coughing, in a closed and poorly ventilated building.

It can also be caused by ingestion, by consuming contaminated food, water or milk.

Infected cattle constitute the main source for sheep, when the species coexist or share the same plots and water points.

Certain wild species can maintain the bacteria and contaminate pastures depending on the region.

The disease progresses more quickly if the animal is weakened by another disease, a deficiency or parasitism.

Mixed holdings where sheep and cattle share buildings, plots or water points, particularly if the cattle herd has experienced cases.

Closed, overcrowded and poorly ventilated buildings.

Purchase of animals without control or quarantine.

Gatherings, markets, fairs and transhumance.

Regions where bovine tuberculosis is still circulating, or where a wildlife reservoir is present.

Older animals, the disease taking years to develop.

Animals that are weakened, parasitized, deficient or suffering from other chronic diseases.

Family production and consumption of raw milk without heat treatment.

Transmission

The main transmission is respiratory, through the air, in confined spaces: closed buildings, crowded sheepfolds, transport.

Digestive transmission exists: contaminated water, food and especially milk, which explains the contamination of young people and humans who consume raw milk.

Sharing plots, water points and buildings with infected cattle is the most important factor in sheep.

Infected animals can shed the bacteria long before showing any signs: a herd can therefore be contaminated by an apparently healthy animal.

Animal movements, purchases and gatherings spread the disease between farms.

For humans, the most classic route is the consumption of raw milk and unpasteurized dairy products; the respiratory tract mainly concerns people working in close contact with infected animals.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Tuberculosis is never diagnosed based on signs alone: they are not characteristic and many chronic diseases of sheep resemble them.

The veterinarian first rules out the much more common causes of chronic weight loss and coughing in sheep: digestive and pulmonary parasitism, pulmonary adenomatosis, maedi-visna, caseous lymphadenitis, pasteurellosis, deficiencies.

Screening is based on tests carried out by the veterinarian in an official setting, including skin testing and blood tests. Their interpretation in sheep is more delicate than in cattle and is strictly the responsibility of the veterinarian.

Confirmation comes through the laboratory, on organ or lymph node samples.

Lesions discovered at the slaughterhouse are, in practice, the main gateway to diagnosis: this is why slaughterhouse returns should never be ignored.

Any suspicion must be reported to the veterinary services. The consequences, herd controls, movement restrictions and decisions concerning the animals are subject to the regulations in force and not a personal choice.

The veterinarian will systematically look for a link with a cattle herd or a source in the environment.

Treatment

There is no treatment for farm animals with tuberculosis.

It is not a question of cost or difficulty: treating animals would foster carriers, prevent the sanitation of livestock and pose a major public health risk, in particular by promoting bacteria resistant to drugs used in humans.

The action to be taken is defined by the veterinary services: it is based on screening, the elimination of animals recognized as infected, the control of movements and the sanitation of buildings.

Affected carcasses and organs are excluded from consumption at the slaughterhouse.

The role of the breeder is to report, cooperate with controls and apply hygiene measures: this is what protects his herd, his neighbors and his family.

Any antibiotic self-medication should be absolutely avoided in this context.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Avoid contact between uncontrolled sheep and cattle: separate buildings, separate plots, separate water points. This is the most important measure in small ruminants.

Only introduce animals of known origin and respect planned quarantines and controls.

Participate in screening campaigns and follow the instructions of veterinary services.

Properly ventilate buildings, avoid overcrowding, let light in: the bacteria survives poorly in light and dry air.

Clean and disinfect buildings, clean out litter, and leave a crawl space when possible.

Never consume or sell raw milk: pasteurization or boiling eliminates the risk. This point is essential for breeder families and for children.

Monitor slaughterhouse returns and seek advice from the veterinarian in the event of a seizure.

Maintain the herd in good general health: weakened animals develop disease more easily.

Report any animal that loses weight and coughs for a long time without explanation.

Possible complications

Slow decline and death of the affected animal.

Silent diffusion in the herd, a single animal can contaminate the others for months before being spotted.

Contamination of cattle on the farm, with the ensuing regulatory and economic consequences.

Seizures at the slaughterhouse and economic losses.

Restrictions on movement, blocking of sales and official measures on exploitation.

Human contamination, particularly children, through the consumption of raw milk: this is the most serious consequence and the reason for all surveillance.

When to see a veterinarian

An animal has been slowly losing weight for weeks without explanation, despite a good diet and controlled parasitism.

A dry cough persists in one or more animals, particularly during exercise or indoors.

Lymph nodes are swollen under the jaw or at the entrance to the chest.

The slaughterhouse notifies you of lesions or a seizure: contact the veterinarian even if the herd appears healthy.

Your neighboring cattle herd or yours have experienced cases of tuberculosis.

You consume raw milk from your animals: talk to the veterinarian, regardless of any sign of illness.

Transmission to humans

Animal tuberculosis is transmitted to humans and remains a public health concern in many regions.

The most common route of contamination is through food: consumption of raw milk and unpasteurized dairy products from infected animals. Children are particularly exposed and develop serious forms, particularly lymph node and digestive.

The respiratory tract mainly concerns people in close and prolonged contact with infected animals in confined spaces: breeders, shepherds, people working in construction, veterinarians, slaughterhouse staff.

In humans, the disease progresses slowly: persistent cough, long-term fever, night sweats, weight loss, fatigue, swollen lymph nodes. Medical treatment exists and it is effective, but it is long and requires to be followed to the end.

Anyone with a cough that lasts several weeks, with weight loss and fever, should consult a doctor and tell them that they are working with ruminants.

The most effective protective measure, by far, is to never consume raw milk: boiling the milk eliminates the food risk, including for other communicable diseases such as brucellosis and Q fever.

Ventilating buildings, avoiding confined spaces with coughing animals and washing your hands complete the protection.

Prognosis

In animals, the progression is always towards worsening: the disease does not heal spontaneously and cannot be treated.

An animal can, however, live a long time with limited lesions, contaminating those around it: it is this silent carriage which makes the disease difficult to eliminate.

At the scale of a herd and a territory, sanitation is possible: it is based on screening, elimination of infected animals and control of movements, and it has given good results in many regions.

The public health prognosis is directly linked to a simple habit: where milk is systematically boiled or pasteurized, food transmission to humans disappears.

Frequently asked questions

Does tuberculosis really exist in sheep?

It is rare, because sheep are not a very receptive species, but it does exist, especially when sheep live in contact with infected cattle. Its rarity does not diminish its importance: it is a disease transmissible to humans and subject to mandatory notification.

Can we treat a sheep with tuberculosis?

No, and it's not a question of means. Treating animals would maintain carriers, prevent herds from being sanitized and promote bacteria resistant to drugs used in humans. The course of action to be taken is determined by the veterinary services.

Can I drink my sheep's milk?

Not believed. Boiling milk is the most effective measure to protect your family, and it also protects you from the much more common brucellosis and Q fever. This is particularly important for children, who develop the most severe forms.

My sheep is coughing and losing weight, is it tuberculosis?

This is unlikely, because other much more common diseases give this picture in sheep: pulmonary parasites, adenomatosis, maedi-visna, caseous lymphadenitis. The vet will rule them out first. But chronic weight loss with cough should never be left without explanation.