bacterial disease Reindeer, Caribou Transmissible to humans

Reindeer brucellosis

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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?

Reindeer brucellosis is an infectious disease caused by a bacteria of the genus Brucella, mainly Brucella suis biovar 4 in this arctic and subarctic species. It mainly affects the reproductive system and causes abortions, infertility and sometimes joint damage. It is a disease present in wild or farmed reindeer and caribou in northern regions (Scandinavia, Russia, North America). It also represents a risk for humans, particularly hunters and breeders who handle carcasses.

Key point

Mandatory notifiable disease in many countries due to its zoonotic nature and its economic impact on livestock farming.

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:

Abortion Vulvar discharge Infertility Swollen or missing testicle Lameness Swelling Fatigue Retained placenta Difficult birthing

In females, the most visible sign is abortion, often at the end of gestation, sometimes accompanied by abnormal vulvar discharge. Some females retain their placenta after giving birth or have difficulty giving birth normally. Infertility or repeated reproductive failures are common.

In males, swelling of one or both testicles may be observed, sometimes accompanied by pain.

Both sexes can develop joint swelling or lameness related to inflammation of the joints or bursae. A general state of fatigue or depression may accompany the infection, but many infected animals show no visible signs for a long time.

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 disease is caused by a bacteria of the Brucella genus, mainly Brucella suis biovar 4 in reindeer, a variant adapted to Arctic deer. This bacteria preferentially settles in reproductive tissues and certain lymph nodes.

Semi-domestic herds in close contact with infected wild reindeer are at greater risk. The concentration of animals during gathering or giving birth favors the spread. Geographic areas where the disease is endemic in wildlife (parts of Siberia, Alaska and Scandinavia) are at increased risk. Contact with wild boars or pigs infected with a close strain can also play a role.

Transmission

Transmission occurs mainly through direct contact with birthing products (placenta, fetal fluids, abortions) which contain a large quantity of bacteria. The ingestion of food or water contaminated by these secretions is a major route of contamination between reindeer. The bacteria can also pass through the mucous membranes or through small skin wounds. Sexual transmission is possible. Humans are mainly contaminated by handling infected carcasses, by cutting up an animal or by contact with blood or viscera, more rarely by consuming undercooked meat or unpasteurized products.

Diagnosis and care

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

The veterinarian relies on the history of the herd, clinical signs (abortions, joint or testicular swelling) and above all on serological blood tests which look for antibodies against Brucella. Confirmation may require isolation of the bacteria from collected tissues (placenta, lymph nodes, joint fluid) in a specialized laboratory, because handling this bacteria requires special precautions due to the risk to humans.

Treatment

There is no antibiotic treatment recognized as effective and reliable to eliminate the bacteria in infected reindeer, the bacteria lodging in areas that are difficult for medicines to access. Health management is therefore essentially based on the identification and removal of positive animals from the herd rather than on individual curative treatment.

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

Prevention

Prevention is based on serological surveillance of herds and the elimination of positive animals. It is necessary to isolate females who abort and carefully eliminate abortion products, which are very contaminating. Avoiding mixing with wild reindeer or caribou of unknown health status limits the risks. For people handling carcasses, wearing gloves and strict hygiene measures during evisceration reduce the risk of human contamination. No vaccine is currently available and validated for this species.

Possible complications

In reindeer, the disease can lead to lasting infertility, repeated abortions and chronic debilitating joint damage. In humans, untreated brucellosis can develop into a chronic form with prolonged fatigue, joint pain and damage to various organs (heart, nervous system, liver).

When to see a veterinarian

One or more abortions have occurred in the herd.

A male has abnormal swelling of one testicle.

Animals show persistent lameness or joint swelling without obvious traumatic cause.

A person who has handled a reindeer carcass develops a prolonged fever or unexplained joint pain.

Transmission to humans

Reindeer brucellosis is transmissible to humans, primarily through contact with blood, viscera or abortion products during carcass handling or evisceration. In humans, it causes undulating fever, sweating, intense fatigue and joint pain that can become chronic if the disease is not treated quickly. Hunters, breeders and people working in slaughtering are the most exposed and must use appropriate protection.

Prognosis

The individual prognosis is reserved for reproductive function, the infection often being chronic and spontaneous recovery rare. The adult animal's vital prognosis is generally not directly affected, but the breeding value is greatly reduced. At the herd level, the disease can have a significant economic impact if left uncontrolled.

Frequently asked questions

Is meat from an infected reindeer dangerous to eat?

Thoroughly cooking the meat destroys the bacteria and greatly reduces the risk. The main danger comes mainly from handling raw carcasses, blood and viscera, not from well-cooked meat.

Can we treat a reindeer with brucellosis?

There is no reliable antibiotic treatment to cure an infected reindeer. Management is done by screening and removing positive animals from the herd.

How does a herd get brucellosis?

Most often by contact with the products of an abortion (placenta, fluids) from an infected female, or by mixing with wild reindeer carrying the bacteria.

Is there a vaccine to protect reindeer?

No, there is currently no validated and available vaccine to prevent brucellosis in reindeer.