Brucellosis of pinnipeds
Brucellosis of pinnipeds is an infectious disease caused by a bacteria of the genus Brucella, a variant adapted to marine mammals called Brucella pinnipedialis. It affects seals, sea lions and elephant seals, including southern and northern...
What is it?
Brucellosis of pinnipeds is an infectious disease caused by a bacteria of the genus Brucella, a variant adapted to marine mammals called Brucella pinnipedialis. It affects seals, sea lions and elephant seals, including southern and northern elephant seals. This bacteria mainly resides in the reproductive tract and lymph nodes. It is present in many wild populations around the world, often without causing visible signs.
Key point
Brucellosis of pinnipeds is a zoonosis to be particularly monitored by professionals in contact with marine fauna, due to the risk of transmission to humans when handling contaminated tissues.
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:
In elephant seals, the infection very often remains silent, without any detectable external signs.
When signs appear, we may observe abortions or premature births, progressive weight loss, unusual fatigue and sometimes fever.
The reproductive organs may be affected: swelling of the testicles in males, vulvar discharge in females, or reduced fertility.
Swollen lymph nodes may also be noticed upon close examination, as may internal lesions affecting the lungs or nervous system in some rarer cases.
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 pinnipedialis, a species specifically adapted to seals and sea lions. It can colonize the genital tract, udder, lungs and central nervous system of the infected animal.
Living in dense colonies favors transmission between individuals, particularly during periods of reproduction and parturition.
Direct contact with placenta, aborted fetuses or genital secretions from an infected animal greatly increases the risk.
Young animals and pregnant females seem more vulnerable to clinical forms of the disease.
The animal's general immune state, often weakened by stress, malnutrition or other infection, also plays a role.
Transmission
Transmission occurs mainly through direct contact with contaminated tissues, such as the placenta or aborted fetuses, as well as through genital secretions. Ingestion of contaminated prey or exposure to seawater shared by the colony may also play a role. Transmission from mother to offspring during gestation or breastfeeding is possible.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is based on blood samples to look for antibodies against Brucella, as well as bacterial cultures from suspicious tissues such as placenta, milk or lymph nodes.
Molecular biology techniques (PCR) also make it possible to identify the bacteria more quickly and precisely.
In wild animals, diagnosis is often made during population studies, necropsies or treatment of stranded animals.
Treatment
In wild animals, individual treatment is rarely implemented due to the practical difficulties of capture and monitoring.
In the context of care in a specialized center, prolonged antibiotic treatment may be considered by the veterinary team, under strict supervision.
Disease management at the population level mainly involves epidemiological surveillance rather than systematic individual treatment.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no vaccine available for this disease in pinnipeds.
Prevention is mainly based on monitoring wild populations and limiting human contact with sick or dead animals.
For professionals handling these animals (biologists, keepers, veterinarians), wearing personal protective equipment is essential when handling reproductive tissues, placentas or cadavers.
Good hygiene of hands and equipment after any contact with an elephant seal, alive or dead, limits the risk of transmission.
Possible complications
Possible complications include long-term infertility, recurrent abortions, chronic infections of the joints or nervous system, and general weakness leading to other opportunistic diseases.
When to see a veterinarian
An elephant seal found emaciated, listless or having difficulty moving.
Observation of an abortion, fetus or placenta on a beach frequented by these animals.
Presence of abnormal swellings in the genitals or lymph nodes.
Any human contact with suspicious tissue or a dead animal must be the subject of rapid medical attention.
Transmission to humans
Brucella pinnipedialis can infect humans, although documented cases remain rare. Transmission occurs primarily through direct handling of contaminated tissues, bites, or exposure to aerosols during necropsies. In humans, the infection can cause fever, joint pain and prolonged fatigue. Anyone who has been in contact with a sick or dead pinniped should seek medical attention and report this exposure.
Prognosis
The prognosis varies depending on the severity of the attack. Many infected animals remain carriers without ever developing visible clinical disease. When clinical signs appear, notably reproductive or neurological complications, the prognosis becomes more guarded, especially in the absence of possible treatment in the wild.
Frequently asked questions
Is pinniped brucellosis common in elephant seals?
Serological studies show that exposure to Brucella is quite widespread in some wild populations, but most infected animals show no visible signs of illness.
Can an infected elephant seal transmit the disease to humans?
Yes, a risk exists especially during direct contact with reproductive tissues, a placenta or during a necropsy. Wearing protective equipment is recommended for exposed professionals.
Can we treat a wild elephant seal with brucellosis?
Individual treatment is very difficult to implement in a wild animal. Management is mainly based on monitoring and, in a specialized center, on possible antibiotic treatment supervised by veterinarians.
How do you know if an elephant seal carries the bacteria?
Only blood tests or laboratory analyzes carried out by wildlife specialists can confirm an infection, because clinical signs are often absent or not very specific.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
CDC — Centers for Disease Control and Prevention
Content reviewed by the TunisieVet editorial team · Updated 23 September 2026
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