Brucellosis infection in dogs

Brucellosis is a rare bacterial disease in the UK but there has been a marked increase in the number of cases since 2020, in line with the increase in dogs imported from Eastern Europe. It is considered endemic in the Americas, parts of Asia, Africa and Eastern or Central Europe.

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Brucellosis is an infectious bacterial disease that causes reproductive failure and other problems. The bacterium Brucella canis is the usual cause in dogs. The bacteria enters the dog’s body via mucosal membranes, eg via ingestion/oral, venereal, or at birth. Infection can also be congenitally acquired, if a pup is born to an infected mother. Venereal transmission of Brucella canis is the most common route of infection, ie contact with semen during mating. The bacteria can be shed in urine and in the fluids associated with giving birth. Brucellosis is zoonotic which means there is a risk of transmission to humans.

In pregnant dogs, abortion is the most consistent sign but otherwise, there may be no outward signs that your dog is infected. It is possible that the puppies may be born alive but they may die within a few hours. Those that survive can be a source of infection. If the puppies die 10-20 days after mating (aborted fetal membranes are often eaten by the female dog and go unnoticed), owners may not have realized that their dog had been pregnant. Owners may also notice that their dog has a prolonged vaginal discharge for several weeks.

Infected male dogs may be infertile or subfertile and have scrotal/testicular swelling which may be painful. Scrotal dermatitis may be seen due to excessive licking in response to the pain.

Non-genital forms of brucellosis can include a painful, stiff back (due to diskospondylitis), lethargy, weight loss, loss of coordination, enlarged spleen (splenomegaly), and ocular changes.

Your veterinarian may not have seen a case of Brucella canis before since the disease is not endemic in the UK. If your veterinarian suspects your dog has been imported from a country where B.canis is endemic, they will want to carry out screening tests (which may include blood, biochemistry tests and urine tests). Your veterinarian will also wear protective clothing (PPE) to protect themselves from becoming infected. You will be advised to keep your dog away from other dogs and people, ie your dog will have to be quarantined at home, until the results are determined. Breeding of the dog should not be allowed if an infection is suspected.

Brucellosis is difficult to treat, with no guarantee of success. Antibiotic treatment is not recommended currently in the UK due to the lack of elimination of the pathogen, high rate of relapse and cost. Euthanasia may sadly have to be considered. This is the only way to completely remove the risk of transmission to other dogs and to humans. If used, a long course of antibiotics is required to treat brucellosis and frequent repeat treatments may be required. There is also no way to determine that treatment has been completely successful. Brucella positive dogs should be neutered to reduce their risk of transmitting infection; they will require antibiotics around the time of neutering to reduce the risk of shedding infection and protect the veterinary personnel involved. Neutering does not eliminate infection.

The prognosis for dogs infected with Brucella canis is guarded – the infection is difficult to treat and relapses are common. Male dogs are likely to be infertile. If tested positive, a dog is considered positive for life and both male and female dogs should not be used for breeding.

Brucella canis is a serious bacterial disease of dogs that is difficult to treat. It is also zoonotic – other dogs, owners and other people that handle the dog, including veterinarians and laboratory staff who test samples, can be infected. Most contact with infected dogs carries a low risk of infection, but people who come into contact with large numbers of the bacteria are considered at higher risk. Cases are most commonly reported following contact with aborting bitches, birthing fluids and from canine genital secretions. The bacteria may also be found in the dog’s body fluids, such as urine, blood, and saliva. Fortunately, cases of human infection are rare, and the infection is relatively mild (headaches, fatigue, enlarged glands, mild fever). Immunocompromised persons, young children and pregnant women would be considered at higher risk if they were to acquire infection. Infection in non-immunocompromised people is rare and mild.

Brucellosis is a reportable disease in many countries, including the UK. Infected dogs and bitches should be removed from breeding programs. In some countries they may be required to be quarantined. Eradication in kennels or breeding colonies may only be successful after all affected dogs have been euthanized.

Dog owners who have imported dogs from countries where Brucella canis is present, eg Eastern Europe (Romania is the largest source of dogs imported into the UK), should be aware of the potential risks of bringing the disease into the UK and the potential risks of this infection to their dog; screening for infection may therefore be recommended.

Further Reading

Publications

Other sources of information

• Animal Plant and Health Agency (2023) Canine Brucellosis: Summary Information Sheet for Veterinary Staff. Website: www.apha.defra.gov.uk (pdf download).
• UK Health Security Agency (2023) Brucella Canis: Information for the Public and Dog Owners. Website: www.gov.uk.
• Centers for Disease Control and Prevention (CDC) (2021) Brucellosis. Website: www.cdc.gov.
• Public Health England (2021) Human Animal Infection and Risk Surveillance Group – Risk Review and Statement on the Risk Brucella Canis Presents to the UK Human Population. Website: www.gov.uk.