Updated: Oct 12, 2022
Cathy is currently doing her PhD in brucella suis in dogs. This is the most up to date information
Brucella suis- brucellosis in Dogs
What is brucellosis?
Brucellosis is an infection caused by a bacterium called Brucella suis, that is carried by feral pigs. These bacteria can be transmitted from feral pigs to dogs and humans from contact with feral pig meat, blood or other body fluids, such as urine, birthing fluids and semen. It can also be transmitted by eating raw or undercooked feral pig meat.
The bacteria have a preference for living in reproductive tissue so can often cause swollen testicles (orchitis, epididymitis) in male dogs or abortion, infertility, weak puppies and mastitis in female dogs. It can however also cause bone or joint infections and soft tissue abscesses as well as generalised lethargy, anorexia, weakness and non-specific ill health.
Brucella suis is different from other bacteria as it also has the ability to infiltrate the immune system (ie lymph nodes), move around the body and lie dormant or hidden, causing no illness, before infecting a pregnant uterus, an injured joint or the testicles.
How do you know if your dog has brucellosis?
The test for brucellosis in dogs in Australia is a blood test. It is a serology test, which means we are detecting the presence of antibodies in the dog’s serum. Unless your dog has been infected with Brucella suis they cannot produce antibodies against it. No test is perfect so two serology tests are performed, a screening test and then a confirmation test that also gives the level of the antibodies. PCR tests and culture can also be performed on tissue and fluids, but Brucella suis can be a hard bacteria to isolate and difficult to grow, so the serology tests are usually performed first.
These tests are run on request or whenever a dog, with access to feral pigs, is unwell with signs that can be caused by Brucella suis. However, because the bacteria can lie hidden until pregnancy, testing should be performed on any dog with access to feral pigs, male or female, before breeding.
Can I catch brucellosis from my dog?
The main source of the bacteria is from feral pigs, who are the natural host of Brucella suis. The risk from catching Brucella suis from your dog is considered low except when they are having puppies as the bacteria are shed in the large quantities in birth fluid, vaginal discharge and milk. They are also shed from discharging wounds, for example an open weeping scrotum or pus from a large abscess. Brucella suis has not been found in dog urine or saliva, however it is not recommended that children, pregnant women or immunocompromised people handle dogs that have tested positive for Brucella suis.
Can dogs catch brucellosis from other dogs?
It is considered possible that dogs can catch Brucella suis from each other, at times of high risk of shedding - ie whelping, and in the same way humans can potentially catch it from infected dogs. Dog to dog transmission is considered low except in these circumstances and in pups from a positive mother. However, dogs that hunt together are always exposed to the same source of the infection at the same or a similar time and therefore testing of all household dogs is strongly advised.
My dog is positive for brucellosis what can I do?
If your dog has clinical signs or is sick and has been tested by a vet and confirmed to have brucellosis you need to either 1.) treat the dog with a special course of antibiotics and desex them or 2.) euthanase them. Brucellosis is a serious disease that should not be left untreated. Withholding treatment is a welfare issue for the dog and poses a transmission risk for in-contact humans. You should also test all in-contact dogs and discuss having yourself tested with your doctor.
If your dog is not sick but has a positive serology test for Brucella suis we advise treatment with a special course of antibiotics and to seriously consider desexing. It is important that dogs that test positive for Brucella suis are not bred from, as whelping and rearing pups is the time of greatest risk for humans to catch the disease from dogs.
What is the treatment for brucellosis?
Most dogs respond well to treatment, recovering from their clinical illness. Because Brucella suis has special abilities to live within the cells and lie dormant and protected in the body, a different class of antibiotics and always a combination of two antibiotics are used as well as surgery where applicable.
1. Rifampicin – given at a dose of 10-15mg/kg once daily for a minimum of 6 weeks.
This antibiotic can upset the liver on occasions so we advise a blood test to check the liver enzymes at 2-week intervals throughout the treatment. We also advise that the rifampicin is given with food and if the dog doesn’t eat (is depressed or just anorectic) that the rifampicin is not given and you contact the clinic.
2. Doxycycline - given at a dose of 5-6mg/kg twice daily for a minimum of 6 weeks
This antibiotic may make the dogs more prone to sunburn so protecting them direct sunshine is advisable.
Desexing is carried out (where possible) mid- treatment, usually after the first 2 weeks of the antibiotics. This is to lessen the risk of infection, from direct contact with the bacteria, for the veterinarians and their staff.
Brucellosis in humans is considered a treatable, non-contagious disease. It is not so straightforward in dogs. Although most dogs recover well from their illness, it is difficult to measure whether the bacteria have been eradicated. This is because in dogs their antibodies will remain high for many months regardless of whether the infection has been resolved and often because they are commonly re-exposed to feral pigs. However good, affordable treatment and management options are available for your dogs.
If you have any questions or concerns, please contact us at the Border Veterinary Surgery.