Infectious Disease Found in Dogs Has Begun Spreading to Humans

A canine disease that has rarely been reported in humans has been identified in two individuals in the U.K.

Brucellosis caused by Brucella canis was previously only seen in dogs imported into the U.K. but since 2020 has been spreading between local dogs, a report by the Human Animal Infections and Risk Surveillance group released on September 18 reveals.

"As of July 2023, 2 laboratory-confirmed cases of B. canis human infection have been identified in the UK," the report stated. "One case was identified from clinical suspicion after presenting at hospital. A second case had no clinical symptoms, worked at a veterinary practice and was identified through the follow-up of individuals exposed to positive dogs. In both incidents, the implicated dogs were not known to be infected at the time of human exposure, but subsequently tested positive.

"This incident was also the first time dog-to-dog transmission of B. canis had been identified in the UK."

This outbreak among U.K.-native dogs is likely the result of breeding in kennels, leading to contact and mating with imported dogs or the offspring of imported dogs. The disease is endemic in parts of Eastern Europe, including Romania, from where many dogs are imported to the U.K.

B. canis is a bacteria that can infect dogs, and is transmitted via genital, conjunctival, and oronasal mucosae, usually during social, grooming and sexual activities between the dogs.

The disease has an incubation period ranging from weeks to years, the report states. Symptoms of the condition in humans include fever, headaches and muscle pain, and in very rare cases, complications including endocarditis, arthritis, meningitis and even Guillain Barré syndrome, a rare condition in which someone's immune system harms their nerves. There have been no recorded human deaths from the disease.

"There are no reports of human-to-human transmission of B. canis, although this is theoretically possible as blood transfusion, organ transplantation and transmission via contact with reproductive tissues have been reported for other Brucella species, although in very limited numbers," the report states. "This would not generally be considered a commonly occurring pathway for human-to-human transmission."

To prevent the spread among dogs, the U.K. government is considering setting up B. canis screening to prevent infected animals from entering the country. The report says that because of B. canis' ability to withstand antimicrobial treatment, the only surefire way to prevent a dog from spreading the disease is euthanasia.

"Euthanasia of infected dogs is considered the only way to completely remove the risk of future onward transmission," says the report. "The decision to euthanise is a matter for the owner(s) and their private veterinary surgeon and their willingness to accept the residual risks, which will vary on a case-by-case basis, if this course of action is not taken. If an infected animal is not euthanised, the dog may be neutered and concurrently treated with a course of antimicrobials."

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