Brucella canis: what vets need to know

​

A letter in the Vet Record (20/27 February 2021) from the UK Chief Veterinary Officer (CVO) highlighted a marked increase in cases of Brucella canis in Great Britain. Prior to 2020, just 2 cases of B canis were confirmed by APHA, both in imported dogs. At the time of the CVO’s letter more than 40 cases had been reported. Most of the cases were in imported rescue dogs, although the largest case involved a breeding establishment in England where imported and UK-bred dogs were found to be infected.

Public Health England (now the UK Health Security Agency) subsequently published a review by the Human Animal Infections and Risk Surveillance (HAIRS) group. This was a qualitative description as a full risk assessment had not yet been possible. Evidence gaps were highlighted as a concern, however people at greatest risk of exposure to B canis were identified as those with potential contact with contaminated materials, particularly fluids associated with breeding and parturition.

B canis was made a reportable animal pathogen in England, Scotland and Wales in 2021 and the disease is notifiable in Northern Ireland.

The current picture

Cases continue to be monitored. Between 2020 and 2022, 143 positive cases were identified associated with 100 distinct B canis incidents. Data is currently available to the end of quarter 3 in 2023- 160 positive cases associated with 134 distinct incidents. One of the incidents in 2023 was a complex case involving an unlicensed breeding premises, where the index dog (the source case for the incident) originated from a breeder and had produced at least 2 litters. Increased levels of awareness and testing may be a factor in the increase in case numbers.

Of the 134 incidents in 2023, 129 were associated with the importation of the index dog into the UK. Whilst 80 of the index dogs were identified as being from Romania, it is likely a reflection that Romania is by far the biggest source of commercially imported dogs into the UK. Brucella canis is present in other EU member states, therefore consideration should also be given to the Brucella canis status of imported dogs from countries other than Romania.

To date, there have been 2 laboratory-confirmed cases of B canis infection in humans; one involved an individual who fostered a dog imported from Eastern Europe. The dog whelped / aborted shortly after arrival. The foster carer was subsequently hospitalised and both they and the dog were confirmed positive. The second case involved a person working in a veterinary practice and was asymptomatic.

What do vets need to know?

The HAIRS risk assessment has recently been updated, as have APHA information documents. BSAVA’s Scientific Information Document and most recently the joint policy position from BVA, BSAVA, SPVS and BVNA provide incredibly useful resources. The latter provides a good summary of the various tests available as well as clear recommendations for veterinary professionals and Government. Key takeaways from the information available include:

• The risk of B canis infection to humans is considered very low to low. Veterinary staff are at greater risk of exposure to infected material and fall into the low-risk category.
• Bacterial culture is the only test for which a positive result definitively confirms infection.
• A single serological test does not definitively confirm infection status. For most cases B canis testing should be by SAT and iELISA, 3 months after potential infection.
• If a dog tests positive with no clinical signs or history of direct exposure , this alone should not be used to decide on a route of treatment. Ideally, it should be isolated and retested in 4-6 weeks.
• Dog breeders, charities and organisations importing dogs should be encouraged to screen for B canis prior to import.
• If an imported dog has clinical signs that might suggest B canis infection, appropriate PPE should be used, and laboratory staff warned that B canis is suspected when submitting samples for testing.

Isolation and positive cases

Although B canis is primarily shed in the fluids associated with reproduction and parturition, it can also be shed in other bodily fluids such as urine, blood and saliva. Isolation between tests, or if a dog is positive, involves limited to no direct or indirect contact with other dogs and ensuring excreta (urine and faeces) is not accessed. Similarly, limited contact with people, especially the old, young, pregnant or immunocompromised.

Management of positive cases need to be discussed with the owner. Treatment is not recommended due to the poor success rate, with euthanasia the only definitive means of eliminating the pathogen. If owners elect to treat, this should involve neutering, with peri-operative antibiotics to reduce the risk of infection to veterinary staff, extended courses of multiple antibiotics, monitoring and management of lifestyle (isolation and restriction).

The challenges of managing and the impact on dog welfare should be considered, and equally the impact of multiple antimicrobial use with no guarantee of success.

Looking ahead

There are most definitely still gaps in our knowledge regarding B canis, including the disease and its impact in humans and the potency of non-reproductive routes of infection. It is important that effort is made to fill those evidence gaps.

BVA, BSAVA, SPVS and BVNA have recommended legislative change to manage the import of B canis infected dogs, including:

• mandatory pre-import testing for non-endemic disease (this would ideally require specified reference labs to be fully effective)
• better recording of imports and relevant diagnostic results
• appropriate legislation and enforcement to prevent the import of puppies and pregnant bitches (sadly the Kept Animals Bill was dropped in 2023, however there is a new Bill on the horizon).

​