Reproductive infections can silently end a breeding career — and one of them, Brucella canis, is also a human health concern. This article covers what breeders need to know, and why testing before breeding isn’t optional in most well-run programs.
The most important first
- Brucella canis is a bacterial infection that causes infertility, abortion and testicular disease in dogs.
- It spreads primarily through breeding and contact with reproductive fluids or aborted material.
- It is zoonotic — it can infect humans, though transmission to people is uncommon with normal precautions.
- Testing before breeding, and every six months or every cycle for actively breeding dogs, is the standard recommendation.
- An infected dog should be removed from a breeding program; there is no reliable cure that restores safe breeding status.
What Brucella canis does
Brucella canis is a bacterium that causes a serious, largely reproductive disease in dogs. In bitches, it can cause infertility, early embryonic loss, and late-term abortion, often accompanied by uterine infection. In males, it commonly causes epididymitis, scrotal swelling, and progressive testicular atrophy, with infertility as a common outcome. The infection is spread mainly through contact with infected reproductive fluids, semen, vaginal discharge, urine, and aborted or birth material — meaning mating itself, whelping complications, and even contaminated surfaces or bedding can all be transmission routes within a kennel.
Why it’s a human health concern too
Brucella canis is zoonotic, meaning it can infect people, generally through contact with an infected dog’s urine, reproductive fluids or tissues. Human infection is uncommon in the general population, but the risk is real enough — and more serious for immunocompromised people — that veterinary and public health guidance consistently recommends gloves and careful hygiene when handling whelping, aborted material, or reproductive fluids from any dog whose Brucella status isn’t confirmed negative.
Breeders and anyone helping at births are more exposed than most people. People who are pregnant or immunocompromised, and young children, may be at higher risk of serious illness. Wash hands thoroughly after handling dogs, and consider gloves, a mask and eye protection at whelpings. In people, infection can cause flu-like symptoms such as fever, tiredness and aching joints. If you feel unwell after contact with a positive dog, tell your doctor about the exposure.
In practice
A breeder brings in an outside stud for a mating without requesting recent Brucella testing, assuming the dog’s apparent good health and the stud owner’s reputation are enough. Testing after the fact — prompted by an unexplained abortion in the bitch — reveals Brucella infection, now potentially present throughout the kennel. Routine pre-breeding testing on both dogs, regardless of reputation or apparent health, is what would have caught this before it happened rather than after.
(Illustrative, composite scenario.)
(Illustrative, composite scenario.)
What screening looks like in practice
Both dogs in a planned mating should be tested for Brucella canis before breeding, and dogs used repeatedly for breeding are generally recommended to be retested every six months or before each breeding cycle, since a single negative result doesn’t guarantee ongoing status. Some sources give at least once a year as the minimum for studs, so treat six-monthly testing as the stricter, recommended standard. Test availability varies between countries and labs (the classic rapid slide agglutination test has been discontinued in the US), so ask your veterinarian which test their lab uses and how positive results are confirmed; a positive or equivocal result should be followed up and discussed with a vet before any further breeding is considered, and infected dogs are generally excluded from breeding permanently, since reliable, guaranteed-clearing treatment isn’t considered available. This kind of screening sits alongside the pre-breeding health checks that should happen before any mating is finalized.
A negative test only reflects the dog’s status up to a few weeks before the sample. Antibodies usually take two to four weeks to appear after infection, and sometimes up to two to three months. For this reason, many veterinary sources advise keeping new dogs separate on arrival and testing them both at the start and at the end of a quarantine period of about two to three months. Maiden bitches, unused males and spayed or neutered dogs can also be infected, so test every dog before it joins your breeding group or household of breeding dogs. Screening tests can also give false positives, so a positive or unclear result should always be confirmed with a different, more specific test before decisions are made.
If a dog tests positive
Stop all breeding, sales and movement of dogs until your veterinarian advises otherwise. Every dog on the premises, including puppies and any dog the positive dog has mated, should be tested. Repeat testing is usually needed over several months until no new positives appear. In many US states, and in some other countries, canine brucellosis is reportable, and animal-health or public-health officials may set conditions for the dog’s management. Infection is considered lifelong, and treatment does not reliably clear it.
The bacterium does not survive long in the environment, and common household disinfectants kill it. Remove bedding, discharge and other organic material first, then clean and disinfect.
When to call your vet
- A bitch aborts (most often in the last few weeks of pregnancy, around days 45–55), has stillborn puppies, or repeatedly fails to conceive without a clear reason.
- A male develops a swollen, painful or shrinking scrotum or testes, or his fertility drops.
- A Brucella result comes back positive or unclear — stop breeding and ask how it will be confirmed.
- A new dog arrives, or a dog has mated outside your kennel, and you need a testing plan for the quarantine period.
- You handle an abortion: wear gloves, keep the material chilled and sealed for your vet (it is one of the best samples for testing), and remember the bitch can shed bacteria for several weeks afterwards.
- If in doubt, call — your vet would rather hear from you early.
Work on it
A few minutes here will teach you more than re-reading the article.
Ask yourself
- Do I know the current Brucella canis testing status of every dog in my breeding program?
- Would I request Brucella testing results from an outside stud or bitch before agreeing to a mating?
- Do I know the correct hygiene precautions for handling whelping or aborted material safely?
Find out & check
- Find out where you can get Brucella canis testing done and how often it’s recommended for your dogs.
- Check whether Brucella canis testing is a legal or club-required condition for breeding in your area.
Do one thing
- Confirm the Brucella testing status of both dogs before finalizing your next planned mating.
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Sources & further reading
- Cornell University Riney Canine Health Center — Canine Brucellosis. vet.cornell.edu
- Merck Veterinary Manual — Brucellosis in Dogs. merckvetmanual.com
- American Kennel Club — Brucellosis: Dog Breeders Shouldn’t Skip Testing for This Dangerous Disease. akc.org
- UK Health Security Agency (GOV.UK) — Brucella canis: information for the public and dog owners. gov.uk
- Merck Veterinary Manual — Breeding Soundness Examination of Male Dogs. merckvetmanual.com
- Purdue University Croney Research Group — Canine Brucellosis: a quick guide. caninewelfare.centers.purdue.edu
Where evidence is limited, recommendations rest on established practice and expert judgment, and may be updated as knowledge develops.
Next steps
- Read next: Infertility in the bitch and dog.
- Related: Pre-breeding health checks · Semen and artificial insemination · Reproductive infections and how to prevent them.
- Return to the area hub: Reproduction and fertility.