Brucellosis Testing for Dogs: What Every Breeder Must Do Before Mating

Canine brucellosis is one of the few diseases that can end a breeding program permanently — and it spreads at mating. Here is what every breeder needs to know.

Canine brucellosis is caused by the bacterium Brucella canis. It is one of the most serious infectious diseases in dog breeding because it is highly contagious between dogs, spreads directly during mating, causes reproductive failure, has no reliable cure once established, and can be transmitted to humans. A single undetected infected dog can spread the disease through an entire kennel before anyone knows it is there.

Testing before every mating is not optional for responsible breeders. It is the baseline.

What Is Canine Brucellosis?

Brucella canis is a bacterial infection that primarily targets the reproductive system in dogs. In intact males, it causes epididymitis, prostate inflammation, and infertility. In intact females, it causes early embryonic death, late-term abortion (usually between days 45-55 of pregnancy), stillbirths, and the birth of weak puppies that often die quickly.

The disease persists in the body for months to years. Infected dogs may show no symptoms initially, appear completely healthy, and still transmit the bacteria during mating.

How Does It Spread?

Brucellosis spreads primarily through:

• Sexual contact — vaginal secretions and semen carry very high bacterial loads
• Aborted materials — placenta, fetal tissue, and discharge from an infected female are extremely contagious
• Urine — to a lesser degree, particularly in males
• Blood — via biting or direct contact with open wounds

It does not spread easily through casual contact like sniffing or sharing water bowls, but any contact with reproductive fluids or aborted material should be treated as a contamination risk.

Testing Before Mating: What Test, and When?

Every dog involved in a breeding — both the stud and the dam — should be tested before the mating takes place. This applies to every breeding, even if the dog was tested six months ago, even if you know the owner, even if the dog has been bred before without issue.

The RSAT (Rapid Slide Agglutination Test)

The most common in-clinic screening test. Results in minutes. High sensitivity but a significant false-positive rate. A positive RSAT should always be confirmed with a more specific test.

The AGID (Agar Gel Immunodiffusion) Test

More specific than the RSAT. Used to confirm positive RSAT results. Widely used as a secondary confirmation test.

PCR Test (Polymerase Chain Reaction)

The most sensitive and specific test currently available. PCR tests detect bacterial DNA directly rather than the dog's antibody response, which means it can catch infections earlier and is not subject to the false-positive issues of agglutination tests. PCR is increasingly the preferred test for breeders who want the highest level of confidence.

Timing

Test no more than four weeks before the planned mating. Earlier than that and a dog could become infected in the interim.

What Happens If a Dog Tests Positive?

A confirmed positive Brucella canis test is a serious situation. There is no validated cure. Antibiotics can reduce clinical signs and bacterial shedding but do not reliably eliminate the infection. Dogs that have been infected are generally considered to be lifelong carriers.

The responsible course of action:

1. Do not breed the dog. Do not allow sexual contact with any other dog.
2. Isolate the dog from other intact dogs immediately.
3. Contact your veterinarian for guidance on management.
4. Notify any other breeders whose dogs may have had contact.
5. Consider spay/neuter — removing the reproductive organs significantly reduces the bacterial load and risk of transmission.

Brucellosis is a notifiable disease in some US states, meaning veterinarians may be legally required to report confirmed cases to state animal health authorities.

Human Health Risk

Brucella canis can infect humans. People most at risk include breeders who handle vaginal discharge during whelping, fluids from aborted litters, or semen during collection.

Symptoms in humans include fever, fatigue, muscle aches, and headaches — a flu-like illness that can persist for weeks. Immunocompromised individuals, pregnant women, and children are at higher risk of serious illness.

Use gloves when handling any reproductive discharge, aborted material, or semen. Wash hands thoroughly. If you suspect exposure, consult a physician.

Building Brucellosis Testing Into Your Breeding Program

Make testing a non-negotiable condition in every stud contract and dam owner agreement:

• Stud owner provides a negative test (within 4 weeks) before the dam arrives
• Dam owner provides a negative test (within 4 weeks) before travel or breeding
• Copies of both test results are attached to the stud contract
• Either party has the right to refuse the breeding if current test documentation is not provided

This is not about distrust — it is about protecting both dogs, both breeders, and the future puppies.

Summary

Brucellosis is the most preventable serious disease in dog breeding. Test both dogs within four weeks of every mating, use the most specific test your budget allows (PCR if possible), and never allow a breeding to proceed without a current negative result from both parties. A single positive test that stops a breeding could save your entire program.