Veterinary Guidance for Brucellosis

Key points

  • Animals like dogs, cows, feral swine, and marine mammals can pass brucellosis to other animals and people.
  • Animals may not show signs of brucellosis.
  • Veterinarians have a higher risk of brucellosis from close contact with infected animals.
  • Veterinarians should take precautions when handling animals with suspected brucellosis, vaccine, or samples.
Veterinarians examining a dog on a table.

What veterinarians need to know about brucellosis

Brucellosis is an infection caused by bacteria of the genus Brucella. People who work with animals and animal tissues and body fluids, including animal caretakers, are at higher risk of brucellosis infection.

Brucellosis in livestock

In general, Brucella species have a host preference, but they are not host-specific. For example, Brucella abortus primarily affects cattle, elk, and bison. But other animal species such as sheep and goats may be infected as well. Brucella suis, primarily affects domestic pigs, feral swine, and caribou, but dogs, cattle, and horses can also be infected. Brucella melitensis is mainly associated with sheep, goats, and camels, but cattle, dogs, and even fish can have the infection.

Brucellosis affects livestock operations by causing spontaneous abortion or weak offspring, reduced milk production, or infertility. There are no successful, affordable treatments for brucellosis in livestock.

More information about brucellosis in livestock‎

The United States Department of Agriculture (USDA) has more information about brucellosis in large animals, including symptoms, testing, diagnosis, and reporting.

There is a B. abortus RB51 attenuated live vaccine for cattle. Even if cattle are vaccinated according to label recommendations, in rare cases, vaccinated animals may not clear the vaccine within the regular three days' time and shed RB51 in milk or other secretions. People who consume unpasteurized milk or milk products from cattle chronically infected with RB51 may also become infected.

Brucella vaccine, RB51, and raw milk products‎

If you're vaccinating cattle for B. abortus and are aware of raw milk sales at the farm, consider the potential transmission of the RB51 strain of brucellosis to people who consume raw milk products.

Brucellosis in marine mammals

Multiple marine mammals that have been stranded in the Gulf of Mexico, Atlantic, and Pacific coasts since 2010 have had laboratory evidence of brucellosis. Marine-associated brucellosis cases in people have occurred worldwide. Individuals who come in contact with marine mammals, particularly those stranded or visibly ill, are potentially at risk for infection from B. ceti or B. pinnipedialis. Report stranded animals to a local stranding network.

Brucellosis in dogs

B. canis causes brucellosis in dogs and can cause infection in people. People who work closely with animals and come into contact with reproductive tissues and fluids are at higher risk of contracting brucellosis, including breeders, shelter or boarding facility staff, and veterinarians.

Owners should understand that B. canis infection in dogs is considered a non-curable disease. If owners choose to attempt treatment, emphasize that their pet may continue to shed the bacteria anyway. Educate owners about the disease and how to prevent transmission if their dog is infected with B. canis:

  • Use gloves when handling urine and feces
  • Pick up excrement with disposable bags
  • Wash hands thoroughly for 20 seconds with antimicrobial soap after exposure, and dry with a clean cloth
  • Disinfect surfaces their dog uses regularly while wearing gloves, and allow disinfectant to sit for 10 minutes before scrubbing or wiping them away
  • Don't allow the pet to be exposed to other people or animals.
  • Designate a separate area for the dog to urinate and defecate
  • Maintain serial testing to monitor disease persistence or relapse in the dog

More information for veterinarians‎

Read more about brucellosis in dogs in the Merck Veterinary Manual.


The average onset to development of clinical brucellosis signs is 2-4 weeks after exposure.

Animals infected with Brucella may exhibit a wide variety of clinical signs, while many can be asymptomatic. Reproductive failure is most the common sign. In females, signs include:

  • Abortions during late gestation
  • Stillbirths
  • Endometritis and placentitis
  • Infertility
  • Weakened young
  • Persistent vaginal discharge

In males, signs include:

  • Epididymitis
  • Orchitis
  • Prostatitis
  • Scrotal edema
  • Swelling or atrophy of the testicles
  • Secondary scrotal dermatitis from intense licking

Non-reproductive signs in both male and females are non-specific:

  • Regional or general lymphadenitis
  • Discospondylitis
  • Uveitis
  • Splenomegaly
  • Lethargy or exercise intolerance
  • Anorexia
  • Poor hair coat
  • Behavioral changes

Mortality is rare except in the fetus or newborn.

If you're sending a sample to a lab, note the suspected brucellosis so laboratory professionals can take the proper precautions to avoid infection.

Veterinarians and animal professionals who encounter or suspect brucellosis should follow local guidelines for disease reporting to state animal health officials.

Local health departments should also be alerted to possible infections due to its zoonotic potential.

Preventing brucellosis in veterinary staff

Brucellosis is transmitted from animals to people by direct contact with infected blood, placentas, fetuses, or uterine secretions, or through the consumption of infected meat and raw milk and milk products.

Risk of exposure is greatest for veterinarians during high-risk activities:

  • Handling aborting animals or during birth
  • Specimen draws during clinical examination
  • Surgical procedures
  • Disinfection and cleaning of contaminated environments
  • Vaccination of livestock

You can inhale aerosolized Brucella organisms, the bacteria can enter your body through your eyes or broken skin, or you can be exposed when you have an accidental needle stick injury. To lower your risk of infection during high-risk activities or if you suspect brucellosis in an animal you're examining or vaccinating, wear the following PPE:

  • Disposable latex or rubber gloves
  • Disposable gown
  • N95 respirator
  • Face shield or eye protection

If you're administering RB51 vaccine, wear personal protective equipment (PPE), including gloves and eye protection. The animals being vaccinated should be properly restrained to reduce the chance of needle sticks or eye splashes.

If you think you've been exposed to brucellosis, including the RB51 cattle vaccine strain, contact your health care provider. You may need post-exposure prophylaxis (PEP), which includes 21 days of two suitable antibiotics. If you were exposed to RB51, rifampin should not be part of the PEP regimen as RB51 is resistant to rifampin.

Pet owners should contact their local or state health department if they have been exposed to brucellosis.

Brucella is killed by many common disinfectants. Mix them according to manufacturer instructions and let them sit on surfaces for at least 10 minutes before you wash them away.

If the surface has fecal, urine, vaginal, birthing, or other bodily fluids, apply degreaser first, then disinfect. Effective disinfectants include:

  • Quaternary ammonium disinfectants (QADs)
  • 1 – 2.5% sodium hypochlorite disinfectants
  • 70% ethanol
  • Isopropyl alcohol
  • Iodine-containing disinfectants