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BRUCELLOSIS

Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.


Brucellosis is a zoonosis. Zoonoses are diseases that are transmissible between animals and humans. Some of these diseases are extremely serious and potentially life-threatening others cause only transient, mild disease. At the time an animal appears ill there is no way of knowing whether or not it is a zoonosis. For this reason it is important to follow basic hygiene precautions such as washing hands after handling animals, not allowing animals to soil eating implements or plates. If your animal is ill use protective plastic gloves and clear up and dispose of any mess (eg urine and faeces) as soon as possible .

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Description
Brucellosis is an infectious disease that can affect many species including farm animals, pet animals and humans

Cause

The cause of brucellosis is a small, gram-negative, aerobic coccobacillus, which lives intracellularly and the strain involved depends upon the species of animal infected :

  • Dogs (domesticated and wild Canidae)- Brucella canis. In USA, Japan and some South American countries. Dogs are also susceptible to B.abortus and B.suis following ingestion of infected tissue (eg placenta or aborted fetuses)  from livestock. The infection can be transmitted transmucosally via semen and vaginal discharges both of which contain high concentrations of the organism in infected individuals. It can also be transmitted oronasally following access to infected tissues. Bitch milk is not thought to be an important route of transmission to puppies. Urine can contain significant numbers of Brucella organisms especially in male dogs. B.canis is short-lived outside the body.

Transmission can also occur through contaminated instruments, blood transfusions and artificial insemination (AI). Dogs in which AI is being contemplated should be screened for brucellosis prior to the procedure.

  • Cats - B.suis
  • Cattle, Sheep and Goats - Infection occurs usually by ingestion, and in the case of B.ovis by the conjunctival route.
    • Brucella abortus Cattle mainly - sheep and goats occasionally. Widespread.
    • Brucella melitensis Sheep and goats mainly, cattle occasionally. Rare US. Common Mediterranean and South and Central Americas
    • Brucella ovis. Sheep only. Most often causes epididymitis in rams.. Seen in the western USA, Europe, Africa , Australia and New Zealand.

 

  • Horses. Brucella abortus Associated with fistulous withers but not usually abortion or infertility.

 

  • Humans - most cases have resulted from contact with aborting bitches or cattle  with B.canis or B.abortus. Infection with B.melitensis can be severe.

Breed Occurrence

Dogs - Beagles and Labrador Retrievers have been reported to have a higher prevalence to infection with B.canis than other breeds in southern United States. Worldwide the prevalence rate in dogs ranges from 1-28%, being higher in stray dog populations in depressed areas.

Signs

Dogs - Signs are variable, non-specific and in adults include :

  • Abortion (usually 45-60 days gestation)
  • Diskospondylitis
  • Endophthalmitis and glaucoma
  • Epididymitis
  • Fever 
  • Infertility
  • Lymphadenomegaly
  • Meningoencephalitis
  • Osteomyelitis
  • Poor coat (dry and lusterless)
  • Poor exercise tolerance
  • Scrotal dermatitis
  • Splenomegaly
  • Testicular atrophy (in chronic cases)
  • Uveitis (anterior) and corneal oedema

In puppies signs include :

  • Fever
  • Hyperglobulinaemia
  • Leukocytosis
  • Neonatal death
  • Seizures

Cattle, Sheep and Goats  Causes abortion - usually after the fifth month of pregnancy (cattle) and in the last 2 months of pregnancy (goats and sheep). Other signs include lameness, mastitis and orchitis.

Horses. Associated with fistulous withers but not usually abortion or infertility

Humans  The following signs have been associated with B.canis infection: 

  • Abscesses (rare)
  • Arthritis (rare)
  • Depression 
  • Endocarditis (rare)
  • Fever (undulant)
  • Fatigue
  • Hepatitis (rare)
  • Lymphadenomegaly
  • Meningitis (rare)
  • Weight loss

Complications

Dogs : Bitches that abort a litter due to B.canis can have normal litters afterwards, but they can also have reproductive failures.

Diagnosis

Dogs - Serology tests or bacteriological culture and isolation. Antibiotics should not be administered prior to testing.

Cattle, Sheep and Goats isolation of the organism from infected tissues, or maternal serology. Positive complement fixation test for B.ovis  in ewes does not confirm active infection as they can maintain high 

Humans - Serology and bacteriology.

Treatment

Dogs : In the laboratory Brucella spp are susceptible to several antibiotics, but because the organisms live inside cells their effectiveness is questionable. It is probably impossible to clear prostate gland infection and treated males usually become infertile. Clinically normal but infected females can transmit the infection to surviving puppies, so they should be removed from the environment. Infected pets should not be used for breeding - even if they have been treated and appear healthy.

In the environment B.canis is short-lived and susceptible to most disinfectants eg quaternary ammonium compounds.

Cattle, Sheep and Goats  - Long-acting oxytetracycline and streptomycin has been recommended, but treatment of infected individuals is controversial. A vaccine (reduced dose of  strain 19 given at 4-12 months age) is available in some countries and this reduces the  likelihood of abortion and shedding of Brucella abortus at parturition. Registration of vaccination schemes and test and slaughter policies are also in force depending upon local regulations.

Humans Tetracycline gives good results.

Prognosis

Dogs : Good but long term asymptomatic carriers exist as a potential zoonotic risk, and relapses may occur.

Humans : Good

Long term problems

Infected dogs should be removed from farms and prevented from coming into contact with livestock, and probably should not be kept in close contact with humans. 

 

Updated January 2016