Brucellosis

Brucellosis

Causative Agent

A potentially zoonotic disease of ungulates and the carnivores that feed on them. Caused by the bacteria Brucella abortus and Brucella suis type 4.
Brucella bacteria generally cause chronic infections.

Click on the photo to enlarge.

Swollen “knee” joint of caribou due to brucellosis.

Distribution

Geographic:

Was once worldwide, but now has limited distributions due to government eradication programs.
In Canada, there are two forms of the disease associated with the two species of bacteria listed above: specifically in Wood Buffalo National Park, northeastern Alberta, affecting primarily wood bison (B. abortus), and barren-ground caribou and reindeer (B. suis type 4) elsewhere.
There is no reported occurrence of brucellosis in BC in any species. The greatest risk is if an infected wood bison from Wood Buffalo National Park disperses to northeastern BC and contacts a native or captive bison population.

Seasonality:

Risk of exposure increases prior to and during calving season due to presence of large numbers of bacteria in fetal fluids.

Hosts, Transmission and Life Cycle

Brucella abortus

Hosts:

Bison and potentially other ungulates.

Sexually mature animals are more susceptible than immature animals.

B. abortus has also been discovered in wolves, fox and moose within Wood Buffalo National Park.

Transmission and Life Cycle:

Transmission rates are greater in highly social animals.

Bacteria enter the body through mucous membranes and are spread through the lymph nodes and spleen.

If pregnant, the bacteria invades the uterus and placenta, restricting the transfer of nutrients to the fetus as well as producing toxins, potentially leading to fetal death or the birth of an infected fetus

In social ungulates, bacteria are spread from direct contact with infected animals. This includes:

discharge from the vagina

aborted fetuses

sexual intercourse

mechanical transmission through flies

inhalation of bacteria

contaminated food

Carnivores are thought to be exposed through the consumption of infected animals, the placenta or aborted fetuses.

Moose are unusually susceptible to this B. abortus and often die of the infection.

Brucella suis type 4

Hosts:

Barren-ground caribou and reindeer

May also “spill over” into wolves, dogs, and bears.

Transmission and Life Cycle:

Very similar to that of B. abortus except different species are involved.

Signs and Symptoms

Wildlife:

Wildlife may not show signs of the disease and instead appear healthy.
Signs of disease in infected animals vary according to species but are primarily found in the reproductive tracts of both sexes, these include:
- inflammation of the testicles or uterus
- retained placentas
- fluid-filled swellings of the forelegs.
Abortion may occur during late pregnancy; calves that are born may be weak.
Less commonly, infection with Brucella bacteria may cause arthritis, formation of abscesses in lymph nodes , and inflammation of mammary tissue.

Humans:

Disease begins within a week or up to several months after exposure.
B. suis type 4 elicits more serious effects in humans than B. abortus.
Blood becomes infected and is first accompanied by a fever. Symptoms include:
- chills
- profuse sweating
- weakness and fatigue
- joint pain
Brucella bacteria localize in the lymph nodes and spleen.
If untreated, the disease may last from weeks to months with the potential for serious effects on the brain, joints, bones or heart.

Meat Edible?

Do not cut into diseased parts or meat that has had fluid from the uterus spilled on it
Meat can be safely consumed if cooked thoroughly – however, freezing, smoking, drying or pickling will not kill the bacteria.
Brucella bacteria may be found in the bone marrow and liver.
Meat from an infected carcass or a carcass thought to be infected should NOT be fed to domestic cats or dogs.

Human Health Concerns and Risk Reduction

People at risk of contracting brucellosis include: abattoir workers, veterinarians, farmers and wildlife personnel.
Hunters are not perceived as being at high risk of exposure to Brucella bacteria as the timing of hunting relative to the breeding season limits exposure.
Humans may contract the infection through skin abrasions, mucous membranes, or the conjunctiva of the eyes when they handle infected animals during activities such as:
- butchering
- inhalation
- handling fetuses or afterbirth
- contact with raw meat or the secretions and excretions of the genital system
- ingestion of infected animals
Symptoms of Brucella infection in humans include:
- weakness and fatigue
- lack of appetite
- sweating
- muscle and joint pain
- fever
- mental inattention and depression

Samples for Diagnosis

Tissues to be collected for diagnosis include: lungs, stomach contents, spleen (of fetus or calf), affected joints, reproductive tract, and lymph nodes.
Appropriate safety gear (protective clothing, eyeware, gloves) should be used if cutting into an animal suspected of being infected with Brucella bacteria.
Hands, knives, clothes and cutting surfaces should be thoroughly cleansed with hot soapy water after handling an animal suspected of having the disease.
Immunological tests of live animals can also determine the presence of Brucella bacteria.