Parasites and Diseases

A Field Guide


Swollen caribou “knee” joint due to brucellosis. - Alaska Department of Fish and Game (ADFG)

Swollen caribou “knee” joint due to brucellosis.

Swollen caribou scrotum due to brucellosis. - Alaska Department of Fish and Game (ADFG)

Swollen caribou scrotum due to brucellosis.

What causes brucellosis?

  • Brucellosis is a highly contagious disease caused by bacteria called Brucella suis biovar 4 in caribou and reindeer. It is spread in the afterbirth and fluids during calving and breeding.

Where does brucellosis occur?

  • Brucella suis biovar 4 occurs naturally in caribou and reindeer in North America and Siberia and has also been found in muskoxen and moose.
  • Brucella is most common in the four arctic caribou herds (Western Arctic, Teshekpuk, Central Arctic and Porcupine herds) but recently caused disease in the Mulchatna herd. Predators such as bears and wolves are exposed when they feed on infected caribou.
  • Humans can be infected by Brucella suis biovar 4 through contact with infected fluids or consuming under cooked meat or bone marrow.

What are the signs of brucellosis?

  • Caribou may appear healthy and not show any signs of disease.
  • Brucellosis usually affects the reproductive organs and leg joints.
  • Often, caribou will have swollen scrotum or leg joints (especially a large bump on the ‘knee’ of the front leg).
  • When butchering, you are unlikely to notice anything specific
  • The testicles or womb may be swollen.
  • In people brucellosis often causes a high fever that frequently comes and goes.

How can I protect myself? [can infect people]

  • You can get brucellosis through exposure to contaminated parts. The bacteria can enter through cuts or scratches in your skin or through your eyes, nose or mouth. You can also get brucellosis by eating infected meat that has not been fully cooked.
  • Do not cut into diseased parts.
  • Do not spill fluid from swollen joints or the womb onto the meat.
  • Use extreme care when handling any fetal membranes or aborted tissues.
  • Wash your hands, knives, and food preparation surfaces with hot soapy water after handling the animal.
  • Report any animals suspected of having brucellosis to your nearest ADF&G biologist.

Can I eat the meat? [can infect dogs]  [cook well]

  • Meat from animals with brucellosis should be thoroughly cooked to 160 degrees.
  • Freezing, smoking, drying and pickling do not kill Brucella.
  • Do not consume bone marrow raw bone marrow as this poses high risk
  • Do not feed diseased parts to dogs.

How to report/sample

  • Report caribou with a swollen knee or scrotum.
  • Email photos and a relative location or caribou herd to
  • If you harvest an caribou you suspect may have Brucellosis, save the limb or swollen part without opening and submit along with a leg bone and lower jaw.
  • These may be frozen until delivering to your local ADF&G office.

For more information