Besnoitiosis

Besnoitiosis

Causative Agent

Besnoitiosis is caused by the unicellular protozoan parasite Besnoitia tarandi.

	Click on the photo to enlarge.

	Hair loss and crusty skin on the face of a caribou infected with besnoitiosis.

Distribution

Geographic:

Several species of Besnoitia are found around the world that can infect both wild and domestic herbivores. B. tarandi is known to occur in BC.

Seasonality:

Warmer months of the year; eggs passed in the feces of carnivores require a warm
and moist environment to become infective.

Hosts, Transmission and Life Cycle

Hosts:

Requires both an intermediate host (in BC: has only been seen in caribou, are reported elsewhere in mule deer) and definitive host (carnivore: species in BC not known).

Transmission and Life Cycle:

An intermediate host ingests eggs that mature within the gastrointestinal tract.
Within host cells, generations of asexual reproduction occur beginning first in the walls of blood vessels followed by reproduction in various organs and tissues forming relatively large cysts (up to 1mm in diameter).
When cyst-containing tissues are ingested by a definitive carnivore host, cysts break open within the intestine and eventually differentiate into female and male components and invade the tissues of the intestinal wall.
Eggs are produced and are excreted in the feces and become infective once in the external environment. Contaminated vegetation is ingested by the herbivore host and the cycle repeats.
Transmission between intermediate host independent of definitive hosts may occur through biting insects.

Signs and Symptoms

Clinical signs are observed only in intermediate hosts and never in definitive hosts.
Infected animals usually appear healthy and signs can vary. Cysts observed in eyes of caribou may not be present several days later.
High density of cysts on the skin can increase the thickness of the skin while decreasing its elasticity, resulting in the formation of cracks allowing for bacteria to enter and cause infection.
Severe lesions have been seen in captive animals with localized hair loss, fluid seepage and hemorrhage , especially when large numbers of cysts are observed on joints of the lower limbs, face and nasal cavity, and less often in the eye. Skin, subcutaneous tissue and the white of the eye may look like “sandpaper”.
Thickening of skin within the nasal passages can obstruct breathing.
Blockage of blood vessels may be observed in B. tarandi infections.
These severe signs have not been observed in wild ungulates in BC.
When skinning the lower legs of an infected animal, the cysts can be observed as small clear to white spheres. Cysts are hard and have a slight roughness that gives the underlying connective tissue the appearance of being sprinkled with “corn meal”.

Meat Edible?

Human Health Concerns and Risk Reduction

Samples for Diagnosis

Submission of lower limb or examination of the white of the eye can be used for diagnosis.

Similar Diseases

Lesions from severe Besnoitiosis may resemble sarcoptic mange, bacterial dermatitis and ringworm.