Toxoplasmosis Cook Thoroughly Do Not Feed To Pets Transmissable To Humans
Causative Agent
  • Toxoplasmosis is a disease caused by the protozoan parasite, Toxoplasma gondii.
Click on image to enlarge.
Toxoplasmosis Life Cycle
Life cycle of Toxoplasma gondii.
  • Common throughout the world.
  • Unknown.
Hosts, Transmission and Life Cycle
  • Domestic or wild cats are the definitive host, with feral cats being the main reservoir for this parasite. Cougars (Felis concolor) in British Columbia have been reported to harbor this parasite.
  • Other wildlife in BC and North America known to act as intermediate hosts and to have suffered clinical effects of toxoplasmosis include:
    • moose (Alces alces), pronghorn antelope (Antilocapra americana), mule deer (Odocoileus hemionus), and white-tailed deer (O. virginianus);
    • black bear (Ursus americanus), red fox (Vulpes vulpes), skunk (Mephitidae), opossum (Didelphis virginiana), mink (Mustela vison), and other small mammals.
  • Toxoplasmosis is also a potentially serious zoonotic disease. A waterborne epidemic occurred in 1995 in Victoria, BC and affected a number of humans.
Transmission and Life Cycle:
  • Refer to above life cycle diagram
  • Cats ingest cysts of T. gondii that are contained in the tissues of intermediate hosts. Cysts then disintegrate within the stomach and small intestine.
  • After multiplication and reproduction within the walls of the intestines, egg-like oocysts are passed in the feces. Oocysts can survive in the environment for several months and are extremely resistant to disinfectants, freezing, and drying.
  • Within a few days in the external environment oocysts become infective and are ingested incidental to feeding or drinking in areas contaminated with cat feces.
  • Cysts form in the tissues of intermediate hosts, primarily in muscle and nervous tissue and, to a lesser extent, in lungs, liver and kidney. Cysts may persist for years.
  • The cycle continues when a cat consumes meat contaminated with cysts.
  • Humans may enter this cycle either by consuming meat contaminated with cysts or through ingestion of food or water contaminated by cat feces.
Signs and Symptoms
  • Outward signs are rarely observed in cats or intermediate hosts.
  • In humans symptoms may include:
    • fever;
    • fatigue;
    • muscle pains and sore throat;
    • in more severe cases, inflammation of the brain and eyes, birth defects and even death can occur in patients with suppressed immune systems.
Meat Edible?
  • Meat is edible if cooked thoroughly to at least 67ºC.
  • When skinning infected animals, care should be taken, as viable parasites may be present even if the infected animals show no outward signs of disease.
Human Health Concerns and Risk Reduction
Health Concerns:
  • Toxoplasmosis is of considerable risk to pregnant women, as T. gondii can be readily transmitted from the mother through the placenta to the developing fetus.
  • Complications in the developing fetus may lead to diminished vision, mental deficiencies, convulsions and hydrocephalus (enlargement of the skull caused by fluid accumulation).
  • Some of these complications may not appear until later in life.
Risk Reduction:
  • Hands, utensils and cutting surfaces should be washed with soap and water after handling meat.
  • Thoroughly cook meat (see above).
  • Pregnant women should avoid contact with cat litter boxes, soil, raw meat and aborted animals.
  • Cats should be fed dry, canned or cooked food, not allowed to hunt out of doors, and not allowed to scavenge from household garbage.
  • When gardening, gloves should be worn and vegetables thoroughly washed prior to consumption.
Samples for Diagnosis
  • Microscopic and immunologic examination of secretions, excretions, body fluids and other tissues collected either at necropsy or through biopsy of live tissue will help to determine the presence of T. gondii.
  • Whole carcasses should be submitted for necropsy.
Further Reading
Return to Manual Home Page Disease List - Body Region Affected Disease List - Causative Agent or Risk Factor Disease Surveillance Form Glossary Contact Information
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