Toxoplasma gondii or T. gondii is also a protozoan parasite, like giardia. However, is it related to the coccidian protozoa, rather than giardia. It can infect all warm-blooded animals, including people. One unique fact about T. gondii is, it needs a cat to complete its life cycle and become infectious. Animals infected with toxoplasmosis rarely show symptoms, due to it being extremely well adapted. Many cats will be infected with toxoplasmosis and not show symptoms. It has the same symptoms in people as animals, unless they are immunocompromised or pregnant. The effect of toxoplasmosis in individuals with compromised immune systems can be life-threatening.
The life cycle of T. gondii.
The only known definitive host for Toxoplasma is members of the feline family. Without the feline host, the parasite is unable to complete its life cycle. The life cycle begins in an infected cat. They will shed oocysts (eggs) in its feces for 1-3 weeks. These feces need 1-5 days incubation time for the oocysts to become infectious. Once infectious, they are picked by an intermediate host by eating contaminated soil, plant life, or drinking contaminated water. When ingested by the intermediate host, they become tachyzoites (rapidly dividing). At this stage, they begin to affect and damage the tissues of its host. Following the tachyzoites (rapidly dividing) stage, T.gondii slow down becoming bradyzoites. They have now migrated into the muscles of the intermediate host and become a cyst. When the intermediate host is consumed, the bradyzoites become tachyzoites again. If this intermediate host is consumed by a cat, the whole life cycle will start again.
How is it contracted?
Once a cat has shed the oocysts (eggs), and they have reached the infectious stage, they can be picked up in a number of ways;
- From the feline feces directly- If there are litter boxes in your house, remember to clean them out daily! Fresh oocysts are not infectious. They will need at least 24 hours to become infectious. Remove the possibility right away and WASH YOUR HANDS.
- Cover sandboxes – Cats will use sandboxes as an outdoor litter box. It is best to keep them covered to eliminate any chances of infection.
- Gardens/ vegetable – This is a less likely way to contract the disease but is possible. Cats will release oocysts (eggs) in the garden, which then will contaminate the soil of your fresh veggies. Always wash your veggies before eating them and peel when you can.
- Ingesting contaminated meat – Lamb, pork and venison are especially likely to be infected with T. gondii. Always make sure to cook your food to the proper temperature. Wash and sanitize cutting boards, cooking surfaces and prep areas.
- Drinking contaminated water – In 1995, there were 110 cases of toxoplasmosis in the Greater Victoria area from contaminated drinking water. Since then, Victoria has taken precautions to make sure it does not happen again. Drinking contaminated water is now very uncommon in Canada.
How will it affect my pets?
For most pets, there will be no obvious symptoms and will go unnoticed. However, if the pet’s immune system is compromised, T. gondii will continue to replicate and spread. It will cause damage to the tissue surrounding the parasite. You may notice eye discharge, diarrhea, respiratory disease, liver disease, or neurological signs.
How does T. gondii affect humans?
T. gondii will affect humans the same way it affects our pets. For healthy mature individuals, there will be no symptoms or mild flu-like symptoms. For someone with a compromised immune system, it will continue to replicate and be fatal. Pregnant women who have been previously exposed to the parasite carry no risk of transmission to the fetus, as long as she was exposed prior to becoming pregnant. If she is exposed to the parasite after getting pregnant, there can be a risk to the fetus. It can cause miscarriages and birth defects.
Is there a treatment?
Toxoplasmosis is difficult to diagnose. There are blood tests to determine if the cat has been exposed to the parasite, but this does not necessarily mean the parasite is present and active at the time of testing. If it is determined the parasite is present, it is treated with antibiotics.
Written by: Alouette Animal Hospital