Toxoplasmosis is a common disease caused by the parasite toxoplasma gondii, which can infect virtually all species of warm-blooded animals.
Toxoplasmosis in cats
Cats are the definitive hosts of the parasite, meaning that once they become infected (usually by eating infected prey animals), the parasite multiplies in their intestines and eggs are shed in their waste. These eggs are called oocysts.
Humans and all other animals are intermediate hosts, meaning the parasite can live in their systems but doesn’t reproduce.
Cats most often become carriers of toxoplasmosis by hunting and eating an infected wild animal. However, they can also contract the disease if they come into contact with infected cat waste or eat raw or undercooked meat.
The parasite then multiplies in the cat’s intestines and eggs are shed in their waste for the first two weeks.
Most cats become immune to the disease through exposure to the parasite, however, those who aren’t already immune may experience mild diarrhoea and loss of appetite. The disease can also affect their lungs, liver and nervous system; kittens who have been exposed to the parasite in the womb are the most vulnerable.
If your cat is showing the symptoms of toxoplasmosis, your vet will be able to prescribe antibiotics to help slow down the process of infection. There is currently no absolute cure for toxoplasmosis, but treatment is very effective.
Toxoplasmosis in humans
Humans can become infected through contact with cat waste, but it’s much more common to contract it through unhygienic handling of raw or undercooked meat and drinking contaminated water.
Up to half of the world’s population is infected by toxoplasmosis without any symptoms, as most healthy people are immune to the disease. When illness does occur, symptoms include fever, swollen lymph glands, headache, sore throat and muscles aches and pains.
People with a weakened immune system are more at risk of falling seriously ill from the disease. This is because they’re less able to fight off the disease.
People who are more at-risk include:
- pregnant women – although thought to be rare, toxoplasmosis can cause miscarriage, stillbirth or birth defects
- those with weakened immune systems – for example, if you have HIV or you’re going through chemotherapy. The infection may affect the eyes or brain.
There are a number of ways you can prevent toxoplasmosis if you’re at a higher risk of infection.
If you’re pregnant or have a weak immune system:
- wear gloves while gardening
- wash your hands before preparing food and before eating
- wash hands, knives and chopping boards thoroughly after preparing raw meat
- wash fruit and vegetables thoroughly to get rid of any soil traces
- avoid eating raw or undercooked meat, salami or Parma ham while pregnant
- avoid eating unpasteurised goats’ milk or any products made from it (studies show goats’ milk products carry a higher risk compared to cows’ milk)
- use disposable gloves when cleaning out litter trays
- don’t touch or handle pregnant sheep of lambs.
Does toxoplasmosis cause mental illness?
There is a theory that toxoplasmosis causes mental illness, but more studies are needed before a direct link can be made.
Rodents who have been affected by the disease appear to lose their inhibitions, becoming more adventurous and seemingly unperturbed by cat odours.
Similar risky behaviours have been observed in humans and some evidence links the parasite to a very slight rise in cases of schizophrenia.
However, it’s important to remember that these small studies do not prove that the parasite is the cause of the condition. Larger studies are needed to find out more information.