What is toxoplasmosis?
Toxoplasmosis is a disease caused by a single-celled parasite called Toxoplasma gondii. This parasite is found worldwide and can cause disease in humans – hence it is known as a zoonotic disease. Cats play a vital role in the life-cycle of this parasite, allowing it to reproduce, although it does not usually cause disease in this species. It is more problematic for other warm-blooded animals and humans that become infected, where it can cause severe disease in those with weakened immune systems, pregnant woman and young children. It is therefore important to be aware of this parasite and to take steps to protect yourself from the risk of infection if you are in a high-risk group.
How is it spread?
The life-cycle of Toxoplasma gondii is complex and includes definitive and intermediate hosts – both are required in order for the parasite to complete its life-cycle. The definitive host is the cat (including wild and domestic species) – the parasite is well adapted to this host, meaning that it rarely causes disease in cats. They are normally infected by eating raw meat or (more commonly) rodents that are infected with the parasite. The parasite multiples in the small intestine and produces eggs that are then shed in the cat’s faeces. They are only shed for a couple of weeks before the cat’s immune system stops the parasite from reproducing; at this point, most cats clear the infection. However, in some cases the parasite burrows into the wall of the small intestine and travels to other parts of the body where they can form cysts in the tissues. These cats can become chronically infected with Toxoplasma and it can cause clinical disease – toxoplasmosis.
The eggs that have passed out in the cat’s faeces can then infect other warm-blooded animals (including humans) that act as the intermediate host for Toxoplasma. No eggs are produced within these hosts, but infection can potentially cause severe disease in high-risk individuals whose immune response does not appropriately deal with the parasite. Humans can be infected by an infected cat, but are more commonly infected through contact with contaminated soil (e.g. gardening without gloves), eating undercooked meat that may contact Toxoplasma cysts e.g. pork, beef or unwashed fruit or vegetables.
What are the symptoms of toxoplasmosis in cats?
Although Toxoplasma rarely causes clinical disease in cats, it can do so in some cats where they are unable to clear the infection and the parasite forms cysts around the body. Symptoms may then include:
- Loss of appetite
- Weight loss
- Breathing difficulties (caused by pneumonia)
- Seizures and tremors (due to effects on the nervous system)
- Eye problems
- Jaundice (yellowing of the tissues due to liver disease)
How is it diagnosed?
The vet may be suspicious of toxoplasmosis based on the clinical history and physical examination, although given that the symptoms can be vague and non-specific this is not always the case. It can only be diagnosed using special blood tests that need to be sent to a laboratory, and even then it is not always completely clear-cut.
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How is it treated?
Given the difficulty with diagnosis and the time taken for the blood test results take to come back from the laboratory, cats are often started on treatment if the vet is suspicious of Toxoplasma. This is fairly straightforward as it involves an extended course of antibiotics – usually clindamycin. Other treatment may be needed for cats that are more severely affected, with the choice dependant on the clinical signs and severity of disease.
There is no vaccine for Toxoplasma gondii.
Will my cat recover?
As discussed, most cats will not be particularly unwell when they are infected and will clear the infection quickly. However, for the small percentage of cats that are not able to clear the parasite, and so where persistent infection is present, the prognosis will depend on the severity of the disease and the response to treatment. Unfortunately for some cats toxoplasmosis can prove fatal.
How can I prevent catching Toxoplasma?
Various precautions can be taken to reduce the risk of catching Toxoplasma. These are especially important for those that are more at risk of severe disease, including pregnant women, babies and young children, immunocompromised individuals and the very elderly. These steps include:
- Avoiding contact with the litter tray if possible (if there is someone in the household that can empty it for you). It is best that the litter is emptied daily, as the eggs only become infectious between 1-5 days after leaving the cat.
- Cover children’s sand pits to prevent them being used as a litter tray by your cat.
- Wear gloves when gardening.
- Wash hands after preparing raw food (in case it contains parasitic cysts).
- Ensure meat is thoroughly cooked.
- Thoroughly wash fruit and vegetables before eating.