Toxoplasmosis in cats | Vets & Clinics

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Toxoplasmosis in cats

Toxoplasmosis in cats is a disease caused by the parasite Toxoplasma gondii. It is a coccidian, obligate intracellular parasite.

Although it can infect many animals, including humans, the parasite’s most distinctive feature is that cats are its only definitive host, as they are the only animal that release T. gondii oocysts into the environment.

Veterinary medicine and care

Toxoplasmosis in cats is spread through oral transmission when they ingest cysts found in other animals’ tissues or faeces. Note that it can also be spread by transplacental transmission.

The extraintestinal phase of the Toxoplasma life cycle is caused by the ingestion of sporulated oocysts or cysts directly from tissues. The microorganism passes into the bloodstream and spreads to all of the cat’s tissues.

The formation of cysts is typical of toxoplasmosis in cats. The immune system is responsible for stopping the intracellular replication of tachyzoites, so cysts form in tissues such as muscle, viscera or the central nervous system. If the immune system does not function properly, then tissue necrosis occurs, due to tachyzoite replication, instead of cyst formation.

Clinical signs of toxoplasmosis

The clinical signs of toxoplasmosis in cats depend on the Toxoplasma life cycle. They are very mild during the enteroepithelial cycle. Infected cats may also suffer vomiting and diarrhoea, especially kittens.

Cell necrosis, however, occurs during the extraintestinal phase as a result of tachyzoite replication. Other signs are due to immune complex deposition and include dyspnoea, cough, lameness, jaundice, fever, lymphadenopathy, muscle pain, pancreatitis, uveitis, retinochoroiditis and even encephalitis.

Toxoplasmosis treatment

The treatment of choice for toxoplasmosis in cats remains clindamycin for 30 days. This treatment resolves the clinical signs rapidly, except for any ocular or neurological problems.

The treatment for ocular lesions is topical clindamycin combined with topical or systemic corticosteroids.


This depends on the severity of lesions and the location of cysts. The worst cases are those which involve central nervous system compromise.

A point of particular concern for cat owners is the risk of catching toxoplasmosis from their own cat. This issue is much more pronounced in homes with pregnant women or immunosuppressed individuals. However, the risk of infection remains very low because:

  • The low probability of cats ingesting cyst-infected tissues
  • Even if this does occur, the animal has to sporulate the oocysts and this process only lasts between 1 and 5 days

Therefore, if the patient is seropositive and there are no oocystes in its faeces, then there is no risk of infection.

If, on the contrary, the cat is seronegative, strict hygiene measures must be followed, especially in high-risk groups such as pregnant or immunosuppressed individuals.

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