Toxoplasmosis — infection with the protozoan parasite Toxoplasma gondii — is common in cats and has important implications for both feline welfare and public health. Understanding the disease in cats and the risks to humans enables appropriate management decisions.
Lifecycle and Epidemiology
Cats are the definitive host of Toxoplasma gondii — only felines can complete the parasite's sexual lifecycle and excrete the environmentally resistant oocysts in faeces. Primary infection in cats occurs through ingestion of tissue cysts in prey animals (rodents, birds) or raw meat. Following initial infection, cats shed oocysts in faeces for approximately 1–3 weeks only — after which most cats develop immunity and do not re-shed unless severely immunocompromised.
Clinical Disease in Cats
Most cats infected with Toxoplasma show no clinical signs. Occasionally, particularly in immunocompromised cats (FIV, FeLV, or steroid therapy), clinical toxoplasmosis occurs with signs including:
- Fever, inappetence, and lethargy
- Respiratory signs (pneumonia)
- Neurological signs (seizures, ataxia, behavioural changes) — from neural tissue cysts
- Uveitis (eye inflammation) — one of the more common presentations in cats
- Hepatitis and jaundice
Diagnosis and Treatment
Serology (IgG and IgM titres) can demonstrate exposure. IgM elevation or rising IgG titres suggest recent or active infection. Treatment with clindamycin (12.5–25 mg/kg twice daily for 4 weeks) reduces replication and clinical signs but does not eliminate encysted parasites.
Public Health Considerations
Toxoplasmosis is a significant zoonosis. Immunocompromised individuals and pregnant women are at highest risk — congenital infection can cause miscarriage, stillbirth, or severe neurological damage in the fetus. Key risk reduction measures:
- Pregnant women should not handle cat litter — or should use gloves and wash hands thoroughly
- Litter trays should be cleaned daily — oocysts require 1–5 days to sporulate and become infectious
- Feeding cats cooked or commercially prepared food eliminates the primary infection route
- The greatest human toxoplasmosis risk is undercooked meat, not cats — evidence should reassure most cat owners
Welfare Significance
While most cats remain clinically well, welfare concerns arise in immunocompromised cats with active disease — particularly neurological and respiratory presentations. Cats with suspected toxoplasmosis require veterinary assessment and appropriate treatment. The public health significance of toxoplasmosis means that clear owner communication about risk reduction is an important component of veterinary consultations involving outdoor cats.