Toxoplasmosis in cats - a quick review

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This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Toxoplasmosis is a serious zoonosis which veterinarians should be educating their clients about....particularly clients who are at risk. Good management and basic hygiene are all prerequisites to minimising the risk of transmission from cats to humans.

Toxoplasmosis infection in many species - including humans and cats - does not cause any clinical signs in most patients. However, an unborn fetus, very young children and immune-deficient individuals are at high risk from this single-celled parasite and can develop serious disease. In some parts of the USA 30% of the childbearing-age women in the population have been exposed to Toxoplasma spp and it is present in 10% of HIV positive patients.

Most infected humans show no signs of the disease, but when they occur they include :

  • Fever
  • Headaches
  • Sore throat
  • Nasal congestion
  • Cough
  • Loss of appetite
  • A skin rash
  • Swollen lymph nodes (lymphadenopathy)
  • Joint pain
  • Hepatitis

Humans get infected from :

  • Eating undercooked infected meat - usually goat, mutton or pork.
  • From contact with oocysts shed in cat faeces - direct or indirect through contact with  soil, or cat litter.
  • In-utero from an infected mother (congenital infection)
  • From infected organ transplantation (rare)

Human workers most at risk include :

  • Animal handlers
  • Veterinarians

In cats the organisms lifecycle is as follows :

  • Cat ingests the infectious agent (T. gondii) in food - eg by eating an infected rodent
  • The cat starts passing oocysts in it's faeces 3-4 days after eating the contaminated food
  • Oocysts continue to be shed in the faeces for only 10-14 days after initial infection ** So cats which test positive to Toxoplasmosis do not necessarily represent a serious risk to the human population. 
  • The cat shows no signs of illness
  • The oocysts take 1-5 days to mature in the soil or litter.** So contact with fresh faeces carries a low risk of transmission compared with contact with "old" faeces.
  • Oocysts are then infectious to animals and humans
  • If ingested - these infective oocysts cross the intestinal wall, enter the bloodstream and encyst in various end-tissues including the brain. 
  • The parasite remains viable inside the cysts indefinitely in living animals, and for several days after the individual dies.

Recommendations to minimise the risk of  transmission of T gondii from cats to humans :

  • Basic hygiene - wear disposable gloves when handling cat faeces, contaminated soil, litter trays.
  • Clean out litter trays daily - so removing faeces before the infective stage oocysts have developed
  • Wash hands rigorously after handling cat litter trays or contaminated soil.
  • Prevent children playing in areas known to be contaminated with cat faeces - soil borders in gardens, sand pits, and so on.
  • Prevent direct contact between potentially infected cats (especially rodent eaters) and pregnant women, young children and people with a compromised immune system. 


Updated October 2013