Toxoplasmosis in CatsToxoplasmosis (toxo) infection is a parasite infection caused by Toxoplasma gondii (T. gondii). This parasite is a coccidian-type organism of the same family as Coccidia and Cryptosporidium. The cat is the definitive host for T. gondii, which lives deep in the cells for much of its lifecycle and is difficult to kill with conventional antibiotics.
Life Cycle and TransmissionThe three major modes of transmission are congenital from mom, ingestion of infected tissue, and ingestion of oocyst-contaminated food or water. Cats are the definitive host of T. gondii, meaning that the parasite completes its life cycle in the cat and becomes an adult. Cats shed the T. gondii oocyst in feces for one to two weeks after first exposure, but they rarely show any symptoms during the oocyst shedding.
Other mammals become infected by ingesting the oocysts, which then penetrate the intestinal tissue. Infection can occur from ingesting contaminated food or water and also by ingesting the infected tissue of birds or rodents. Prenatal infection in all mammals can cause serious issues for embryos and even result in abortion, and clinical issues may be influenced by immune suppression from stress of pregnancy. All warm-blooded mammals can acquire toxoplasmosis infection, and it is not well understood why some become ill and some do not.
Clinical PictureMost cats do not show clinical signs. All animals, besides cats, are intermediate hosts and the clinical picture depends on what tissue is affected with the toxo cyst. If the brain has cyst presence or neurologic tissue, there will be neurologic symptoms such as ataxia, circling, seizures, twitching or tremors. If a fetus is infected, symptoms include stillbirth, birth defects, fading kittens or organ failure.
DiagnosisPCR testing is now available and is very accurate at detecting toxo circulating in the feces, blood or tissue. However, the presence of the parasite does not mean that there is a clinical issue; it only means that the organism is present.
Titers are ran on blood and can tell you whether infection occurred and if antibodies are present. Antibodies alone usually won't clear the infection, but they do help prevent clinical issues and shedding of the oocysts in the feces. When the immune system is stressed, toxoplasma can reactivate and you can see clinical toxoplasmosis reoccur.
Toxo can be diagnosed by examining the tissues of an aborted fetus.
TreatmentTreatment is difficult as the toxoplasma organism spends most of its time deep inside the tissue. Clindamycin is still the preferred treatment of infected animals and humans, but other antibiotics that penetrate the cells are effective as well. Treatment does not prevent cats from producing antibodies that prevent subsequent shedding if exposed again.
Toltrazuril (Baycox) is commonly used in purebred kittens to prevent Coccidia and toxoplasmosis. One European paper was presented where a cattery was cleared of toxo using Baycox.
PreventionPets should be restricted from hunting and eating potential intermediate hosts such as birds and rodents. If feeding meat to pets, freezing and cooking the meat will kill the parasites. A balanced, commercial diet is safe from parasite issues.
Human PreventionBecause toxoplasmosis can infect all warm-blooded mammals including humans, there are certain precautions that pregnant women should take. Pregnant women should avoid contact with a cat's litter box. The cleaning of the litter box should be done by someone else. Pregnant women should avoid eating raw or undercooked meat, especially goat or pork. Ask your obstetrician for more recommendations on toxoplasmosis.
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Don Bramlage, DVM, Former Director of Veterinary Services at Revival Animal Health
The materials, information and answers provided through this website are not intended to replace the medical advice or services of your personal veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.