Toxoplasmosis in Cats

While all warm-blooded animals can be intermediate hosts of this disease, only cats are definite hosts. This means that the parasite can only produce eggs while infecting a cat. The parasite multiplies in the intestines and produces millions of eggs which then exit the body in feces. These eggs begin to exit three to ten days after infection has occurred and continue to exit for another 10-14 days thereafter.

The single-celled parasite, Toxoplasma gondii  (T. gondii), can cause infection in virtually all warm-blooded animals. This disease is referred to as toxoplasmosis. Though it is present in 20-60 percent of cats, it only manifests itself as a significant disease in rare cases. Cats with immune deficiencies (such as feline leukemia virus, feline immunodeficiency virus or feline infectious peritonitis) and young kittens are the most susceptible to toxoplasmosis. 

The infection of T. gondii tends to affect many parts of the body including the neural system, the liver and the muscles of the cat. Possible symptoms are as follows:

• Fever
• Lethargy
• Vomiting and diarrhea
• Loss of appetite
• Difficulty eating
• Inflammation of the eye (both uveitis and retinitis)
• Abnormal pupils
• Blindness
• Personality changes
• Circling
• Pressing head against the wall
• Paralysis
• Ear twitching
• Seizures
• Loss of coordination 
• Sensitive to touch
• Muscle pain
• Incontinence
• Hepatitis (liver disease) causing jaundice
• Enlarged lymph nodes
• Pneumonia

To become infected and develop toxoplasmosis, the cat must come in contact with T. gondii or its eggs. The eggs can live for 18 months or longer in water or soil. Common causes of exposure include:

• Contact with parasite outdoors
• Eating of raw meats infected with T. gondii
• Hunting of small mammals
• A bite or scratch from an infected cat
• Drinking water contaminated by T. gondii
• Sharing a litter box with an infected cat

Your veterinarian will need your cat’s complete medical history before attempting diagnosis. They will assess all symptoms present in the cat and compare them with signs of toxoplasmosis. Even though the parasite’s eggs are often present in the fecal matter, it is generally not tested due to results mimicking many other parasitic infections.

A lab test that will generally be performed measures the antibodies in the cat. IgG and IgM (immunoglobulin G and M) are both antibodies that form in the blood after infection from T. gondii. If many IgG antibodies are found, the cat has most likely developed immunity to the parasite. If many IgM antibodies are found, the cat is currently infected and is most likely dispelling eggs. If no antibodies are found, the cat is susceptible to infection but is not currently diseased.

Another test that might be performed is a microscopic examination of tissue impression smears (surface sample). These tests look for distinctive pathological changes and the beginnings of tachyzoite (one of three infectious stages of T. gondii) development.

There currently is no cure for toxoplasmosis. Treatment is available to help slow down the process of infection and aid the cat in handling the stages of infection. 

Different antibiotics can be prescribed to disable the progression of parasitic infection. Clindamycin is often prescribed to disseminate the T. gondii organisms. Pyrimethamine along with sulfadiazine or trimethoprim sulphonamide can be administered to stop reproduction of T. gondii. The antibiotics are given immediately and are taken until at least several symptom-free days have passed. If no improvement is seen in three days, rediagnosis may be necessary.

Most cats respond favorably to these treatments. Once again young cats and cats with immune suppression tend to fare worse.

If you have other cats it is important to take precautions to ensure they also do not become infected. Clean the litter box carefully with scalding water on a daily basis. T. gondii requires one to five days once exited from the cat to become infectious, so daily removal of feces can prevent the spreading of the parasite. Thoroughly wash hands after removal of cat waste. Pregnant women or people undergoing chemotherapy treatment should not handle the litter box as they are vulnerable to toxoplasmosis development.

Keep your cats indoors to prevent contact with the parasite. Also, do not allow your cat to eat raw meats. T. gondii produces cysts in the animals it infects that can spread the disease if eaten.