Toxoplasmosis is a disease caused by a parasite named Toxoplasma gondii (T. gondii). This parasite is very common and shows up in pets, people and nearly all other warm-blooded mammals. In spite of this, the parasite does not usually cause any real problems in cats.
Life Cycle of the Toxoplasmosis Parasite
T. gondii has two different types of hosts:
- Wild and domestic cats. These are called definitive hosts because the parasite can only produce eggs (oocytes) when it infects a cat.
- People, other pets and other animals. These intermediate hosts can become infected, but the parasite cannot produce eggs while inside in them.
Cats can pick up the parasite by eating prey or raw meat that is infected. Once inside a cat’s digestive system, the parasite can multiply and produce eggs.
Between three and 10 days after becoming infected, a cat will pass the parasite’s eggs in its feces. This continues for up to three weeks. Millions of eggs can be produced during this time. The eggs are very hardy and can survive outside a cat’s body for over a year.
Some of the parasite can also change form while inside the intestine and spread to other parts of the body. The cat’s immune system will eventually control this infection, causing the parasite to go into a “resting” state. These dormant cysts lodge in the muscles and brain.
Before an animal other than a cat can become infected, the eggs in the environment have to go through a process called sporulation. This takes five days. Once eaten, these eggs form cysts in tissues of the intermediate host. These cysts can infect other animals if the tissue is eaten.
Symptoms of Toxoplasmosis
Most cats infected with T. gondii will never develop any symptoms. However, cats that have a suppressed immune system have difficulty fighting the infection once the parasite moves out of the intestines and into the rest of the body.
Common causes for a weakened immune system include feline immunodeficiency virus (FIV) and feline leukemia virus (FELV). Young kittens may also not be able to fight off the parasite infection because their immune system is not fully developed.
The most common symptoms of toxoplasmosis in cats include:
- Fever
- Loss of appetite
- Lack of energy
The parasite can also cause problems in other parts of the cat’s body, such as:
- Pneumonia
- Eye problems, including inflammation or blindness
- Poor coordination, difficulty chewing or swallowing, seizures and other nervous system issues
Diagnosis of Toxoplasmosis
To diagnose toxoplasmosis, your feline veterinarian uses several tests, such as:
- Physical exam
- History of the cat’s symptoms
- Blood tests, to look for things such as the presence of antibodies to the parasite, which are compounds produced by the immune system to fight the infection
- Removal of a small piece of tissue (biopsy) to look for the presence of the parasite
Cats shed the parasite in the feces. However, the parasite looks similar to other parasites that may be in the feces, so this is not a reliable way to diagnose infection.
Treatment of Toxoplasmosis
Cats with toxoplasmosis can be treated with certain medications, such as:
- Antibiotics, usually Clindamycin
- Other drugs that keep the parasite from reproducing
Treatment continues until several days after the signs of infection have gone away. Most cats respond to treatment, so if symptoms remain, the cat may have another condition.
How Does Toxoplasmosis Affect People?
It is unlikely for a person to pick up the parasite from an infected cat. Cats only shed the parasite for a few days after they become infected. They also do not carry the parasite’s eggs in its fur. In addition, indoor cats that do not eat raw meat or hunt prey are usually not infected. Experiencing cat bites and scratches is also unlikely to cause an infection in a person.
People are more likely to become infected by:
- Handling unwashed fruits and vegetables
- Eating raw meat or unpasteurized dairy products
- Gardening without gloves while touching sand or soil with cat feces in them
- Touching their mouth with unwashed hands after cleaning a litter box
Two groups of people have a higher risk of becoming infected:
- Infants born to infected mothers can pick up the parasite from the mother before birth. Children infected at birth will often not show any symptoms until later in life, including loss of hearing or vision, mental retardation or death. If a woman is infected before she becomes pregnant, her child is most likely protected by her immune system. Some doctors recommend that women wait for up to six months after infection to become pregnant.
- People with suppressed immune systems, such as those with AIDS or who are having a medical treatment that weakens the immune system, are also at higher risk. Symptoms of parasite infection in these people include enlarged lymph nodes, eye or central nervous system problems or heart or lung disease.
To reduce the risk of picking up T. gondii from a cat:
- Avoid cleaning the litter box (if you are high risk) or wear disposable gloves and wash your hands afterwards (if you are not at high risk).
- Wear gloves while gardening or digging in the sand or soil and wash your hands afterwards. Keep outdoor sandboxes covered.
- Keep your cat indoors and do not feed it raw meat.
- Change the litter box daily, because it takes five days for the parasite’s eggs to become infectious.
- Do not handle or adopt stray cats. Pregnant women should also wait until after the baby is born to adopt a new cat.
- Avoid drinking untreated water or eating raw meat.
- Wash fruits and vegetables thoroughly.
- Wash kitchen equipment and utensils that have touched raw meat or fresh fruits and vegetables.
If you feel your cat may be suffering from toxoplasmosis, contact our office, so we can schedule an exam. We will diagnose your cat and suggest appropriate treatment options.