Toxoplasmosis in Cats

What Is Toxoplasmosis in Cats?

You might have heard before that if you’re pregnant or plan to become pregnant, you should re-home your cat because of a disease called toxoplasmosis. This is a legitimate concern for pregnant people and their babies, but there’s no reason to re-home your cat because of the condition. 

Toxoplasmosis is caused by the protozoal parasite Toxoplasma gondii. It is a relatively common disease that is found worldwide in animals, birds, and even humans. Fortunately for our feline friends, the disease is generally mild, but given its zoonotic potential (meaning it can be transmitted to people), it is important to recognize its health implications.   

Causes of Toxoplasmosis in Cats

In order to better know how to diagnose, treat, and prevent toxoplasmosis, it’s helpful to understand the organism’s complicated lifecycle and how it infects hosts.  

In general, the parasite affects two different kinds of hosts:  

• Definitive—Hosts necessary for the sexual reproduction of the parasite, which are then shed in the feces as oocysts (similar to eggs). Cats are the definitive hosts for the parasites. 

• Intermediate—Hosts in which the parasite reproduces asexually, or by producing “daughter” organisms that split from the “mother” organism. Parasites in intermediate hosts pass through two distinct life stages: tachyzoites (fast-reproducing) and bradyzoites (latent form). All non-feline animals, including animals, can serve as intermediate hosts and become infected. 

Cats can become infected by all three T. gondii life stages (oocysts, tachyzoites, and bradyzoites) by:  

• Ingesting feces containing infectious oocysts 

• Eating tissues (i.e., uncooked meat or wildlife) containing the brady-/tachyzoite phases 

• Passage of tachyzoites from mother to fetus during pregnancy 

Once in the feline intestines, T. gondii can either produce oocysts, which are then passed in the stool, or can replicate to become tachyzoites, which migrate throughout the body, affecting multiple organs. Symptoms are variable depending on which organs become affected.  

The oocysts that are passed in the feces are not infectious at first, but they become infectious after a period ranging from 1 to 5 days, when they undergo a process called sporulation. These oocysts can remain in the environment for many months.

This remarkable ability to survive in the environment is partly to blame for their success. Researchers estimate that about a third of the human population is infected with T. gondii, and the organism has been shown to infect animals like sea otters miles away from the site of the original cat defecation after rains washed the infected feces into the watershed. While concerning, do not fret too much, there are certain precautions you can take to minimize your risk as noted below.  

Symptoms of Toxoplasmosis in Cats

Symptoms are often mild and can go unnoticed in otherwise healthy cats. Symptoms are related to the organ(s) affected by the tachyzoite, which may include: 

• Lethargy 

• Decreased appetite 

• Weight Loss 

• Fever 

• Difficulty breathing 

• Jaundice 

• Behavioral Changes 

• Vision loss 

• Weakness 

• Lack of coordination/ circling 

• Neck pain 

• Seizures 

The prognosis depends on the severity of the diagnosis and is typically worse when the lungs or liver are involved. It’s important to note that cats who are showing symptoms are unlikely to be shedding the infectious oocysts.   

How Veterinarians Diagnose Toxoplasmosis in Cats

Diagnosing toxoplasmosis can also be challenging as oocysts are rarely identified in routine stool exams, and the identification of oocysts does not mean the cat needs to be treated. Antibody titer testing (a test to determine infections) can be performed to help exclude the disease altogether if negative, or aids in the likelihood of finding infection, if positive.

A Cerebrospinal fluid (CSF) test (used to examine at fluid that surrounds the brain and spinal cord) and tissue samples (biopsies) can be analyzed for the presence of tachyzoites.

Treatment of Toxoplasmosis in Cats

Treatment in cats usually consists of a 2-4 week course of the antibiotic clindamycin and may be combined with other therapies including supportive care. It has been reported that cats shed oocysts only once in their lifetime since they develop immunity after the initial infection.  

Antibody testing can help confirm if your cat has been previously exposed.

Preventing Human Exposure to Toxoplasmosis

Below are a few helpful tips on ways you can take precautions to minimize your exposure:  

• Make sure to give your cat properly cooked/commercially prepared food. 

• Prevent exposure of your cat to the outdoors and ingestion of outdoor wildlife. 

• Wash all your fruits and vegetables thoroughly. 

• Avoid raw or undercooked meat and any associated kitchen utensils and wash your hands thoroughly with soap and water after contact. Ensuring your food is thoroughly cooked will eliminate any tachy-/bradyzoite cysts that it might have contained. 

• Wear gloves while gardening and keep sandboxes covered (or any other “cat-suitable” toilet locations). 

• Scoop the litterbox daily (it takes 1-5 days for the oocysts to become infectious, so day to week old feces pose a much higher risk). If you are immunocompromised or immunosuppressed, it is recommended to have someone else scoop the litterbox for you.  

Pregnant women should be more vigilant as it is known that T. gondii can cross the placenta and babies exposed can have significant birth defects.   

Recovery and Management of Toxoplasmosis in Cats

Most infected cats do not actually suffer from the disease itself, but essentially act as carriers for the disease to be promulgated so it would be rare for them to be shedding oocysts and be suffering acutely from the disease itself.   

However, if the cat does acquire the infection and tachyzoites start migrating throughout the body, it is at this point that the animal’s immune system kicks in and mounts a resistance. If it’s effective, the tachyzoites will be forced back into the bradyzoite stage and lie dormant in the unaffected organ(s). They may remain dormant for many years and are unlikely to cause future problems.  

Unfortunately, young and immunocompromised (FeLV or FIV+) cats are less likely to survive as they are less able to build a sufficient immune response and defense.