Toxoplasmosis in Cats and What It Means for Pet Owners

Key Points

• Toxoplasmosis is a parasitic disease that affects approximately 11 percent of the U.S. population over the age of six. 

• Handling cat feces, drinking contaminated water, and eating undercooked meat are the most common ways of contracting the parasite. 

• The Toxoplasma parasite is particularly dangerous for babies, pregnant women, seniors, and people with compromised immune systems. Infants born with toxoplasmosis may have eye and brain damage. 

• Veterinarians treat cats with Toxoplasma with antibiotics such as clindamycin or azithromycin. 

• Avoid handling your cat’s waste at all costs if you're pregnant.

Cats are vectors of various diseases for people and other animals. If they're allowed to go outdoors and interact with other cats, they can catch parasites, viruses, bacteria, and fungi and then pass them on to their owners. 

This article details everything you need to know about toxoplasmosis, a disease primarily transmitted by cats and contaminated food and water. Read on to find out how common the parasite Toxoplasma is, how it’s transmitted and treated, and how to protect yourself and your cat against it. 

What Is Toxoplasmosis?

Toxoplasmosis is a disease caused by a parasite called Toxoplasma gondii. It's considered a zoonosis, a condition animals pass to humans. 

This health issue is common in people regardless of whether they own pets. According to the Centers for Disease Control and Prevention, up to 11 percent of the U.S. population six years and older (or about 40 million individuals) carry it or have been infected with the parasite.

How Common Is Toxoplasma in Cats?

Although cats are capable of passing Toxoplasma to humans, the likelihood of this happening is relatively low. Around 15 to 40 percent of all cats have been infected with the parasite at some point, but the infection must be active in order for it to be transmissible.

The infection is much more common in cats that go outdoors as they come into contact with other animals that pass the parasite to them. Pets can be exposed to Toxoplasma oocysts — the cells of the parasite that are shed through feces — simply by walking in areas where other cats have defecated.

How Is Toxoplasma Transmitted to Other Animals and Humans?

As stated above, a Toxoplasma infection must be active for a cat to transmit it to their owners and other animals in the home. Because the primary source of infection resides in the cat’s feces, pet owners can become infected with the parasite by cleaning their cats’ litter boxes while not wearing gloves. 

Once the cat releases the oocysts in their feces, they contaminate their paws or re-infect themselves by trying to cover up their waste in the litter box and then grooming themselves. Some oocysts survive for a short time on the cat’s fur around the anus. 

Toxoplasma contamination can also occur after ingesting undercooked meat or food cut by contaminated utensils, drinking contaminated water, and receiving blood transfusions from other infected animals and humans. Women can pass the infection to their unborn children during pregnancy.

What Disease Does Toxoplasma Cause in Pets?

The Toxoplasma parasite takes multiple forms depending on the host and how it's carried.

If any animal or human accidentally ingests Toxoplasma oocysts, they primarily end up in the intestines. Over time, these oocysts multiply into tachyzoites, which spread from the primal infection site — the intestines — to any tissue in the host’s body. Tachyzoites evolve into bradyzoites, parasitic cysts that attack organs such as the brain and muscles.

However, if your cat’s immune system functions normally, it renders the infection dormant before it spreads to other parts of the body. In a study published in the Korean Journal of Parasitology, researchers Kyu-Sung Ahn, et. al. report: "After the first infection, cats develop tissue cysts in the muscle, nervous system and other organs, and are considered to be immune to reshedding of oocysts for the rest of their lifetime."

Toxoplasma causes health complications and symptoms in pets with less capable immune systems, such as kittens, seniors, and pregnant cats, along with those suffering from infectious diseases such as feline leukemia virus or feline immunodeficiency virus.

Some discernible clinical signs include:

• Jaundice, a sign of liver failure

• Respiratory complications, including pneumonia

• Vision impairment, including blindness

• Central nervous system complications ranging from disorientation, seizures, and personality changes to difficulty chewing and swallowing food

• Digestive distress in the form of diarrhea and vomiting

Most cats that become infected with Toxoplasma gondii show no clinical symptoms, so the infection often goes unnoticed. If a cat seems healthy, there's no reason for owners to take them to the veterinarian, making diagnosis challenging.

If you're unsure about whether or not your cat is infected, your vet can perform a quick test for an active Toxoplasma infection. Because the infection is so widespread in cats, it's recommended that new cat owners get their pet tested as soon after adoption as possible.

Why Is Toxoplasmosis Dangerous for Humans?

Like cats, the majority of people who become infected with Toxoplasma don’t show any clinical signs, especially if they have fully functioning immune systems. Infants, seniors, and people with weakened immune systems, such as those undergoing autoimmune diseases or cancer treatment, are more vulnerable to the parasite.

Severe toxoplasmosis in vulnerable individuals causes the following symptoms:

• Vision problems ranging from blurred or reduced vision to eye inflammation and redness

• Swollen lymph nodes 

• Muscle aches

• Fever

• Headaches

• Lung or heart inflammation 

According to an August 2023 article by NutritionFacts.org, a Toxoplasma infection is sometimes associated with psychiatric disorders, including self-harm, memory impairment in older individuals, and schizophrenia. Infants who contract the infection during pregnancy can be born with eye or brain damage. 

Toxoplasmosis Treatment for Cats

If your cat is diagnosed with toxoplasmosis, your vet should treat the infection immediately. Toxoplasma gondii is not a typical parasite because it doesn't respond to classic anti-parasitic medication. Only antibiotics are effective at killing it. Common antibiotics include clindamycin, which your pet must take for up to four weeks, trimethoprim sulphonamide, and azithromycin.

To ensure the treatment is effective, your cat must undergo additional testing for Toxoplasma until they test negative. Don't interrupt the treatment if you notice your cat feeling better, as there's no guarantee that they're parasite-free. 

Depending on your cat’s health status, your vet may also prescribe anti-inflammatory medication consisting of corticosteroids. Don't administer these drugs to diabetic pets or those suffering from autoimmune or other metabolic diseases. 

Pets with acute toxoplasmosis (those who have been recently infected) require IV fluid therapy and analgesics and must be monitored for pancreatitis, hepatic failure, encephalitis, and cardiomyopathy.

Toxoplasmosis Treatment for Humans

It's challenging to treat this zoonotic disease as the infection must be active when therapy is administered. If you don't test positive for Toxoplasma but show symptoms, your doctor may prescribe symptomatic medication depending on the organs affected. 

If you test positive, the most common medications currently used for treating Toxoplasma infections in humans are clindamycin, sulfadiazine, spiramycin, trimethoprim-sulfamethoxazole, and leucovorin. To combat the side effects of anti-parasitic medication, take supportive medications such as vitamins from the B complex. 

The recommended length of treatment is two to six weeks until you test negative. Pregnant women diagnosed with Toxoplasma must take the treatment until the end of pregnancy. Infants born with toxoplasmosis must undergo treatment for a full year.

Is It Safe to Change Your Cat’s Litter Box During Pregnancy?

It is not safe to change your cat's litter box if you're pregnant. If you don't intend to house your cat elsewhere during your pregnancy, get them tested for Toxoplasma by a vet. Tests for humans are readily available, too, so contact your doctor as soon as possible. 

Even if your cat doesn’t have an active Toxoplasma infection, it's best to have someone else remove your cat’s waste and clean the litter box while you're pregnant. Or, consider a self-cleaning litter box. If this isn't possible, practice excellent hygiene when changing your cat’s litter. Wear disposable gloves and remove the litter entirely without touching it. Use disinfectants on both the litter box and the scoop, and wash your hands thoroughly afterward.

Protecting Yourself and Your Cat Against Toxoplasmosis

There’s no guarantee that you or your cat won't be exposed to the parasite. However, there are measures to take to prevent your cat — and, by extension, you and your family — from coming in contact with a contaminated source or infected animal. 

First and foremost, don't allow your cat to go outdoors. Indoor cats are much healthier than their outdoor counterparts when it comes to contracting infectious diseases or parasites. They also have a lower risk of passing these diseases to people. Feral cats often carry and pass along the parasite, fostering a continuous circulation of Toxoplasma in the wild. 

Second, deworm your cat on a regular basis, depending on your vet’s recommendations. It's recommended to deworm outdoor cats every three months, while indoor-only cats require treatment once every six months. 

Finally, avoid a raw meat diet. Cooked meat is safer and healthier for both cats and humans as it has a very low chance of carrying dangerous germs or parasites.

If you're pregnant or if your immune system is compromised, follow these steps to protect yourself:

• Avoid changing your cat’s litter as much as possible.

• Keep your cat indoors at all times and have them periodically tested for Toxoplasma. 

• Avoid adopting a new cat or kitten.

• Wash fresh produce carefully. 

• Wash all utensils and kitchen tools carefully with dish soap after handling raw meat. 

• Wear gloves when gardening, as soil has the potential of carrying Toxoplasma oocysts. 

• Don't give your cat raw or undercooked meat products. 

Keeping Everyone Healthy

Like any other pets, cats can transmit zoonotic diseases to their owners. Toxoplasmosis is a health risk that every cat owner should be aware of. Develop a proactive mindset to prevent infection, including not letting your cat go outside, not handling cat feces if you're pregnant or immunocompromised, and practicing excellent hygiene around the litter box.

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