When the word "parasite" is used in a sentence referring to a pet, it can be unsettling. But being aware of the parasites that can affect your cat is essential. This is especially true for toxoplasmosis since it can also infect humans. Understanding toxoplasmosis, how it's spread, and the symptoms, will help you protect your cat and your family.

What is Toxoplasmosis?

Toxoplasmosis is a worldwide disease caused by the protozoan parasite Toxoplasma gondii (also referred to as T. gondii). It can infect all warm-blooded animals as well as humans. Wild and domestic cats are the only definitive hosts for Toxoplasma gondii. This means that the parasite can only sexually reproduce in cats. It can then be shed in the cat's poop, where it can infect other animals and people.

How Do Cats Get Toxoplasmosis?

Cats become infected with T. gondii by ingesting rodents, other small mammals, or birds that are already infected, or eating undercooked meat from an infected animal^1,3. They can also be infected by licking or consuming something that has been contaminated with poop from another cat shedding the parasite^1,3. Kittens can also be infected before birth or from drinking the mother cat's milk if she is infected, though this is rare³.

How is Toxoplasmosis Transmitted?

Once a cat is infected, the parasite is then shed in the cat's poop for up to two to three weeks following the start of the infection^1,3. The start of shedding varies depending on how the cat was infected, starting three to ten days after infection by eating prey, or up to 48 days after infection from poop contamination³. Once it's passed in the poop, it takes one to five days for the parasite to become infective to others^1,3.

This well-adapted and hardy parasite can live in the environment for months (and sometimes years). It can contaminate any of the following:

• Soil
• Water
• Fruits
• Vegetables
• Gardens
• Sandboxes
• Grass
• Litter boxes
• Any other place that a cat may poop

Remember, you can't tell if the soil or anything else is contaminated because the organism is microscopic and can't be seen with the naked eye.

Toxoplasmosis Symptoms in Cats

Despite being infected, most cats show no signs of being sick. Some immunocompromised cats may have clinical signs such as fever, loss of appetite, and lethargy. This could include cats with feline leukemia virus, feline immunodeficiency virus, and kittens.

Certain symptoms are dependent upon the location of the parasite within the body. If T. gondii infects the lungs, it can lead to pneumonia and difficulty breathing. When the parasite affects the liver, a cat's skin and mucous membranes become jaundiced (yellow). When the eyes are infected, several parts of the eye become inflamed, the pupil size becomes abnormal, and blindness can occur. The effects on the central nervous system include lack of coordination, increased sensitivity to touch, personality changes, circling, head pressing, twitching ears, trouble chewing and swallowing, seizures, and the inability to control urination and defecation. But, again, most cats show no signs.

How Toxoplasmosis Is Diagnosed in Cats

A diagnosis of toxoplasmosis is based on a cat's history, presenting symptoms, and blood tests. The blood test measures two types of antibodies, IgG and IgM, to T. gondii. If the levels of IgG are high and the cat appears healthy, this indicates that the cat has been exposed to the organism and is likely immune and not shedding it¹. An active infection is indicated if the levels of IgM are high. This supports starting treatment in cats with suspected symptoms of toxoplasmosis, though a conclusive diagnosis requires microscopic examination of tissue samples from the cat, which is often not performed¹. Toxoplasmosis may be difficult to diagnose. Your veterinarian may have to do several tests.

If there are no antibodies in a healthy cat, this indicates that the cat is susceptible to infection and would shed the organisms via its poop into its environment for up to two to three weeks.

Toxoplasmosis Treatment in Cats

Once it's determined that a cat is showing clinical signs of toxoplasmosis, treatment involves an antibiotic. Corticosteroids are used if there's evidence of significant inflammation in the body, especially in the eyes or central nervous system¹.

Treatment should be started immediately and continued until a few days after all symptoms have resolved. Improvement should be noted within two to three days. If your cat doesn't improve, a re-evaluation of the diagnosis is important¹.

How to Protect Your Cat from Toxoplasmosis

To protect your cat, and potentially yourself, from infection, consider doing the following:

• Keep Your Cat Indoors or Watch Them Closely When Outside
  This reduces the chance they will eat infected animals, eat contaminated grass, or dig in contaminated soil.
• Avoid Raw Meat Diets
  Uncooked meat can be a source of infection. Commercial dry and canned foods have a lower risk of contamination.
• Support Your Cat's Immune System
  Talk to your veterinarian about supplements like probiotics, omega-3 fatty acids, and others.

Is Toxoplasmosis Dangerous to Humans?

Handling contaminated items can put you at risk of infection if proper safety measures aren't followed. The chance of human infection from cats is relatively low because cats only shed the parasite for a short time¹. Frequent removal of poop from the litterbox (before the parasite can become infective), wearing gloves, and washing hands afterwards minimizes the risk of infection¹. In the U.S., people are more likely to be infected by eating unwashed fruits and vegetables or undercooked meat than by handling cat poop¹.

It's estimated that more than 60 million people in the U.S. are infected¹. The good news is that toxoplasmosis seldom causes significant health issues for healthy individuals. Healthy people who become infected generally have no symptoms². But there are risks to be aware of, especially for pregnant individuals and the immunocompromised (young children, the elderly, and those with immune-impairing medical conditions). The Centers for Disease Control and Prevention (CDC) has labeled toxoplasmosis as one of five neglected parasitic infections of people because of its prevalence¹.