Cat Toxoplasmosis: Can Humans Get It Too?

Yes! But when it comes to cat toxoplasmosis, perhaps you should blame your butcher, and not your cat. Let's explore the health risks, signs, symptoms, and treatment for you and your cat.

Cat Toxoplasmosis: Are You At Risk?

You may have heard that cat toxoplasmosis may be transmitted to you by your cat.

You may also know that this can occur without any symptom at all displayed by either one of you.

So, it is possible that everyone in your household, including you and your cat, could be infected and you might not even know it.

Should you be concerned?

The Humane Society of the United States and the Centers for Disease Control (CDC) tell us that with respect to contracting any disease from your cat, pets pose minimal risk. Keeping your cat indoors reduces risk even further.

Certain groups are at higher risk. Those include:

  • Those with compromised immune systems
  • People with AIDS/HIV
  • People on chemotherapy
  • The elderly
  • Anyone born with congenital immune deficiencies
  • Pregnant women (risk being of congenital toxplasmosis)
  • People who have received organ or bone marrow transplants

The most reliable data from respected sources shows that while it is possible to contract toxoplasmosis from your kitty, undercooked or raw meat may be more likely to blame. As with any subject, there are conflicting reports on this ailment. Let's explore what reliable sources have to say about toxoplasmosis, your cat, and you.

What is Cat Toxoplasmosis?

Toxoplasmosis is a disease that is found in most mammals (including cats and humans) and birds. It is caused by Toxoplasma gondii (T. gondii) - a parasitic protozoan (single-celled organism).

According to reports from the Centers for Disease Control, the Toxoplasma parasite is found throughout the world, and as many as 60 million people in the United States may carry it.

Infections of toxoplasmosis of varying rates are found in other countries around the world. It varies by region as well, but the estimates are that anywhere between 20% and 80% of populations may have it.

Toxoplasmosis symptoms in humans, however, are relatively rare, causing few people to seek treatment. Cats that are infected may or may not show signs of the disease as well.

Let's examine some of the facts about cat toxoplasmosis, and look at the role cats play in transmission of the organism. We'll look also at the cat human connection, and some details on symptoms. Then we'll discuss what you can do about prevention, and treatment if needed.

Cat Toxoplasmosis: Cats Are The Best Hosts

You probably already knew that cats can contract and carry toxoplasmosis. What you may not know are a few important details about the part that cats (and other animals) play in transmission.

Parasites require a host in which to carry on their life cycle. Wild and domestic cats are the definitive hosts for Toxoplasma, which means that the cat is the only animal in which T. gondii reaches sexual maturity.

This, in turn, means that an infected cat can pass "oocysts," an infective spore form of the organism, in its feces. Of all the possible cat parasites, T. gondii is the one most closely associated with cats by lay people.

Other warm blooded animals, such as sheep, pigs, goats, and humans, act as intermediate hosts and do not pass the infective form in their feces. They can, however, infect other animals if their infected tissues (containing tissue cysts) are consumed.

Cat Toxoplasmosis: Transmission

According to expert sources on cat toxoplasmosis and feline and human health, the primary means by which people acquire toxoplasmosis is NOT direct contact with cats. In fact, sources including the CDC, veterinary schools, and the Humane Society of the United States, all state that raw or improperly cooked meat is most likely to blame.

The CDC also tells us that human toxoplasmosis infection may be acquired in several ways:

  1. ingestion of undercooked infected meat containing Toxoplasma tissue cysts
  2. ingestion of the oocyst from fecally contaminated hands or food
  3. organ transplantation or blood transfusion
  4. transplacental transmission (congenital toxoplasmosis)
  5. accidental inoculation of tachyzoites (actively multiplying form of Toxoplasma seen during acute infection)

The parasites form tissue cysts, most commonly in skeletal muscle, myocardium, and brain; these cysts may remain throughout the life of the infected person.

The primary means of acquiring a toxoplasmosis infection is through eating raw or undercooked meat, especially pork. The primary means by which your indoor cat would acquire the disease would also be by eating raw or undercooked meat. This is one argument against the so called raw meat diets that are promoted by some as being better for your cat.

The primary means by which your outdoor cat would contract the disease is the same, with the addition of an infected bird or rodent that your cat has caught as prey, or by walking on contaminated soil. This is a good reason for keeping your cat indoors, and not letting her roam or hunt.

Shortly after your cat is first infected, the Toxoplasma organism will grow and multiply in the cat's gut for about 3 to 10 days, producing oocysts. Then, for up to a two week period, your cat can produce and shed Toxoplasma oocysts in the feces.

These oocysts in the feces "ripen" (sporulate) and become infectious between one and five days later. It is during this one to two week period that it would be possible for you to acquire the disease from sporulated oocysts.

In order for that to happen, you would have to ingest (directly or indirectly) the sporulated oocysts. Since cats normally become immune after their first infection, this process typically only happens once in their lives.

Since this is a very specific and time restrictive set of circumstances, we can conclude that transmission of toxoplasmosis from cats to humans is difficult.

Expert sources agree. In fact, the Humane Society says that it's difficult for infected cats to transmit toxoplasmosis to their care givers.

Toxoplasmosis: Cats and Humans

In the United States, cats have become more and more popular over the years and have eclipsed dogs as the number one household pet. Many households have more than one cat. This means that cats and humans are in more close contact situations than ever before.

What you would think we should see then is an overall rise in the frequency of cat toxoplasmosis being transmitted to people.

Interestingly, this is not the case. According to the CDC, the most reliable method of determining infection levels tells us that the rate of infection in people in the US declined from the 1960s to the 1990s.

Human Toxoplasmosis: Symptoms

In most cases, in both animal and human toxoplasmosis infection, it does not cause any symptom at all. If symptoms are present, they may resemble the "flu," and can include:

  • Fatigue
  • Fever
  • Swollen lymph glands
  • Muscle aches and pains
  • Generally feeling unwell
  • Inflammation of the lungs
  • Inflammation of the heart muscle
  • Eye problems, such as blurred or loss of vision
  • Occasional sore throat

In the immunocompromised, the symptoms can be more serious. Those living with HIV/AIDS, receiving chemotherapy or that have recently had an organ transplant can develop symptoms of severe toxoplasmosis infection:

  • Headache
  • Confusion
  • Poor coordination
  • Seizures
  • Severe lung problems
  • Severe inflammation of the retina (ocular toxoplasmosis)

Cat Toxoplasmosis: Symptoms

The Cornell Feline Health Center says that like most humans, cats usually do not show any clinical signs of infection with Toxoplasma. Older felines are not as likely to be affected as are kittens and young adult cats. When cats do show symptoms of toxoplasmosis, they tell us...

"Lethargy, depression, loss of appetite, and fever are typical early nonspecific signs. Pneumonia, manifested by respiratory distress of gradually increasing severity, is the outstanding sign in many cats. Hepatitis (inflammation of the liver) may cause vomiting, diarrhea, prostration, and jaundice (yellowing of the mucous membranes). Inflammation of the pancreas and enlargement of lymph nodes also occur. Toxoplasmosis can also affect the eyes and central nervous system, producing inflammation of the retina or anterior ocular chamber, abnormal pupil size and responsiveness to light, blindness, incoordination, heightened sensitivity to touch, personality changes, circling, head pressing, twitching of the ears, difficulty in chewing and swallowing food, seizures, and loss of control over urination and defecation.

In some cases, coinfection with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) may predispose a cat to develop toxoplasmosis."

In reviewing lists of cat illness symptoms it's clear that many of these symptoms can be caused by other diseases, so definitive diagnosis by a veterinarian is required.

Here is more information on toxoplasmosis symptoms.

Treatment For Toxoplasmosis

Treatment is not normally required for a healthy person who is not pregnant. Symptoms, if any, will usually go away within a few weeks. For pregnant women, or people with weakened immune systems, treatment may be recommended.

Toxoplasmosis can have extremely serious implications for AIDS patients, as well as pregnant women. Toxoplasmosis is one of the leading causes of death to AIDS patients. With respect to pregnancy, it can cause miscarriage or still birth, and a host of birth defects.

Medications commonly used to treat the disease are spiramycin, pyrimethamine, and sulfadiazine. See your health care provider for proper treatment.

One treatment for toxomplasmosis seems right from the SyFy channel. This treatment for "Crazy Cat Lady Syndrome" uses gold nanoparticles and lasers to burn away the disease.

Toxoplasmosis: Prevention

There are a number of things you can do to prevent both cat and human toxoplasmosis. While this list is not all inclusive, every step you take can reduce your risk. If you are in one of the high risk groups, these steps can be significant..

  • Do not eat raw or undercooked meat. If you touch raw meat, do not touch your face.
  • Cook all meat completely (to an internal temperature of 160° F and until it is no longer pink in the center or the juices run clear).
  • Wash your hands, cutting boards, utensils, and sink with soap and warm water.
  • Wash all raw vegetables and fruits thoroughly.
  • Get someone else to empty the cat’s litter box.
  • Have the litter box cleaned every day or more than once per day to avoid sporulation of oocysts.
  • If you do clean the litter box, where disposable rubber gloves and a mask to avoid breathing dust. Wash your hands after cleaning the litter box.
  • Avoid sandboxes as cats may use them as litter boxes.
  • Do not feed your cat raw or undercooked meat.
  • Keep your cat inside to prevent it from hunting rodents or birds that could be infected.
  • Keep your cat inside to prevent it from coming in contact with contaminated soil, plants, or insects.
  • Wear gloves when gardening. Keep your hands away from your eyes, mouth, and nose. Wash your hands when finished.
  • Do not drink unpasteurized dairy products, especially goat's milk.
Pregnant woman feeding canned foodA pregnant woman feeding her cat canned food in order to avoid Toxomplasmosis infection.

The CDC says that cats should not be fed raw meat, food scraps, or be allowed access to live prey.

It is worth noting that if your cat has not been outside or fed undercooked meat for at least 3 weeks, and no other risk factors are present, that there is very minimal risk.

This is because there is very little chance that she will be shedding oocysts, even if she did contract cat toxoplasmosis prior to that time.

You should also note that some sources state that for purposes of congenital transmission, acquiring toxoplasmosis up to six months prior to pregnancy can be considered the same as contracting it during pregnancy!

See my cat toxoplasmosis pregnancy connection page for more information.

One very important piece of information with respect to AIDS patients is that most of the time the symptoms from toxoplasmosis are from previous infections. In other words, they contracted toxoplasmosis earlier in life, and they are experiencing a serious infection simply because their immune systems are compromised.

Always take your cat to your veterinarian if you witness symptoms of cat toxoplasmosis or signs of any other health condition.

Recommended Reading on Cat Toxoplasmosis:

Toxoplasmosis - the CERHR page on toxoplasmosis

Toxoplasmosis - cat toxoplasmosis information from Cornell Feline Health Center

Cat and Human Health Issues - including cat toxoplasmosis and other zoonotic diseases.

Photo Credit: James Gathany

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