Can you get Toxoplasma gondii by eating cat feces? Who made up such a disgusting rumor?

If you have a cat, you have probably heard of Toxoplasma. If you have a cat and want to have children, I guess you have had arguments with family or friends over Toxoplasma. Some people have never even heard of Toxoplasma, but insist that you can't keep pets while pregnant.

So, what exactly is this Toxoplasma gondii that can frighten expectant mothers or their families?

Toxoplasma is not a worm

Toxoplasma gondii, commonly referred to as Toxoplasma, is an intracellular parasite that can travel through the bloodstream to various parts of the host's body. Although the word "worm" is in its name, Toxoplasma is not an animal, but a vesicular parasite belonging to the SAR supergroup.

Toxoplasma gondii has only one serotype, but its pathogenicity to different hosts varies in different regions, so its isolates can be divided into type I, type II and type III.

There are three main forms of Toxoplasma gondii in its life cycle: trophozoites (tachyzoites), cysts (containing the parasite, also called bradyzoites) and oocysts. Among them, the official description of the appearance of tachyzoites is "crescent-shaped", and tachyzoites are also a common form during acute infection, so people call this parasite "Toxoplasma gondii".

Toxoplasma gondii in this life

The life cycle of Toxoplasma gondii can be described as "different paths leading to the same destination". Toxoplasma gondii has a wide range of intermediate hosts - a total of more than 200 warm-blooded animals (including humans) can be infected with Toxoplasma gondii, such as pigs, cattle, sheep, horses, chickens, dogs, cats and other livestock and poultry, as well as wolves, foxes, wild boars, bears and other wild animals.

Fortunately, cats are the sole definitive host of Toxoplasma gondii, which limits the spread of Toxoplasma gondii in nature (because cats have few natural enemies in the wild, and few animals are infected with Toxoplasma gondii by preying on cats). Otherwise, this guy would have already spread rampantly in nature.

Life cycle of Toxoplasma gondii. After the oocysts and cysts of Toxoplasma gondii are swallowed by cats, the sporozoites and bradyzoites will multiply in the body of the cat to form oocysts. After the oocysts are excreted with feces, they can develop into sporulated oocysts and then be swallowed by the intermediate host. They can then form tachyzoites in the intermediate host and continue to multiply, producing cyst walls in the host's cells and forming cysts again. Image: Merck Manuals Consumer Edition

Cats aren't the only ones who can get infected

Although many people will associate cats with Toxoplasma gondii, in fact, from the perspective of living habits, dogs are more susceptible to Toxoplasma gondii infection than cats, because dogs often go out for walks, which increases the risk of infection with Toxoplasma gondii; and under the premise of scientific breeding, cats stay indoors most of the time, so the probability of infection with Toxoplasma gondii is not high.

However, since cats are the final hosts of Toxoplasma gondii and Toxoplasma gondii only produces new eggs in cats, only cats can spread toxoplasmosis, while dogs or other animals cannot spread Toxoplasma gondii.

Most cats do not show clinical symptoms after being infected with Toxoplasma gondii, but when the infected organs (such as the lungs, liver, and eyes) become necrotic, they will show clinical symptoms, generally manifested as anorexia, fever, lethargy, difficulty breathing, and eye lesions.

For pets, the route of infection is similar. Animals can become infected with Toxoplasma gondii after eating infected raw meat. Free-range domestic cats are at a higher risk of infection because they prey on wild rodents or birds.

So for the safety of your cats and wild animals, please don't let your cats roam free!

Why do we always emphasize pregnant women?

In fact, anyone is at risk of infection with Toxoplasma. About 25% of people worldwide are serologically positive for Toxoplasma. In developed countries, Toxoplasma is one of the most common parasites infecting humans. The positivity rate of Toxoplasma serum antibodies in China is about 6%.

In the first few weeks of infection, the infected person may show cold-like symptoms, and a small number of people with weakened immunity (such as AIDS patients) may experience swollen and painful lymph nodes, as well as symptoms in the lungs, eyes, etc. However, most healthy adults show almost no symptoms.

Toxoplasma gondii can survive in the host's body in the form of cysts for months or even years. The infected people or animals are so-called "asymptomatic carriers."

The reason why we emphasize that it can infect pregnant women is that Toxoplasma can be transmitted to the fetus through the placenta, and the probability of mother-to-child transmission is about 30% to 50%.

If an infant is infected with Toxoplasma gondii in early pregnancy, it can cause serious consequences, including miscarriage, fetal malformation or stillbirth; if it occurs in late pregnancy, the fetus may be born prematurely, or may have no clinical symptoms at birth, but develop eye diseases or mental development disorders months or years after birth.

Should I send the cat away after the baby becomes pregnant?

Toxoplasma does not appear out of thin air, so if your cat is not infected with Toxoplasma, it will not spread toxoplasmosis.

What if your cat is infected with Toxoplasma gondii? Generally speaking, the conditions for cats to transmit Toxoplasma gondii to humans are quite harsh:

1. This is the first time that the cat is infected with Toxoplasma gondii (because if a cat has been infected with Toxoplasma gondii before, it will generally not excrete a large number of eggs when it is infected again);

2. The cat excretes feces containing eggs within 1 to 2 weeks (cats infected with Toxoplasma gondii for more than 3 weeks generally stop excreting eggs);

3. This feces containing worm eggs, after 1-3 days under suitable conditions, forms spores (worm eggs are not infectious before forming spores);

4. If a person comes into contact with the poop, for example, eats something directly without washing hands after cleaning the poop, I am not asking you to eat poop; or if a cat comes into contact with the poop and then touches human food, and the person eats the food directly, there is a possibility of infection with Toxoplasma gondii (heating food to 70℃ for more than 10 minutes can kill the eggs).

The process of human infection with Toxoplasma gondii perfectly illustrates the principle that "diseases come from the mouth."

How to prevent Toxoplasma gondii?

Unfortunately, there is no vaccine for toxoplasmosis yet, but by understanding the conditions under which Toxoplasma is transmitted, we can take steps to significantly reduce the risk of infection.

Cat habits

Once again, do not let your cat roam freely! When walking your cat outside, you must strictly supervise your cat to prevent it from eating outdoor plants and animals, and avoid contact between your cat and wild animals;

Remember to wash your hands after touching the cat;

Feed regular cat food and avoid feeding unprocessed raw meat;

Clean cat litter in time every day and disinfect the litter box regularly;

Deworm your pets regularly, as their roundworms and hookworms can also be transmitted to humans.

Personal Hygiene

Make sure heated food is cooked thoroughly;

After handling raw meat, you need to clean the knife and cutting board promptly and wash your hands carefully;

Wash vegetables and fruits thoroughly before eating them raw.

For pregnant women

You don’t need to separate from your cat or other pet, but you can take a break from cleaning up the poop;

You can take your cat to a pet hospital for a blood test to test IgG and IgM. The veterinarian will give you their judgment and advice.

After confirming that the cat is not infected with Toxoplasma gondii, temporarily restrict the cat from going out.

Only by looking at Toxoplasma gondii scientifically and rationally can we better avoid Toxoplasma gondii infection. Pet cats and Toxoplasma gondii are not a necessary and sufficient relationship. For pregnant women, as long as they develop good cat-raising habits and pay attention to personal hygiene, they can avoid the risk of infection.

This article is the 135th article in the 6th year of the Species Calendar, from the author of the Species Calendar @SamKakeru.