I hope that after reading this, everyone will be able to correctly understand Toxoplasma gondii and not abandon your pets casually!

Author: Professor Zu Shuxian, Clinical Epidemiology Research Office, Anhui Medical University In recent years, the number of domestic cats and dogs kept as pets has increased. Many newspapers and periodicals have published articles warning the public that cats and dogs can cause toxoplasmosis and cause terrible fetal malformations. Although this is necessary, it is a pity that many articles are not accurate enough, and some are exaggerated and sensational, causing unreasonable panic among the public and causing many small animals to be abandoned. This article provides answers to several questions frequently asked by pet owners.

1. What is toxoplasmosis?

Toxoplasma gondii is an infection caused by a parasitic Toxoplasma gondii. Toxoplasma infection is very common around the world. About 16 to 40% of adults in the United States and the United Kingdom have been infected, and some surveys have reached 70%. In Europe, 50-80% of adults in mainland China and Latin America have been infected, and as high as 90% in France. From 1985 to 1990, surveys conducted in 23 provinces, municipalities, and autonomous regions in my country found that most of the rates were below 10%, which was significantly lower than that in foreign countries. The vast majority of normal people infected with Toxoplasma gondii have no symptoms or very mild symptoms. It is not known when they were infected. Only a few people have fever, swollen lymph nodes, headache, and muscle and joint pain when they are first infected (or called primary infection). And abdominal pain, after a few days or weeks as the body develops immunity, the symptoms disappear, but the cysts formed remain in the body for months, years or longer, and generally heal on their own. However, for patients with severe immune deficiencies, such as AIDS patients, if infection occurs, the consequences will be serious. Infections in pregnant women can be transmitted to the fetus, and serious consequences may occur.

　2. How is Toxoplasma gondii transmitted?

The first is to eat undercooked meat, especially pigs and sheep. Almost all mammals and birds, such as rats, pigs, sheep, cattle, rabbits, chickens, ducks, geese, etc., can be infected with Toxoplasma gondii, and the infection rate is very high. The source of human infection mainly comes from the meat of these animals. For example, if the temperature of the meat is not high enough and the time is too short, and the Toxoplasma gondii is not killed, there is a risk of infection. Contamination of raw meat or meat cutting boards can also be contagious. Contaminated sheep and milk can also be transmitted. The above-mentioned low Toxoplasma infection rate in the Chinese population may be related to the Chinese people's habit of eating cooked meat. Dogs can also be infected with Toxoplasma gondii, but their feces and excrement are not contagious, and they will not be infected if they do not eat dog meat. Some people say that "dogs are closely related to humans and are one of the important sources of infection for humans." Others blame their children for having "mental retardation, congenital heart disease, or an extra finger" because they have dogs at home. They are all baseless.

Infected cat feces are an important source of infectionsource. Cats and felines are the ultimate hosts of Toxoplasma gondii. Infected cats excrete cysts in their feces, which usually lasts from 1 week to 20 days, and rarely longer; this period is the infectious period. According to surveys around the world, about 1% of cat feces contain Toxoplasma gondii cysts. The cysts in cat feces need to develop in the outside world for 2 to 5 days before they become infectious, so when to dispose of cat feces is very important. Cystic zygotes can survive in water and moist soil for several months or longer. Therefore, food, drinking water, and even dust contaminated by cat feces can be transmitted to humans by eating them. In areas where meat is fully cooked, cats are an important source of infection for humans. However, many other animals that serve as intermediate hosts can also transmit. For example, there are many pastures with very few cats, and many cattle and sheep are infected; there are also some islands in the world that do not have cats, and the infection rate among island residents is still very high. Therefore, an important domestic book "Human Parasitology" said: Since the infection rate of domestic animals as intermediate hosts is very high, from the source of human infection, the contamination of cat feces is not as important as eating undercooked meat.

Toxoplasma gondii infection in pregnant women can be transmitted to the fetus, resulting in congenital infection. Since congenital infection of the fetus may have serious consequences, it is very important. However, only pregnant women who have not been infected with Toxoplasma gondii before pregnancy can transmit the first (primary) infection to the fetus during pregnancy. If a pregnant woman has been infected with Toxoplasma gondii before pregnancy, she is no longer infected. Danger.

3. What are the dangers of congenital Toxoplasma infection to the fetus?

If congenital infection occurs in the first 3 months of pregnancy, about 40% of the fetuses may be seriously damaged, resulting in miscarriage, stillbirth or neonatal diseases, or may have eye, brain or liver lesions or malformations after birth, such as retinochoroiditis, cataracts, Calcification in the brain, hydrocephalus, microcephaly, intellectual disability, jaundice, and hepatosplenomegaly. Less than 3% of infections that occur in the third trimester of pregnancy are serious.

In 1996, a study on the impact of Toxoplasma gondii on fetuses at the University Hospital of Helsinki, Finland, found that among 16,733 pregnant women they tested for serum antibodies, only 42 had primary infection, and 36 of them had received spiramycin treatment. , Long-term follow-up results showed that 4 cases of congenital toxoplasmosis occurred in their children, 2 cases had severe neurological lesions, and 2 cases had no clinical symptoms. The remaining children born to pregnant women with primary infection are no different from the children of other pregnant women in terms of growth, development and intelligence.

4. Should pregnant women undergo routine serum Toxoplasma antibody testing?

Although countries such as France and Austria require routine Toxoplasma antibody testing for pregnant women, the method is to conduct a serum antibody test early in pregnancy. If it is negative (that is, there has been no infection), the pregnant woman is told to pay attention to preventing infection and reexamine regularly; once a pregnant woman is found to have For acute infection, treatment with spiramycin should be performed while the fetus isAmniocentesis and ultrasound. If it is proven that the fetus is infected, the pregnant woman will be treated with sulfonamide plus pyrimethamine; if the fetus is found to have obvious symptoms, the parents may consider terminating the pregnancy. But whether this approach is worth pursuing is still debated. Because the chance of maternal infection during pregnancy and fetal infection is very small, the British and American studies concluded that this kind of screening is not worth doing routinely.

Screening pregnant women for infections is a serious public health issue. It is generally believed that it must be determined based on local epidemiological studies. First of all, the inspection and treatment principles must be clear. The screening method must have high accuracy, systematic inspection and treatment must be continuous, acceptable to the public, and cost-benefit analysis shows that it is indeed very effective.

Many hospitals in our country are now conducting common Toxoplasma antibody tests on pregnant women. In some hospitals, the examination and treatment are not standardized. The examination is just an examination. The result does not matter and no treatment is done. More than once, someone asked me about the meaning of the test results: What should I do if it is positive? Should I receive treatment or terminate the pregnancy? Some results have been contradictory. The test result in one hospital is positive, but the reexamination or another hospital test turns out to be negative. Why? Therefore, the quality of reagents and tests must be high, screening methods must be standardized, and clinicians must be familiar with the meaning and judgment of serological test results. False positive and false negative results caused by low experimental quality not only waste patients' money, but also It also causes anxiety to patients and their families, brings great mental burden, and even causes irreparable losses.

The chance of infection among pregnant women in our country may be smaller than that in foreign countries. Therefore, our country should first conduct evaluative research in qualified hospitals and then formulate relevant policies. Before a clear policy is established, it should not be blindly implemented universally.

5. How to prevent and treat Toxoplasma gondii infection?

First, pay attention to dietary hygiene. Meat should be fully cooked and avoid contamination of cooked food with raw meat.

Second, cats should be kept at home, fed cooked food or ready-made cat food, and not allowed to hunt outside. Because cats are infected by eating infected mice or birds, or eating food contaminated with cat feces.

Third, pay attention to daily hygiene, remove cat feces every day, and wash hands carefully after contact with animal excrement.

Fourth, unless the serum test of pregnant women proves that they have been infected with Toxoplasma gondii, pregnant women should avoid contact with cats and their feces during pregnancy.

Fifth, Toxoplasma infection can be treated with a variety of simple and effective drugs, such as sulfonamides plus pyrimethamine, and spiramycin. Treatment must be carried out according to medical advice. Timely treatment of infection in pregnant women can reduce the chance of fetal infection.

Editor’s note:

Every mother wants to give her children the best growing environment. This is human nature. Unfortunately, JudaMost gynecologists do not understand the science of domestic animals, and they just advise expectant mothers to stay away from pets, and even sound alarmist, causing unnecessary panic. Blindly giving away a harmless dog will make the dog fearful, depressed, and its health and temperament will deteriorate. The old owner will also damage his health due to longing and guilt. It is really an unnecessary tragedy. Women who have dogs should do a TORCH test before preparing to become mothers.

The examination of Toxoplasma gondii is one of the four items it contains. If the TORCH test report shows that you have been infected with Toxoplasma gondii, you can welcome the arrival of your baby with peace of mind; but if the result shows that you are infected, you cannot get pregnant for the time being. Toxoplasma gondii mainly exists in the intestines and stomachs of stray cats, but is generally not found in domestic cats. If you have kept cats for many years, even if you have been infected with Toxoplasma gondii, you have already produced antibodies in your body, and it doesn’t matter.