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Parasitic disease, is it far from us?


Human Parasitic disease is a kind of infectious disease caused by parasites invading various systems of the human body. In recent years, the incidence rate of Parasitic disease in China has decreased year by year, but Parasitic disease is still a common and frequently occurring disease of human beings. Modern Parasitic disease (edited by Duan Yinong, etc.) classified Parasitic disease into 93 categories, including protozoal diseases, nematodiasis, trematosis, tapeworm diseases, other Helminthiasis and Arthropod diseases. Clinical Parasitic disease collected prevention and control information of more than 200 Parasitic diseases[1].

China was once one of the countries with the most serious epidemic of Parasitic disease in the world. In 1988-1992, the first national human parasite sampling survey found that the parasite infection rate among the population was as high as 62.63%, of which the Parasitic disease infection rate in Hainan Province was the highest, 94.74%. China focuses on the prevention and control of "five major Parasitic diseases", such as schistosomiasis, malaria, filariasis, kala azar, hookworm disease, etc. In addition, there are many Parasitic diseases that seriously threaten the health of our people. At the beginning of the founding of the China, about 100 million people in the country were threatened by schistosomiasis; More than 70% of the total counties at that time were affected by malaria; More than 30 million patients with filariasis; About 530000 patients with black fever; More than 100 million people are infected with hookworm[2]. In 1989, the Law of the China on the Prevention and Control of Infectious Diseases listed some common Parasitic diseases as Class B or Class C infectious diseases. Parasitic disease is a public health problem that hinders social and economic development in China.

According to statistics, as of 2014, China has reported a total of 320 parasitic animals in the human body. According to the definition, parasitism refers to the relationship between two organisms living together, one of which benefits and the other suffers. Therefore, Parasitic disease usually refers to the process of human parasites invading and parasitizing the human body, growing and developing in the human body, reproducing and expelling from the body, and then entering the next host to continue infection.

In the Law of the China on the Prevention and Control of Infectious Diseases[3] revised in 2004, amoebic dysentery, schistosomiasis and malaria were classified as Class B infectious diseases, and leishmaniasis, Echinococcosis and filariasis were classified as Class C infectious diseases, showing a low prevalence trend. In 2020, there were 29517 cases of advanced schistosomiasis in China, and schistosomiasis control entered the elimination stage. In China, malaria has been eliminated and localized. The prevalence rate of hydatid patients is 0.07%. The national report in 2015 showed that the infection rate of rural worms was 3.25%, and the infection rate of intestinal protozoa was 0.79%. After long-term planning and prevention, the infection rate of Parasitic disease fell to the lowest level in history, and the country was in a low prevalence state.

With the impact of climate and environment, production and lifestyle changes, and increasingly frequent international exchanges, some rare Parasitic disease, malaria and other imported cases are increasing, which has become an important public health problem at present.

At present, the common Parasitic disease mostly occur in cattle, sheep, pigs and other domestic animals, some of which can parasitize on the human body, invade the human blood, digestive tract and other parts, causing damage to human health.

The parasitic relationship is relatively complex, as they can coordinate and constrain each other. For the convenience of research, parasites and hosts are divided into various types[4]:

1. Specialized host parasites

The entire life cycle or stage of a parasite is completed within a specific host.

2. Facultative host parasites

Refers to certain parasites that mainly live outside the host and can also live inside the host.

3. Internal parasites

It refers to the continuous parasitism in the host's tissues or organs to complete its life cycle, which usually has a significant impact on the host.

4. Extracorporeal parasites

Refers to the parasite that has been parasitizing outside the host to complete its life cycle, usually without causing any impact on the host, but this type of parasite will come into contact with the host's surface, suck blood, and leave.

5. Conditional pathogenic parasites

Refers to certain parasites that do not interfere with each other and coexist peacefully with the host, forming invisible infections. When the host's immune system decreases, these parasites are able to reproduce in large numbers and cause diseases.

Parasitic disease is a kind of epidemic disease, and its epidemiological characteristics are as follows:

1. Locality

The endemic of Parasitic disease is mainly affected by climate, geographical location, people's living habits and production methods. The prevalence of Parasitic disease will also be affected by seasonality.

Due to the wide variety of parasites, the life history of various parasite types is diverse, mainly divided into the following two types:

1. Direct growth and development history

2. Indirect growth and development history

Below are some common types of parasites and their effects on the human body.

1. Ascaris lumbricoides:

Ascaris lumbricoides is a type of nematode parasite that parasitizes in the human intestine. They are mainly infected through food and water through the mouth, developing, maturing, and reproducing in the human body. After being infected with roundworms, the human body may experience symptoms such as indigestion, abdominal pain, and diarrhea. The methods to prevent roundworm infection include washing hands frequently, handling food properly, and avoiding eating raw meat.

2. Plasmodium:

Plasmodium is a parasite transmitted through the bite of female Anopheles mosquitoes. After infecting the human body, they will invade red blood cells and produce new malaria parasites through division, causing red blood cells to rupture, leading to hemolytic anemia and causing symptoms such as fever, chills, and headaches. Due to the emergence of drug resistance, antimalarial therapy has become increasingly difficult, and the development of new malaria vaccines has become an urgent task in the medical community today.

3. Ticks:

Ticks are a widely distributed parasite that feeds by adsorbing on the skin of mammals and birds. They are the main vector of Lyme disease. This disease can cause joint pain, fatigue, and neurological damage.

4. Nematodes:

Nematodes are a type of tiny parasite, some of which can parasitize within the human body. For example, whipworms parasitize in the human large intestine, causing symptoms such as inflammation, diarrhea, and anemia.

5. Trichomonas:

Trichomonas is a kind of common venereal parasite, which can cause infections such as Vaginitis and Urethritis. Conducting safe sex and conducting regular examinations is an effective way to prevent trichomonas infection.

In addition to its impact on humans, parasites have also had a significant impact on the animal world. Some parasites, such as sea algae mites and shark parasites, invade the host in a covert manner and have a negative impact on its growth and reproductive ability. These parasites have also become an important research topic for biodiversity conservation.

For human beings, some suggestions can be made to prevent Parasitic disease infection:


Maintain good personal hygiene habits, wash hands frequently, consume fully cooked food, and avoid consuming unprocessed and rotten food.


Pay attention to preventing mosquito and tick bites, try to wear long sleeved clothing and pants when entering mosquito dense areas, and use mosquito repellents. In high-risk areas, mosquito nets can be used in bed.


Regularly check the health status of pets and livestock animals to prevent pet bacteria, mites, and other parasites from infecting humans.


Avoid contact with patients with infectious diseases, such as STD patients, hepatitis patients, etc.


Get vaccinated. Parasitic infections in some regions (such as Africa) can be prevented through vaccines, such as malaria vaccines.

Diagnosis is the key to discover and treat Parasitic disease. First of all, we should formulate and implement the medium-term and long-term plans for the prevention and control of key Parasitic disease. The prevention and control principles of "adjusting measures to local conditions, classifying guidance, highlighting key points" should be implemented in all places, and the implementation of parasitic disease prevention and control should be promoted from point to area. Secondly, the prevention and control of Parasitic disease should be included in the western development and the important content of solving the "three rural" problems. Parasitic disease mostly occurs in rural areas and among ethnic minorities. Through the "three trips to the countryside" activity, the Disease burden of farmers and herdsmen can be reduced, and the spread of Parasitic disease caused by frequent personnel mobility can be avoided. The publicity and education of Parasitic disease prevention and control is an important measure to reduce the harm from Parasitic disease. Only by letting the masses know the harm of Parasitic disease, can we attract the attention of all sectors of society and form a complete and effective Parasitic disease prevention and control mechanism.






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