Why can parasites survive in humans? Does the immune system attack parasites?

The parasite was a behemoth compared to white blood cells, but they attacked it without fear. While it is uncertain whether we will win or lose this time, most of the time, our immune system will win. So, there will be many times in our life that we will be infected with bacteria, viruses, and parasites, but many times the immune system has already killed them before we know it.

Only when the external enemy is too strong, or too stupid, (most parasites will form a balance with the host after finding it, after all, the host is killed in minutes, and they have nowhere to parasitize), the immune system is in full force, and finally the whole line collapses, we realize what is happening. Viruses and bacteria enter the body through wounds, (helper T cells can recognize the peptides of viruses and bacteria and use killer T cells, macrophages, B cells to release antibodies), so this is the microcosm, that is, the immune system only includes your blood, kidneys and other organs. And the parasite enters through the mouth, wound (the difference here, because the parasite is a large animal, so the immune system is not effective at all) and the one that enters the stomach is even less likely to kill, although the pH of a person can even corrode the outer plastic of the car, but the outer layer of the parasite has a special substance that prevents being killed.

will attack, but parasites have multiple immune evasion mechanisms. These include changes in the antigenicity of the parasite surface, such as antigenic mutation, antigenic camouflage, and changes in the host's immune response through a variety of disruption mechanisms. But the mechanism is not well studied.

There are many times in life that people are infected with bacteria, viruses, and parasites, but many times the immune system has killed them before we know it. Let's start with the low of the level. Anisakis usually completes its life cycle in fish or other marine organisms, it does not complete its life cycle in humans.

Humans can be infected with anisakis when they eat raw meat, so people are more susceptible to anisakariasis in sashimi-loving regions such as Japan, the Netherlands and parts of South America. It's actually easy to prevent Anisakis worm, just handle it well when cooking. The U.S. Food and Drug Administration recommends that anisakis nematodes be killed when the fish is boiled at temperatures above 60 degrees Celsius, or that the fish be refrigerated at minus 20 degrees Celsius for seven days.

One reason is that the body's own immune system determines the presence of parasites.

The human immune system has evolved to avoid the effects of many bacteria on the human body, but parasites are an exception, parasites are not just parasitic in humans, but a variety of organisms can be their hosts. The immune system of the host itself cannot detect the existence of parasites, so many people still don't feel when the parasites have grown up to be very big, because their immune systems are not abnormal, and the body is not threatened to produce a stress response. Another reason is that these parasites subconsciously do not attack the host.

Why is the epidemic and distribution of parasitic diseases so clearly endemic?

climatic conditions; Geographical distribution of intermediate hosts or vector arthropods, population habits, and modes of production.

Briefly describe the types of parasite life history.

Direct type: no intermediate host is required to complete the life cycle, and the eggs or larvae during the infection period directly infect the human.

Indirect: An intermediate host is required to complete the life cycle, and the larvae develop throughout the intermediate host to the infectious stage and then infect humans through the intermediate host.

Briefly describe some of the key measures for parasitic disease control.

Control of infectious agents: Census of infected people and patients, detection and treatment of reservoir hosts.

Cutting off transmission routes: management of faeces, management of water, good sanitation and hygiene, control or eradication of vector arthropods and intermediate hosts.

Protection of susceptible persons: collective and individual protection, drug protection, change of bad eating habits, improvement of production methods and conditions, etc.

First of all, the human environment is suitable for them to survive.

Secondly, because they have the ability to resist the attack of the immune system.

The water contains bacteria and planktonic insects, this raw water is not drunk by ordinary people, otherwise it may cause bacillary diarrhea and diarrhea, and it is generally killed after boiling, and the potential harm is other toxic chemicals in it.

The thread-like insects in the sewage are generally visible to the naked eye, there are many types, and there is generally no great harm, I don't know which one you are talking about, the known harm is schistosomiasis, schistosomiasis parasitizes the mesenteric venous vessels of humans and mammals, and the eggs enter the liver with the bloodstream, or are excreted with the feces. The eggs hatch into larvae in water for several hours. The larvae burrow into the snail in water and develop into the maternal larvae, daughter larvae, and cercariae.

Cercariae escape from the snail into the water, encounter humans and mammals, and then burrow** into the juvenile worm, and later enter the veins or lymphatic vessels to cause schistosomiasis.

Look what kind of worm it is, the human body is generally not immune to parasites.

The human body has the ability to resist the invasion of foreign objects, and the strength depends on the individual's physique.

Under normal circumstances, the human body should not kill parasites automatically.

Look at whatever. Generally, it depends on the medication.

Some parasites are able to evade the immune effects of the host.

Immune evasion. Human parasites are parasites that use humans as their hosts. It can be divided into two categories: internal parasites and external parasites. Most of them belong to protozoa, nematozoa, flattened animals, annelids, and arthropods.

In parasitology, protozoa are commonly referred to as protozoa, and nematozoa and flattened animals are collectively referred to as helminthes. Most of the important species of endoparasites include protozoa, nematodes, flukes, and tapeworms.

You can't say yes or no.

The situation of people is different in different periods, and different people are different. Many children will have parasites in their early years, which are related to unhygienic habits and living environment, eating food, and adults will also have parasites, some scabies, mites, etc., which are very common to cause diseases, and some people in the intestines will have roundworms and so on. The pathology of various diseases is different, sometimes people are sick and there may be parasites, but after the disease is cured, there are none, so this can not be generalized, you can check the information about human parasites, some people have parasites, but some people may really not, you say for example, some people suffer from immune deficiency, he lives in the sterile room every day, even the bacteria are gone, where are the worms?

So there are extreme examples, but maybe quite a few of us have some parasites in them.