Bayer's acute diarrhea was once infected with bacteria, so it is entirely possible that he was infected with parasites.
In fact, after Mr. Bei ate crabs raw at the seaside for the first time, he will never eat crabs again in future movies. He will also remind the audience that crabs are full of parasites because he went back and fell ill after eating crabs that time. It may be infected by a parasite.
In addition to strong psychological quality and appetite, Mr. Bei should have a very strong medical security team behind him. He can have a regular physical examination and let the doctor handle it.
Besides, although Mr. Bei is a "person standing at the top of the food chain", he doesn't eat everything, such as frogs and snakes that have never been eaten raw, because these two animals are most likely to carry parasites, and the parasites they carry are usually more dangerous. Moreover, like polluted water and rotten food, Mr. Bei won't touch it.
Let's introduce parasites.
I. Introduction
Parasite refers to a creature, which lives on another animal most of the time, called host, and at the same time, it causes damage to the parasitized animal.
Parasites are characterized in that all living things parasitize or attach themselves to the host in a way called parasitism, so as to obtain nutrition or shelter for their survival, development or reproduction. Many small animals live in a parasitic way and attach themselves to larger animals. Parasites are also viruses.
Second, the basic information
Chinese name
parasite
Foreign name
parasite
explain
Eating other animals most of the time?
belong to
pathogen
supplement
Living habits
Third, the morphological characteristics
Parasites are characterized in that all living things parasitize or attach themselves to the host in a way called parasitism, so as to obtain nutrition or shelter for their survival, development or reproduction. Many small animals live in a parasitic way and attach themselves to larger animals. Parasites are also viruses.
Organs developed by parasites to adapt to parasitic life, such as the new skin of Taenia solium, the head segment with hook and sucker, the degenerated intestine, the segmented propagator of leech and sucker; Or the morphological changes of parasites, such as Candiru's body will expand after feeding blood. These two points ensure that they are successfully fixed on the human body. A beef tapeworm can grow from a fertilized egg to 2 meters long in 10 weeks. The infected person didn't feel anything at first. A few weeks later, it was found that the feces contained active insect segments. Each insect segment can contain 50,000 fertilized eggs.
Due to the influence of parasitic environment, parasites can change in shape and structure. For example, the left and right sides of fleas are flat, so that they can walk between fur; Most worms parasitic in the intestine are very long to adapt to the narrow and long intestinal cavity. Some organs degenerate or disappear, such as intestinal tapeworm, which has a long parasitic history. Its digestive organs are completely degraded by absorbing nutrients from the body wall. Some organs are developed, such as the reproductive organs of parasitic nematodes in the body, which account for almost all of the original body cavity. For example, the length of the ovary and uterus of female ascaris lumbricoides is 15 ~ 20 times of the body length to enhance the oviposition ability; The digestive tract length of some blood-sucking arthropods is greatly increased to facilitate a large number of blood-sucking. For example, ticks can endure hunger for several years after sucking blood once. The emergence of new organs, such as trematodes and tapeworms, evolved into sucker as a fixed organ due to the need of settlement and attachment.
Ascaris lumbricoides, an intestinal parasite, has substances that inhibit trypsin and chymotrypsin in its body wall and body cavity fluid. These enzyme inhibitors in worm epidermis can protect worms from protease in host small intestine.
Fourthly, the clinical manifestations of parasitic infection.
Parasites parasitize the cells, tissues or cavities of the host, causing a series of injuries, which are not only seen in protozoa, adults, but also in migrating larvae. Their influence on the host is manifold.
Traditional Chinese medicine has long recognized that parasites can cause diseases, and called them "insect accumulation". Most of these diseases are caused by careless diet, eating cold fruits and unclean food, and damp heat caused by long-term brewing of insects. Symptoms such as abdominal pain, poor appetite, yellow face and emaciation are common in insect accumulation; In severe cases, syncope, abdominal distension, vomiting and even paralysis may occur. There are many insects parasitic in the human body, such as roundworms, pinworms, tapeworms, schistosomiasis, cysticercosis and so on. Its onset has its own characteristics. For example, if ascaris lumbricoides is parasitic in the intestine, abdominal pain will occur. Ancylostomiasis often manifests as sallow and emaciated, and foreign bodies are eaten by mistake; Patients with pinworm disease often complain of pruritus in anus and perineum, where white pinworm can be found directly; Taeniasis has mild symptoms, and people often seek medical treatment because of white bands or insect segments found in feces; Schistosomiasis, due to its hepatosplenomegaly and poor blood circulation, causes water and liquid to stop gathering and form "abnormal swelling".
Grasp nutrition
The substances needed for the growth, development and reproduction of parasites in the host mainly come from the host. The more parasites there are, the more nutrients they take away. For example, ascaris lumbricoides and tapeworms parasitize in the intestine, seize a lot of nutrients, and affect the intestinal absorption function, resulting in malnutrition of the host; Another example is that hookworms attach to the intestinal wall to absorb a lot of blood, which will lead to anemia in the host.
② Mechanical damage
Parasites can damage or oppress the parasitic site and its adjacent tissues and organs. Some parasites, especially when they are large and numerous, are quite harmful. For example, roundworms can twist into balls and cause intestinal obstruction. Echinococcus is parasitic in the liver. At first, it had no obvious symptoms. Later, it grew up and oppressed the liver tissue and other organs in the abdominal cavity, resulting in obvious symptoms of oppression. In addition, the migration of larvae in the host will cause serious damage. For example, when Ascaris lumbricoides larvae migrate in the lungs, they will pierce the capillaries in the alveolar wall, resulting in bleeding.
③ Toxicity and the function of antigen substance.
The secretion, excreta and decomposition of dead worms of parasites have toxic effects on the host, which is the most important type of harm to the host by parasites. For example, when Entamoeba histolytica invades the intestinal mucosa and liver, it secretes histolytic enzymes, lyses tissues and cells, and causes intestinal wall ulcers and liver abscesses of the host; The excreta secreted by Schizogonimus may affect the hematopoietic function of the host and cause anemia. In addition, the metabolites of parasites and the decomposition products of dead insects have antigenicity, which can sensitize the host and cause local or systemic allergic reactions. For example, the secretion of miracidium in Schistosoma eggs causes immunopathological changes in the surrounding tissues-egg granuloma, which is the most basic pathological change and the main pathogenic factor of schistosomiasis. Another example is that the antigen of Plasmodium forms an immune complex with the corresponding antibody, which is deposited on the basement membrane of glomerular capillaries, causing glomerulonephritis with the participation of complement, the cyst wall of echinococcosis ruptures, and the cyst fluid enters the abdominal cavity, which can cause allergic shock and even death of the host.
⑷ allergic reaction
Parasites usually cause host allergies and cause tissue damage. This is one of the pathogenic effects of parasites. Hypersensitivity is generally divided into four types, namely type I, type II, type III and type IV. The first three types are antibody-mediated hypersensitivity, and the fourth type is mainly T cell and macrophage-mediated hypersensitivity. These four kinds of hypersensitivity reactions are also called immediate hypersensitivity, cytotoxic hypersensitivity, immune complex hypersensitivity and delayed hypersensitivity respectively.
⑤ Immune response
Parasites and their products are foreign bodies to the host, which can cause a series of reactions, that is, the host's defense function, and its main performance is immunity. Host's immunity to parasites is manifested in the response of immune system to recognize and remove parasites, some of which are defensive responses. For example, the host's stomach acid can kill some parasites that enter the stomach. Some reactions show that worms in the organization are restricted, surrounded or even eliminated. Immune response is the main manifestation of host's action on parasites, including nonspecific immunity and specific immunity.
The results of the interaction between host and parasite can usually be divided into three categories:
(1) The host has eliminated the parasites in the body, which can prevent reinfection.
② The host has destroyed most of the parasites in the body or failed to destroy them, but it is relatively resistant to reinfection. Therefore, the parasitic relationship between host and parasite has been maintained for a long time, which is found in most infected or infected parasites.
③ The host can't control the growth or reproduction of parasites, showing obvious clinical symptoms and pathological changes, thus leading to parasitic diseases. If not treated in time, serious people will die.
In short, the relationship between parasites and hosts is extremely complex, and any factor can neither be regarded as isolated nor overemphasized. Understanding the nature of parasite relationship and the interaction between parasite and host is the basis of understanding the occurrence and development of parasitic diseases, and also the basis of preventing and treating parasitic diseases.