The harm of parasites to the human body

Parasites parasitize in the cells, tissues or passages of the host, causing a series of damages, which are seen not only in protozoa, adult worms of worms, but also in migratory larvae, and their role in the host is multifaceted.

Chinese medicine has long recognized that parasites can cause diseases, and called them "insect accumulation", mostly caused by careless diet, eating raw cold melon fruits and unclean food caused by hot and humid endogenous, brewing insects, and accumulating for a long time. Symptoms such as abdominal pain, poor appetite, and yellowish thinness are common; in severe cases, there will be nausea, bloating, vomiting, and even fouling. There are many insects that parasitize the human body, generally including roundworms, pinworms, tapeworms, schistosomiasis, cysts and so on. Its pathogenesis has its own characteristics, such as roundworm parasitism in the intestine, then abdominal pain occurs; hookworm disease is often manifested as yellow muscle thin, predatory foreign body; patients with pinworm disease often complain of and perineal itching, and can be found directly in these parts of the white fine linear pinworm; tapeworm disease symptoms are mild, often because of the white bands or segments found in the feces and seek medical treatment; schistosomiasis because of its liver and spleen enlargement, blood flow is not smooth, and the water stops to form swelling.

(a) Capture nutrition

The substances needed for the growth, development and reproduction of parasites in the host mainly come from the host, and the more parasites there are, the more nutrients are seized. For example, roundworms and tapeworms parasitize in the intestine, seize a large amount of nutrients, and affect the absorption function of the intestine, causing host malnutrition; another such as hookworm attached to the intestinal wall to absorb a large amount of blood, can cause host anemia medical ' education network collection and collation.

(2) Mechanical damage

Parasites can cause damage or compression to the site of parasitism and its nearby tissues and organs. Some parasites, especially in large individuals, are quite serious when they are more numerous. For example, roundworms can twist into clumps and cause intestinal obstruction. Echinococcus parasitizes in the liver, has no obvious symptoms at first, and then gradually grows to compress the liver tissue and other organs in the abdominal cavity, and obvious symptoms of compression occur. In addition, the migration of larvae in the host can cause serious damage, such ascaria larvae penetrating the capillaries of the alveolar wall when migrating in the lungs, which can cause bleeding.

(c) the role of toxicity and antigenic substances

The parasite's secretions, excrement, and decompositors of dead insect bodies all have toxic effects on the host, which is one of the most important types of ways in which parasites harm the host. For example, when intrahistole amoebic invades the intestinal mucosa and liver, it secretes lysozyme, dissolves tissues and cells, causing ulcers and liver abscesses in the intestinal wall of the host; the secreted excrement of Taenia broad-segmented taenia may affect the hematopoietic function of the host and cause anemia. In addition, the metabolites of the parasite and the decompositors of the dead insect body are antigenic, which can sensitize the host and cause local or systemic allergic reactions. For example, the secretion of hairy worms in schistosomiasis eggs causes immunopathological changes in the surrounding tissues - granulomatous tumors of worm eggs, which is the most basic lesion of schistosomiasis and the main causative factor. Another example is the antigenic substance of Plasmodium malariae and the corresponding antibody to form an immune complex, deposited in the glomerular capillary basement membrane, with the participation of complement, causing glomerulonephritis. As well as the rupture of the sac wall of the bulbous larvae, the sac fluid enters the abdominal cavity, which can cause the host to undergo anaphylactic shock or even death.

(4) Hypersensitivity reactions

Parasites in the host often induce the host to produce hypersensitivity reactions, causing tissue damage. This is one of the pathogenic effects of parasites. Hypersensitivity reactions are generally divided into four types, namely I., II., III., IV., the first three types are antibody-mediated hypersensitivity reactions, and type IV. is mainly t-cell and macrophage-mediated hypersensitivity reactions. These four hypersensitivity reactions are also called rapid-onset hypersensitivity reactions, cytotoxic hypersensitivity reactions, immune complex hypersensitivity reactions and delayed hypersensitivity reactions.