Trichinosis

Introduction to Trichinosis Trichinosis (trichinellosis) is a zoonotic parasitic disease caused by Trichinella spiralis (Trichinellaspiralis). It is prevalent among mammals and is infected by raw or semi-cooked pork containing Trichinella cysts. The main clinical manifestations are gastrointestinal symptoms, fever, myalgia, edema and blood eosinophilia. basic knowledge The proportion of illness: 0.0024% Susceptible people: no specific population Mode of transmission: insect vector transmission Complications: pulmonary edema, bronchial pneumonia, pleural effusion, pericardial effusion

The cause of trichinosis

(1) Causes of the disease

Trichinella spiralis (referred to as Trichinella spiralis) belongs to the linear animal gate, nematode, Trichinella, the insect is small, the front end is thin, dioecious, male size (1.4 ~ 1.6) mm × (0.04 ~ 0.05) mm; female The worm is (3 ~ 4) mm × 0.06mm, and its body length is more than 1 times that of the male. The digestive tract of the adult includes the mouth, the pharynx, the intestine and the anus, the reproductive organs are single-tube type, and the male has testicles. The vas deferens, the seminal vesicle and the ejaculatory duct, the ejaculatory duct and the rectum are opened in the cloaca, and there are two bell-shaped mating leaves at the rear end of the worm body. The sperm is discharged between the two mating leaves, and there is no cross-bone.

The genital organs of the female have ovaries, fallopian tubes, fertilized sacs and uterus. The uterus is longer than the ovaries. Undivided egg cells are visible inside. The vaginal opening has developed into mature larvae. The vagina is divided into thin-walled parts and thick walls. In the shorter part, the vulva is opened at 1/5 of the front end of the worm.

Scanning electron microscopic observation of Trichinella spiralis adults and larvae, the male and female adult worms have a crack-like opening in the center of the apex of the anterior part of the body, and a cone-shaped thorn is extended from the center. The mouth is surrounded by a wide-angled ampule with a bilateral symmetry, which is wing-shaped or butterfly-like. There is also an elliptical protrusion around the mouth. There are 12 to 14 symmetrically arranged small depressions on the outer surface of the wing-shaped bulging. It may be the hole of the head sensor. The front end of the larvae is not as developed as the adult, only from a crack. Extending a cone of thorns in the mouth, the epidermis and larvae are smooth and have no microvilli or micropores, and the annular wrinkles are at right angles to the body axis. The opening of the subcutaneous gland cells on the epidermis of the adult is the lenticels. In a single column, from 1/2 to l/3 after the body is a double column. The upper part of the lenticulus is covered with a special cap, which is formed by the secretion of subcutaneous glands. The larvae have no lenticels on the surface, and the genital holes are not in the larval stage. Obviously, the adult larvae are more developed. The female genital tract is a vulva, mostly crack-like, sometimes semi-circular. The male genitalia shows a pair of mating appendages, which are wooden ear-like protrusions with a Y-shaped side. There are two pairs of mastoid or small nodules, belly A pair of finger-like, rivet-like backside conical, the end of a female and larvae anal orifice, no male anal hole, cloacal opening plays the role of the anal orifice, the size of the larvae is approximately 100m × 6m.

Adults and larvae of Trichinella are parasitic in the same host, but they cannot develop from larvae to adults in the same host. The host must be replaced in the middle. Humans and pigs, cats, dogs, rodents and other mammals are susceptible to infection and parasitism. The Trichinella female larvae in the pig intestine produce larvae through the blood circulation to the skeletal muscle, and the humans are infected by eating the larvae-containing pork. After the cysts enter the new host, they are digested by the gastric juice and in the duodenum. Larvae, parasitic in the duodenum, jejunum and ileum, with the intestinal mucosa as a prey, after 5 to 6 days, after 4 times of molting, become adult, males and males die after mating, excreted from the intestine, females Continue to grow up, and deep into the intestinal mucosa, began to produce larvae, the life expectancy of females can reach 1 to 2 months, each female can produce 1500-2000 larvae, and a few larvae produced on the surface of intestinal mucosa are excreted from the intestinal lumen. Most of the larvae in the mucosa are transported to the organs and body cavity of the whole body through the blood circulation through the lymphatic vessels or venules, but only when they reach the skeletal muscle can they develop into cysts, and the time of the larvae in the blood circulation is 8~ after infection. 25 days is the most As early as 9 days after infection, the skeletal muscle can be reached. As the female continuously discharges the larva, the larvae that gradually enter the skeletal muscle can last for 1-2 months.

When the larva reaches the skeletal muscle, it breaks through the microvessels and continues to grow to 1 mm with the prolongation of time. The amphipathic differentiation occurs. Due to the stimulation of its metabolites, the nearby muscle fibers gradually surround the larvae, forming a fusiform cyst within about 1 month. After 7 to 8 weeks of maturity, the size of the cyst is about (0.25 ~ 0.5) mm × (0.21 ~ 0.42) mm, after 6 months from the calcification of the poles, the larvae in the capsule will die, sometimes 3 to 5 In the year, the mature capsule re-enters the new host and repeats its life history. The Trichinella larvae capsule has strong resistance in skeletal muscle, and can survive for 57 days at -12 °C, 2 to 3 months in carrion, and 70 °C. The cyst larvae are killed, but the larvae in the deep muscles can still maintain vitality, so the time of frying and steaming is insufficient, and the disease can also occur after eating.

(two) pathogenesis

The incidence of this disease is related to the habit of eating raw pork, but has nothing to do with age, gender, occupation and season. The incidence of the disease and the severity of the disease are related to the degree of infection. If you eat more than 5 capsules containing live larvae. /kg body weight can be fatal, but there are reports, biopsy contains 75 larvae / g muscle, clinically cured without any special treatment, the lesion varies with the number of larvae entering the human body and its developmental stage and the human body's response to Trichinella The infection of those who have been infected is lighter; if there are many insects, the intestinal mucosa in the larval invasion and parasitism has congestion, edema, hemorrhage and superficial ulcer, so there are many gastrointestinal symptoms in the early stage, when the larva migrates , there are inflammatory reactions in the passage, such as acute endarterial and adventitial inflammation, systemic vasculitis and edema, focal or extensive pulmonary hemorrhage in the lungs, pulmonary edema, bronchial pneumonia and pleural effusion Involved in the central nervous system with non-suppurative meningitis changes and increased intracranial pressure, occasional larvae in the cerebrospinal fluid, only larvae found in the myocardium, pericardial effusion or larvae, myocardium and endocardium are water , hyperemia, myocardial focal rupture and necrosis, lymphocytes, eosinophils and neutrophil infiltration, apparently due to worm toxicity and allergic reactions caused by larval passage, when larvae invade skeletal muscle fibers The effects of toxic substances produced by worm body toxins and their metabolites and muscle fibers on the human body may cause toxic myocarditis, hepatic cell steatosis and swelling of kidney cells.

The larvae and cysts in skeletal muscle are most common in the lingual, pharyngeal, cervical, pectoralis, abdominal, diaphragm and intercostal muscles. These muscles are frequent, blood flow is abundant, and more larvae enter the muscles. The lower glycogen content is conducive to the formation of cysts. Due to the stimulation of larvae and their metabolites, there are interstitial myositis around the worms, muscle fibrosis, and the worms gradually distort, eventually forming cysts, and the capsules are fusiform. The long axis is parallel to the muscle fibers. There is usually only one larva in one capsule, and there are very few 2-3 or more larvae. The muscle cells around the cyst are infiltrated with inflammatory cells. After a long period of time, the muscle fibers are atrophied and the inflammatory reaction is alleviated. Calcification, larval death, leaves some foreign body reaction.

Larvae are rarely found in the myocardium. Some people think that the myocardium has higher resistance, is not suitable for larvae to survive and re-enter the blood circulation; or the myocardium is weak, unable to limit the larvae to the muscle fibers; Keep the larva unable to stay.

In addition to the above-mentioned major organ and tissue lesions, larvae are occasionally found in the retina, pancreas, liver, kidney, placenta, breast, lotion, bile, bone marrow, lymph nodes, cerebrospinal fluid, causing corresponding damage and symptoms.

Trichinosis prevention

1. Strengthen health publicity and education, not raw food or uncooked pork.

2. Improve the method of raising pigs, rationally build pig pens, promote captive breeding, isolate sick pigs, feed pigs without worms and viscera, and feed should be warmed at least 55 °C to prevent pig infection, pig manure composting fermentation deal with.

3. Rodent control: The rodent is the host of the disease, and try to kill the rats, so as not to pollute the food and pig food.

4. Strengthen pork hygiene inspection. Pork that is not approved for hygiene is not allowed to be listed. In particular, pork from individual vendors should be supervised by health. Slaughterhouse pork should be inspected in detail. For example, pork should be refrigerated at -15 °C for 20 days or -18 °C. 24h, making it harmless.

Trichinosis complications Complications pulmonary edema bronchopneumonia pleural effusion pericardial effusion

Severely infected lung, myocardial and central nervous system are also involved, corresponding to focal (or extensive) pulmonary hemorrhage, pulmonary edema, bronchial pneumonia and even pleural effusion; myocardial, endocardial congestion, edema, interstitial inflammation and even Myocardial necrosis, pericardial effusion; non-suppurative meningoencephalitis and increased intracranial pressure, blood eosinophils are often significantly increased (except for very severe cases), toxic due to worm body toxins and their metabolites and muscle fiber destruction The effects of substances on the human body may lead to toxic myocarditis, hepatic cell steatosis and swelling of kidney cells.

Trichinosis Symptoms Common Symptoms Muscle Pain Pain Remnants Hot Peritonitis Low Heat Nausea Weightless Wind Group Gastrointestinal Symptoms

The incubation period is 2 to 46 days, most of which are within 14 days. According to the developmental stages of larvae in the body, the degree of invasion and the degree of lesions, the clinical manifestations can be divided into small intestine invasion period, larval migration period and cyst formation period, but each stage. There is no regularity and no obvious boundary. The severity of symptoms depends on the larvae invading the organs and parts and the degree of infection. Those with mild infections may be asymptomatic or have mild gastrointestinal symptoms and myalgia. The clinical manifestations of severe infections are complicated. Diverse, even within 3 to 7 weeks after the onset of illness.

1. Intestinal invasion: It is early, from the beginning of infection to the development of larvae into adults in the small intestine. Because larvae and adults penetrate the intestinal mucosa, feeding on intestinal villi, causing mucosal congestion, edema, hemorrhage and superficial ulcer, so early Gastrointestinal symptoms occur. About half of the patients have nausea, vomiting, diarrhea, abdominal pain, constipation, anorexia, etc., which decrease in about 1 week, but most of them still feel tired, chills and low fever.

2. Larval migration period: It is an acute phase, mainly caused by inflammatory reactions caused by larval migration, such as acute endarteritis, systemic vasculitis, edema, myalgia and fever. The main cause of fever is 1 after infection. Week, irregular or missed heat type, heat is generally 38 ~ 40 ° C, can also be as high as 4l ° C, fever can last 2 weeks to 2 months or more, with headache, sweating and various allergic rash, larvae migration May be associated with wheal or maculopapular rash, intramuscular cysts can form fibrosis or calcification into nodules, muscle pain caused by larvae reaching skeletal muscles began to form cysts, muscle swelling and induration, with obvious tenderness, Often systemic, but the gastrocnemius is the heaviest, with a little touch, the pain is unbearable, almost paralyzed, severe cases can also have chewing, swallowing and speaking difficulties, hoarseness, pain when breathing and moving eyes, muscle The pain can last from 3 to 4 weeks to more than 2 months.

Edema is first seen in the eyelids, face and ankles. It can spread to the whole body, limbs and trunk, and even pleural effusion, ascites and pericardial effusion. The edema often appears in the course of about 1 week, lasting 2 to 4 weeks, and there are many respiratory symptoms. Found 2 weeks after the onset, there is a paroxysmal cough, heavier at night, mostly dry cough or white foam sputum, occasional bloodshot, severe chest pain, lung snoring, chest opening with hilar shadow enlargement and variable lung parenchyma Infiltration, severe cases of heart and nervous system symptoms, arrhythmia, systolic murmur in the apex, pericardial friction or pericardial effusion, heart failure, cardiogenic asthma and coma, convulsions, etc. Cardiopulmonary failure is often an important cause of death .

Others have conjunctival and scleral edema, congestion, hemorrhage, blurred vision or diplopia, about 2/3 cases have finger (toe) sub-abdominal hemorrhage, individual cases have obvious lymph nodes, parotid swelling and pain, internal organs or limbs There are thrombosis, pulmonary infarction, peritonitis and other complications, and a few cases have temporary hepatomegaly.

3. The formation period of the capsule: the recovery period, with the formation of cysts in the muscle, the acute inflammation subsides, systemic symptoms such as fever, edema and myalgia gradually reduce, the patient is significantly thin, fatigue, myalgia and induration are still sustainable In the end, the symptoms disappeared completely due to calcification of the cyst wall and larval death. The severe cases were cachexia, and died due to collapse, toxemia or myocarditis.

History and typical clinical manifestations, acute phase laboratory tests showed elevated peripheral blood eosinophils, which lasted for several months, intradermal test, immunofluorescent antibody test, enzyme-labeled immunosorbent test and viscous floc test. A positive reaction occurred 2 to 4 weeks after infection, and further confirmation of the need for muscle biopsy to find Trichinella larvae.

1. Epidemiological data: In the epidemic area, there is a history of raw or innocuous pork or other animal meat and meat products before the disease, or there are collective cases, which provide important clues for the diagnosis of this disease.

2. Clinical manifestations: First, there are gastrointestinal symptoms, followed by fever, edema, myalgia and eosinophils are significantly increased, should be highly suspected of this disease, need to further pathogens.

3. Pathogen examination: commonly used muscle biopsy to find larvae or serum immunological examination, if there is a positive finding can be diagnosed.

Trichinosis check

1. Blood picture: moderate anemia and white blood cell increase during the active period of the disease, the total number is (10 ~ 20) × 109 / L, eosinophils are significantly increased, with the highest incidence of 3 to 4 weeks; up to 80% to 90 %, lasts for more than half a year; severe infection, low immune function or bacterial infection may not increase.

2. Pathogen examination: If there is leftover residual meat, the specimen should be taken to check the capsule, or pepsin digestion treatment, centrifuge, take the sediment to methylene blue staining microscopic examination, find larvae, or feed the residual meat to the animal (large Rats, after 2 to 3 days, check their intestinal larvae, such as the Trichinella larvae can be diagnosed, if 10 days after the onset, muscle biopsy can be done, often taking deltoid or gastrocnemius biopsy, the positive rate is higher.

In the early stages of diarrhea, larvae can be found in the stool. During the transition period, larvae can be found in the centrifuged blood, milk, pericardial fluid and cerebrospinal fluid.

3. Immunological examination:

(1) Intradermal test: 0.1 ml of Trichomonas larvae leaching antigen (1:20001:10000), 15-20 min after intradermal injection, pimple>1 cm, blush diameter>2 cm; and control 0.1% Thioglycol 0.1ml, the skin test was positive when the other side of the forearm was injected intradermally, this method has higher sensitivity and specificity, the method is simple, and the result is obtained quickly.

(2) Serological examination: detection of specific antibodies in patients with serum by Trichinella soluble antigen is helpful for diagnosis, and can be used for slide agglutination, latex agglutination test, complement fixation test, convective immunoelectrophoresis, indirect immunofluorescent antibody test and enzyme-linked Immunosorbent assay and other serum antibodies are detected, and the sensitivity and specificity of the two are better. For example, the serum antibody in the recovery period is more than 4 times higher than the acute phase, which is more diagnostic.

After treatment, the serum antibody of Trichinella patients can exist for a long time, so antibody positive can not distinguish between patients with current disease and those who have been infected with previous infections. In recent years, domestic patients have used monoclonal antibody and polyclonal antibody double-antibody sandwich ELISA to detect serum circulating antigen. The positive rate was 67.7% (21/31) and 72.2% (26/36), while 50 normal people and 142 other nine parasitic diseases were negative, and only 1 of 20 patients with cysticercosis (5) %) is positive, and the positive result of serum circulating antigen indicates that there is live parasite in the body, so it can be used as a diagnosis and can evaluate the curative effect.

(3) Others: Muscle biopsy can find larvae of the hairy larvae. Urine routine examination may have proteinuria and granules or waxy casts and red blood cells. During the course of 3 to 4 weeks, the globulin is increased and albumin is reduced, even the ratio is inverted, and the immunoglobulin IgE is significant. Raise.

Can be used for X-ray, B-ultrasound, ECG and other checks.

Diagnosis and identification of trichinosis

diagnosis

Diagnose based on:

1 1 to 2 weeks before the disease (1 ~ 40d) to eat raw pork and other history;

2 clinical features are mainly fever, muscle pain and edema, rash, etc., early stage may have gastrointestinal symptoms, the total number of white blood cells and eosinophils increased significantly;

3 diagnosis depends on muscle biopsy to find larvae or (and) serological examination.

The disease should be differentiated from food poisoning, bacillary dysentery, typhoid fever, leptospirosis, influenza, pneumonia, nephritis, rheumatic fever, angioedema, pulmonary infarction, dermatomyositis and other diseases. The disease should be poisoned with food. , bacillary dysentery, typhoid, leptospirosis, flu, pneumonia, nephritis, rheumatic fever, angioedema, pulmonary infarction, dermatomyositis and other diseases.

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