Basic information on Trichinella spiralis

Trichinella larvae parasitize in the muscle fibers, the general formation of capsule, capsule was lemon-like, containing a slightly bent like a spiral of larvae. The capsule consists of two layers of connective tissue. The outer layer is very thin, with a large number of connective tissue; inner transparent glass-like, cell-free.

A parasitic worm of the genus Aschelminthes, Nematoda, under the name Trichinella spiralis. Worldwide distribution. Length of 1.5 to 4 mm (0.06 to 0.2 inches). (Trichinosis), a serious disease in humans and other mammals (pigs, dogs, cats, bears, foxes, and mice). Mating in the small intestine of the host, and then the female into the intestinal wall to produce larvae, the larvae were blood flow to the body parts. In the muscle growth, about 16 days after maturation, capsule encased in the larvae around the formation. Muscle containing cysts are swallowed by a suitable host, the larvae further development, in the host intestine mature and reproductive. Trichinella adult parasitic in the small intestine, called intestinal Trichinella; larvae parasitic in striated muscle, called muscle Trichinella spiralis.

Diagnosis of Trichinella spiralis

If the raw food or unripe meat history, the typical clinical symptoms and eosinophilia, you can suspect the disease. From the leftover meat or patients with skeletal muscle biopsy specimens to find the larvae or capsule, can be confirmed. Intradermal test, precipitation test, fluorescent antibody test and enzyme-linked immunosorbent assay and other immunological tests, mostly in the 2 to 4 weeks after infection was positive. The disease should pay attention to food poisoning, rheumatism, dermatomyositis, nodular polyarteritis and other diseases identification.

Clinical manifestations

Trichinella human intake of living Trichinella cystic capsule, the capsule by the gastric juice digestion, the release of the larvae in the duodenum, about 5 to 7 days, the larvae molt 4 times after the development of adult. Small intestinal mucosa by larvae invasion and congestion, edema, the patient may have abdominal pain, diarrhea, nausea, vomiting and other symptoms, sustained 3 to 5 days to ease. Male and female adult mating, the female into the intestinal mucosa output larvae. In addition to a small number attached to the surface of the intestinal mucosa from the intestinal discharge, the vast majority of larvae along the lymphatic vessels or venous flow through the right heart to the lungs, and then systemic circulation to reach the body organs, tissues and body cavity. But only the invasion of striated muscle larvae can continue to develop in the formation of muscle fibers between the longitudinal axis parallel to the muscle fibers and fusiform capsule. Larvae into the blood circulation can cause heterosexual protein response, patients with persistent high fever, urticaria, rash, eyelids and facial swelling and other symptoms, peripheral blood eosinophils also increased significantly. Due to the stimulation of larvae and its metabolites, striated muscle, small blood vessels and the surrounding interstitial inflammatory response, the patient felt muscle pain, the limbs for the muscle. In severe cases, chewing, swallowing and pronunciation difficulties. If the larvae invade the heart and central nervous system, can cause arrhythmia, pericarditis, convulsions and coma and other serious symptoms, these symptoms last 1 to 2 months, muscle pain, sometimes for several months. Larval muscle fibers in the curl was "U" -shaped or spiral, where the muscle cells of the expansion, the formation of fusiform muscle cavity surrounded by insects. With the gradual formation of capsule, acute inflammation subsided, the symptoms ease, but the patient is still thin, fatigue. Physical recovery takes about 4 months.

Morphological Traits of Trichinella spiralis

Adult body small, to the front gradually taper, female length 3-4mm, males less than 2mm. People due to ingestion of Trichinella cysts containing raw mammals (mainly pigs) and disease. Trichogramma containing Trichinella cysts can also be pigs, dogs, cats, rats and other food intake, therefore, the disease can also be spread in these animals. The prognosis of the disease is generally good, a few died of toxic shock, heart failure, pneumonia, meningoencephalitis and other serious complications. General ingestion of the capsule up to 5 kg per kilogram of body weight can be fatal. The disease is a worldwide distribution, all eating pork or pork products in areas where there are reports of human infection. According to the early 1970s data estimates, about 1.5 million people in the United States with Trichinella muscle capsule, the number of new infections per year up to 15 to 300,000. The rate of human infection and the presence of local foci and raw dietary habits of meat. Fresh cattle, mutton is affected, may be due to cattle, sheep and other food into the contaminated feed, weeds caused.

Causes of infection

People are due to ingestion of cysticercus containing cysticercosis of animals or half of the meat and infection. Cysticercus strong resistance, low temperature, pork in the cysticercus in -15 ℃ to be stored for 20 days before death, -12 ℃ can live 57 days, 70 ℃ soon die, in the carrion can survive 2 to 3 month. Salad, pickled, smoked and rinsed food methods often can not kill larvae. The incidence of eating raw meat accounted for more than 90%. Cut raw meat knife or chopping board, such as cut cooked food, people eat contaminated cysticercus cooked food, spread one of the ways.

How to prevent Trichinella spiralis?

Strengthen food hygiene management and publicity and education, do not eat raw or immature mammals meat and meat products. Pork frozen at -15 ℃ for 20 days, can be cysts to kill. To promote scientific pig, keep the pig clean, feed should be heated to 55 ℃ or more, eliminate rats and other preservation of the host.