form
Fasciola hepatica
Fasciola hepatica and Fasciola zingiberensis belong to Fasciola family and are one of the large trematodes. The differences between ginger worms are as follows: 1) The adult is slender, and there is a cone-shaped protrusion at the front end of the body, which is called the cone; 2) The abdominal sucker is small and inconspicuous, which is located at the level of the base of the head cone; 3) Intestinal branches have many side branches; 4) There are two testicles with fine branches, accounting for about half of the worm's body area; 5) The ovary is small with fine branches.
biography
The adult Fasciola hepatica is parasitic in the hepatobiliary duct of definitive host, and its intermediate host is rotavirus. In China, Galbatruncatula, G. Pervia, Radixauriculata and R. swinhoei have been confirmed.
Life history includes 1 ~ 2 generation cercariae and 1 ~ 3 generation cercariae. After the cercaria escapes from the snail, it forms cysticercosis on aquatic plants such as aquatic plants. After the metacercariae is ingested by the final host, the metacercariae that has been taken out of the intestine passes through the intestinal wall, invades the liver through the abdominal cavity, and then enters the bile duct, or enters the bile duct through the mesenteric vein or lymphatic vessels. In the process of migration, some larvae can stay in the lungs, brain, orbit, subcutaneous and other organs for heterotopic parasitism, causing damage. It takes l0 ~ 1 1 week from metacercariae infection to adult oviposition. Adults can lay about 20000 eggs a day. The longest record of parasitism in sheep is 1 1 year, and it can reach 12 ~ 13 years in human body.
Fasciola hepatica
Cause disease
The harm of Fasciola hepatica is mainly manifested in two aspects: 1) the damage of larvae to various organs, especially liver tissue, leads to inflammatory reaction of liver and liver abscess, and presents acute symptoms such as high fever, abdominal pain, urticaria, hepatomegaly and eosinophilia in blood; 2) Mechanical stimulation of bile duct and chemical stimulation of metabolites by adults cause bile duct inflammation, bile duct epithelial hyperplasia and fibrosis around bile duct. Hyperplasia of bile duct epithelium is related to the large amount of proline produced by worms. Bile duct fibrosis can cause obstructive jaundice, liver injury can cause changes in plasma protein (hypoproteinemia and hyperglobulinemia), bile duct hyperplasia and enlargement can compress liver parenchyma and cause atrophy, necrosis and even cirrhosis, and can also involve gallbladder and cause corresponding diseases. The clinical manifestations of Fasciola hepatica can be divided into three stages: acute, latent and chronic. There are also a few asymptomatic carriers.
1, the acute phase (equivalent to the migration process of child worms in tissues, also known as the invasive phase) occurs 2 ~ 12 weeks after infection, with sudden high fever and abdominal pain, often accompanied by flatulence, vomiting, diarrhea or constipation, hepatomegaly, anemia and obvious increase of eosinophils in blood. Some patients may also have symptoms of lung and skin allergy. This period lasts about 2-4 weeks.
2. In the incubation period (usually about 4 months after infection, which is equivalent to that the worm has entered the bile duct), the patient's acute symptoms are relieved or disappeared, and there is no obvious discomfort or mild gastrointestinal discomfort for several months or years, while the lesion is developing.
3. Chronic stage (the stage of cholangitis and bile duct epithelial hyperplasia caused by adult parasitism in bile duct, also known as obstructive stage) mainly includes fatigue, right upper abdominal pain or biliary colic, nausea, fatty food anorexia, anemia, jaundice, hepatomegaly, etc.
4. Ectopic damage (also known as Fasciola hepatica) When the child worm moves in the abdominal cavity, it can penetrate or reach the lungs, stomach, brain, orbit and subcutaneous with the blood flow. The diagnosis is usually made after surgery. In places that are used to eating cattle and sheep livers, worms can parasitize the pharynx, causing ginger leaf disease in the pharynx.
Experimental diagnosis
Fasciola hepatica
The eggs obtained by fecal microscopy are the basis for the diagnosis of Fasciola hepatica, but they should be differentiated from ginger eggs and echinococcosis eggs.
Immunological detection is helpful for the diagnosis of acute bile duct obstruction and ectopic parasites. For example, ELISA, IHA and IFA have high sensitivity in detecting specific antibodies in patients' serum.
Epidemiology and prevention
Fasciola hepatica is distributed all over the world. There are endemic areas in some foreign regions. The population infection rate in China is 0.002% ~ 0. 1.7 1%, distributed in 15 provinces and cities, with the highest infection rate in Gansu province. It is estimated that the number of infected people in China is about 6.5438+0.2 million.
Fasciola hepatica parasitizes a wide range of hosts, including cattle and sheep, pigs, horses, dogs, cats, donkeys, rabbits, monkeys, camels, elephants, bears, deer and other animals. Human infections are mostly caused by eating raw stems and leaves of aquatic plants such as watercress. In the low-lying and humid swamp, the feces of cattle and sheep pollute the environment. There are snails, cattle and sheep are more likely to cause infection when eating grass.
prevent
People infected mainly pay attention to food hygiene and don't eat aquatic plants raw. Bidine is the first choice for patients. Other drugs include praziquantel, albendazole and trichlorobenzene.