Schistosomiasis

　　The liver fluke is about 2.0～5.0 cm × 0.8～1.3 cm in size, with a flat ventral and dorsal surface, resembling a leaf shape, and deep reddish-brown in color. The anterior end is cone-shaped and called the rostrum, and the body suddenly becomes wider behind the rostrum, known as the shoulder peak. The oral sucker is smaller and located at the top of the body, while the ventral sucker is slightly larger and located at the base of the rostrum. The eggs are very large, elliptical, light yellow-brown, with thin eggshells that are divided into two layers. One end has a small lid. The eggs are filled with many yolk cells.

　　The life cycle of Schistosoma hepaticum: The adult worms lay eggs in the bile ducts of the definitive host, which are excreted into the intestines with bile and mixed with feces. In water at 22～26℃, they develop into miracidia eggs in 9～14 days and quickly penetrate into the snail. Inside the snail, they develop into cercariae through two generations of sporozoites and rediae. After escaping from the snail, they swim underwater. When they come into contact with the body of an animal (plant or decaying matter), they shed their tails and form cysts, attaching to water objects (such as aquatic plants), their shape resembling a felt hat. When the host eats aquatic plants containing cysts, the cysts are digested by the intestinal digestive fluid, and the released cercariae enter the abdominal cavity and develop into larvae. After about 48 hours in the abdomen, the larvae penetrate the liver capsule and enter the liver parenchyma, continuing to develop with liver tissue as their nutrition. After wandering in the liver for about 6 weeks, they finally enter the bile ducts to parasitize. It takes about 4 weeks for them to develop into adult worms. From the infection of the cyst to the detection of eggs in the feces, the shortest time is 10～11 weeks, and each adult worm can lay about 20,000 eggs per day. The lifespan of the adult worms in the human body can reach 12 years.

　　Schistosomiasis mainly causes digestive diseases. The obstruction caused by the worms leads to bile stasis, resulting in jaundice and biliary colic; the compression of the dilated bile ducts can cause atrophy and necrosis of liver tissue, and complications such as bile duct hemorrhage may occur. Long-term repeated infections can lead to biliary cirrhosis. When there are many worms, they can also block the bile ducts, causing obstructive jaundice. In severe chronic patients, long-term chronic infection can lead to severe anemia. Schistosomiasis infection can also be complicated by pancreatitis, diabetes, and other pancreatic diseases, and complications such as ulcer disease, chronic gastritis, chronic colitis, and other gastrointestinal diseases. Children often have significant malnutrition and growth and development disorders, leading to dwarfism.

　　The incubation period of schistosomiasis varies, ranging from a few days to 2 to 3 months. Clinically, it can be divided into acute stage, chronic stage, and ectopic damage.

　　1. Acute stage

　　The acute stage is mainly caused by the migration of the larvae in the abdominal cavity and liver, such as the symptoms that may lead to severe consequences when combined with bacterial infection. The symptoms and signs during this period are not completely the same, mainly including irregular fever (38～40℃), right lower quadrant pain, loss of appetite, abdominal distension, diarrhea, or constipation. There may also be cough, chest pain, wet rales and pleural friction rubs over the right chest, and most patients have liver enlargement, a few have splenomegaly and ascites. The above symptoms can last for about 4 months and then subside, and gradually enter the chronic stage.

　　2. Chronic stage

　　After the acute symptoms subside, there may be no obvious discomfort for several months or even years, and some symptoms may reappear during this period, such as abdominal pain, diarrhea, irregular fever, recurrent urticaria, jaundice, anemia, hypoalbuminemia, and hyperimmunoglobulinemia. The latter two are due to the injury of the bile duct epithelium caused by the parasitic worms, erosion, and the worms feeding on blood (each worm causes the host to lose about 0.5ml of blood per day), leading to chronic inflammation and hyperplasia of the bile ducts caused by the adult worms, resulting in bile duct fibrosis and liver cirrhosis. It can also be caused by the obstruction of the bile duct by the adult worms or the formation of bile duct stones, leading to obstructive jaundice, which can further develop into biliary cirrhosis.

　　3. Ectopic Lesions

　　Schistosomiasis mansoni metacercariae can migrate and penetrate into or be carried by blood flow to organs and tissues outside the liver, such as abdominal wall muscles, causing lesions. In some Middle Eastern regions, there is a habit of eating raw sheep liver among the population. The worms寄生 in the bile ducts of sheep liver can invade the human pharynx, causing local edema and congestion, leading to difficulty in swallowing and breathing, deafness, and asphyxia, which is known as pharyngeal Schistosomiasis mansoni.

　　Prevention of Schistosomiasis mansoni lies in controlling the source of infection and cutting off the transmission route. In endemic areas, it is necessary to strengthen the work of general surveys, which can be started with skin tests for screening, followed by fecal examinations for positive cases. All those with positive egg findings in fecal examinations should be given medical treatment.

　　Strengthen the management of domestic animals, grazed in designated areas to avoid water contamination. Do not feed raw fish, shrimp, or fish viscera to cats, dogs, pigs, etc., to prevent infection. The feces of these animals should also be managed to prevent them from entering waterways and fish ponds. Drinking water (including livestock) should be separated from general water use, and drinking water should be disinfected regularly. Domestic animals with infections should be dewormed if possible. Wild animals that are reservoir hosts should be culled as necessary. This includes regular deworming, feces composting, and pasture rotation, as well as the eradication of intermediate hosts such as snails. If people have a history of eating raw fish, it is recommended to undergo liver function tests and liver B-ultrasound examinations.

　　The examination items for Schistosomiasis mansoni include five aspects, the specific content is as follows:

　　1. Blood Routine Examination

　　White blood cells and eosinophils are significantly increased, especially during the acute stage, with white blood cell counts usually ranging from (10-43)×10^9/L, and the highest eosinophil count can reach 0.79. Erythrocyte sedimentation rate accelerates, reaching up to 164mm/h, with hemoglobin levels typically between 70-110g/L, but can be lower.

　　2. Liver Function Examination

　　Liver function is abnormally increased during the acute stage, with elevated ALT and AST, increased serum bilirubin during the chronic stage, decreased albumin, and globulin levels can increase to 51-81g/L. The albumin/globulin (A/G) ratio is inverted, and IgG, IgM, and IgM levels are elevated, while IgA remains normal.

　　3. Etiological Examination

　　A positive result from the etiological examination is a basis for diagnosis, but in the early stage of acute infection, eggs are often not found. Generally, eggs can be detected 2 to 3 months after infection. The eggs can be detected from feces using methods such as water washing sedimentation, modified Kato-Katz method, or mercury-aldehyde iodine concentration method. The sedimentation or centrifugation of duodenal drainage fluid also has a high positive rate.

　　Abdominal exploration may find adult worms or eggs in the bile duct, and the presence of worms or eggs in laparoscopic biopsy or other tissue pathology examination can also serve as a basis for diagnosis.

　　4. Immunological examination

　　Serological immunological examination can be performed using soluble antigen of the worm body, and methods can be selected such as enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody test (IFA), indirect hemagglutination test (IHA), and counterflow immunoelectrophoresis (CIE). The serological test results have cross-reactions with other schistosome infections, but they still have an important auxiliary diagnostic significance in the early stage of infection when schistosome eggs cannot be detected. For example, detecting the circulating antigen of the liver fluke in the serum is more valuable than detecting antibodies. The detection of the schistosome antigen in the patient's feces is positive as early as the sixth week after infection, which has an early diagnostic significance.

　　5. Ascites examination

　　Ascites is straw-colored with a cell count of 1000×10⁶L/L above, mainly eosinophils.

　　Patients with schistosomiasis mansoni should be given a high-calorie, high-protein, and high-vitamin diet to help strengthen their physique and promote recovery due to the high fever that consumes a large amount of energy, leading to a decrease in overall function. For some patients with decreased appetite, fresh and tasty, easily digestible foods should be provided, with small and frequent meals. All cold, fried, sour and spicy, smoking and drinking, and greasy foods should not be eaten. Those with ascites should also avoid salt.

　　Schistosomiasis mansoni is mainly treated with medication, including the following aspects:

　　1. Thiacetamide treatment: This is a commonly used drug for the disease, with a dose of 40-60mg/d, taken orally in three divided doses, given every other day, with a course of 10-15 days, and then a second course after an interval of 5-7 days. The efficacy is usually observed on the third day of treatment, with the body temperature returning to normal within 3-6 days, and the clinical symptoms gradually improving, and the enlarged liver gradually shrinking.

　　The dose of praziquantel is 60mg/(kg·d), taken for 3 days. The advantage of this product is that the patient's tolerance is good and the course is short. However, some people believe that the efficacy is not significant, even ineffective.

　　The dose of trichlorophenazole is 10mg/kg body weight, taken all at once. This product was used in the veterinary field in 1983, applied to humans for the first time in 1989, and recommended by the WHO as a medicine in 1997. It is used more in Egypt, and there have been no reports in China. In addition to treating the pathogen, other measures should be taken, such as using sensitive antibiotics to treat concurrent bacterial infections, surgical treatment for obstructive jaundice, etc.