Schistosomiasis fasciolaris

　　First, Etiology

　　1. Morphology

　　The adults are flat and plump, pinkish in color when alive, resembling slices of fresh ginger, hence the name. The body length is 20 to 75 mm, width 8 to 20 mm, and thickness about 2 to 3 mm, making it the largest schistosome parasitizing humans. The adults have one oral and one ventral acetabulum. The adults are hermaphroditic, with the uterus filled with a large number of eggs. The eggs are elliptical, pale yellow, with a size of (130 to 140) mm × (80 to 85) mm, making them the largest nematode eggs in humans. The eggshell is thin and even, with a slightly indistinct operculum at one end, near which there is an unfertilized ovum cell, surrounded by 20 to 40 yolk cells.

　　2. Life Cycle

　　The adult worms adhere to the duodenum and jejunum mucosa of the definitive host or pigs, and after fertilization (either intraspecific or interspecific), the fertilized eggs are excreted into the体外 through feces. Each adult worm can produce 15,000 to 20,000 eggs per day. The eggs enter the water with feces, and when the temperature is suitable, the cells inside the eggs divide and develop into mature miracidia. After being exposed to light, the miracidia hatch from the eggs and enter the intermediate host, the planorbid snail, where they develop into sporocysts → mother rediae → daughter rediae → cercariae. The cercariae continuously escape from the snail body, adhere to the surface of surrounding aquatic plants, and form cysts. Cysts have strong vitality in moist conditions but are susceptible to dryness and high humidity. When the intermediate host eats the cyst, the cyst wall breaks down in the small intestine due to the action of intestinal fluid, and the cercariae escape and adhere to the intestinal mucosa to absorb nutrients from the intestinal lumen, and can develop into adults within 1 to 3 months. The lifespan of adults in humans is 4 to 4.5 years, and in pigs, about 1 year.

　　Second, Pathogenesis

　　The acetabular muscles of Schistosoma japonicum are well-developed and have a strong adhesive force, which can cause inflammation, pinpoint bleeding, edema, and ulcerative abscess formation in the mucosa of the small intestine and nearby tissues. The adhesive site often has a large number of neutrophils, lymphocytes, and eosinophilic granulocytes. The mucosal epithelial cells secrete a large amount of mucus, and in severe cases, the intestinal wall may bleed. The parasites attach to the host's intestinal wall, absorb intestinal nutrients, and cover the intestinal mucosa, obstructing the absorption and digestion of the intestines, leading to intestinal dysfunction and malnutrition. The metabolic products and secretions of the parasites can cause pathological reactions in the host and an increase in eosinophils. The severity of the lesions is often related to the number of parasites in the host's body, usually several to dozens, and in severe cases, up to hundreds or even thousands. Most of the parasites can form clumps to block the intestinal wall, causing intestinal obstruction.

　　Allergic reactions, intestinal obstruction, granulocyte infiltration, pulmonary and intestinal bacterial infections, etc.

　　Allergic reactions, also known as hypersensitivity reactions, refer to a specific immune response characterized by physiological dysfunction or tissue cell damage in the body after the first response to certain antigens, and then again when exposed to the same antigen. The skin allergies people encounter in daily life, such as skin itching, redness, and swelling, are all allergic reactions.

　　Intestinal obstruction refers to the obstruction of the passage of intestinal contents in the intestines. It is a common acute abdominal condition that can be caused by various factors. Initially, the obstructed segment of the intestine undergoes both anatomical and functional changes, followed by fluid and electrolyte loss, intestinal wall circulatory disorders, necrosis, and secondary infection. Ultimately, it can lead to sepsis, shock, and death.

　　Granulocyte infiltration usually refers to neutrophil infiltration, which is a type of white blood cell. Granulocyte infiltration refers to the inflammatory response caused by foreign bodies, where neutrophils aggregate at the site of inflammation, and the intracellular proteolytic enzymes and other chemical substances are released, causing damage to the blood vessels and surrounding tissues.

　　The incubation period is 1 to 3 months. Mild cases may have mild symptoms or no symptoms, while moderate to severe cases may present with anorexia, abdominal pain, intermittent diarrhea (often malabsorptive feces), nausea, vomiting, and other gastrointestinal symptoms. Abdominal pain is often located in the upper abdomen and lower right costal region, with a few cases around the umbilicus, occurring in the morning on an empty stomach or after meals, mainly characterized by abdominal pain, occasionally with severe pain and colic. Patients often have hyperactive bowel sounds, increased intestinal motility, intestinal distension. Many patients have a history of spontaneous expulsion or vomiting of worms. Children often have neurological symptoms such as poor sleep at night, bruxism, convulsions, etc. A few patients may develop edema and ascites due to long-term diarrhea and severe malnutrition. Severe late-stage patients may experience exhaustion, collapse, or secondary bacterial infections in the lungs and intestines, leading to death. Occasionally, the worms may clump together, causing intestinal obstruction.

　　All those with a history of consuming aquatic plants raw in areas where fascioliasis is prevalent, accompanied by varying degrees of gastrointestinal symptoms, should be considered for the disease. Diagnosis depends on the detection of Fasciola japonica eggs in the feces. A positive result can often be obtained with three smears of feces. For those with fewer eggs, the formalin-ether concentration method can be used to concentrate the eggs, thereby improving detection rates.

　　To prevent the spread of this disease, it is first necessary to strengthen health education and publicity. Eat cooked water chestnuts, lotus seeds, etc., or wash them thoroughly with water and peel them with a knife before eating them raw. At the same time, good fecal management should be done. Feces that have not been treated for sterilization should not be used as fertilizer for planting aquatic plants in ponds and paddy fields. The feed for pigs should also be properly treated to prevent infection; pigs should not be allowed to be placed near the edges of ponds and fields with aquatic plants.

　　Various methods of concentrating egg samples can improve detection rates, but the diagnosis of fascioliasis also requires consideration of the number of parasites and clinical manifestations. The former can be obtained by the method of counting eggs to get a rough impression. The patient's red blood cell count and hemoglobin level often slightly decrease, the white blood cell count slightly increases, and eosinophils can increase to 10% to 20%, occasionally up to 40%. Occasional positive reactions may be observed in the fecal occult blood test. Schistosoma japonicum eggs can be found by direct smear method or sedimentation method for concentrating eggs. The former is prone to missed diagnosis in mild cases, while the latter can improve detection rates. Quantitative transparency method (i.e., modified Katayama smear method) can be used, which can both qualitatively identify and count the eggs.

　　X-ray examination shows delayed bone growth or dwarfism.

　　In order to prevent the spread of this disease, it is first necessary to strengthen health education and publicity, and to eat cooked water chestnuts, water caltrop, etc., or wash them thoroughly with water and peel off the skin before eating. At the same time, good feces management should be done, and feces that have not been treated with non-pathogenic methods should not be used as fertilizer for ponds and paddy fields with aquatic plants. The feed for pigs should also be properly treated to prevent pigs from being infected;

　　It is prohibited to place pigs on the edges of ponds and fields with aquatic plants. In areas where fascioliasis is prevalent, non-pathogenic septic tanks should be established, biogas pools promoted, and feces and urine sealed for storage, which can generally kill fasciolia eggs in 18 days. Adding 1:1000 of quicklime to feces can kill eggs after 3 hours.

　　It should be prohibited to wash feces near water sources such as rivers, lakes, reservoirs, and not to pour feces into rivers, lakes, and reservoirs, which is an effective measure to prevent the entry of eggs into the water.

　　First, deworming

　　1. Areca 30 grams, crushed and soaked in 500 milliliters of water overnight, decocted for 1 hour, taken on an empty stomach in the morning, taken for 2-3 days consecutively.

　　2. Areca 10 grams, black and white five each 15 grams, ground into fine powder, divided into two packets, taken with sugar water on an empty stomach, taken for 3-5 days consecutively.

　　3. Areca 30 grams (crushed), Biotae seed 30 grams (crushed), raw rhubarb 6 grams (added later), Guangmu xiang 4.5 grams, decocted with cold water, taken for 2-3 days consecutively.

　　Second, adjustment

　　1. Modified Xiangsha Liujunzi Decoction, invigorating the spleen and Qi, transforming dampness and regulating Qi, suitable for the treatment of mild cases after deworming. If there is a lack of appetite and decreased food intake, add Massa medicata fermentata 1 gram, each 10 grams of malt and wheat; if there is diarrhea, add Yam 10 grams, Dolichos 6 grams; if there is night sweats, add Oyster shell 30 grams (first decocted with浮小麦30 grams.).

　　Prescription example:

　　Codonopsis 10 grams, Atractylodes 10 grams, Poria 10 grams, Yam 10 grams, Dolichos 10 grams, Pinellia 10 grams, Tangerine peel 6 grams, red dates 5 pieces, Massa medicata fermentata 10 grams, Licorice 6 grams

　　2. Modified Baizhen Decoction, tonifying Qi and blood, suitable for the treatment of severe cases after deworming. If there is a lack of strength and emaciation, add Astragalus 10 grams, lotus seed 10 grams;

　　Anemia, add Polygonum multiflorum 10 grams, red dates 5 pieces; edema, add Alisma 10 grams, Job's tears 10 grams.

　　Prescription example:

　　Astragalus 10 grams, Codonopsis 10 grams, Atractylodes 10 grams, Poria 10 grams, Angelica sinensis 10 grams, Polygonum multiflorum 10 grams, Raw earth 10 grams, White peony 10 grams, Red dates 5 pieces, Licorice 6 grams