Schistosomiasis is a disease caused by the Schistosoma japonicum in the human portal vein system. The schistosome undergoes six developmental stages: egg, miracidium, mother sporocyst, daughter sporocyst, cercaria, and adult. Patients with schistosomiasis excrete eggs in their feces, which hatch into miracidia within one day in water. Upon encountering an Oncomelania snail, the miracidia penetrate its body and develop over 7–8 weeks into sporocysts and then cercariae. The cercariae leave the snail and swim in water. When humans or animals come into contact with contaminated water, the cercariae penetrate the skin, travel through the bloodstream via the lungs, and eventually reach the portal vein, where they mature into adults. The adult worms pair up, mate, and migrate to the small veins of the intestinal wall to lay eggs. The pathological changes caused by schistosomiasis vary depending on its developmental stage in the human body, but the final outcome is severe.

bubble_chart Clinical Manifestations

1. Invasion Stage After contact with contaminated water, localized skin may develop small urticaria, followed by the formation of papules or small blisters, known as "cercarial dermatitis." When the cercariae pass through the lungs, they can cause cough, chest pain, hemoptysis, and urticaria.
2. Acute Stage When the schistosomes mature, mate, and lay eggs in the portal venous system of the liver, acute symptoms may appear due to the child's reaction to the foreign eggs (common bletilla tuber). Fever (which may be remittent, intermittent, or irregular) occurs, along with loss of appetite, abdominal distension and fullness, abdominal pain, diarrhea, or dysentery. The liver and spleen may enlarge, with possible tenderness in the liver area, and jaundice may occasionally occur. This stage mostly occurs in summer and autumn and generally gradually resolves after more than a month.
3. Chronic Stage After the acute stage, many mild cases may show no symptoms, so this stage can be considered a transitional phase between the acute stage and the advanced stage. This period can last for over 10 years. Upon entering the late stage [third stage], symptoms may include fever (often low-grade, rarely high), loss of appetite, abdominal distension and fullness, diarrhea, or bloody stools, with significant enlargement of the liver and spleen.
4. Advanced Stage Liver cirrhosis, hypersplenism, ascites, and massive bleeding due to varices in the lower esophagus may occur. This stage is uncommon in children. If it does occur, anterior pituitary dysfunction may lead to dwarfism.
5. Ectopic Lesions Adult worms may be found in the lungs, where they can also lay eggs. In other locations, such as the brain, encephalitis, meningitis, spasms, epilepsy, or space-occupying sexually transmitted disease-like lesions may develop.

bubble_chart Auxiliary Examination

1. Stool routine examination for parasite eggs or hatching miracidia; repeated examinations can increase the positive rate.
2. Blood tests show increased eosinophils in the early stage, while advanced stages may present with leukopenia, grade I anemia, and manifestations of hypersplenism.
3. Sigmoidoscopy in the early stage reveals visible congestion and edema of the intestinal mucosa, along with yellow or white small granules. In advanced stages, the mucosa becomes thickened, rough, and may exhibit ulcers and scars. During the examination, mucosal smears can be taken to check for parasite eggs.
4. For suspected lung damage, X-ray examination during the acute phase may reveal pneumonia-like shadows or changes resembling foxtail millet-sized subcutaneous nodules.
5. For suspected brain damage, electroencephalography (EEG), cranial CT, or magnetic resonance imaging (MRI) can be performed for diagnosis.
6. Antigen intradermal test: A local papule diameter >0.8 cm within 15 minutes of injection is considered positive. Due to cross-reactivity with Clonorchis sinensis and Paragonimus, false positives should be excluded. 7. Other serological tests, such as the circumoval membrane precipitation test and cercarial membrane test, exhibit high specificity, with positive rates exceeding 95%.

bubble_chart Diagnosis

Epidemiological history: Resided in an epidemic area and had a history of contact with contaminated water.

bubble_chart Treatment Measures

(1) General Therapy

Enhance nutrition and provide liver-protective treatment.

(2) Pathogenic Treatment

1. Praziquantel: A non-antimony antischistosomal drug suitable for patients at all stages. After administration, it excites the activity of schistosomes and causes muscle spasms, depriving them of their ability to adhere to blood vessel membranes and migrate against the flow in the portal vein, thus being swept into the liver by blood flow—a process known as hepatic shift. After hepatic shift, adult worms can die in large numbers, but this Yaodui has poor efficacy against juvenile worms and no killing effect on eggs. The total dose is 120mg/kg, divided over 4 days, or 10mg/kg per dose, three times daily, or 15mg/kg per dose, twice daily. For advanced-stage patients or those with weaker constitutions, the dose is 5mg/kg per dose, three times daily for 8 consecutive days, totaling 120mg/kg. Side effects are rare, but some patients may experience grade I elevation of alanine aminotransferase; electrocardiograms may show T-wave depression, and occasional atrial premature beats may occur. Therefore, caution is advised for patients with heart disease or abnormal liver function.
2. Nithiocyanamine: This drug rapidly induces hepatic shift in schistosomes, achieving mass killing; it is primarily used for acute-stage, early chronic-stage, some advanced-stage, and cerebral schistosomiasis cases. The total dose is 6–7mg/kg (not exceeding 300mg), divided equally over 3 days, taken once daily. Side effects include dizziness, lack of strength, vertigo, nausea, abdominal pain, etc. Severe cases may experience ataxia, and liver damage may occur, leading to jaundice and elevated transaminase levels. Therefore, it is contraindicated for patients with heart, liver, or kidney diseases.
3. Furapromide: This Yaodui is more effective at killing juvenile worms than adult worms, so its efficacy when used alone is suboptimal. It is suitable for acute-stage cases, with rapid fever-reducing effects. The dose is 50–60mg/(kg·d), divided into 2–3 doses daily for 14–20 consecutive days. Side effects include decreased appetite, nausea, abdominal pain, diarrhea, muscle fleshy rigidity spasms, and neuropsychiatric symptoms. It is contraindicated for patients with a history of mental illness, severe neuro Guanneng disorders, peptic ulcers or upper consumptive thirst digestive tract bleeding, as well as acute or chronic hepatitis and nephritis. Additionally, it decomposes quickly in the body after oral administration, resulting in low blood concentrations, so its efficacy when used alone is not ideal.
4. Furadiamine: Its effects are the same as furapromide, but the dose is smaller, and side effects are fewer. When combined with trichlorfon, the efficacy is better. Dosage and administration: Day 1: 15mg/(kg·d), Day 2: 20mg/(kg·d), from Day 3 onward: 25mg/(kg·d), with the daily dose divided into three administrations, taken for 11 consecutive days. On Days 2, 4, and 6 of treatment, trichlorfon is administered intramuscularly concurrently. Side effects include abdominal pain, diarrhea, etc.
5. Trichlorfon: A low-toxicity organophosphorus compound. It has synergistic effects when combined with furapromide or furadiamine. For older children, the dose is 3mg/kg per administration (total dose not exceeding 150mg), diluted with sterile water for injection and administered intramuscularly once on Days 2, 4, and 6 of the furapromide or furadiamine treatment course. Side effects may include dizziness, headache, chest tightness, palpitation, etc.

For advanced-stage patients with splenomegaly and hypersplenism, splenectomy may be performed, which can alleviate hypersplenism symptoms postoperatively.

bubble_chart Prevention

1. Thoroughly treat the patients.
2. Strengthen the management of feces and water sources to completely eliminate snails.
3. Enhance personal protection.