Overview
Schistosomiasis is an endemic parasitic disease caused by Schistosoma intermedia parasitizing the intestinal veins. Most patients have no obvious symptoms after infection. In severe cases, there may be sudden pain in the left iliac bone, abdominal pain and diarrhea.
Etiology
The adult size of the worm varies with the host and is easily confused with other species of schistosomes. Male worms are 11.5～14.5mm long and 0.3～0.5mm wide; there are 2～7 testes, 4 are common, and the small spines are distributed on the ventral, lateral and dorsal surfaces from the posterior part of the testes, and there are small nodules on the epidermis. Female worms were 13-24 mm long and 0.2-0.25 mm wide, with ovaries located between the intestinal branches, mostly twisted in a spiral pattern. Intrauterine worm eggs averaged 140 μm × 37 μm, and about 25% to 60% of the worms began to lay eggs 80 days after infection, with a maximum of 122 eggs per worm. Eggs were spiny at the end, slightly curved, positive for Lou-Ni staining reaction, and positive for acid-resistant staining of the eggshell. Fixed with Bouin’s solution, the middle of the trichinae was concave in the form of spectacle glass. The glandular secretions of the caecilians were granular and thread-like. Sticky secretions from the glands behind the abdominal suckers of the caecilians gave them a tendency to aggregate.
Symptoms.
Symptoms are unremarkable in most patients with infection. Severe infections may be characterized by sudden onset of pain in the left iliac bone. Liver biopsy reveals eosinophilic abscess formation around the worm eggs. Proctoscopy may reveal rectal mucosal enteropathy, mucosal congestion near the rectal valve, inflammation of the intestinal wall, or polyp formation, and the patient may have obvious gastrointestinal symptoms, blood and mucus in the stool, and urgency and heaviness. The other type is the non-inflammatory reaction type, only mucosal thickening is seen, and there are worm eggs inside.
Examination
1. Pathogen examination
The diagnosis can be confirmed by finding typical eggs in the stool and rectal mucosa, or by detecting trichinae in the fecal hatching. The eggs stain positively for acid resistance. The characteristic feature of the eggs is the spectacled glassy shape of the larvae.
2.Ziehl-Neelsen staining method
The egg shells of Schistosoma intermedia can be stained red.
3. Serologic examination
The serum reaction of Schistosoma intermedia is weak, and the positive rate of indirect immunofluorescence is high.
4.Auxiliary examination
Liver biopsy shows eosinophilic abscess formation around the eggs. Enteroscopy can see mucosal congestion near the rectal valve, inflammation of the intestinal wall or polyp formation.
Diagnosis
The disease can be diagnosed on the basis of epidemiologic data (prevalent in western Central Africa, Zaire, Cameroon, Gabon and other countries), history of exposure to infected water, clinical manifestations, and laboratory search for eggs.
Differential diagnosis
1. Mekong schistosomiasis should be differentiated from typhoid fever, amoebiasis, cornual tuberculosis, viral hepatitis, dysentery, portal and post-necrotic cirrhosis.
2. Acute schistosomiasis has been misdiagnosed as typhoid fever, amoebic liver abscess, cornual tuberculosis and so on. Acute schistosomiasis blood eosinophils increased significantly is an important basis for differentiation from the above diseases.
3. Chronic schistosomiasis hepatosplenomegaly should be differentiated from jaundice-free viral hepatitis. The latter loss of appetite, fatigue, pain in the liver area and liver function impairment are more obvious. Viral hepatitis serologic examination can have positive viral antigen.
4. Pathogenetic examination is easy to distinguish from amoebic dysentery, chronic bacillary dysentery. Schistosomiasis patients with diarrhea, blood in the feces hatch positive, and the number of trichinae is higher.
5. According to the clinical symptoms can have been initially identified with advanced schistosomiasis and portal and necrotic cirrhosis. Late schistosomiasis liver function damage is less severe, jaundice, spider nevus and liver palms are less common, there is splenomegaly, and there is a history of chronic diarrhea and blood in the stool. However, it is still necessary to rely on multiple pathogenetic and immunologic tests to make a definitive identification.
Complications
1. Complications of liver fibrosis
More than 2/3 of patients with advanced schistosomiasis have varices in the lower esophagus or fundus of the stomach. The rupture of varices causes upper gastrointestinal hemorrhage in 16.5%-31.6% of patients, which is the main complication of schistosomiasis fibrosis. Clinical symptoms include large amount of vomiting blood and black feces, which can cause blood pressure drop and hemorrhagic shock, with a case fatality rate of about 15%. About half of the patients have a history of repeated hemorrhage. Ascites or hepatic encephalopathy may occur after massive bleeding from the upper gastrointestinal tract. Hepatic encephalopathy is less common in advanced schistosomiasis than in portal and post-necrotic cirrhosis, which is reported to account for 1.6% to 5.4% in China, and the duration of the disease is also longer. In addition, late schistosomiasis ascites complicating primary peritonitis and gram-negative bacillus sepsis is not uncommon.
2. Intestinal complications
Schistosoma eggs can be found in up to 31% of the resected appendix specimens of patients in endemic areas, which is often a cause of acute appendicitis, and the appendix is more likely to be perforated, and can be complicated by peritonitis or limited abscesses.
Schistosomiasis caused by severe colonic lesions to the narrowing of the intestinal lumen, can be complicated by incomplete intestinal obstruction, to be located in the sigmoid colon and rectum more. In addition, mesenteric and greater omental lesions may adhere to form intra-abdominal masses. Colonic granulomas in patients with schistosomiasis can be complicated by colon cancer. The patients are younger, most of them are adenocarcinoma, less malignant and metastasize later.
Treatment.
Praziquantel has excellent efficacy in the treatment of interstitial schistosomiasis infections. Nilidazole can also be used for 7 days.
Prognosis
With early treatment, the prognosis is generally good. The prognosis for patients with severe complications is poor.