Schistosomiasis

Abstract

Schistosomiasis is caused by a group of trematode parasites belonging to genus Schistosoma and is a waterborne disease affecting large populations in Africa, Asia, and South America. The important human pathogens include Schistosoma haematobium, Schistosoma mansoni, and Schistosoma japonicum apart from some animal schistosomes which can cause human infection. Freshwater snails act as the intermediate hosts while humans and animals such as cattle, rodents are the definitive hosts. The parasite resides in the vesical and intestinal venous plexuses, and the pathology is primarily due to the eggs produced by the adult worms in the intestine or the urinary bladder. The clinical manifestations depend on the site of infection, the infecting species, and the parasite load. This condition is commonly diagnosed by detection of eggs in urine or stool after concentration, but serological tests and molecular assays are also available. Praziquantel is the drug of choice for all forms of schistosomiasis. In the absence of a vaccine, prevention of water pollution and eradication of snails remain the only viable methods for prevention .

Case Study

A 55-year-old male presented with chief complaints of haematuria and dysuria of 7-month duration. After the initial workup when no abnormalities were detected, an ultrasound abdomen was done, which revealed a mass on the left wall of bladder. On cystoscopy papillary tumour-like lesions were seen, and transurethral resection of the lesion was performed. Histopathology revealed high-grade papillary carcinoma and eosinophilic spherical structures resembling parasite eggs. The patient was again interviewed, and a detailed history was obtained. It was revealed that the patient had worked in Libya for about 10 years, and during that time he had travelled to neighbouring countries in North Africa like Tunisia, Egypt, Morocco, etc. About 4 years back, he had developed an itchy lesion on his leg and a rash which had disappeared after a few days. The patient was tested for antibodies against S. haematobium and S. mansoni, and the S. haematobium IgG was found to be elevated. A diagnosis of bladder carcinoma due to S. haematobium was made, and apart from adjunctive therapy for bladder carcinoma, Praziquantel was prescribed for the patient.

• 1. What is the mechanism of bladder carcinoma in chronic urinary bilharziasis?

• 2. What is the reason that children and young adults commonly suffer from the disease and not the adults?

• 3. What are the commercial diagnostic kits available for the diagnosis of schistosomiasis?

Research Questions

• 1. What are the protective antigens that can be used to develop effective vaccines against various Schistosoma species, and what should be the strategies for testing the vaccine efficacy in field conditions?

• 2. What inexpensive, rapid point-of-care tests can be used for the diagnosis of schistosomiasis?

• 3. How to understand the transmission patterns using remote sensing and geographical information system techniques?

• 4. What measures can be effective in the control of schistosomiasis?