Parasitology — MCQs

Question 1: Katayama fever is seen in which of the following?

• A. Schistosoma mansoni (Correct Answer)
• B. Schistosoma japonicum
• C. Schistosoma haematobium
• D. Schistosoma mekongi

Explanation: **Explanation:** **Katayama Fever** is an acute clinical manifestation of **Schistosomiasis** (Bilharziasis). It is a systemic hypersensitivity reaction (Type III hypersensitivity) to the antigens released by migrating schistosomulae and the onset of initial egg production. 1. **Why Schistosoma mansoni is correct:** While Katayama fever can occur with several species, it is most classically associated with **S. mansoni** and **S. japonicum**. In the context of standard medical examinations like NEET-PG, when multiple species are listed, *S. mansoni* is frequently the preferred answer due to its high prevalence and classic association with the intestinal/hepatosplenic form of the disease where this acute syndrome is most documented. 2. **Analysis of Incorrect Options:** * **S. japonicum:** While it causes Katayama fever (often more severely than *S. mansoni*), it is less commonly tested as the primary answer in general parasitology questions unless the geographic context (East Asia) is specified. * **S. haematobium:** Primarily causes urinary schistosomiasis (terminal hematuria). While acute symptoms can occur, it is rarely the classic presentation for Katayama fever compared to the intestinal species. * **S. mekongi:** A localized species (Mekong River basin) that causes intestinal disease similar to *S. japonicum* but is a rare cause compared to the major species. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogenesis:** Immune complex deposition (Serum sickness-like illness). * **Clinical Features:** Fever, chills, cough, urticaria, lymphadenopathy, and significant **eosinophilia**. * **Intermediate Host:** Freshwater snails (*Biomphalaria* for *S. mansoni*; *Oncomelania* for *S. japonicum*; *Bulinus* for *S. haematobium*). * **Infective Stage:** Cercaria (penetrates skin). * **Diagnostic Feature:** *S. mansoni* eggs have a characteristic **lateral spine**. * **Drug of Choice:** Praziquantel.