- Fever is a hallmark of acute schistosomiasis (Katayama fever), reflecting the body's systemic hypersensitivity reaction to the migrating schistosome larvae and eggs.
- This phase typically occurs weeks after initial infection and is characterized by high, intermittent fevers often accompanied by malaise and urticaria.
- The fever results from a type III hypersensitivity immune complex reaction triggered by antigen release from schistosomula and eggs.
- Other symptoms such as jaundice or hematuria are more characteristic of chronic schistosomiasis stages or specific organ involvement, not the acute febrile syndrome.
- Thus, fever is the most consistent and diagnostic clinical feature of the acute phase.

Reference: Davidson’s Principles and Practice of Medicine, 24th Edition, Chapter: Infectious Diseases, Page 701.