Global distribution, clinical characteristics, and outcomes of human intestinal capillariasis, 2000-2025: a systematic review.

backgroundIntestinal capillariasis, caused by Capillaria philippinensis, is an uncommon but potentially fatal parasitic infection associated with the consumption of raw or undercooked freshwater fish. Despite its sporadic occurrence, its clinical severity and diagnostic challenges warrant a comprehensive synthesis of available evidence. This systematic review aimed to summarize the geographic distribution, risk factors, clinical manifestations, diagnostic approaches, and treatment outcomes of human intestinal capillariasis.

methodsA systematic search of six electronic databases (PubMed, Scopus, EMBASE, Web of Science, Nursing & Allied Health Premium, Ovid) was conducted to identify studies published between January 2000 and August 2025. Eligible studies included case reports, case series, and observational studies investigating C. philippinensis infection in humans. Study selection was performed independently by two reviewers, while data extraction was conducted by one reviewer using a standardized template and independently verified by a second reviewer, with discrepancies resolved through discussion. Data were extracted and synthesized narratively following the PRISMA 2020 guidelines.

resultsThirty-two studies involving 348 patients were included, comprising studies from Asia (25/32), Africa (6/32), and South America (1/32). The burden of intestinal capillariasis was high in symptomatic or high-risk groups (5.0-23.0%) but extremely low (< 0.01%) in community-based or routine screening populations. Consumption of raw or undercooked freshwater fish was consistently identified as the principal risk factor. Clinical features were highly consistent across studies, characterized by chronic watery diarrhea, abdominal pain, weight loss, and peripheral edema. Hypoalbuminemia was the hallmark laboratory abnormality, frequently accompanied by electrolyte disturbances and anemia. Diagnosis relied primarily on stool microscopy, although limited sensitivity often required repeated examinations; histopathology and polymerase chain reaction provided important adjunctive confirmation in selected cases. Co-infections with other intestinal parasites were commonly reported. Treatment with albendazole or mebendazole was generally effective, with comparable outcomes between agents; however, delayed diagnosis was associated with severe complications and occasional mortality.

conclusionsIntestinal capillariasis is an underrecognized foodborne infection with a consistent clinical and laboratory profile across study designs. Early diagnosis through repeated stool examination and timely treatment with benzimidazoles is critical to improving outcomes. Strengthening food safety practices and enhancing surveillance are essential to reduce disease burden.