Intestinal Parasitic Infection in Humans: A Critical Narrative Review of Pathophysiology, Clinical Implications and Prevention
Mt Farzana Yasmin
Department of Pharmacy, ASA University, Dhaka, Bangladesh.
Majedul Hoque *
Department of Pharmacy, Jahangirnagar University, Dhaka, Bangladesh.
*Author to whom correspondence should be addressed.
Abstract
Intestinal parasites remain among the most widely distributed infectious agents of humans, yet the relationship between parasite carriage and disease continues to be interpreted inconsistently across parasitology, paediatrics, nutrition and public health. This review examines how helminths and enteric protozoa injure the gastrointestinal tract, what clinical consequences follow from that injury, and how far current preventive strategies address the mechanisms involved. Literature was identified through structured searching of open bibliographic and full-text sources, supplemented by citation tracking and examination of institutional documents, with priority given to peer-reviewed mechanistic studies, cohort investigations, randomised trials and quantitative syntheses. Three findings dominate the synthesis. Epithelial barrier disruption, altered mucosal immunoregulation and interference with nutrient handling are reproducibly demonstrated in organoid, animal and human tissue systems, but the quantitative link between these mechanisms and population-level morbidity remains weakly specified. The clinical burden attributable to intestinal parasites is unevenly evidenced: hookworm-associated iron loss and invasive amoebic and strongyloidal disease rest on comparatively firm ground, whereas claims about growth faltering, cognitive development and long-term functional bowel disease depend on observational data whose confounding structure has not been resolved by the available trials. Prevention has been dominated by anthelmintic distribution to school-aged children, an approach that reduces the intensity of infection but leaves transmission, protozoal infection and reinfection largely untouched. Community-wide treatment, improved sanitation, more sensitive molecular diagnosis and candidate vaccines each address part of the problem, and recent trial evidence indicates that interruption of transmission is achievable in some ecological settings but not reliably so. Persistent uncertainties include the causal weight of subclinical parasite carriage, the pathogenic status of commonly detected protozoa, the trajectory of anthelmintic efficacy, and the extent to which climatic change will redistribute exposure. Progress will depend less on additional prevalence surveys than on mechanistically informed longitudinal studies and on trials designed around transmission rather than around individual worm expulsion.
Keywords: Soil-transmitted helminths, Giardia duodenalis, intestinal barrier function, environmental enteric dysfunction, preventive chemotherapy, anthelmintic efficacy, water, sanitation and hygiene