MOLECULAR SOURCE ATTRIBUTION OF FOODBORNE AND WATERBORNE ZOONOTIC PARASITES: A ONE HEALTH REVIEW OF TRANSMISSION PATHWAYS AND SURVEILLANCE GAPS

Abstract

Foodborne and waterborne zoonotic parasites remain major One Health threats because their transmission connects humans, livestock, companion animals, wildlife, food systems, water sources, soil, wastewater, and contaminated environments. This review synthesizes current knowledge on molecular source attribution of three key protozoan parasites, Cryptosporidium spp., Giardia duodenalis, and Toxoplasma gondii, which represent major models for multi-host and environmentally mediated transmission. The review highlights how conventional detection methods confirm parasite presence but often fail to identify the origin, reservoir, or direction of transmission. Molecular tools, including PCR, qPCR, sequencing, gp60 subtyping, multi-locus genotyping, PCR-RFLP, whole-genome sequencing, metabarcoding, environmental DNA, and spatial molecular epidemiology, provide higher-resolution evidence for linking human infections with animal, food, water, and environmental sources. Major transmission pathways discussed include meat-borne exposure, fresh produce contamination, raw milk and dairy products, drinking water, recreational and surface water, wastewater reuse, irrigation water, soil persistence, and direct contact with animal reservoirs. The review further examines livestock, companion and stray animals, wildlife, and human activities as drivers of reservoir overlap and environmental contamination. Despite major advances, important surveillance gaps remain, including fragmented human–animal–environment monitoring, limited standardized molecular protocols, weak evidence for transmission direction, under-sampling of food and environmental matrices, poor integration of epidemiological and molecular data, and limited genomic capacity in low-resource settings. This review proposes an integrated molecular One Health surveillance framework based on matched sampling, high-resolution typing, data integration, source attribution, and targeted control actions to improve prevention of foodborne and waterborne zoonotic parasite transmission.