A Contribution Toward Understanding Trematode Diversity in Freshwater Snails of the Southwestern Kathmandu Valley, Nepal

Background Freshwater snails serve as intermediate hosts for trematode parasites and play a key role in transmitting various parasitic diseases. Snail‐borne trematodiases pose important public and veterinary health risks in South Asia, where freshwater snails sustain transmission in agricultural and periurban waters. However, data from the Kathmandu Valley remain limited and fragmented across habitats and seasons. Objectives This study aimed to determine the diversity and distribution of cercarial larvae in freshwater snail species from the southwestern part of the Kathmandu Valley, Nepal. Methods From July to October 2023, a total of 1893 snail samples were collected from grazing swamps, ditches, paddy fields, and canals. The samples represented five genera within four families: Lymnaea acuminata and Radix spp. (Lymnaeidae), Gabbia orcula (Bithyniidae), Physa acuta (Physidae), and Indoplanorbis exustus (Planorbidae). Cercarial infections were examined using the light‐induced shedding method. Results Four of the five snail species examined harbored trematode cercariae, with an overall prevalence of 3.01% (57/1893), while Radix spp. showed no infection. Nine cercarial morphotypes were identified: Amphistome, Mutabile, Cercariaeum, Echinostome, Gymnocephalus, Cystophorous, Parapleurolophocerous, Xiphidiocercariae , and Brevifurcate apharyngate distome cercariae . The infection prevalence varied significantly by month (Fisher’s exact test, p = 0.001), peaking in July (5.56%), August (4.95%), and by habitat ( p = 0.001), with the highest prevalence in grazing swamps (4.91%). A significant positive correlation was observed between snail length and infection rate ( r = 0.781, p < 0.001), with medium‐sized Lymnaea (18–26 mm) and Gabbia (10–13.9 mm) exhibiting the highest infection rates. Conclusions Elevated infection occurred in July‐August and among larger swamp‐dwelling snails. The presence of diverse trematode cercariae, including zoonotically important types, underscores potential public and veterinary health risks and highlights the need for further studies on definitive hosts and control strategies. These patterns provide actionable guidance for risk mapping and prioritizing seasonal, habitat‐focused surveillance and control in the Kathmandu Valley.