Seasonal Distribution and Cercarial Shedding of Spp. Snails: Implications for Urogenital Schistosomiasis Control in the Simiyu Region, Northwestern Tanzania

Overview

Journal Curr Res Parasitol Vector Borne Dis

Date 2025 Feb 24

PMID 39989476

Authors

Nyanda C Justine

Humphrey D Mazigo

Antje Fuss

Bonnie L Webster

Eveline T Konje

Klaus Brehm

Andreas Mueller

Affiliations

Soon will be listed here.

Abstract

Urogenital schistosomiasis is a neglected tropical disease of significant public health concern caused by the trematode species . Its transmission is localised and heterogeneous, with seasonal occurrences in Tanzania primarily facilitated by spp. snails, which serve as intermediate hosts. To plan effective, data-driven control measures, it is crucial to understand the epidemiology of schistosomes in these snails. This study aimed to investigate the seasonal distribution, abundance, and spp. infections (assessed cercarial emergence) in spp. snails in two districts, Maswa and Meatu, in the Simiyu Region of Tanzania. Malacological surveys were conducted at 90 sites in total, comprising sites in 35 rivers, 32 ponds, and 23 branching streams. Each study site was sampled once during the rainy season and once during the dry season. Snails were collected using a standard scoop- and handpicking technique by two people for 15 min at each site. The collected snails were morphologically identified and subjected to a cercarial emergence experiment. Water physicochemical characteristics were recorded simultaneously with snail collection using a portable multiparameter water meter. The data were analysed using STATA v. 17. A total of 4997 spp snails were collected from 90 sites in the two districts. Of these, 91.4% (95% CI: 90.5-92.1%) were morphologically identified as and 8.6% (95% CI: 7.8-9.4%) were identified as . spp. snail abundance was almost evenly distributed across seasons, with 50.4% (95% CI: 48.9-51.7%) collected during the dry season and 49.6% (95% CI: 48.2-51.0%) collected during the rainy season. Water temperature and salinity were significantly negatively correlated with snail abundance (both < 0.001). spp. cercarial emergence followed a seasonal pattern and was significantly higher during the rainy season ( = 0.005). Our findings underscore that was the most abundant freshwater snail distributed at nearly all the study sites during the rainy and dry seasons. Therefore, appropriate snail control strategies are recommended to complement ongoing schistosomiasis control strategies in the Simiyu Region.

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