Browsing by Author "Civitello, David"

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Mapping of snail intermediate host habitats reveals variability in schistosome and non-schistosome trematode transmission in an endemic setting
(ELSEVIER, 2025) Angelo, Teckla; Starkloff, Naima; Civitello, David; Mahalila, Moses; Kinung’hi, Safari
The intermediate snail host of Schistosoma haematobium, the etiological agent of urogenital schistosomiasis, serves as a critical sentinel for tracking the spread of associated disease risks. In addition to S. haematobium, Bulinus spp. snails also transmit S. bovis to cattle as well as several non-schistosome trematodes to cattle and wildlife. Identifying transmission foci of these multi-parasite hosts is critical for targeted and effective One Health intervention. We investigated 467 waterbodies in 86 villages across six districts in northwestern Tanzania. A total of 43,348 Bulinus nasutus were collected across three survey phases from November 2020 to August 2021. Across all snails, 0.63% were emitting schistosome cercariae. There was a significant increase in schistosome prevalence during the year, with a peak in the dry season (June-August 2021). Furthermore, of the 25,052 snails collected in the latter two phases (March to August 2021), 4.9% were infected with non-schistosome trematodes, exceeding prevalences of schistosomes at all spatial scales. Co-infections were uncommon, with only 0.05% of snails concurrently emitting both schistosome and non-schistosome parasites. These infection patterns were consistent across village and district levels. Waterbodies used by cattle had higher schistosome prevalence than waterbodies isolated for human use. Surprisingly, non-schistosome prevalence was equal in both of these waterbody types. This suggests that cattle have an indirect role in schistosome transmission, requiring the separation of waterbody usage between cattle and humans and extending snail control in dry season to water- bodies used by cattle. By contrast, water permanence and school proximity did not impact snail or parasite presence. Targeted interventions should focus on local water use dynamics, with attention to the potential in- direct role of cattle in schistosome transmission.
Spatio-temporal variability in transmission risk of human schistosomes and animal trematodes in a seasonally desiccating East African landscape
(The Royal Society, 2024-01-10) Starkloff, Naima; Angelo, Teckla; Mahalila, Moses; Charles, Jenitha; Kinung'hi, Safari; Civitello, David
Different populations of hosts and parasites experience distinct seasonality in environmental factors, depending on local-scale biotic and abiotic factors. This can lead to highly heterogeneous disease outcomes across host ranges. Variable seasonality characterizes urogenital schistosomiasis, a neglected tropical disease caused by parasitic trematodes (Schistosoma haematobium). Their intermediate hosts are aquatic Bulinus snails that are highly adapted to extreme rainfall seasonality, undergoing prolonged dormancy yearly. While Bulinus snails have a remarkable capacity for rebounding following dormancy, we investigated the extent to which parasite survival within snails is diminished. We conducted an investigation of seasonal snail schistosome dynamics in 109 ponds of variable ephemerality in Tanzania from August 2021 to July 2022. First, we found that ponds have two synchronized peaks of schistosome infection prevalence and observed cercariae, though of lower magnitude in the fully desiccating than non-desiccating ponds. Second, we evaluated total yearly schistosome prevalence across an ephemerality gradient, finding ponds with intermediate ephemerality to have the highest infection rates. We also investigated dynamics of non-schistosome trematodes, which lacked synonymity with schistosome patterns. We found peak schistosome transmission risk at intermediate pond ephemerality, thus the impacts of anticipated increases in landscape desiccation could result in increases or decreases in transmission risk with global change.