Test-treat-track-test-treat (5T) approach for Schistosoma haematobium elimination on Pemba Island, Tanzania

Trippler, Lydia; Taylor, Lyndsay; Ali, Mohammed Nassor; Najim, Sarah Omar; Khamis, Khamis Seif; Hattendorf, Jan; Juma, Saleh; Ame, Shaali Makame; Kabole, Fatma; Ali, Said Mohammed; Knopp, Stefanie

doi:10.1186/s12879-024-09549-w

Cited by 3 publications

References 31 publications

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Impact of chemical snail control on intermediate host snail populations for urogenital schistosomiasis elimination in Pemba, Tanzania: findings of a 3-year intervention study

Trippler,

Ali,

Masoud

et al. 2024

Parasites Vectors

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Background The World Health Organization (WHO) has set the goal of eliminating schistosomiasis as a public health problem globally by 2030 and to interrupt transmission in selected areas. Chemical snail control is one important measure to reduce transmission and achieve local elimination. We aimed to assess the impact of several rounds of chemical snail control on the presence and number of the Schistosoma haematobium intermediate snail host (Bulinus spp.) in water bodies (WBs) on Pemba Island, Tanzania, a setting targeted for elimination of urogenital schistosomiasis. Methods During the three annual intervention periods of the SchistoBreak study implemented in the north of Pemba from 2020 to 2024, malacological surveys were conducted up to four times per period in WBs of hotspot implementation units (IUs). Present freshwater snail species, vegetation, and WB characteristics were recorded. If Bulinus were found, the snails were inspected for Schistosoma infection and snail control with niclosamide was conducted. Results Across the three intervention periods, a total of 112 WBs were identified in 8 hotspots IUs. The spatial distribution of WBs with Bulinus per IU was heterogeneous, ranging from 0.0% (0/15) of WBs infested in one IU in 2022 to 80.0% (8/10) of WBs infested in one IU in 2021. Bulinus presence was significantly associated with lower pH values in WBs (odds ratio: 0.2, 95% confidence interval 0.1–0.4). A total of 0.2% (6/2360) of collected Bulinus were shedding Schistosoma cercariae. Following snail control, the number of Bulinus decreased or remained absent in 56.7% (38/67) of visits at WBs when compared with the previous visit in 2021, 54.9% (28/51) in 2022, and 33.3% (32/96) in 2023. In a total of 43.1% (22/55) of initially infested WBs, no Bulinus were found in the survey round conducted a few weeks after the first application of niclosamide. However, 25.4% (14/55) of WBs showed a pattern of recurring Bulinus presence. Conclusions The distribution of WBs containing Bulinus was very heterogeneous. The percentage of Bulinus with patent Schistosoma infection in our study area was extremely low. Repeated niclosamide application reduced the number of Bulinus in WBs, but snails often recurred after one or multiple treatments. While chemical mollusciciding can reduce snail numbers, to fully break the S. haematobium transmission cycle, timely diagnosis and treatment of infected humans, access to clean water, sanitation, and health communication remain of prime importance. Trial registration: ISRCTN, ISRCTN91431493. Registered 11 February. 2020, https://www.isrctn.com/ISRCTN91431493 Graphical Abstract

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Impact of chemical snail control on intermediate host snail populations for urogenital schistosomiasis elimination in Pemba, Tanzania: findings of a 3-year intervention study

Trippler,

Ali,

Masoud

et al. 2024

Parasites Vectors

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One-year impact of behavioural interventions on schistosomiasis-related knowledge, attitude and practices of primary schoolchildren in Pemba, Tanzania

Ndum,

Trippler,

Najim

et al. 2024

Infect Dis Poverty

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Background Elimination of schistosomiasis as a public health problem and interruption of transmission in selected areas are goals set by the World Health Organization for 2030. Behaviour change communication (BCC), coupled with other interventions, is considered an essential measure to reduce the transmission of Schistosoma infection. Focusing on elimination, we assessed the 1-year impact of BCC interventions on schistosomiasis-related knowledge, attitude and practices (KAP) of schoolchildren in hotspot schools versus low-prevalence schools that did not receive the interventions. Methods School-based cross-sectional surveys were implemented in 16 schools on Pemba Island, Tanzania, in 2020 and 2022, respectively. The schistosomiasis-related KAP were assessed in children attending grades 3–5, using pre-tested questionnaires. Between the surveys, in 2021, children from hotspot schools were exposed to BCC interventions. The difference in mean knowledge and attitude scores, respectively, between schoolchildren from hotspot and low-prevalence schools during the survey in 2022 was determined with a linear mixed-effect model. Results In the five hotspot schools that received BCC interventions, 315 children participated in the survey in 2020 and 349 in 2022. There was a 21.0% increase in children with moderate knowledge and a 13.8% decrease in no knowledge; a 8.3% increase in good attitude and a 19.2% decrease in poor attitude; 3.4% and 3.2% fewer children reported to use waterbodies for washing clothes or body, respectively. In the 11 low-prevalence schools without BCC interventions, 778 children participated in 2020 and 732 in 2022. The percentage of children with poor knowledge (56.4% and 63.1%) and poor attitude (55.3% and 53.1%) remained relatively stable from 2020 to 2022, but 4.9% and 3.0% less children reported to use waterbodies for washing clothes or their body, respectively. In 2022, the difference in mean knowledge scores was 0.8 [95% confidence interval (CI): 0.5−1.1] and the difference in mean attitude scores was 0.6 (95% CI: 0.4−0.7) between children in hotspot compared with low-prevalence schools. Conclusions After one year of implementation, the BCC interventions markedly improved the KAP of exposed children. Complemented by improved access to clean water and sanitation, BCC holds promise to contribute successfully to the achievement of schistosomiasis control and elimination targets. Trial registration ISRCTN, ISRCTN91431493. Registered 11 February. 2020, https://www.isrctn.com/ISRCTN91431493. Graphical Abstract

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A pilot investigation of bovine schistosomiasis on Unguja Island, Zanzibar raises a new concern for elimination of urogenital schistosomiasis

Ame,

Juma,

Juhász

et al. 2024

Preprint

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Our pilot parasitological investigation of cattle, supplemented with molecular DNA characterisation of encountered schistosomes, sheds first light upon bovine schistosomiasis on Unguja Island, Zanzibar. During February 2024, a total of 99 cattle were examined. Of these, 47 were exported animals from the Tanzanian mainland, designated for slaughter at two governmental abattoirs (Kisakasaka & Muwanda), and 52 were free-grazing animals sampled from four grazing locations within the island’s North and Central regions. Upon visual inspection of 31 cattle carcasses at Kisakasaka for adult worms, prevalence of schistosomiasis was 51.6%, whereas upon faecal miracidia hatching test (MHT) was 80.6%. At Muwanda, only faecal MHT was used, finding a much lower prevalence of 12.5%. In free-grazing animals, prevalence of schistosomiasis by MHT was 0.0%. At Muwanda the animal quarantine paddock was in disrepair, inclusive of a large pond now acting as a watering point. Here, numerous Bulinus forskalii sp. were found. Whilst no snails were observed to shed schistosome cercariae, molecular xenomonitoring did detect a pre-patent infection prevalence of 10.8%, with Schistosoma bovis firmly incriminated. Molecular DNA characterisation of adult schistosomes (n = 19) by real-time PCR and high resolution melt profiling, alongside DNA sequencing, also identified S. bovis although two worms were putative S. bovis-S. mattheei hybrids. Atypical intrauterine eggs of S. bovis were noted upon microscopy of a worm pair. A broader screen of 92 miracidia confirmed S. bovis and 3 miracidia as S. bovis-S. mattheei hybrids. Contrasting with Pemba Island, Zanzibar, where autochthonous transmission of S. bovis can occur, bovine schistosomiasis on Unguja Island currently appears restricted to imported animals alone. However, the seminal detection of putative S. bovis-mattheei hybrids, alongside the current inadequate quarantine facilities at Muwanda, raises a new concern that such hybrid schistosomes may escape and enter the island’s hinterland. Should this happen, surveillance and control of urogenital schistosomiasis on Unguja would be compromised and further complicated. We therefore strongly recommend immediate repair and improved maintenance of governmental animal quarantine facilities. Future epidemiological surveys of imported cattle are now well-justified, not only to better understand the full repertoire of hybrid schistosomes present but also to develop appropriate mitigating interventions.

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Test-treat-track-test-treat (5T) approach for Schistosoma haematobium elimination on Pemba Island, Tanzania

Cited by 3 publications

References 31 publications

Impact of chemical snail control on intermediate host snail populations for urogenital schistosomiasis elimination in Pemba, Tanzania: findings of a 3-year intervention study

Impact of chemical snail control on intermediate host snail populations for urogenital schistosomiasis elimination in Pemba, Tanzania: findings of a 3-year intervention study

One-year impact of behavioural interventions on schistosomiasis-related knowledge, attitude and practices of primary schoolchildren in Pemba, Tanzania

A pilot investigation of bovine schistosomiasis on Unguja Island, Zanzibar raises a new concern for elimination of urogenital schistosomiasis

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