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. 2022 Nov;69(6):3153-3159.
doi: 10.1111/tbed.14692. Epub 2022 Sep 12.

Evidence for local transmission and maintenance of schistosomiasis in an urban neighbourhood in Northeast Brazil

Camila F Chaves  1 , Gilberto Sabino-Santos  2   3 , Fernanda Mac-Allister Cedraz  1 , Pedro Santos-Muccillo  1 , João Ricardo Filho  1 , Vanessa S Zanardi  1 , Vanessa T Moretto  1 , Adriano P C Santos  1 , Fabiano Simões  1   4 , Lucio M Barbosa  1   5 , Luciano K Silva  1 , Mitermayer G Reis  1   6   7 , Ronald E Blanton  2
Affiliations

Evidence for local transmission and maintenance of schistosomiasis in an urban neighbourhood in Northeast Brazil

Camila F Chaves et al. Transbound Emerg Dis. 2022 Nov.

Abstract

Schistosomiasis is a tropical neglected disease commonly associated with rural areas; however, urban schistosomiasis has been reported worldwide, and increasing urbanization is one of the most important demographic shifts of the 20th and now 21st centuries. The pattern of urbanization is not uniform so that within the same city the rates and sources of population increase vary. Here, we report on the parasite composition in one neighbourhood in the metropolitan area of Salvador, Bahia, Brazil. Using epidemiological data and population genetics, we find evidence for local transmission and maintenance of Schistosoma mansoni infection within an urban population and little contribution from rural-urban migration. Our findings provide direction for local mitigation strategies and to assist the public living in this neighbourhood to interrupt the local transmission cycle.

Keywords: Schistosoma mansoni; migration; population genetics; urbanization.

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Conflict of interest statement

Competing Interests

The authors declare no conflict of interest.

Figures

Figure 1.
Figure 1.
Study area: Pirajá neighborhood in Salvador city, State of Bahia, north-eastern Brazil. (A) Pirajá (black) is shown within the municipal area of Salvador, Bahia, Brazil. (B) Study area and distribution of points along the Cobre River basin where the community in Pirajá often gets in contact with water: (P1) Represa do Cobre, (P2) Barragem Sete Quedas, (P3) Córrego do Campo, (P4) Vala da Baixa da Fonte, (P5) Cachoeira de Nanã. This map was generated using QGIS version 3.18.3 (Zürich-CH).
Figure 2.
Figure 2.
Genetic differentiation for Schistosoma mansoni: percentage (%) of lifetime between 51 infra-populations and the component population of parasites of the native-borne (Dic) in Pirajá neighborhood, Salvador-BA, Brazil, 2019, using 15 microsatellite loci (smms2, smms13, smms16, smms3, smms17, smms18, smms21, smda23, sm13–478, 1f8a, 29e6a, smu31768, lg3_sc36b, sc23b, smd28). (A) Principal component analysis comparing genetic distances for the % of lifetime in Salvador-BA, Brazil. Support values were calculated by bootstraps with 1000 iterations. The first two principal components were graphed. Component 1: eigenvalue= 0.112, 39% of variance; Component 2: eigenvalue= 0.059, 21% of variance. (B) Network array comparing genetic distances for % of lifetime in Salvador-BA, Brazil. Network nodes represent individuals from the infra-population. Links represent genetic distances. Larger nodes mean more interaction and thicker lines more similarities. For all analyses genetic distances using Dic were applied as variance-covariance matrix.
See this image and copyright information in PMC

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