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. 2015 Jul 21;9(7):e0003831.
doi: 10.1371/journal.pntd.0003831. eCollection 2015.

Mapping of Schistosomiasis and Soil-Transmitted Helminths in Namibia: The First Large-Scale Protocol to Formally Include Rapid Diagnostic Tests

Affiliations

Mapping of Schistosomiasis and Soil-Transmitted Helminths in Namibia: The First Large-Scale Protocol to Formally Include Rapid Diagnostic Tests

José Carlos Sousa-Figueiredo et al. PLoS Negl Trop Dis. .

Abstract

Background: Namibia is now ready to begin mass drug administration of praziquantel and albendazole against schistosomiasis and soil-transmitted helminths, respectively. Although historical data identifies areas of transmission of these neglected tropical diseases (NTDs), there is a need to update epidemiological data. For this reason, Namibia adopted a new protocol for mapping of schistosomiasis and geohelminths, formally integrating rapid diagnostic tests (RDTs) for infections and morbidity. In this article, we explain the protocol in detail, and introduce the concept of 'mapping resolution', as well as present results and treatment recommendations for northern Namibia.

Methods/findings/interpretation: This new protocol allowed a large sample to be surveyed (N = 17,896 children from 299 schools) at relatively low cost (7 USD per person mapped) and very quickly (28 working days). All children were analysed by RDTs, but only a sub-sample was also diagnosed by light microscopy. Overall prevalence of schistosomiasis in the surveyed areas was 9.0%, highly associated with poorer access to potable water (OR = 1.5, P<0.001) and defective (OR = 1.2, P<0.001) or absent sanitation infrastructure (OR = 2.0, P<0.001). Overall prevalence of geohelminths, more particularly hookworm infection, was 12.2%, highly associated with presence of faecal occult blood (OR = 1.9, P<0.001). Prevalence maps were produced and hot spots identified to better guide the national programme in drug administration, as well as targeted improvements in water, sanitation and hygiene. The RDTs employed (circulating cathodic antigen and microhaematuria for Schistosoma mansoni and S. haematobium, respectively) performed well, with sensitivities above 80% and specificities above 95%.

Conclusion/significance: This protocol is cost-effective and sensitive to budget limitations and the potential economic and logistical strains placed on the national Ministries of Health. Here we present a high resolution map of disease prevalence levels, and treatment regimens are recommended.

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Conflict of interest statement

The authors declare that no competing interests exist.

Figures

Fig 1
Fig 1. Map of Northern Namibia’s governmental regions and constituencies.
Regions are color-coded, with dark green for Caprivi, light green for Kavango (Phase 1), blue for Oshikoto, purple for Ohangwena, orange for Oshana and pink for Omusati (Phase 2). Constituencies are number-coded: 1 –Kabe, 2 –Katima Mulilo Rural, 3 –Katima Mulilo Urban, 4 –Sibinda, 5 –Linyati, 6 –Kongola, 7 –Mukwe, 8 –Ndiyona, 9 –Mashare, 10 –Rundu Rural West, 11 –Rundu Rural East, 12 –Rundu urban, 13 –Kapako, 14 –Kahenge, 15 –Mpungu, 16 –Tsumeb, 17 –Guinas, 18 –Eengondi, 19 –Okankolo, 20 –Omuthiyagwiipundi, 21 –Omuntele, 22 –Onyaanya, 23 –Onayena, 24 –Oniipa, 25 –Olukonda, 26 –Okongo, 27 –Epembe, 28 –Omundaungilo, 29 –Eenhana, 30 –Ondobe, 31 –Oshikango, 32 –Ohangwena, 33 –Omulonga, 34 –Endola, 35 –Engela, 36 –Ongenga, 37 –Okaku, 38 –Ongwediva, 39 –Ondangwa, 40 –Uukwiyo, 41 –Okatyali, 42 –Opundja, 43 –Uuvudhiya, 44 –Oshakati East, 45 –Oshakati West, 46 –Okatana, 47 –Otamanzi, 48 –Elim, 49 –Etayi, 50 –Oshikuku, 51 –Okalongo, 52 –Ogongo, 53 –Anamulenge, 54 –Outapi, 55 –Okahao, 56 –Tsandi, 57 –Onesi, 58 –Ruacana. Rest of the country (in grey) is not included in this report.
Fig 2
Fig 2. Dynamics of schistosomiasis in northern Namibia (299 schools, 17 896 children ages between 3 and 19).
A) Binomial distribution of schistosomiasis in schools, color-coded according to transmission following WHO guidelines [36]: low transmission is 0.1–9.9% prevalence, moderate transmission is 10–49.9% prevalence and high transmission is prevalence level equal or above 50%. B) Age-frequency distribution of schistosomiasis, with red dashed line indicating the overall average of 9.0%, and vertical confidence intervals. For more information see Appendix 1.
Fig 3
Fig 3. Schistosomiasis prevalence in the study area.
A) Distribution of surveyed schools; B) Local Moran’s I results for schistosomiasis prevalence.
Fig 4
Fig 4. Dynamics of hookworms in northern Namibia (61 schools and 3 659 children ages 4 to 18).
A) Distribution of schistosomiasis in schools, color-coded according to transmission following WHO guidelines:[36] low transmission is 0·1–19·9% prevalence, moderate transmission is 20·0–49·9% prevalence and high transmission is prevalence level equal or above 50%. B) Age-frequency distribution of schistosomiasis, with red dashed line indicating the overall average of 12·2%, and horizontal confidence intervals. For more information see Appendix 1.
Fig 5
Fig 5. Prevalence of schistosomiasis (urogenital, intestinal and any type) and hookworm infections by constituency.

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