Epidemiological Study and Evolution of Monospecific and Low Transmission Schistosomiasis Guineensis Foci in Absence of Praziquantel Chemoprevention: Edea and Eseka in Cameroon

Cyrille Bruno MOGO¹, Leopold Gustave LEHMAN² and Thomas KUETE^3,

¹Center for Medical Research in Health and Priority Pathologies, Institute of Medical Research and Medical Plant Studies, Yaoundé 13033, Cameroon

²Faculty of Sciences, The University of Douala, Cameroon

³Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, Cameroon

Cite this paper:
Cyrille Bruno MOGO, Leopold Gustave LEHMAN and Thomas KUETE. Epidemiological Study and Evolution of Monospecific and Low Transmission Schistosomiasis Guineensis Foci in Absence of Praziquantel Chemoprevention: Edea and Eseka in Cameroon. American Journal of Epidemiology and Infectious Disease. 2026; 14(1):1-8. doi: 10.12691/ajeid-14-1-1

Abstract

Implementation of chemoprevention with praziquantel against schistosomiasis significantly decreased prevalence and intensities of infection in moderate to heavy transmission settings. However, evolution of schistosomiasis transmission pattern in previously known low transmission areas remains of concern. This study aimed to evaluate prevalence and intensities of infection of human Schistosoma infection and specific snail intermediate hosts cercaria shedding in Edea and Eseka, two previously known monospecific hypoendemic Schistosoma guineensis transmission foci in Cameroon, then compare data to previous epidemiological surveys. This community-based cross-sectional study was undergone in 2024 in Edea and Eseka by collecting socio-demographic data, stool and urine samples from consenting dwellers. Stool and urine samples were processed using Kato-Katz and urine centrifugation techniques respectively to count Schistosoma eggs under microscope. Parasitic loads and intensities of infection were determined. Schistosoma intermediate hosts were collected in waterbodies at human-water contact sites, identified using shell morphology specific identification keys, then tested for cercarial shedding. Data were compared to previous epidemiological reports in 1969 and 1981. Data were statistically analyzed considering a p-value < 0.05 as significant. Of a total of 502 dwellers included in the study, 444 provided stool samples and 448 urine samples in the two areas. Only S. guineensis eggs were detected in humans with a prevalence of 0% (0/215) and 1.7% (4/229) at Edea and Eseka respectively. Being adolescent (p=0.008) and attending waterbodies for bathing and fishing or laundry (p=0.02) were associated to S. guineensis infection. Only Bulinus forskalii were harvested in the two areas. Of the 43 alive B. forskalii collected, the prevalence cercariae shedding was 0%. Compared to epidemiological data gathered 45 years ago, the prevalence of S. guineensis infections has decreased significantly in the two sites. Prevalence of schistosomiasis has decreased in Edea and Eseka, S. guineensis remaining the only specie. Infected subjects harbor low to moderate intensities of infection. Bulinus forskalii were cercariae free.

Keywords:
Bulinus forskalii cercaria shedding low transmission praziquantel chemoprevention schistosomiasis Schistosoma guineensis Edea Eseka Cameroon

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References:

[1]	World Health Organization “Assessing schistosomiasis and soil-transmitted helminthiases control programmes: monitoring and evaluation framework”. Geneva: World Health Organization, 2024. Licence: CC BY-NC-SA 3.0 IGO. Available at https://iris.who.int/.
[2]	Gryseels, B., Poldman, K., Clerinx, J., Doumengue, J. and Kestens. L, “Human schistosomiasis”, The Lancet 368(9541), 1106-1118. Sept 2006.
[3]	Same-Ekobo, A, “Freshwater snails’ fauna in Cameroon”. Doctorate thesis, Faculty of Sciences, University of Rennes, France, 388 pages. 1984 [in French].
[4]	Ratard, R.C., Kouemeni, L.E., Ekani Bessala, M.M., Ndamkou, C.N., Greer, G.J., Spilsbury, J. and Cline B.L, “Human schistosomiasis in Cameroon I. Distribution of schistosomiasis”, American Journal of Tropical Medicine and Hygiene, 42(6), 561-572. Jun1990.
[5]	Tchuem Tchuenté, L.A., Dongmo Noumedem, C., Ngassam, P., Kenfack, C.M., Feussom Gipwe, N., Dankoni, E., Tarini, A. and Zhang, Y, “Mapping of schistosomiasis and soil-transmitted helminthiasis in the regions of Littoral, North-West, South and South-West Cameroon and recommendations for treatment”, BMC Infectious Diseases, 13, 602. Dec 2013. http:// www. biomedcentral.com/ 1471-2334/13/602.
[6]	World Health Organization, “Guidelines: preventive chemotherapy to control soil-transmitted helminth infections in at-risk population groups ISBN 978-92-4-155011-6. World Health Organization, Licence: CC BY-NC-SA 3.0 IGO, 87 pages. 2017. http://apps.who.int/iris.
[7]	Tchuem Tchuenté, L.A., Kamwa Ngassam, R.I., Sumo, L., Ngassam, P., Dongmo Noumedem, C., Luogbou Nzu, D., Dankoni, E., Kenfack, C.M., Feussom Gipwe, N., Akame, A., Tarini, A., Zhang, Y. and Angwafo III, F.F, “Mapping of schistosomiasis and soil-transmitted helminthiasis in the regions of Centre, East and West Cameroon”. “PLoS Neglected Tropical Diseases”, 6(3), e1553. March 2012.
[8]	World Health Organization, “Schistosomiasis and soil-transmitted helminthiases: progress report, 2021”, “Weekly Epidemiological Record”, 48(97), 621-632. Dec 2022. http://www.who.int/wer.
[9]	World Health Organization, “Schistosomiasis and soil-transmitted helminth infections. The fifty-fourth World Health Assembly, WHA54.19 Agenda item 13.3 22, 2 pages. May 2001.
[10]	World Health Organization. Guidelines on control and elimination of human schistosomiasis. Geneva, World Health Organization, 2023. https://www.who.int/publications/i/item/9789240041608.
[11]	World Health Organization, “WHO guideline on control and elimination of human Schistosomiasis”, Geneva: World Health Organization, Licence: CC BY-NC-SA 3.0 IGO. 2022. Available at https://iris.who.int/.
[12]	World Health Organization, “Schistosomiasis and soil-transmitted helminthiases: progress report, 2023”, Weekly Epidemiological Record, 99(48), 707-718. Nov 2024b. http://www.who.int/wer.
[13]	Ministry of Public Health, Cameroon/National Programme for the Control of Schistosomiasis and Intestinal Helminthiasis, “Towards elimination of schistosomiasis and soil-transmitted helminthiases in Cameroon. A road map for paradigm shifts 2021-2030, National Programme for the Control of Schistosomiasis and Intestinal Helminthiasis”, 68 pages. March 2021. Web site: www.pnlshi.org.
[14]	Kokaliaris, C., Garba, A., Matuska, M., Bronzan, R.N., Colley, D.G., Dorkenoo, A.M., Ekpo, U.F., Fleming, F.M., French, M.D., Kabore, A., Mbonigaba, J.B., Midzi, N., Mwinzi, P.N.M., N’Goran, E.K, Polo, M.R., Sacko, M., Tchuem Tchuenté, L.A., Tukahebwa, E.M., Uvon, P.A., Yang, G., Wiesner, L., Zhang, Y., Utzinger, J. and Vounatsou, P., “Effect of preventive chemotherapy with praziquantel on schistosomiasis among school-aged children in sub-Saharan Africa: a spatiotemporal modelling study”, LancetInfectious Diseases, 22(1):136-149. Jan 2022.
[15]	World Health Organization, “Ending the neglect to attain the Sustainable Development Goals: A road map for neglected tropical diseases 2021-2030”, World Health Organization, 196 pages. Jan 2020. Available at http://apps.who.int/iris.
[16]	Deschiens, R., Delas, A., Ngalle-Edimo, S. and Poirie, A., “Schistosoma intercalatum schistosomiasis in the Federal Republic of Cameroon”, Bulletin of the World Health Organization, 40, 893-898. 1969. [in French].
[17]	Ripert, C., Carrié, J., Pagbe, J.J., Ravinet, L., Deniau, M., and Same Ekobo, A., “An epidemiological study of bilharziasis caused by S. intercalatum in Eseka and Edéa (Cameroon). Effects of treatment with praziquantel”, Arzneimittel-Forschung/Drug Research, 31(3a):584-589. 1981. [in French].
[18]	Pagès, J.R., Jourdane, J., Southgate, V.R. and Tchuem Tchuente, L.A., “Reconnaissance de deux espèces jumelles au sein du taxon Schistosoma intercalatum Fisher, 1934, agent de la schistosomose humaine rectale en Afrique. Description de Schistosoma guineensis n. sp.”, Taxonomy, Ecology and Evolution of Metazoan Parasites, 2, 139-146. 2003.
[19]	Ripert, C., “Schistosomiasis intercalatum and urban development in Central Africa”, Bulletin de la Société de Patholologe Exotique, 96, 3, 183-186. 2003. [in French].
[20]	Tchuem Tchuenté, L.A., Southgate, V.R., Njiokou, F., Njiné, T., Kouemeni, L.E. and Jourdane, J., “The evolution of schistosomiasis at Loum, Cameroon: replacement of Schistosoma intercalatum by S. haematobium through introgressive hybridization”, Transactions of the Royal Society of Tropical Medicine and Hygiene, 91(6), 664-665. 1997.
[21]	Njiokou, F., YimtaTsemo, L.C., Kuete, T. and Same Ekobo, A., “Dynamics of intestinal schistosomiasis in Cameroon: evolution of transmission in the mixed zone of Nkolmébanga, Lékié”, Medécine Tropicale, 64(4), 351-354. 2004. French. PMID: 15615385. [in French].
[22]	Nsangou Ngapna, M., Owona, S., Ateba, C.B., Manga, Tsimi V., Ondoa, J.M. and Ekodeck G., “Assessment of relative active tectonics in Edea-Eseka region (SW Cameroon, Central Africa)”, Geology, Environmental Sciences, 2020.
[23]	National Institute of Statistics / Regional Office of the National Institute of Statistics, “Statistical yearbook of the Littoral region: collection of statistical information series on economic, social, political and cultural activities of the region until 2021”, 516 pages. 2022 Edition.
[24]	World Health Organization, “Basic laboratory methods in medical parasitology”, World Health Organization, 69 pages. 1991.
[25]	Cheesbrough, M., “District laboratory practice in tropical countries (Part 1, 2nd ed., 462 pages.)”, Cambridge University Press 2005. https://www.cambridge.org/9780521676311.
[26]	World Health Organization, “Preventive chemotherapy in human helminthiasis : coordinated use of anthelminthic drugs in control interventions : a manual for health professionals and programme managers”, World Health Organization, 74 pages. 2006.
[27]	Brown, D.S. and Brown, D.S., “Freshwater snails of Africa and their medical importance”, CRC Press, 608 pages. 1994.
[28]	Brown, D.S., Kristensen, T.K., “A field guide to African freshwater snails. West African species”, Danish Bilharziasis Laboratory, Charlottenlund, 55 pages. 1993.