Ahead of Print - Schistosome Interactions within the Schistosoma haematobium Group, Malawi - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Ahead of Print - Schistosome Interactions within the Schistosoma haematobium Group, Malawi - Volume 25, Number 6—June 2019 - Emerging Infectious Diseases journal - CDC

Volume 25, Number 6—June 2019

Research Letter

Schistosome Interactions within the Schistosoma haematobium Group, Malawi

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Bonnie L. Webster, Mohammad H. Alharbi, Sekeleghe Kayuni, Peter Makaula, Fenella Halstead, Rosie Christiansen, Lazarus Juziwelo, Michelle C. Stanton, E. James LaCourse, David Rollinson, Khumbo Kalua, and J. Russell Stothard 

Author affiliations: Natural History Museum, London, UK (B.L. Webster, D. Rollinson); Ministry of Health, Qassim, Saudi Arabia (M.H. Alharbi); Liverpool School of Tropical Medicine, Liverpool, UK (M.H. Alharbi, S. Kayuni, F. Halstead, R. Christiansen, E.J. LaCourse, J.R. Stothard); Medical Aid Society of Malawi, Blantyre, Malawi (S. Kayuni); Research for Health Environment and Development, Mangochi, Malawi (P. Makaula); Ministry of Health, Lilongwe, Malawi (L. Juziwelo); Lancaster University Medical School, Lancaster, UK (M.C. Staton); Lions Sight First Eye Hospital, Blantyre (K. Kalua)

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Abstract

Molecular analysis of atypical schistosome eggs retrieved from children in Malawi revealed genetic interactions occurring between human (Schistosoma haematobium) and livestock (S. mattheei and S. bovis) schistosome species. Detection of hybrid schistosomes adds a notable new perspective to the epidemiology and control of urogenital schistosomiasis in central Africa.

Urogenital schistosomiasis is a waterborne disease transmitted by certain freshwater snails that occurs throughout much of sub-Saharan Africa. Until recently, this disease was attributed solely to Schistosoma haematobium, which was considered to have limited zoonotic potential (1). However, genetic analysis of natural infections with noninvasive larval sampling (2) has provided new evidence. In West Africa, for example, species interactions with hybrid combinations of S. haematobium and the bovine or ovine species of S. bovis and S. curassoni are commonly encountered in humans and snails (3). Although key biologic features of hybrids may not always be apparent, the risk for zoonotic transmission along with enhanced definitive and intermediate host compatibilities needs investigation (2,3). The recent emergence and persistent transmission of S. haematobium–bovis hybrids on the Mediterranean island of Corsica (4) demonstrates the public health impact of such genetic introgression.

Figure. Investigation of atypical schistosome eggs retrieved from children in Malawi. A) Locations where urine samples containing Schistosoma haematobium eggs were collected from children in Mangochi (Samama village, 14°41′74.65′′S, 35°21′75.80′E), Chikhwawa (Mpangani...

Genetic analysis of S. haematobium group species in central and southern Africa is a high priority. Atypical egg morphologies suggest a capacity for natural hybridization of S. haematobium with the bovine species S. mattheei, later confirmed with biochemical markers and experimental infections demonstrating viable progeny (3). During ongoing surveillance of urogenital schistosomiasis in Chikhwawa District, Malawi, we encountered atypical S. haematobium eggs in urine samples from several infected children (5). We report the further genetic characterization of atypical eggs collected from epidemiologic surveys of children within Chikhawa, Nsanje, and Mangochi Districts (Figure, panel A).