Transactions of the Royal Society of Tropical Medicine and Hygiene (2004) 98, 296—298 Emergence of Schistosoma mansoni in the Niger River valley, Niger Amadou Garba* , Rabiou Labbo, Zilahatou Tohon, Ali Sidiki, Amadou Djibrilla Centre de Recherches Médicales et Sanitaires (CERMES), Ministry of Health, B.P. 10887, Niamey, Niger Received 12 May 2003; received in revised form 26 September 2003; accepted 1 October 2003 KEYWORDS Emergence; Schistosomiasis; Schistosoma mansoni; Niger River valley; Niger Summary Urinary and intestinal schistosomiasis are both endemic in Niger with a dominance of Schistosoma haematobium. This study pointed out the appearance of the infection to S. mansoni in the Niger River valley, where it was until then unknown in Niger. In one year the prevalence increased from 5.9 to 19.5%. © 2004 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved. 1. Introduction Schistosoma haematobium and S. mansoni are both endemic in Niger although S. haematobium is the most prevalent parasite and is present in all geographical areas of the country. It prevails particularly in the Niger River valley (NRV) where an intensive rice growing irrigated zone has been developed since 1955, to achieve self-sufficiency in food. Malacological surveys have also shown the widespread distribution of Bulinus truncatus, the main snail host responsible for the transmission of urinary schistosomiasis (Labbo et al., 2003). In 1988, infections with S. mansoni were de- scribed for the first time in the far south of the country in the Dallol Foga valley (Mouchet et al., 1988) and were confined within this area alone (Campagne et al., 1999; Chippaux et al., 2001). Biomphalaria pfeifferi, the intermediate host of S. mansoni, was shown to be present in Dallol Foga valley; it has been also recorded in the mountain of A¨ ır, north of the country (Fischer-Piette, 1950). * Correspondingauthor.Tel.: +227-752045; fax: +227-753180. E-mail address: garba@cermes.ne (A. Garba). This situation changed considerably after the malacological survey by Labbo et al. (2003) when B. pfeifferi was found in 5 villages along the NRV north of Niamey. This finding urged us to carry out a parasitological survey in this area, to see if local transmission of S. mansoni now occurred. 2. Materials and methods During April and May 2002, a parasitological survey was undertaken among school children of 11 villages located between Niamey and the Mali border along the NRV, including the villages where B. pfeifferi was found (Figure 1). In May 2003, we carried out a survey on a random sample of 20% of the population aged ≥2 years in the village of Namarigoungou af- ter a census. Examination of urine by filtration was performed on all the subjects. The examination of stool was done after MIF (merthiolate iodine for- mol) concentration technique in school children and with the Kato-Katz technique in 2003 in the general population. In each school, half of the overall number of children was randomly selected. The age of the 0035-9203/$ – see front matter © 2004 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved. doi:10.1016/S0035-9203(03)00070-1