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Schistosomiasis is endemic in the Bauchi area of Nigeria but little information is available on transmission patterns on basis of which an effective strategy for control can be developed. Consequently, a longitudinal study on the population dynamics of freshwater snails was under taken in 10 sites selected after a preliminary study. Three schistosome intermediate host snails namelyBulinus globosus, Bulinus truncatusandBiomphalaria pfeifferiall of which carried patent infections were encountered. The population of infected snails showed similar patterns of fluctuation among the different sites. Population density generally increased following the rains and peak densities occurred during the last part of the raining season and/or beginning of the dry season. This was followed by a decline during the dry season owing to an increase in temperature and dessication in some sites. Transmission was observed to be generally focal. In the temporary habitats, transmission was highly seasonal having a short duration of three months spanning from October to December. However, in the few perennial habitats, there was prolonged transmission extending from October of one year to March of the succeeding year. Findings of this study would be invaluable in planning and implementation of schistosomiasis control in Bauchi area, Nigeria.

Schistosomiasis is ranked second to malaria among parasitic diseases of socio-economic and public health importance. One of the crucial factors in monitoring the current and future status and distribution of S. haematobium infection in Nigeria is to improve the knowledge on the freshwater snails that play an indispensable role in its transmission. The present study was undertaken to delineate potential transmission areas of urogenital schistosomiasis in Osogbo Metropolis using snail intermediate hosts and human-water contact as indicators. The major rivers/streams were visited bimonthly at various locations between April and July, 2016 and snail samples were collected using scoopers. The snails were identified morphologically and exposed to artificial light for cercaria shedding. Human water contact activities were observed at the sites where snails were recovered and relative index of exposure was calculated for each activity. Of the nine locations visited, only four were positive, namely; Gbodofon (Osun River), Isale Osun (Osun River), area 264 (Oniti Stream) and Gbonmi (Okoko Stream). Even though, none of the exposed snails shed cercaria, the human activities were observed at the sites. The results showed that 49.7% of the human contacts were for swimming followed by Fishing (32.2%), cloth-washing (10.1%) and spiritual/ritual bath (8.0%). Swimming has the highest relative index of exposure (RIE=30231) while spiritual/ritual bath has the least (RIE=96). The presence of the snail intermediate hosts at the four sites coupled with human water activities as observed in the present study suggest the risk of urogenital schistosomiasis at the study-area. Keywords: Bulinus species; schistosome; human water contact; Osogbo; Nigeria

The Bulinus genus acts as intermediate hosts for larval development of the parasite belonging to Schistosoma group (Digenea, Platyhelminthes). Despite their importance in the transmission of these parasites, the evolutionary history of this genus is still not very clear. Development of management plans to control these parasites transmission requires a deeper understanding of the past events that have affected the population diversity and distribution of Bulinus species. The objective of this study was to learn more about the population structure and phylogeny of several Bulinus species originating from different African countries using three types of molecular markers: the partial mitochondrial gene Cox1, the nuclear ribosomal gene (ITS, 18S and 28S), and six microsatellites loci. Concerning the phylogeography of this genus, high levels of genetic diversity were detected in the seven studied species, with clear segregation between individuals and the presence of many haplotypes, even within same species from the same locality. Our results showed lower diversity within B. truncatus populations in North Africa (Egypt) compared to individuals from Sub-Saharan Africa, which may suggest that B. truncatus may have colonized Egypt from Sub-Saharan Africa. About the genetic structure of B. truncatus, high rate of heterozygosity, and strong genetic structure were noted in Egyptian populations of B. truncatus. This structure is reflected by the existence of four distinct clusters characterized by relatively low gene flew rate between subpopulations. Our work allowed better understanding of phylogeny and genetic structure of this genus. These informations can be used to develop new approach for controlling the parasite transmission., Les mollusques d’eau douce du genre Bulinus servent d’hôtes intermédiaires pour le développement des stades larvaires des parasites du groupe Schistosoma (Digenea, Plathelminthes). Malgré leur importance dans la transmission de ces parasites, l'histoire évolutive de ce genre reste à clarifier. L’élaboration des plans de gestion de transmission de ces parasites nécessite une bonne connaissance de la biologie des bulins, de la structure génétique de ces populations afin de clarifier l’histoire évolutive de ce genre et son rôle dans la coévolution hôte /parasite. Fort de cela, nous nous sommes proposée d’étudier d’une part la phylogénie de sept espèces des bulins originaires de plusieurs pays africains à l’aide de trois types de marqueurs moléculaires : la région de l’ADN mitochondrial (Cox1), les séquences ribosomiques nucléaires (ITS, 18S et 28S) et d’autre part la structure génétique des populations égyptiennes de B. truncatus à l’aide des marqueurs microsatellites. Les résultats portant sur l’étude phylogénétique ont permis de mettre en évidence des niveaux élevés de diversité haplotypique et nucléotidique chez les sept espèces étudiées. De nouveaux haplotypes ont été détectés dans chaque pays, et semblent spécifiques à la région. En revanche, nous avons détecté une diversité génétique inférieure au sein des populations égyptiennes de B. truncatus par rapport aux individus originaires de l'Afrique sub-saharienne, ce qui pourrait suggérer une existence plus récente de B. truncatus en Afrique du Nord (Egypte), par rapport à l’Afrique noire (Cameroun et Sénégal). Quant à l’étude de la structure génétique de B. truncatus, un taux d’hétérozygotie élevé, et une forte structuration ont été détectés chez les populations égyptiennes de B. truncatus. Cette structuration se traduit par l'existence de quatre clusters bien distincts, et elle est caractérisée par un taux relativement faible de flux de gènes. Nos travaux ont permis d’avoir une meilleure compréhension de la phylogénie et la structure génétique de ce genre. Ceci permettra de proposer une nouvelle approche pour la lutte contre cette parasitose.Discipline