Fasciolid flukes cause fascioliasis, an helminthic disease of humans and livestock and which is transmitted by specific freshwater snails of the family Lymnaeidae, within a frame of transmission and epidemiology pronouncedly influenced by climate factors and environmental conditions. In Africa, fascioliasis is caused by the two species Fasciola hepatica and F. gigantica, giving rise to important economic losses in husbandry throughout. Research on human infection has focused on northern Maghreb countries and Egypt, whereas studies on the wide region southward from the Sahara have only been sporadic. The present Thesis includes the genetic characterisation of the lymnaeid species found in selected endemic countries: Marocco, Algeria, Egypt, Senegal, Burkina Faso, Nigeria, Tanzania, South Africa, and the islands of Madagascar and Cape Verde. Molecular markers used were the ITS-2 and the ITS-1 spacers of the nuclear ribosomal DNA. The molecular results obtained show the presence of different valid species. Radix natalensis appears to be the original African species showing the largest geographical distribution, with R. n. caillaudi as a form having spread northward up to the Nile Delta in a phenomenon which has been dated by means of a study of snails from the Old Egypt period and a molecular clock analysis. The phenotypic characteristics of adults, clusters and eggs of R n. caillaudi have been studied by means of CIAS (Computer Image Analysis System). The remaining snails analysed demonstrate the poorness of the lymnaeid fauna of that continent, including but a few introduced species such as Galba truncatula, Lymnaea (Stagnicola) fuscus, Radix auricularia, R. balthica, L. schirazensis and Pseudosuccinea columella. The retrospective study shows that human fascioliasis in Maghreb countries only concern sporadic patients diagnosed in hospitals. This situation is completely opposite to that found in Egypt, where human fascioliasis proves to be a serious public health problem throughout the Nile Delta, maily in its northern parts. Prevalences reported reach up to 19.0% in several communities, significantly higher in females and mainly affecting 5-15-year-old children. Epidemiological data from Egypt suggest a seasonal transmission interrupted by a very hot summer. Transmission and epidemiological data indicate that Maghreb countries and Egypt should not be included within the same transmission pattern and epidemiological situation. The Maghreb is characterised by the disease being caused by only F. hepatica transmitted by G. truncatula, whereas in Egypt there is local overlap of the two fasciolid species and intermediate forms transmitted by G. truncatula, R. n. caillaudi and P. columella in a way which also appears significantly different from the situation of the disease in the Near East.

Fasciolid flukes cause fascioliasis, an helminthic disease of humans and livestock and which is transmitted by specific freshwater snails of the family Lymnaeidae, within a frame of transmission and epidemiology pronouncedly influenced by climate factors and environmental conditions. In Africa, fascioliasis is caused by the two species Fasciola hepatica and F. gigantica, giving rise to important economic losses in husbandry throughout. Research on human infection has focused on northern Maghreb countries and Egypt, whereas studies on the wide region southward from the Sahara have only been sporadic. The present Thesis includes the genetic characterisation of the lymnaeid species found in selected endemic countries: Marocco, Algeria, Egypt, Senegal, Burkina Faso, Nigeria, Tanzania, South Africa, and the islands of Madagascar and Cape Verde. Molecular markers used were the ITS-2 and the ITS-1 spacers of the nuclear ribosomal DNA. The molecular results obtained show the presence of different valid species. Radix natalensis appears to be the original African species showing the largest geographical distribution, with R. n. caillaudi as a form having spread northward up to the Nile Delta in a phenomenon which has been dated by means of a study of snails from the Old Egypt period and a molecular clock analysis. The phenotypic characteristics of adults, clusters and eggs of R n. caillaudi have been studied by means of CIAS (Computer Image Analysis System). The remaining snails analysed demonstrate the poorness of the lymnaeid fauna of that continent, including but a few introduced species such as Galba truncatula, Lymnaea (Stagnicola) fuscus, Radix auricularia, R. balthica, L. schirazensis and Pseudosuccinea columella. The retrospective study shows that human fascioliasis in Maghreb countries only concern sporadic patients diagnosed in hospitals. This situation is completely opposite to that found in Egypt, where human fascioliasis proves to be a serious public health problem throughout the Nile Delta, maily in its northern parts. Prevalences reported reach up to 19.0% in several communities, significantly higher in females and mainly affecting 5-15-year-old children. Epidemiological data from Egypt suggest a seasonal transmission interrupted by a very hot summer. Transmission and epidemiological data indicate that Maghreb countries and Egypt should not be included within the same transmission pattern and epidemiological situation. The Maghreb is characterised by the disease being caused by only F. hepatica transmitted by G. truncatula, whereas in Egypt there is local overlap of the two fasciolid species and intermediate forms transmitted by G. truncatula, R. n. caillaudi and P. columella in a way which also appears significantly different from the situation of the disease in the Near East.