ORIGINAL PAPER Taxonomic position and geographical distribution of the common sheep G1 and camel G6 strains of Echinococcus granulosus in three African countries S. Maillard & M. C. Benchikh-Elfegoun & J. Knapp & J. M. Bart & P. Koskei & B. Gottstein & R. Piarroux Received: 12 May 2006 / Accepted: 11 July 2006 / Published online: 3 October 2006 # Springer-Verlag 2006 Abstract The taxonomic and phylogenetic status of Echi- nococcus granulosus strains are still controversial and under discussion. In the present study, we investigated the genetic polymorphism of E. granulosus isolates originating from three countries of Africa, including a region of Algeria, where the common G1 sheep and the camel G6 strains coexist sympatrically. Seventy-one hydatid cysts were collected from sheep, cattle, camels, and humans. Two mitochondrial markers (cox1 and nad1) were used for strain identification. Two nuclear markers (actII and hbx2) were used to study the possible occurrence of cross-fertilization. Despite the heterogeneity observed among the G1 isolates, they were all localized within one robust cluster. A second strong cluster was also observed containing all of the G6 isolates. Both strains appeared as two distinct groups, and no cases of interbreeding were found. Thus, the attribution of a species rank can be suggested. We also found the Tasmanian sheep G2 strain for the first time in Africa. Because of the slight variations observed between the common sheep and the Tasmanian sheep strains, further studies should be carried out to elucidate the epidemiolog- ical relevance of this genetic discrimination. Introduction Cystic echinococcosis (CE), caused by the larval infection with the Cestoda Echinococcus granulosus, is a highly endemic zoonosis in the ruminant breeding areas of North Africa. The parasite is mainly transmitted in a synan- thropic cycle generally involving dogs (large stray populations) and livestock animals (sheep, cattle, goats, and camels; Thompson and McManus 2001). DNA-based studies have shown that the species E. granulosus is composed of heterogeneous groups of genetic variants, defined as “strains” (McManus 2002). In various studies, strains were often characterized after polymerase chain reaction (PCR) amplification by sequencing mitochondrial markers in cytochrome c oxydase 1 and nicotinamide adenine dinucleotide (reduced form; NADH) dehydroge- nase 1 genes. Each identified haplotype, ranging from genotypes 1 to 10, was associated with particular host specificity and epidemiological patterns (Bowles and McManus 1993; Bowles et al. 1992; Thompson et al. 1995; Eckert and Thompson 1997). For example, the common sheep G1 strain is widespread and has been mainly identified in Mediterranean and semiarid breeding areas as being carried by sheep and cattle. In contrast, the Parasitol Res (2007) 100:495–503 DOI 10.1007/s00436-006-0286-9 S. Maillard : J. Knapp : J. M. Bart : R. Piarroux SERF (“Santé Environnement Rural-Université de Franche-Comté”), Parasitology Department, University of Franche-Comté, Besancon, France M. C. Benchikh-Elfegoun Laboratory of Parasitology, Veterinary Department, University of Mentouri, Constantine, Algeria P. Koskei Faculty of Veterinary Medicine, Addis Ababa University, Debre Zeit, Ethiopia B. Gottstein Institute of Parasitology, University of Bern, Bern, Switzerland S. Maillard (*) Laboratoire de Parasitologie, Equipe de recherche SERF, Faculté de Médecine-Pharmacie, 19 Rue Ambroise Paré, 25000 Besançon, France e-mail: maillard_steph@yahoo.com