Cystic echinococcosis in Algeria: cattle act as reservoirs of a sheep strain and may contribute to human contamination

In Algeria, cystic echinococcosis (CE) is a serious economic and public health problem. The common sheep/dog cycle is usually considered as the major source of human contamination. But to date the main strain of Echinococcus granulosus involved in the human contamination and the role of other hosts are still unknown. This paper reports an original work performed in northern Algeria combining field observations and molecular analysis. In a first step, examination of 6237 carcasses in slaughterhouses showed high infection and fertility rates in cattle and dromedaries. Then, in a second step, we used a molecular biology approach to identify the E. granulosus strain(s) involved. Forty-six samples from various origins were collected. They were analysed using comparison of PCR-amplified DNA sequences with one genomic (BG 1/3) and two mitochondrial (COI and NDI) targets. Results show the presence of a "sheep" strain of E. granulosus in North Algeria circulating between cattle and ovines and infectious to humans, whereas in South Algeria, a "camel" strain and a "sheep" strain were found to circulate in camels and in sheep, respectively. This study also reports an ambiguous genotype which resembled the "sheep" strain genotype (G1) on the basis of the partial COI gene sequence, whereas on the basis of the partial NDI gene sequence, it was similar either to the "sheep" strain (G1) or to the "camel" strain (G6). Besides its basic interest, our study confirms the role of other hosts (mainly cattle) in leading to transmission to humans and suggests that control measures should not only target sheep. (C) 2003 Elsevier B.V. All rights reserved.