Etude épidémiologique et moléculaire d’Echinococcus granulosus en Algérie

Abstract

Molecular typing of strains E. granulosus is essential to define a well adapted strategy to fight against cystic echinococcosis (KE) because, strains differ in various pathogenic factors for humans, duration of the prepatent period in HD, antigenic power amplification by the PCR and sequencing of mitochondrial genes of the cytochrom oxydase and NADH dehydrogenase 1 cox 1 NDI 42 were collected to characterize 42 isolates of E granulosus the isolates collected in 28 livestock 4 sheep, 3caprins, 17 camels, cattle and 4 in various slaughters houses and 14 collected in the human surgery services of hospitals located in the South Algeria. The results showed the presence of two distinct genotypes G1 (ovine strains) : 85,71% of ovine strain circulating among sheep and cattle, goats and more than the half of the camels strains are transmissible to humans, whereas genotype G6 (camel strain): 14.28%, moving from camels and found sometimes in other ruminants. The presence of the genotype 1 in camels, suggested as camels whose cysts are the most oftenely fertile could represent in the Southern regions, an indirect source of transmission to humans of this zoonotic strains. The implementation of program against K E due to the shortness of the prepatent period of this species in the definitive host compared to common ovine. Classification within Echinococcus granulosus is currently under discussion. To assess the reproductive potential between G1 and G6 strains, a double infestation experiment was carried out in a dog. Hydatid cysts have been first collected from a cow and a camel. They have been identified as G1 and G6 with Cox I and mitochondrial markers Nad I. Thereafter dog was inoculated with these two protoscolex from cysts. Sixty days after the infestation, 85 adult worms were recovered in the small intestine of the dog. Then, each of the cysts were characterized with nuclear marker locus multi EmsB and compared. The ail to the scolex and gravid proglottids, analyzed separately, gave an identical profile : G1 profile was observed in 70 adults, and the G6 profile in the remaining 15. No worm has presented a hybrid G1/G6 profile. This finding suggests the lack of cross-fertilization between the two strains, and thus, the presence of a strong reproductive barrier. This observation corroborates the recent reclassification of G1 and G6 becoming two distinct species. A recent study was conducted to assess the degree to which the seized offal are destroyed, and if current resources are sufficient to break the cycle of transmission of Echinococcus granulosus. The slaughter houses were selected according to their large size, medium and small and their urban, semi urban and rural locations. The results of the survey show that 19.8% of slaughterhouses are not isolated by a fence and about 30% have not an intact closing, fourth slaughterhouses are accessible to dogs. Whereas, medium and large slaughterhouses are better protected against the access of dogs. Stray dogs are present in surroundings in more than 80% of slaughterhouses, regardless of their size and location, and that the inspection is carried out in the majority of the slaughter houses, meat offal are not saved in more than 30% of slaughterhouses. The survey revealed that infected viscera are left at the disposed of 25,92% of dogs in slaughterhouses whatever their location, and people have free access to infected offal in 16% of slaughterhouses. Incineration is practiced in 61% of large slaughterhouses vs 32.1% and only 6.7% in medium and small abattoirs respectively. the existence of such factors (lack of cloture in many slaughterhouses, presence of stray dogs in the neighborhood, feeding dogs with infected offal, lack of incinerators, the absence of burying viscera of infected cysts hydatid ...) contribute significantly to the persistence of transmission and spread of echinococcosis in intermediate hosts and definitive hosts. All these factors must be taken into account when applying the control program against cystic echinococcosis.