Echinococcus granulosus pig strain (G7 genotype) protoscoleces did not develop secondary hydatid cysts in mice

Echinococcus granulosus, the aetiological agent of cystic hydatid disease, exists as a series of strains or genotypes which differ in biological features. Pig strain (G7 genotype) has been shown to differ from sheep strain (G1 genotype) in phenotypical characters such as intermediate host range, geographical distribution and rate of development of the adult worm. Since in vivo studies of different parasite genotypes can provide insights into host-parasite relationship we analysed for the first time the behaviour of E. granulosus G7 genotype protoscoleces in the murine experimental model. Our results show that G7 protoscoleces were unable to establish a regular infection in mice in contrast to G1 protoscoleces which developed intraperitoneal hydatid cysts. This inability was observed in co-infection experiments, i.e. even in the presence of a controlled immune response that allows G1 genotype protoscoleces establishment. In addition, the implantation of in vitro obtained E. granulosus G7 genotype microcysts resulted in a low percentage of hydatid cysts establishment. These results show a difference in the biological ability of both E. granulosus strains to develop secondary hydatid cysts in mice. We suggest that the comparison of infective and non infective genotypes of E. granulosus in the experimental host can be regarded as a new model to study the mechanisms of infection of Echinococcus spp. This knowledge could provide helpful information for the development of therapies, drugs and/or vaccines against cystic hydatid disease.