At the beginning of the XXI millennium, while working at a general hospital in Mexico City, a young lady arrived with a previous diagnosis of liver amebiasis given six years earlier. Different treatments in various clinical settings were provided. In the hospital, the first approach was an ultrasound study and unexpectedly an Echinococcus granulosus cyst was clearly identified. The patient received adequate treatment and accepted to participate as the index case in an epidemiological survey performed in her community. Inhabitants, dogs, cattle, pigs, and sheep were studied; cysts in humans, pigs, and sheep were searched by ultrasound and dogs by coproantigens, livestock, and dogs were negative for larval or adult stages respectively. The use of ultrasound allowed the detection of two cases (overall prevalence 0.95). DNA of the patient’s cyst recovered by surgery was purified, amplified, sequenced, and multiple alignments were performed and analyzed, identifying to Echinococcus ortleppi. Subsequently, in a population genetics study focused to evaluate the presence and genetic variability of the intestinal tapeworm in dogs and of cystic echinococcosis in livestock in central areas from Mexico, Echinococcus canadensis G7 was identified and was found only in pigs. Based on a genetic network analysis, the following deductions were made: 1) E. canadensis G7 in Mexico is very diverse and was probably introduced from abroad several times from different sources and from different countries; 2) G7 haplotypes grouped in the North American wildlife cluster are placed far from Mexican isolates, thus they might be ruled out as sources of introduction to Mexico; and 3) the species status for G7, formally named E. canadensis, is still controversial, because biologically different strains (G6 to G10) are currently unified, though ecological and genetic data appear to indicate otherwise.
Part of the book: Current Topics in Echinococcosis