Hidatidosis en la Región de Coquimbo, Chileepidemiología en población humana y genotipificación de quistes hidatídicos

Abstract

Cystic echinococcosis (CE) or Hydatidosis is a chronic cosmopolitan zoonosis caused by the metacestode of a complex of cryptic species belonging to Echinococcus granulosus s.l., being Echinococcus granulosus s.s. the species that causes most cases of human CE and is distributed throughout the world. This cestodiasis is a major public health and economic problem for the affected populations, mainly in rural and livestock areas. In South America, Chile is one of the countries where Cystic echinococcosis is endemic, despite this and the intervention programs to control this parasitosis in rural regions and provinces where goat and sheep farming is practiced, this parasitosis is still present, being the regions of Aysén, Magallanes, La Araucanía and Coquimbo, which have the highest prevalence rates. In this study, the prevalence of Cystic echinococcosis and its possible risk factors were determined in four communes of the Limarí province, Coquimbo region, between the years 2016-2017 and the genetic diversity of E. granulosus s.s. in three endemic regions, Coquimbo, La Araucanía and Magallanes, through the sequence of subunit 1 of the mitochondrial gene of the cytochrome oxidase (cox1). A total of 1221 people between 5 - 88 years old were examined with the ELISA method. The risk factors were evaluated by means of a questionnaire in 908 people older than 18 years. The logistic regression method was used to determine the probability of association between the presence of echinococcal infection and risk factors; and schooling and risk factors. Genetic diversity and population structure of E. granulosus s.s. it was evaluated in three endemic regions of Chile, using the sequence of sub unit 1 of the mitochondrial gene of that of cytochrome oxidase (cox1). 46 cysts were sequenced, 6 from the Coquimbo region, 18 from Araucanía and 22 from Magallanes, isolated from different intermediate hosts, bovines, goats, sheep and humans. In this way, it was observed that the general prevalence of CE in the analyzed population was 7.9% (97/1221), 6.71% (21/313) of those under 18 years of age and 8.4% (76 / 908) of the adults, no significant differences were observed between the age groups analyzed. The commune of Punitaqui presents the highest relative frequency 13.33% (12/90) of CE. In the analysis of risk factors for EC, having drinking water in the home and having had Cystic echinococcosis at some stage in life were associated with a higher probability of presenting Cystic echinococcosis. The results of this study show a high endemicity of Cystic echinococcosis in the province of Limarí. Likewise, all the hydatid cysts analyzed were identified as E. granulosus s. s. The strain EG01 predominated, detecting 4 haplotypes, EG01, EG1A, EG1D, EgCLOM16, with a low diversity of haplotypes (Hd = 0.461 ± 0.00637) and one low nucleotide diversity (0.00181 ± 0.00036). The cox1 parsimony network in the Chilean population showed a star shape, where the EG01 haplotype was found in the center. The neutrality indices Tajima`s D and Fu`s Fs were negative for the populations of Coquimbo (D = -0.93302; Fs = -0.003) and Magallanes (D = -0.17406; Fs = -0.121), indicating an excess of rare polymorphic sites, population expansion, and a significant deviation from neutrality. The D of Tajima and Fu`s Fs were positive for the population of La Araucanía (D = 0.8695; Fs = 1.039), showing low levels of rare alleles or lack of rare alleles. The Fisher fixation index by pairs (Fst), show negative values in the Coquimbo-La Araucanía populations (-0.08761). The highest and most significant Fst value was between the La Araucanía-Magallanes populations (0.10703), indicating differences between these populations. Our results show that the population genetic structure of E. granulosus s. s. is complex, due to the presence of different haplotypes in the different regions throughout Chile, which may become even more complex if longer sequences are used, which allow studying the microdiversity of E. granulosus s. s. in the different hosts. Thus, it is suggested that to design future Cystic echinococcosis (CE) control programs, the variability of the strain in each of the endemic regions should be taken into account.