Abstract
Cystic echinococcosis (CE) caused by the larval stage of Echinococcus granulosus sensu lato (s.l.) is one of the most important zoonotic parasitic diseases worldwide and 10 genotypes (G1–G10) have been reported. In China, almost all the epidemiological and genotyping studies of E. granulosus s.l. are from the west and northwest pasturing areas. However, in Heilongjiang Province of northeastern China, no molecular information is available on E. granulosus s.l. To understand and to speculate on possible transmission patterns of E. granulosus s.l., we molecularly identified and genotyped 10 hydatid cysts from hepatic CE patients in Heilongjiang Province based on mitochondrial cytochrome c oxidase subunit I (cox1), cytochrome b (cytb) and NADH dehydrogenase subunit 1 (nad1) genes. Two genotypes were identified, G1 genotype (n = 6) and G7 genotype (n = 4). All the six G1 genotype isolates were identical to each other at the cox1 locus; three and two different sequences were obtained at the cytb and nad1 loci, respectively, with two cytb gene sequences not being described previously. G7 genotype isolates were identical to each other at the cox1, cytb and nad1 loci; however, the cytb gene sequence was not described previously. This is the first report of G7 genotype in humans in China. Three new cytb gene sequences from G1 and G7 genotypes might reflect endemic genetic characterizations. Pigs might be the main intermediate hosts of G7 genotype in our investigated area by homology analysis. The results will aid in making more effective control strategies for the prevention of transmission of E. granulosus s.l.
Highlights
Cystic echinococcosis (CE, known as hydatidosis or hydatid disease) caused by the larval stage of Echinococcus granulosus sensu lato (s.l.) is considered as one of the most important zoonotic parasitic diseases worldwide, affecting pastoral and poor rural communities where people raise livestock in close contact with dogs [1]
Three different cytb gene sequences were obtained from six hydatid cysts identified as G1 genotype, with one to three base differences between one another
Human CE is a cause of serious concern due to increase in morbidity in humans and economic impact of diagnosis and treatment in China; the degree of endemicity of echinococcosis differs with regions in China [22,23]
Summary
Cystic echinococcosis (CE, known as hydatidosis or hydatid disease) caused by the larval stage of Echinococcus granulosus sensu lato (s.l.) is considered as one of the most important zoonotic parasitic diseases worldwide, affecting pastoral and poor rural communities where people raise livestock in close contact with dogs [1]. The disease causes great economic loss in livestock through condemnation of infected organs (mainly liver). Fatal cases of human CE have been reported with inoperable CE cysts of the brain and anaphylactic shock caused by rupture of liver hydatid cysts [2,3]. Humans become infected with CE by ingesting eggs released from dogs or other canids through direct contact with the animals and consumption of food and water contaminated with infected animal feces. Eggs hatch in small intestine and parasite larvae (hydatid cysts) can be found in almost any organ, with the liver being the most common. Clinical symptoms are mainly related to the localization, size, and number of cysts. A recent study described that there seemed to be a relationship between the genotypes and the size of hydatid cysts, in which all the patients infected with G7 genotype showed smaller liver cysts than those infected with G1 genotype [3]
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