Date of this Version
PLoS Neglected Tropical Diseases (June 2014) 8(6): e2937
Editor: Malcolm K. Jones, University of Queensland, Australia
Cystic echinococcosis (CE) is a globally distributed cestode zoonosis that causes hepatic cysts. Although Echinococcus granulosus sensu stricto (s.s.) is the major causative agent of CE worldwide, recent molecular epidemiological studies have revealed that E. canadensis is common in countries where camels are present. One such country is Mongolia.
Forty-three human hepatic CE cases that were confirmed histopathologically at the National Center of Pathology (NCP) in Ulaanbaatar (UB) were identified by analysis of mitochondrial cox1 gene as being caused by either E. canadensis (n = 31, 72.1%) or E. granulosus s.s. (n = 12, 27.9%). The majority of the E. canadensis cases were strain G6/7 (29/31, 93.5%). Twenty-three haplotypes were identified. Sixteen of 39 CE cases with data on age, sex and province of residence were citizens of UB (41.0%), with 13 of the 16 cases from UB caused by E. canadensis (G6/7) (81.3%). Among these 13 cases, nine were children (69.2%). All pediatric cases (n = 18) were due to E. canadensis with 17 of the 18 cases (94.4%) due to strain G6/7. Serum samples were available for 31 of the 43 CE cases, with 22 (71.0%) samples positive by ELISA to recombinant Antigen B8/1 (rAgB). Nine of 10 CE cases caused by E. granulosus s.s. (90.0%) and 13 of 20 CE cases by E. canadensis (G6/7) (65.0%) were seropositive. The one CE case caused by E. canadensis (G10) was seronegative. CE cases caused by E. granulosus s.s. showed higher absorbance values (median value 1.131) than those caused by E. canadensis (G6/ 7) (median value 0.106) (p = 0.0137).
The main species/strains in the study population were E. canadenis and E. granulossus s.s. with E. canadensis the predominant species identified in children. The reason why E. canadensis appears to be so common in children is unknown.
Cystic echinococcosis (CE) is a parasitic zoonosis with a cosmopolitan distribution. Molecular analysis was carried out on 43 hepatic CE cysts from 43 cases confirmed histopathologically at the NCP, Mongolia. Molecular analysis revealed two species, Echinococcus canadensis and E. granulosus s.s. Twenty-three haplotypes of the cox1 gene were identified. All pediatric cases (n = 18) were by E. canadensis. Sixteen of 39 CE cases with data on age, sex, and province of residence were from UB (41.0%), and 13 of these 16 cases were caused by E. canadensis (81.3%). Among the 13 cases from UB, nine were children (69.2%). A total of 31 serum samples from these 43 cases were analyzed for antibody response to rAgB with 22 (71.0%) samples positive by ELISA to rAgB. Thirteen of 20 E. canadensis (G6/7) (65%) and nine of 10 E. granulosus s.s. (90%) were seropositive. CE cases by E. granulosus s.s. showed a higher absorbance value than cases by E. canadensis (p = 0.0137). This is the first study to evaluate age distribution of and antibody responses to rAgB in CE cases caused by the two species in Mongolia. It remains unknown why E. canadensis appears to be more common in pediatric cases.