Prevalence of Soil-Transmitted Helminths and Molecular Clarification of Hookworm Species in Ethnic Ede Primary Schoolchildren in Dak Lak Province, Southern Vietnam

Abstract

To know the infection status of helminths in primary schoolchildren of southern parts of Vietnam, we performed an epidemiological study in Krong Pac district, Dak Lak Province, Vietnam. A total of 1,206 stool specimens were collected from ethnic Ede schoolchildren in 4 primary schools in 2015 and examined by the Kato-Katz technique. In addition, stool cultures were done by the Harada-Mori method to obtain hookworm larvae and then to clarify the species of hookworms infected. The results showed that the helminth infection rate was 25.0%, including 2.0% Ascaris lumbricoides, 0.33% Trichuris trichiura, and 22.8% hookworm infections. The average intensity of infection was 102.0 eggs per gram of feces (EPG) for Ascaris, 36.0 EPG for Trichuris, and 218.0 EPG for hookworms. ITS1 gene sequences of the hookworm larvae were identical with those of Necator americanus (100% homology) reported in GenBank. It has been confirmed in this study that the hookworm, N. americanus, is a dominant helminth species infected in primary schoolchildren of a southern part of Vietnam. Public health attention is needed for control of hookworm infections among schoolchildren in surveyed areas of Vietnam.

Keywords: Ascaris lumbricoides; Trichuris trichiura; Vietnam; hookworm; intensity; prevalence; schoolchildren; soil-transmitted helminth.

Fig. 1.

Eggs (A: before culture; B: egg after hatching) and larvae of Necator americanus.

Fig. 2.

Phylogenetic tree of Necator americanus Vietnam and other strains from part of ITS1 nucleotide sequence estimated by Neighbor-Joining (NJ) using MEGA 6.06 [12]. Note: N. americanus-VN=Vietnamese Necator; other N. americanus was from GenBank (no. LC036565.1, LC036563.1, JF960397.1, JF960401.1, JF960373.1, JF960388.1, and JX159772.1, respectively); Ascaris lumbricoides (EU635693.1 and EU635695.1); Ancylostoma duodenale (AB504715.1); Strongyloides stercoralis (JX489149, JX489151, EF545004, and EF653265); Enterobius vermicularis (DQ823387.1); Trichuris trichiura (AM992995.1 and AM992998.1).