Occurrence of Echinococcusgranulosussensulato and Other Taeniids in Bhutan

Abstract

The present research shows the results of a national study documenting the occurrence and genetic diversity of <i>Echinococcus</i> and <i>Taenia</i> species across Bhutan. Environmental dog faecal samples (n = 953) were collected from 2016 to 2018 in all 20 Bhutanese districts, mainly in urbanised areas. Cystic echinococcosis cysts were isolated from 13 humans and one mithun (<i>Bos frontalis</i>). Isolation of taeniid eggs from faeces was performed by sieving/flotation technique, followed by DNA isolation, PCR and sequence analyses for species identification (gene target: small subunit of ribosomal RNA). Genetic diversity of <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>. was based on the sequence (1609 bp) of the <i>cox1</i> gene. A total of 67 out of 953 (7%) dog faecal samples were positive for at least one taeniid species. From the 670 free-roaming dog faecal samples, 40 (5.9%) were positive for taeniid DNA, 22 (3.2%) of them were identified as <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>. and four (0.5%) as <i>E</i>. <i>ortleppi</i> (G5). From the 283 faecal samples originating from yak-grazing areas, 27 (9.5%) were taeniid positive, including eight (2.8%) infected with <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>. and four (1.4%) with <i>E</i>. <i>ortleppi</i>. <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>. was identified in all isolates from human and the cyst from mithun. A haplotype network (<i>cox1</i> gene) from <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>, including isolates from 12 dogs, two human and one mithun, revealed eight different haplotypes. The most common <i>cox1</i> haplotype was the globally distributed Eg01, followed by Eg40 and Eg37 (previously described in China). Five new <i>cox1</i> haplotypes (EgBhu1-5) originated from human, dogs, and a mithun were identified. The study indicated the contamination of urban areas and pastures with <i>Echinococcus</i> eggs in seven districts in Bhutan. The molecular characterisation of <i>E</i>. <i>granulosus</i><i>s</i>.<i>l</i>. revealed different <i>E</i>. <i>granulosus</i><i>s</i>.<i>s</i>. haplotypes as well as <i>E</i>. <i>ortleppi</i>. The transmission of <i>T</i>. <i>multiceps</i> was documented only in the western part of the country. Considering the zoonotic feature of <i>E. granulosus s.s.</i> and <i>E. ortleppi</i> and the economic impact of coenurosis caused by <i>T. multiceps</i> (also known as gid) in Bhutan, the findings of this study represent a significant contribution towards an epidemiological baseline for the establishment of a national control programme.