Molecular Characterization of Avitellina lahorea Woodland, 1927 (Class Cestoda; Family Anoplocephalidae) Infecting Sheep and Goats Raised in India

PURPOSE

Tapeworms of Avitellina spp. are among those gastrointestinal parasitic helminths which infect wild and domestic ruminants worldwide leading to various clinical manifestations in the ruminant hosts, thereby causing considerable economic losses in livestock production. While these worms are among the major constraints in ruminant livestock raising, there is very meagre molecular information available making their identity error-prone. This study aimed to provide insights into the genetic characterization of these economically important tapeworms.

METHODS

In the present study, we examined 480 guts of slaughtered goats (n = 413) and sheep (n = 67) of which 74 guts were found infected with anoplocephalid cestodes (sheep gut:18; goat gut:56). A total of 27 Avitellina lahorea worms (19 from goat and 8 from sheep) were isolated, fixed, relaxed and stained using Gower's carmine stain. For molecular analyses, the genomic DNA was extracted and fragments of cytochrome c oxidase subunit 1 (cox1) gene, internal transcribed spacer1-5.8S ribosomal RNA (ITS1-5.8S rRNA) gene, and small subunit ribosomal RNA (18S rRNA) gene were amplified and sequenced.

RESULTS

Based on snail-shaped paruterine organs and other morphological and morphometric features, the worms were identified as Avitellina lahorea. The phylogenetic analyses, based on our original cox1 gene sequence and those available from NCBI GenBank, showed Avitellina tapeworms as a sister lineage of Thysaniezia with 14 to 17% genetic divergence. Molecular analyses of 18S rRNA gene sequences depicted the present isolate as one of the species of the genus Avitellina clustering with A. centripunctata as a separate species in the phylogenetic tree with 92% homogeneity in sequences. In conjunction with existing data of internal transcribed spacer1-5.8S rRNA (ITS1-5.8S rRNA) gene, the phylogenetic analysis placed the present isolate among the anoplocephalids as one of the species.

CONCLUSION

The present study is the first molecular report on A. lahorea isolated from sheep and goats with the simultaneous use of a morphological approach, and certainly contributes to bridging the existing gaps in the understanding of these economically important parasites.

Morphological and genetic characterizations of Avitellina tapeworms from domestic ruminants in Senegal: An evidence of specificity among sheep and cattle host

Avitellina tapeworms are common intestinal parasites of ruminants with a worldwide distribution. In Senegal, only Avitellina centripunctata tapeworm has been reported to date, and genetic diversity was previously confirmed by enzymatic analysis. This study aims to clarify the diversity of Avitellina tapeworms isolated from sheep and cattle in Senegal. In total, 613 adult Avitellina tapeworms were collected from sheep and cattle. Morphological analysis by the light microscopy and scanning electron microscopy identified three Avitellina "morphospecies": A. centripunctata and Avitellina sp.2 were detected in sheep while Avitellina sp.3 was identified in cattle. Molecular phylogenetic analysis based on the complete mitochondrial cytochrome c oxidase subunit 1 gene (cox1) sequences revealed that 101 Avitellina tapeworms were divided into 54 haplotypes grouped into three clades, of which two were specific to sheep and one specific to cattle. Three morphospecies corresponded to each of three clades and the maximum pairwise divergence among the clades ranged from 9.7 to 18.5% in cox1. The present study demonstrates the unexpected diversity of Avitellina tapeworms in domestic ruminants, and emphasize the necessity of re-evaluation of the taxonomy of the genus.