Morphology and Molecular Characterization of Parabronema smithii (Cobbold, 1882) (Nematoda: Habronematidae) from Wild Asian Elephant (Elephas maximus maximus) of Sri Lanka

Purpose The aim of the present study was to carry out a detailed study of morphological features and to determine the phylogenetic position of Parabronema smithii (Cobbold, 1882) found in wild elephants in Sri Lanka. Methods Adult worms were collected from stomach ulcers at postmortem examination of wild elephants in the Udawalawe National Park, Sri Lanka. The detailed morphology of P. smithii was studied using light microscopy and, for the first time, scanning electron microscopy. Fifteen morphological characteristics were investigated. The phylogenetic analysis was conducted using the second internal transcribed spacer region (ITS2), and portions of the large subunit ribosomal DNA (28S) and cytochrome c oxidase subunit 1 (cox1). Furthermore, the present study provides a comparison of morphology and morphometrics of Parabronema species that occur in different hosts. Conclusion Parabronema smithii isolated from wild elephants exhibited the key morphological features. Phylogenetic analysis of selected genes revealed that P. smithii is closely associated with P. skrjabini and Habronema spp. Findings of the present study enhance our understanding of the biology and taxonomy of P. smithii in wild elephant in Sri Lanka and will contribute to future phylogeographic studies.