Morphological identification of Nematodirus spathiger nematodes (Nematoda, Molineidae) obtained from the small intestine of sheep

V Melnychuk,V Yevstafieva,A Antipov,M Pishchalenko,O Reshetylo

doi:10.15421/022119

Abstract

Strongyloidiases are caused by nematodes of the suborder Strongylida and are the most widely prevalent group of gastrointestinal helminthiases of sheep in many regions of the world. Among gastrointestinal strongylids, the helminths of the genus Nematodirus are represented by the largest number of species and highest infection rates in sheep. Nematodirosis causes significant economic losses in the sheep industry through decreased sheep productivity, delayed growth and development of young animals, and a reduced resistance to other diseases. Timely and accurate diagnosis of nematodirosis and identification of the pathogen will effectively prevent the disease and help to carry out treatment and prevention measures. Therefore, the aim of the work was to study the definitive morphometric characters of mature males and females of Nematodirus spathiger Railliet, 1896, obtained from the small intestine of domestic sheep. The results of experimental studies showed that nematodes of this species morphologically are characterized by a thin filiform body, a vesicle at the head end and a chitinous tooth in a short oral capsule. The differential morphological features of male nematodes of N. spathiger include specifics of the structure of spicules, their distal end and the shape and location of the rays of the caudal bursa; in females, those are the features of the structure of the vulva and tail end. In identification of male nematodes of N. spathiger, it is proposed to use 40 metric parameters, of which 11 characterize the overall size of the body, esophagus and vesicles, 24 refer to the size of the tail bursa, 5 to the size of the spicules and the enveloping membrane. To help identify the females of N. spathiger, 25 parameters are chosen, of which 14 also characterize the overall size of the body, esophagus and head vesicle, 6 refer to the size of the cuticular formations of the vulva and its location, and 5 to the size of the tail end, the location of the anus and the size of the tail spike.

Highlights

Helminth pathogens have shown a remarkable ability to adapt to anthropogenic changes in the environment, including technological factors
There is a well-defined excretory pore at the point of transition of the esophagus into the intestine (Fig. 1)
Nematodirosis is a very common infection of sheep in many countries, where the Nematodirus fauna can be represented by several species (N. spathiger, N. abnormalis, N. filicollis, N. lanceolatus, N. helvetianus, N. davtiani, N. battus, N. mugosaricus, N. oirathianus), and infection rates range 12–98%

Summary

Introduction

Helminth pathogens have shown a remarkable ability to adapt to anthropogenic changes in the environment, including technological factors. Modern technologies of sheep breeding induce the spread of various parasitic diseases and, first of all, gastrointestinal strongyloidiases, the causative agents of which belong to a large number of different species of nematodes. The helminths of the genus Nematodirus (Nematoda, Molineidae) are represented by the largest number of species and infection rates. 6 species of Nematodirus nematodes were identified from sheep in the USA, and N. spathiger (P – 80.0%) and N. abnormalis (53.0%) were dominant. In Western, Eastern and Northern Africa, the fauna of Nematodirus nematodes is represented by three species, namely N. spathiger, N. filicollis, N. battus, with the average prevalence of 52.8% (Ghada et al, 2011; Akkari et al, 2012; Kelemework et al, 2016; Squire et al, 2018)

Objectives

Methods

Results

Discussion

Conclusion