Why is it important to correctly identify Haemonchus species?

Alessandro Francisco Talamini Do Amarante

doi:10.1590/s1984-29612011000400002

Abstract

Parasitic gastroenteritis caused by Haemonchus spp. is a major cause of economic losses in the livestock industry because it impairs weight gain and increases mortality in cattle and small ruminants, especially in tropical and subtropical areas. The proper identification of the various species, as well as knowledge regarding the epidemiology of parasitic gastroenteritis, is essential for the establishment of sustainable strategies of parasite control. This review focuses on the use of easily applied, low-cost parasitological methods of identifying Haemonchus species on the basis of their morphology. In most studies carried out in Brazil, the distinctions between Haemonchus contortus and Haemonchus placei have not been considered. Many reports of H. contortus, particularly in cattle, might actually represent H. placei. The appropriate identification of species is therefore indispensable. In addition to the measurement of male spicules, new morphological characteristics, such as the synlophe, should be evaluated in order to differentiate between and among species. Measurements of infective larvae in fecal cultures can also indicate the identity of Haemonchus species. This approach can be quite useful in studies that do not involve animal sacrifice, such as studies of anthelmintic resistance based on the fecal egg count reduction test.

Highlights

Parasitic gastroenteritis caused by Haemonchus spp. is a major cause of economic losses in the livestock industry because it impairs weight gain and increases mortality in cattle and small ruminants, especially in tropical and subtropical areas
The proper identification of the various species, as well as knowledge regarding the epidemiology of parasitic gastroenteritis, is essential for the establishment of sustainable strategies of parasite control
This review focuses on the use of applied, low-cost parasitological methods of identifying Haemonchus species on the basis of their morphology

Summary

Introduction

Parasitic gastroenteritis caused by Haemonchus spp. is a major cause of economic losses in the livestock industry because it impairs weight gain and increases mortality in cattle and small ruminants, especially in tropical and subtropical areas. Represent H. placei (HOBERG et al, 2004) This problem is evident in various studies of the epidemiology of Haemonchus infection in ruminants in Brazil. The authors performed a phylogenetic analysis of 25 morphological characteristics and established a list of twelve valid Haemonchus species (Table 2). Of those twelve species, three have been reported in ruminants raised in Brazil: H. contortus, H. similis, and H. placei. Among the parasite species that infect domestic ruminants, male specimens of H. similis are distinguished, because they present spicules that are shorter than those observed for H. placei and H. contortus, whereas the distances of the barbs to distal end of the spicules of H. similis are longer (Table 3).

Synlophe

Spicules and spicule barbs

Infective larvae

Chromosome morphology