Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 24, 2000
Publication Date: N/A
Interpretive Summary: The Haemonchinae includes 3 genera, Haemonchus Cobb, 1898, Mecistocirrus and Ashworthius, commonly referred to as large stomach worms, that are significant pathogens of cattle, sheep, goats and farmed deer, causing significant production losses due to morbidity, mortality, cost of treatment and suboptimal use of contaminated pastures. The synlophe, the system of cuticular ridges distributed longitudinally on the surface of most nematodes in the superfamily Trichostrongyloidea, has been found to be the most sensitive and useful character for identifying and classifying species and genera of the superfamily. The number and distribution of ridges in the synlophes of Mecistocirrus digitatus and Ashworthius sidemi were found to be remarkably similar to the synlophes described earlier by ARS scientists for Haemonchus spp. Despite the similarities, differences among species were identified in specific regions of the nematodes. This information is useful for identifying species and determining relationships among these large stomach worm parasites of cattle, sheep, goats and farmed and wild cervids. The information will be used by scientists to identify known and emerging pathogens, to evaluate biological or chemical control agents, to determine the importance of reservoir hosts such as wildlife, or develop specific diagnostic tools.
The pattern of longitudinal ridges (synlophe) on the external cuticular surface of trichostrongylid nematodes has been shown to be of value for distinguishing species and determining relationships among higher taxa. In the process of studying Mecistocirrus digitatus, the large stomach worm of bovids of Asia that has been imported and established in the Americas, we observed remarkably similar synlophe patterns to those described for 3 species of Haemonchus and to those we examined in a species of Ashworthius. In all 3 genera, the synlophe is absent from the posterior part of the body. Only in Haemonchus does the synlophe extend beyond midbody. In both Mecistocirrus digitatus and Ashworthius sidemi the synlophe extends posteriorly only about 1/4 of body length. In all 3 genera the synlophe consists of about 30 ridges in the region of the esophagus with variation among species in specific areas, including subventral, subdorsal and sublateral ridges. This information is useful for identifying species and determining relationships among these large stomach worm parasites of cattle, sheep, goats and farmed and wild cervids.