Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2000
Publication Date: N/A
Interpretive Summary: Species of the genus Haemonchus are pathogens of cattle, sheep, and goats, causing significant production losses due to morbidity, mortality, cost of treatment and suboptimal use of contaminated pastures. This report describes a new species of Haemonchus with a distinctive pattern of cuticular ridges and spicules, which was previously identified from African ruminants as Haemonchus contortus, the species parasitic in domestic ruminants worldwide. The study is part of an effort to improve the capability to identify these emerging threats to ruminant farming in North America. The information will improve the ability to identify endemic and exotic species that threaten economically important hosts, to evaluate biological and chemical treatment and control agents, determine the importance of reservoir hosts such as wildlife, evaluate emerging or imported pathogens and to prevent the importation of others.
In the course of a revision of the nematode genus Haemonchus Cobb, 1898, commonly referred to as large stomach worms and significant pathogens of ruminants, a new species was discovered in the grey rhebok, Pelea capreolus, and the bontebok, Damaliscus pygarthus, in South Africa. The new species, Haemonchus horaki, was previously reported as a long-spicule form of Haemonchus contortus (Rudolphi, 1803) Ransom, 1911. The new species, compared to H. contortus, can be distinguished by significantly longer spicules (555-615 compared to 383-475); a synlophe with fewer ridges (26 compared to 30 in the region of the posterior part of the esophagus) that extend more posteriorly (within 1 mm of the copulatory bursa in males and post-vulvar in females compared to 2/3 to 3/4 of pre-bursal and pre-vulvar lengths); and, an asymmetrical dorsal lobe with a long dorsal ray divided for more than half of its length forming 2 branches of unequal length (compared to a dorsal ray divided for less than half of its length and forming 2 equal branches in H. contortus).