Skip to main content
ARS Home » Research » Publications at this Location » Publication #63447
Title: KEY CHARACTERS FOR THE MICROSCOPICAL IDENTIFICATION OF CYLICOCYCLUS NASSATUS AND OF CYLICOCYCLUS ASHWORTHI (NEMATODA: CYATHOSTOMINAE) OF THE HORSE, EQUUS CABALLUS

Author
item Lichtenfels, James
item KHARCHENKO, V - INST. ZOOLOGY, UKRAINE
item SOMMER, C - VET & AG UNIV. DENMARK
item ITO, M - INST EPER ANIMALS, JAPAN

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Strongyloid nematodes are a major cause of morbidity and mortality in equids in the United States. Resistance to antiparasitic drugs (currently, the only means of controlling the nematode disease in horses) is common and alternative control methods for these parasites are needed to protect horses in the USA. Considerable research is underway worldwide to develop improved control strategies. This research requires the identification of the more than 40 nematode species that are parasitic in the large colon and caecum of horses. This report provides new information useful for the microscopic identification of several common species of the genus Cylicocyclus that have previously been difficult to identify. The results will be used by researchers worldwide working to control these economically important nematodes.

Technical Abstract: Efforts to develop control methods for nematode parasites of horses have been hampered by difficulties in identifying some nematodes of the genus Cylicocyclus. Cylicocyclus nassatus is characterized by a cuticular shelf on the inner surface of the buccal capsule shelf, a dorsal gutter that is as long as 50% of the buccal capsule depth, 20 elements in the external leaf crown (ELC) and lateral papillae that produce a tall, narrow cuticular extension. Both C. nassatus and C. ashworthi have a short, rounded dorsal bursal lobe in which the proximal branch (of 3 on each side) overlaps 75-80% of the middle branch and a female tail that is slightly longer than the vulva to anus distance. Cylicocylus ashworthi can be distinguished from C. nassatus by the absence of a shelf on the inner surface of the buccal capsule, by its much shorter dorsal gutter that is wider than long and its 25-29 ELC elements and lateral papillae that produce a short, broad extension in the cuticle. C. leptostomus, C. radiatus and C. triramosus males have elongate dorsal bursal lobes in which the proximal branch overlaps less than 50% of the middle branch: females have a tail that is much shorter (C. triramosus) or slightly shorter (C. leptostomus and C. radiatus) than the vulva to anus distance. C. leptostomus is distinguished by a small buccal capsule; C. radiatus by a large buccal capsule without a dorsal gutter; and C. triramosus by an extremely short dorsal gutter, sharply pointed uniformly tapering ELC elements, and ventral and dorsal notches in the mouth collar.