title: Development of Ostertagia leptospicularis in cattle, and the differentiation of infective larvae and female adults from those of O. ostertagi.
abstract: The development of Ostertagia leptospicularis was observed in helminthologically-naive calves. Infective larvae and parasitic stages of the species were also examined in an endeavour to find a reliable means of distinguishing these from comparable stages of O. ostertagi. In the case of infective larvae, it was found that the distance from the tip of the larval tail to the tip of the sheath ("tail length") provided the most simple means of distinguishing between the species (reliability of approximately 97%). The ratio of "tail length" to total body length may be used to provide still greater reliability where this is essential. The rate of development and morphology of the early parasitic stages of O. leptospicularis in calves were found to be similar to those described for O. ostertagi by Rose (1969) and with the exception of late 4th stage males there appeared to be no simple morphological means by which parasitic larval stages of the 2 species could be distinguished. However, adult (5th stage) female O. leptospicularis were found to be distinguishable from those of O. ostertagi (reliability of approximately 98%) on the basis of the position of the cervical papillae in relation to a junction between 2 regions of the central oesophagus. Males, from the late 4th stage, were readily distinguishable on the basis of the spicule structure.
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology*; D005260:Female; D007814:Larva; D010029:Ostertagiasis / Q000469:parasitology / Q000662:veterinary*; D013045:Species Specificity; D014251:Trichostrongyloidea / Q000033:anatomy & histology / Q000254:growth & development* / Q000472:pathogenicity; D014252:Trichostrongyloidiasis / Q000662:veterinary*