Identificação morfométrica de larvas infectantes em cultura pura de estrongilídeos de equídeos (Nematoda: Strongylidae)

Abstract

Morphometric characters for the identification of infective larvae (L3) from Cyathostominae and Strongylinae subfamilies, parasites of equine, are essential for the study of biology, pathology and antihelminthics resistance of nematode parasites responsible for infections in horses. Females of the parasites in study were obtained by deworming or necropsy. After parasitic identification eggs were collected from each female and were cultured by modified Mönning technique, resulting in L3 larvae after eight days at 26 - 28 °C. For the present work females from the following species were considered: Craterostomum acuticaudatum, Poteriostomum imparidentatum, Poteriostomum ratzii, Strongylus edentatus, Strongylus vulgaris, Triodontophorus brevicauda, Triodontophorus serratus and Triodontophorus tenuicollis. The objective of the present work was to define morphological parameters to be considered in morphometric identification of Strongylidae of horses. L3 larvae morphological parameters as, total length of the larvae (with sheath), excretory pore (distance from excretory pore to anterior end), sheath tail length (distance from the anus to the sheath posterior end), maximum larvae width), length of oesophagus, tail length (without sheath) and distal portion (distance from tail end to sheath tail end) were registered. Statistical analyses with Kruskal-Wallis test and Tukey test show that it is possible to use the considered parameters to distinguish the species concerned because there are significant differences between them. Multinomial regression analyses reveal the most relevant parameters to morphometric specific identification. The most suitable model is explained by the variables excretory pore, sheath tail length, body breadth, length of oesophagus and distal portion. However it may be necessary to refer to less representative parameters to accomplish a correct morphometric specific identification. This contribution to the study of equine strongyles infective larvae allows better laboratory work to the knowledge and control of parasitism in horses.