Scanning electron microscopy of different vulval structures in a Mexican Haemonchus contortus isolate.

Haemonchus contortus is a parasite species that affects the health and production of grazing small ruminants in different parts of the world. Scanning electron microscopy (SEM) is an important tool for the study of parasites' morphology and taxonomy as it generates images that appear 3D and are generally easier to interpret than optical microscopy images. This study used the SEM to describe the vulval types of adult H. contortus from a Mexican isolate. A total of 14 adult H. contortus females were obtained from two artificially infected goats. Females were fixed and processed by critical point drying and observed with SEM. A collection of SEM images was obtained from these parasites and those images were used to identify the structures previously described by optical microscopy studies. Two different types of vulval structures were described in this Mexican H. contortus isolate: Type 1 (vulval flap), Type 2 (epiptygma). An unusual vulval structure was reported in a single individual. The Type 1 included vulval flaps of different sizes and spatial dispositions, as well as one or more knobs in different positions around the vulva. The Type 2 shows differences in the epiptygma. The present study suggests that the Mexican H. contortus isolate used in donor animals possess intraspecific polymorphism in vulval structures.