Cuticular ridge patterns applied for identifying adult female worms of Haemonchus species with various vulvar morphological types in infected native goats in Laos.

Abstract

Species of the blood sucking nematode Haemonchus are a main problem in the small ruminant industry worldwide. Haemonchus worms were taken from 68 infected native goats slaughtered in three provinces of Laos in June and July 2019. Cuticular ridge patterns were used for the first time to identify adult female Haemonchus spp. and their vulvar morphs were characterized. The results showed that the variations in vulvar morphology of female Haemonchus spp. presented a knobbed morph as the dominant morphotype and predominant linguiform B subtype was also detected. In total, 270 selected female worms from each vulvar morph type were examined based on their cuticular ridge patterns in cross sections at positions of the esophageal-intestinal junction (EI), the 4 mm region from the anterior end (4 mm), and the mid-body (MB). Only Haemonchus contortus was identified and most worms had constant numbers of ridges at EI, 4 mm, and MB, namely 30, 26, and 22 ridges, respectively, accounting for 99.26%, 97.41%, and 97.04%, respectively, of worms detected, while the lowest variation in the number of ridges was at region EI which is recommended as the single best position. Based on synlophe and ITS2 sequence analysis, it was assumed that H. contortus might dominate in the sample areas with the possible numbers of ridges of H. contortus females in the ranges 29-30, 25-27, and 21-23 for positions EI, 4 mm, and MB, respectively. The cuticular ridge pattern was a useful character for identifying female Haemonchus species in this study and could be utilized as an affordable alternative method for epidemiological studies and as part of parasite control management in native goats of Laos.