Morphological and morphometric variations in Haemonchus contortus infecting Ovines from Kashmir valley, India

Parasitic nematodes pose a significant threat to global livestock production, with Haemonchus contortus emerging as a particularly devastating pathogen in small ruminants. Despite widespread use of anthelmintics, H. contortus continues to evade control measures by developing anthelmintic resistance and adapting to diverse environments. Here, we investigate morphological and morphometric characteristics and the associated variations in recently reported anthelmintic resistant population of H. contortus in sheep from Kashmir valley, a region where small ruminant production faces persistent challenges from this parasite. Examination of 38 Corriedale sheep revealed a prevalence of 47.4%, yielding 864 Haemonchus specimens. Morphometric analysis confirmed all the specimens as H. contortus, with some notable intraspecific variations including larger female body length, male body width, and male esophageal length, as well as more posteriorly positioned cervical papillae in both sexes. Female specimens exhibited three distinct types of vulvar flaps: linguiform (69.09%), knobbed (24.55%), and smooth (6.36%). These findings provide critical insights into the adaptive changes occurring in H. contortus, potentially reflecting evolutionary changes related to anthelmintic resistance, immune evasion, and local selective pressures which can help in developing targeted control strategies and understanding the evolutionary dynamics of this economically significant nematode.