Genetic diversity studies on trematode parasites of Ovines in North Kashmir, India

Trematode infections are recognized as one of the most economically important helminthic diseases hampering the productivity of domestic ruminants globally. The study aimed to estimate the prevalence, identify the epidemiological risk factors, confirm morphological identifications using ITS-2 and 28S rDNA sequencing and analyze the pathological effects for development of suitable control strategies. Examination of 80 gastrointestinal tracts from locally reared sheep in North Kashmir revealed an overall prevalence of 26.25% (21/80; 95% CI: 16.6-35.9). The five species of trematode parasites identified were Fasciola gigantica, Dicrocoelium dendriticum, Paramphistomum cervi, P. epiclitum and Gastrothylax crumenifer. Prevalence was significantly (p < 0.05) affected by the season, age, and sex of the animal, while the body condition, breed, and sampling area had non-significant effect. Infected organs exhibited hemorrhages, necrotic spots, cellular infiltration, biliary fibrosis, and ruminal papillae atrophy. Molecular characterization and sequencing of eight representative isolates using ITS-2 and 28S rDNA confirmed F.gigantica (ITS-2: 550 bp; 28S: 618 bp), with minor nucleotide variation observed only in the 28S region. Amphistome species (G.crumenifer, P.epiclitum, P.cervi) were validated by amplification of ITS-2 (500 bp) and 28S (1200 bp), showing varying nucleotide polymorphisms, particularly in P. epiclitum. For D. dendriticum, only preliminary ITS-2 (450 bp) and 28S (650 bp) rDNA PCR amplification was achieved. The present study provides the first molecular characterization of P. epiclitum from Kashmir, although the parasite has been reported previously based on morphological identification. Based on seasonal prevalence, strategic deworming during late winter/early spring, early to mid-summer, and mid-to late autumn, along with snail control, is recommended to reduce infection pressure and economic losses. The study demonstrates the reliability of ITS-2 and 28S rDNA markers for species differentiation and reveals genetic variability among trematode isolates, highlighting the need for further investigations using additional molecular markers to better understand population structure and genetic diversity. Overall, the findings enhance understanding of trematode diversity in the region and provide useful insights into the origin and dispersal of flukes in Asia.