Abattoir-based prevalence and histopathological analysis of paramphistomes (Platyhelminthes: Digenea) in the livers and rumens of ruminants

Paramphistomosis, a parasitic disease of ruminants caused by flukes of the family Paramphistomidae (Platyhelminthes: Digenea) and leads to significant economic losses. Primarily, their predilection site is rumen as evident from their common name “ruminal flukes” and occasionally find in other visceral organs. This study aimed to determine the prevalence of paramphistome infection in the rumens and livers of livestock followed by histopathological examination of the affected tissues. A total of 384 animals were screened for paramphistome infection at a local abattoir in the Narowal district. Liver and rumen tissue samples from infected animals were excised, fixed in buffered formalin, and processed using the paraffin-embedding technique. Tissue-paraffin blocks were sectioned with the thickness of 5 µm through microtome and stained using the Harri’s Haematoxilin and Eosin methods. The prevalence of paramphistomosis in ruminants was 49.74% with sex and age of host having a statistically significant association (P<0.05) with the magnitude of infection; however, species of host and months were not significantly associated (P>0.05). Of the total cases having rumens positive for paramphistomes, 7.29% were also tested positive for liver infections; however, no adult or immature Fasciola spp. were detected. Infected rumens had significantly (P<0.05) reduced epithelial thickness (30.50 ± 1.83 µm), accompanied by severe hemorrhages in hepatic tissues and blood congestion in hepatic vessels. Further, the central hepatic vein was found having a significantly larger diameter (39.56 ± 2.72 µm) as compared to that of healthy livers (29.76 ± 3.15 µm). The paper provides a maiden data on the paramphistome infection in livers along with rumens of ruminants in Pakistan. Hence, the findings suggest that paramphistome infection may pose a potential threat to nutrient absorption and overall metabolic health in ruminants.