Prevalence and Morphometric Characterisation of Internal Helminth Parasites in Nandus nandus (Gangetic Leaffish) from Arial Beel, Bangladesh

Abstract

Freshwater fishes commonly harbour a wide range of helminth parasites that may affect their health, growth and ecological interactions. Knowledge of helminth infections in Nandus nandus in Bangladesh remains limited. The present study explored the prevalence, mean intensity, mean abundance, organ distribution and morphometric features of internal helminths of N. nandus from Arial Beel, Bangladesh. A cross-sectional survey was conducted during February and March 2025 using 100 fish (44 males and 56 females). Each fish was measured, weighed, dissected and examined under stereo and compound microscopes. Helminths were recovered, fixed, stained, mounted and identified using standard morphological keys. Four taxa were identified: Clinostomum complanatum, Clinostomum giganticum, Bothriocephalus sp. and Pallisentis sp. Clinostomum complanatum was the dominant parasite with a prevalence of 38%, mean intensity of 6.24 and mean abundance of 2.37. The prevalences of C. giganticum, Bothriocephalus sp. and Pallisentis sp. were 7%, 6% and 3%, respectively. Parasite counts were highest in the medium-length group, which made up the majority of the sampled fish. Pearson correlation analysis revealed weak, statistically non-significant associations between host length or weight and parasite count in both sexes. These results provide new epidemiological and morphological data on helminths of N. nandus; however, seasonal and molecular studies are required for further interpretation.