Seasonal dynamics and phylogenetic analysis of Eustrongylides: A zoonotic parasite infesting spotted snakehead (Channa punctata)

Abstract

Eustrongylides are a nematode parasite of fish and fish-eating birds and have a potential health hazard in humans. The present study was designed to determine seasonal dynamics and molecular characterization of Eustrongylides spp. in Channa punctata collected from Trishal, Mymensingh. A total of 385 fish samples were collected and processed, and isolated parasites were examined under a microscope. After morphological examination, twenty (20) parasites were considered for sequencing using the internal transcribed spacer 2 (ITS-2) gene. The isolated parasites were identified as fourth-stage larvae (L₄) of Eustrongylides according to their morphological features. Of 385 fish samples, 79 were infected with Eustrongylides spp., and overall prevalence, mean intensity, and abundance were 20.5%, 1.86 ± 0.18, and 0.38, respectively. The highest prevalence was found in the rainy season (27.8%), followed by autumn (24.3), and the lowest in winter (15.6) and summer (14.6%). Medium-sized fish (24.5%) were more prone to parasitic infestation than smaller (16.6%) and larger (14.5%) ones. Parasites were more abundant in body cavity (79.5%) than muscle (20.5%). Among 20 sequences, one genotype was identified and showed 100% similarities with reference sequences of Eustrongylides spp. The unique clustering pattern confirmed morphological identification as Eustrongylides spp. Detailed molecular study is essential to explore the genetic diversity pattern of Eustrongylides in C. punctata.