Seasonal Dynamics and Host Factors Influencing Eustrongylides spp. Infestation in Spotted Snakeheads, Channa punctata in Mymensingh, Bangladesh

Eustrongylides nematodes represent an emerging zoonotic threat, especially with the increasing global consumption of raw or undercooked fish. The present study aimed to investigate the seasonal variation of Eustrongylides spp. infestation in spotted snakehead, Channa punctata , from August 2020 to July 2021 and to assess the influence of the host. A total of 414 experimental C. punctata , captured from the ditches and beels connected with the Brahmaputra river, were collected for 12 months from three adjacent fish markets under Mymensingh Sadar sub-district, Mymensingh, Bangladesh. Stage four larval (L ₄ ) Eustrongylides spp. were isolated from the abdominal cavity, musculature, and ovaries of 133 sampled fish, washed with 0.85% sterile physiological saline and examined under light microscope using lactophenol. Prevalence was recorded as 32.12%, with a notable mean intensity of 1.53 and an abundance of 0.49. The highest prevalence was found in autumn (45.83%). Larger fish (>18 cm) exhibited a higher prevalence (62.1%) compared to the smaller (<13 cm) (26.5%). Interestingly, females had a higher prevalence and mean intensity of infestation (35.7%, 1.69±0.10) compared to males (27.2%, 1.24±0.06). Results indicated that female and higher-weighted fish exhibit higher parasitic prevalence in C. punctata , likely due to biological and environmental factors and the immunity level of the host.