Echinostoma revolutum Infection in Native Ducks from the Cauvery Delta Region of Tamil Nadu, India: A Case Report

Duck farming is a viable enterprise for poor nomadic farmers in the Cauvery delta region of Tamil Nadu because of the extensive paddy fields. Ducks are generally highly susceptible to various pathogens, including trematode parasites, because their aquatic feeding behaviour facilitates access to snail intermediate hosts. Two dead native ducks were brought by a nomadic farmer to the Department of Veterinary Pathology, Veterinary College and Research Institute, Orathanadu, Thanjavur, for post-mortem examination. The farmer reported bloody diarrhoea, reduced feed intake, and dullness before death. Necropsy of the duck carcasses revealed haemorrhagic enteritis, flukes in the intestine, and operculated eggs in the intestinal contents. The flukes were stained with borax carmine and identified as Echinostoma revolutum on the basis of their morphological features using standard taxonomic keys. Microscopic examination showed an elongated body with a spiny cuticle in the anterior region. A well-developed head collar surrounding the oral sucker bore 37 spines, including a group of five corner spines on each side. The ventral sucker was much larger than the oral sucker and was located in the anterior region. The mid-region of the body contained uterine coils filled with operculated eggs, followed by two slightly branched tandem testes and an ovary. The vitelline follicles were well developed and positioned laterally, extending from the level of the ventral sucker to the posterior end of the body. This study reports the occurrence of Echinostoma revolutum in native ducks from the Cauvery delta region of Tamil Nadu, India.