Host Parasite Interactions and Infection Patternsof Helminths in Catla catla from the Indus RiverAn Ecological and Public-Health Perspective

Abstract

Helminth parasites are a part of the freshwater ecosystems and have an estimateable effect on the health, productivity, and economic value of fish populations. A major food fish of the Indus River system in Pakistan, catla catla (Hamilton, 1822) is one of the most commercially significant species of major Indian carps, yet, its host-parasite interactions have been poorly studied in this region. The current article re-analyzes the results of a survey of 26 Catla taken in the Indus River at Jamshoro, Sindh, during January 2018-January 2020 and interprets the resulting patterns of infections as an ecological and public-health phenomenon. The percentage of hosts that harbored helminths was nine out of 26 (34.6%) and six taxa were identified: trematodes ( Thaparotrema pedicellatum, Isoparorchis trisimilitubis, Echinochasmus sp.), nematodes ( Procamallanus (Spirocamallanus) sp., Rhabdochona sp.), The overall prevalence was led by trematodes (23.07%), with nematodes showing the most common mean intensity (14 worms per infected host). Parasites were categorically divided into four microhabitats, i.e., gall bladder, body cavity/swim-bladder, intestine, and stomach, where 52% of all worms observed were recovered in the intestine. The patterns of infections agreed with the ecology of the host surface/midwater feeding and the availability of the intermediate host locally and the existence of the piscivorous birds along the river. The rediscovery of Echinochasmus has direct food-safety consequences, with several species of the genus being food-borne zoonoses that are carried in undercooked fish flesh. The results emphasize the importance of systematic parasite surveillance of the Indus fishery and provide identified interventions to the fisheries management and consumer protection.

Keywords: Catla catla, host–parasite interactions, prevalence, intensity, microhabitat, transmission, zoonosis, Indus River, fisheries management.