Models suggest pathogen risks to wild fish can be mitigated by acquired immunity in freshwater aquaculture systems

Abstract

The interaction of pathogens between wild and farmed aquatic animal populations is a concern that remains unclear and controversial. Ichthyophthirius multifiliis, a ciliated protozoan parasite, is a pathogen of freshwater finfish species with geographic and host range that causes significant economic losses in aquaculture. Flow-through farming systems may facilitate the transfer of such a parasite with free-living stages between farmed and wild stocks. Here, experimental and field study infection data are used to describe the infection dynamics of Ichthyophthirius multifiliis in rainbow trout using a simple macroparasite model by including host resistance. The study considered flow-through farming systems with a single or two age-class compartments and simulated the transfer of the parasite between farmed and wild fish populations. Results suggest that aquaculture can promote the prevalence of the resistance in wild stocks by increasing the parasite population in the wild environment. At the same time, acquired resistance in the farmed fish population may protect the wild fish population from lethal effects of the parasite by reducing the total parasite population. This study offers a promising mathematical basis for understanding the effects of freshwater aquaculture in disease spread in wildlife, developing risk assessment modeling, and exploring new ways of aquaculture management. Aquaculture production has rapidly increased for the last four decades and is considered a key solution to meet the world food demand 1. At the same time, concerns have been raised about environmental impacts, including infectious diseases in wild fish 2-5. However, most examples of pathogen interactions between farmed and wild fish derive from marine systems, focusing largely on: the salmon louse (Lepeophtheirus salmonis), a parasite that infects wild and farmed salmonids 6-8 , white spot syndrome virus (WSSV), a pathogen found in wild and farmed shrimp 9-11 , and Anguillicoloides crassus, a nematode that emerged in wild European eels 12. Though declines in wild marine stocks have been associated with aquaculture sites introducing or amplifying pathogens 13-17 , such interactions have received little study in freshwater ecosystems 3,18-20. Yet, pathogen transfer from farmed to wild stocks, termed 'spillover' , may be facilitated by commonly used flow-through farming systems in which water is often abstracted from rivers before being discharged back to the river after passing through the farm site 21. The potential impact of freshwater aquaculture on wild fish populations however remains unclear and controversial 22,23. Through a mathematical modeling approach, this study aimed to investigate the potential interactions between aquaculture systems and wild fish stocks based on an important pathogen of freshwater finfish aquaculture, Ichthyophthirius multifiliis, otherwise known as 'Ich'. This is a ciliated protozoan parasite that is globally distributed and causes disease in a wide range of freshwater finfish species, but is of signif...

RETRACTED: Advantage of Species Diversification to Facilitate Sustainable Development of Aquaculture Sector

“…There is also a need to assess potential interspecies pathogens in designing species combination and stocking density. Moreover, combining certain species may trigger spillover interspecific pathogens [68][69][70]. The risk of interspecific spillover is often concerned with introducing exotic species [71], which suggests considering indigenous species to institute species combinations in conventional polyculture systems.…”

Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California

“…Mechanical transmission through migrating birds and other vectors has been reported (Algöet et al 2009; Shahin et al 2022) and is a cause for concern over dissemination into noninfected regions. With the increasing demand for aquaculture production, a growing concern for the interactions between farmed and wild fish is emerging (Murray and Peeler 2005; Vendrell et al 2006; Lafferty et al 2015; Teixeira Alves and Taylor 2020). There is a risk that wild fish will transmit pathogens to farmed fish, causing economically significant losses to producers (Colorni et al 2003; Algöet et al 2009).…”

Analysis of Notifications of Rapid Alert System concerning Parasites in Fishery Products

“…Fishery products represent a valuable source of nutrients and micronutrients that are crucial for healthy and diverse diets (FAO, 2018). The role of these products in the transmission of parasitic diseases to humans has been recognized (Koepper et al, 2020;Teixeira et al, 2020). The range of parasites involved is very wide, including nematodes, trematodes, and cestodes (Huss, 1998;Chai et al, 2005).…”