Quantity and Quality of Aquaculture Enrichments Influence Disease Epidemics and Provide Ecological Alternatives to Antibiotics

Abstract

Environmental heterogeneity is a central component influencing the virulence and epidemiology of infectious diseases. The number and distribution of susceptible hosts determines disease transmission opportunities, shifting the epidemiological threshold between the spread and fadeout of a disease. Similarly, the presence and diversity of other hosts, pathogens and environmental microbes, may inhibit or accelerate an epidemic. This has important applied implications in farming environments, where high numbers of susceptible hosts are maintained in conditions of minimal environmental heterogeneity. We investigated how the quantity and quality of aquaculture enrichments (few vs. many stones; clean stones vs. stones conditioned in lake water) influenced the severity of infection of a pathogenic bacterium, Flavobacterium columnare, in salmonid fishes. We found that the conditioning of the stones significantly increased host survival in rearing tanks with few stones. A similar effect of increased host survival was also observed with a higher number of unconditioned stones. These results suggest that a simple increase in the heterogeneity of aquaculture environment can significantly reduce the impact of diseases, most likely operating through a reduction in pathogen transmission (stone quantity) and the formation of beneficial microbial communities (stone quality). This supports enriched rearing as an ecological and economic way to prevent bacterial infections with the minimal use of antimicrobials.

Positive welfare effects of physical enrichments from the nature-, functions- and feeling- based approaches in farmed rainbow trout (Oncorhynchus mykiss)

“…Structural enrichments have been suspected to represent a bacterial reservoir and vectors for pathogens (Tuckey and Smith, 2001). In contrast, a recent study revealed that a beneficial microbial community introduced by the structures may prevent the development of pathogens through competitive phenomenon (Karvonen et al, 2021). Therefore, fish reared in enriched environments could have an increased resistance through an improved immunocompetence.…”

Hatchery tanks induce intense reduction in microbiota diversity associated with gills and guts of two endemic species of the São Francisco River

“…One of the biggest challenges to the growth of industrial aquaculture is disease control (Zheng et al, 2020;Karvonen et al, 2021). In this context, the commensal microbiota is important in the innate and adaptive immunity of animals (Vadstein et al, 2018;Sehnal et al, 2021;Huang et al, 2022), whose change in composition can promote or mitigate disease states in hosts (Sehnal et al, 2021).…”

Status of Emerging and Reemerging Fish Viral Infections in India

“…In India, the expansion of aquaculture into intensive and semi-intensive methods has been accompanied by an increase in production of fish and shellfish due to high stocking densities. However, stressful environmental circumstances encourage the emergence and spread of infectious diseases through variations in virulence and epidemiological factors [10]. Infectious diseases, especially viral diseases are very difficult to be controlled once established within the culture system [11] due to the peculiar environment where pathogens are constantly lurking for an opportunity when the health status of the host is compromised [12].…”