Deciphering the effect of food availability, growth and host condition on disease susceptibility in a marine invertebrate

Abstract

Food provisioning influences disease risk and outcome in animal populations in two ways. On the one hand, unrestricted food supply improves the physiological condition of the host and lowers its susceptibility to infectious disease, reflecting a trade-off between immunity and other fitness-related functions. On the other hand, food scarcity limits the resources available to the pathogen and slows the growth and metabolism of the host on which the pathogen depends to proliferate. Here, we investigated how food availability, growth rate and energetic reserves drive the outcome of a viral disease affecting an ecologically relevant model host, the Pacific oyster, Crassostrea gigas. We selected fast-and slow-growing animals, and we exposed them to high and low food rations. We evaluated their energetic reserves, challenged them with a pathogenic virus, monitored daily survival and developed a mortality risk model. Although high food levels and oyster growth were associated with a higher risk of mortality, energy reserves were associated with a lower risk. Food availability acts both as an enabling factor for mortality by increasing oyster growth and as a limiting factor by increasing their energy reserves. This study clarifies how food resources have an impact on susceptibility to disease and indicates how the host's physiological condition could mitigate epidemics. Practically, we suggest that growth should be optimized rather than maximized, considering that trade-offs occur with disease resistance or tolerance.

A Sustained Immune Response Supports Long-Term Antiviral Immune Priming in the Pacific Oyster, Crassostrea gigas

“…Interestingly, interplays between metabolic reprogramming and immunity have been evidenced as an ancestral principle that could support innate immune priming in very distant organisms such as C. elegans and mammals (51,57). Previous studies have also already emphasized the potential trade-offs linked to innate immune priming notably on reproduction potential (58)(59)(60) but also between immunity and physiological status in the oyster (61). Interestingly, we observed that the elevated immune baseline in long-term priming did not systematically result in a strong secondary response when facing viral infection.…”

Latitudinal drivers of oyster mortality: deciphering host, pathogen and environmental risk factors

“…Although food availability generally improves the physiological condition of the host and lowers their susceptibility to infectious disease, reflecting a tradeoff between immunity and other functions 37,38 , food scarcity can limit the resources available to the pathogen and slow the growth and metabolism of the host on which the pathogen depends to proliferate [39][40][41] . In the context of oyster-OsHV-1 interaction, greater food availability favors the acquisition of energy reserves but overall increases mortality risk by increasing the growth and metabolism of the host 42 .…”

Microbiota Composition and Evenness Predict Survival Rate of Oysters Confronted to Pacific Oyster Mortality Syndrome

“…The farmed oyster Crassostrea gigas is heavily affected by the Pacific Oyster Mortality Syndrome (POMS) targeting juveniles (Barbosa Solomieu et al, 2015;Pernet et al, 2016). This disease is multifactorial and depends on water temperature (Petton et al, 2015), development stage (Azéma et al, 2017), and oyster diet (Pernet et al, 2019). It is also polymicrobial due to the combined development of viral and bacterial infections (de Lorgeril et al, 2018).…”