Assistant Professor Cal Poly Humboldt Arcata, California, United States
Abstract: Infectious diseases pose major threats to not only human health but economic sustainability and wildlife conservation. A specific research area that remains obscure is how the overall host-associated microbial community responds to pathogen invasion. In many instances, normal host-associated microorganisms can become pathogenic, resulting in co-infection dynamics that exacerbate disease outcomes.These host-microbiome-pathogen interactions, known as within-host community ecology, are typically studied by comparing microbial community dynamics between diseased and healthy hosts. We still lack a unifying framework that may allow for within-host community ecology to predict host susceptibility and co-infection outcomes. This missing framework is particularly limiting in its application to relevant wildlife and agricultural diseases. One potential avenue to facilitate the application of within-host community ecology is to identify etiological agents over the course of disease progression. Here, we aim to address this gap by studying the within-host community dynamics in an ecologically and economically important species, the Pacific Oyster Magallana gigas. M. gigas contends with OsHV-1 every summer during what are called summer mortality events or Pacific Oyster Mortality Syndrome (POMS). POMS begins with the infection of OsHV-1 and primarily affects the hemocytes, followed by changes in the oyster’s microbiota. These changes in the host microbial community have etiological effects, primarily with bacteria from the genus Vibrio. Vibrios become secondary opportunistic pathogens within the oyster, amplifying the effects of viral infection. To evaluate co-infection dynamics, I compared the abundance of Vibrio between oysters with and without the presence of OsHV-1. Infected oysters were collected from Tomales Bay, CA who were moribund during a POMS event, while uninfected oysters were collected in Humboldt Bay, CA. Viral load and change in Vibrio abundance of oysters were determined via qPCR. Results showed individual oysters with a high viral load also exhibited an increase in Vibrio abundance, suggesting a positive linear relationship between these two etiological agents. The trends presented in this study informs aquaculture management of the complete shift in microbial community, reflected by increase in Vibrio abundance, during POMS, effectively broadening the scope of potential treatments. Along with this, the findings of this study emphasize the importance of investigating how co-infections shape host-associated microbial communities. Excluding within-host ecology in disease studies gives us not only an incomplete understanding of the impacts of co-infection, but prevents us from developing solutions for mitigating disease in economically and ecologically important species.
