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Research Project: Examining the Interrelationships Between Virulent Aeromonas Hydrophila and the Microflora of Farmed Catfish

Location: Aquatic Animal Health Research

Project Number: 6010-32000-026-10-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 3, 2017
End Date: Jul 2, 2020

Objective:
Since 2009, severe outbreaks of motile aeromonas septicemia (MAS), caused by a new virulent strain of Aeromonas hydrophila (vAh), have resulted in substantial annual mortalities in the catfish farming regions of west Alabama and East Mississippi. The strain has been sequenced and genetically characterized, yet it remains unclear why vAh exhibits such high pathogenicity in the field while only induces a mild MAS under laboratory conditions. One of the possible explanations is that catfish cultured under commercial practices present an abnormal microbiome (dybiosis) allowing opportunistic pathogens, such as vAh, to overwhelm host defenses. The relationship between dysbiosis and disease has been proven in numerous vertebrate hosts including fish. The Cooperator has conducted extensive studies on fish microbiomes (both gut and skin microbiomes) and, recently, they have characterized how the gut microbiome develops in channel catfish. However, their data came from wild fish or from experimental fish reared under optimal conditions. The objective of this project is to characterize the temporal gut and skin microbial communities of channel and hybrid catfish reared under intensive production practices in west Alabama. In addition, we will characterize the microbial communities associated with pond water, biofilms, sediment, and feed throughout a production cycle. We anticipate the discovery of patterns associated with vAh outbreaks that can be used to predict and control disease outbreaks on farms.

Approach:
In collaboration with the School of Fisheries, Auburn University, we will characterize the catfish (gut and skin) microbiome throughout the growing season. We will focus our efforts on producers that have experienced losses due to vAh in the past and we will use farms that have never experienced outbreaks as controls. Samples will be collected and analyzed as previously pioneered by cooperator's group. A next generation sequencing approach will be used characterize the microbial communities present in each sample. Cooperator's group has developed a pipeline to analyze pyrosequencing data and run appropriate parametric and non-parametric statistical tests to identify significant differences among and between those communities.