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New Solution: Assessing aquatic organism health status non-invasively

09 October 2018

Researchers at the University of Naples Federico II have developed a non-invasive, cost efficient method to detect and identify potential pathogens (viruses, bacteria, protozoa, metazoa, parasites) in aquatic facilities. The eDNA metabarcoding technology enables improved identification of pathogens in local and imported animals without having to sacrifice sentinel animals. This supports quarantine and bio-security measures and prevents potential pathogens spreading to healthy animals, leading to enhanced animal welfare.

Collaborators are sought in any sector using aquatic animal health monitoring to assess and validate this approach technology against current practice. Networks of multispecies aquatic facilities able to provide samples and access to facilities would be valuable for validation studies.  Input from partners who could develop and validate software, to contain searchable DNA sequences of pathogens, would also be welcomed.

The presence of pathogens is routinely used as a measure of animal health in aquatic facilities. Panels of species-specific pathogens and protocols for their identification are available for assessing the health of some species, i.e. zebrafish, Xenopus, and to a lesser degree, Cephalopods. These approaches often use pre- and post- filtration sentinels, moribund fish and symptomatic animal groups, and require samples to be taken from the animals (e.g. necropsy and histopathology of tissues and organs). This eDNA metabarcoding technology uses eDNA extracted from water samples collected, from pre- and post-filtration tanks on each rack (in a recirculating system) during routine facility monitoring. The eDNA is amplified by PCR using primers either specific for a target species or generic for multiple-taxon analysis and then sequenced. The obtained sequences are compared to the GenBank international reference database using bioinformatics tools to identify pathogens. A gap remains between detection of a microbe in the environment and the impact of the potential pathogen on animals, but increased use of this technology will lead to an increased understanding of the links between a microbe's prevalence and an animal's disease. 

This technology has the potential to better assess the presence of pathogens in aquatic facilities, which prevents the movement of animals with subclinical infections that could become lethal upon stress induced by transport and avoids spread to the new facility. This could reduce the number of animals required at the scale of colony management because, due to reduced mortality and morbidity, sentinel fish are required in fewer numbers. In the technology developer’s zebrafish facility, application of this technology has reduced the number of sentinels required from 12 to six animals. Scaled up across aquatics facilities globally this would represent a substantial reduction in animal use. For example, in the UK alone there are around 100 aquatic facilities and if they each use at least 12 sentinels, there is the potential to reduce the number of sentinel animals required across the UK by 600 for each health assessment screening.

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