Publication Abstract

New Developments in Disease Diagnostics.

COST/EUREKA Twin Event, Enkhuizen, Holland

The ability to accurately diagnose disease-causing agents is fundamental to control and eradication. The rapid growth of aquaculture worldwide has brought with it numerous health problems and prominent amongst them, diseases caused by viral, bacterial, fungal and parasitic agents. Traditional techniques for diagnosis have relied on pathogen isolation and identification, using cell culture techniques for viral pathogens and growth on various media for bacterial and fungal pathogens. The discipline of pathology has proved essential for determining the effect of these pathogens on the host and in some cases identifying non-culturable agents. Electron microscopy remains a front-line tool for visualisation of viral infections. These traditional approaches provide the foundation of diagnostic methodology in pathology laboratories worldwide but rely heavily on the skill and experience of the technicians and scientists involved.   Developments in pathogen detection based on antigen labeling and antibody detection provided highly selective techniques, which allowed detection of disease agents in situ and at low levels within the host. However, the advent of molecular approaches such as polymerase chain reaction (PCR) and DNA sequencing has provided specific tools for pathogen identification with extremely low levels of detection. PCR and the allied technique, real time PCR are also amenable for automation and are proving cost effective for large sample numbers. These approaches have also proved invaluable for epidemiological and phylogenetic studies.   Currently developing techniques where multiple pathogens can be screened using microarray technology offer tremendous potential for disease surveillance but issues of sensitivity and validation remain. Laser capture microdissection (LCMD) utilises cold laser technology at the microscopic scale and combined with the increasing ability of molecular diagnostics to work with minute samples enables us to characterise organisms even when they occur singly within tissues. For the future, developments using nanotechnology for the construction of microscopic sensing devices offer possibilities for real-time diagnostics. By these means the detection of pathogens or the earliest host immune response to them may allow extremely early intervention to prevent disease outbreaks. However, it will be important to coordinate research into new diagnostic approaches at the international level via community reference laboratories and expert networks such as the Permanent Advisory Network for Diseases in Aquaculture (PANDA).

Statements:

1. The limits of detection now possible create their own problems for interpretation e.g. clinical disease vs carrier state.
2. It is essential to coordinate developments in disease diagnosis for statutory purposes at the international level.