Highly pathogenic avian influenza (HPAI) is undoubtedly the greatest disease challenge facing the world’s poultry industries since the advent of velogenic Newcastle disease in the late 1920s. Despite the efforts of regulatory authorities in Southeast Asia, the infection has become endemic in many areas of the sub-Continent and occurs sporadically in Eurasia and Western Europe. The traditional approach of depleting infected flocks, imposition of quarantines and application of inactivated homologous vaccines has contained outbreaks but has not eradicated the infection.
The economic impact of H5N1 strain HPAI together with the possibility of extension to humans as a pandemic agent has stimulated research on more effective methods of diagnosis. It is axiomatic that rapid recognition of outbreaks is critical to effective containment. The time required to derive a provisional diagnosis has been successively reduced from viral isolation in eggs (four to seven days) to the application or RT-PCR (one-half day) over the past ten years. A pre-publication report on September 25th, which will appear in detail in a subsequent edition of Nature Medicine describes adaptation of advanced nanotechnology by a research group in Singapore to identify the RNA of HPAI within 30 minutes. According to the brief description of the system, the RNA of the virus collected on a tracheal swab is captured by paramagnetic particles which are transported through the test system by micropropulsion applying microfluidic technology. The system uses superparamagnetic induction in pulses to separate antigen from microdroplets. An ultra-minature PCR assay is conducted on a “lab chip”. This involves sequential concentration of RNA, washing, reverse transcription, thermcycling and assay. The entire process is conducted in a time frame of 30 minutes. Since the novel “Nano-PCR Detector” is still in the development stage, actual field testing to determine sensitivity and specificity has not been performed. It is anticipated that further refinement and scaling up to commercial production could be accomplished within two years. This will provide diagnosticians with a rapid, inexpensive and reliable test for on-farm or bed-side use.
Protection of flocks from HPAI challenge can be accomplished using an effective vaccine. Traditional inactivated oil emulsion vaccines must be administered by injection to individual birds. Genetically engineered pox-vectored vaccines provide limited protection in the presence of maternal antibody against fowlpox. A research team at the University of Maryland reported at the mid-September Northeast Conference on Avian Diseases (NECAD) meeting on a new generation of modified live-attenuated AI vaccines. Mutations in the PB1 and PB2 genes of an attenuated H5N1 AI virus were induced by genetic manipulation. A combination of in ovo administration and boosting at two-weeks post-hatch provided complete protection against challenge at 4 weeks of age using an Asian HPAI H5N1 strain. Challenge of vaccinates was not associated with viral shedding which is regarded as an undesirable sequel of mass vaccination.These examples of new technology illustrate the resourcefulness and ingenuity of research scientists in resolving the problems of emerging diseases. The application of basic principles of nanotechnology, biophysics and immunology produced the innovative diagnostic system. Extending molecular biology to genetic manipulation of the HPAI virus has resulted in a potentially effective vaccine. Continuing to support both basic and applied research will be essential if the Industry is to be supplied with new technology to control and prevent diseases of poultry and livestock.