Diagnosing Avian Influenza in the Framework of Wildlife Surveillance Efforts and Environmental Samples

Prior to the ongoing Asian H5N1 epizootic, it was believed that highly pathogenic avian influenza (HPAI) was a disease of domesticated birds and that wild birds could act only as reservoirs for the low pathogenic form (LPAI) of these viruses. The unprecedented situation in Asia during 2004 and 2005 revealed spillover of HPAI H5N1 infection to naïve populations of wild birds. To date the role wild birds may play in the ecology and epizootiology of HPAI H5N1 appears very different to that in other HPAI epizootics, and is far from being completely understood. Recent outbreaks in Russia and Central Asia, Europe, and Africa indicate transboundary spread of HPAI H5N1. Isolation of the virus from wild birds in Eurasia led to speculation that wild birds may play a role in introducing and possibly secondarily spreading the infection to disease-free areas. Several diagnostic methodologies are available to detect avian influenza infection. Generation of reliable data requires the most appropriate diagnostic approach specific to the aim of the surveillance program and ecology of the virus in both the target population and the environment. Harmonized diagnostic strategies for detection of HPAI H5N1 must be developed and followed worldwide in order to make results comparable and useful to the international scientific community. The OIE/FAO Reference Laboratory in Padova, Italy is involved in extensive surveillance of wild birds sampled in Europe, Africa, and the Middle East. Using results of this program, we developed a set of diagnostic guidelines that could be a basis for a harmonized approach by diagnostic laboratories.