10 Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009 Avian infuenza: Global assessment of potential pandemic of the twenty first century M.B. Abubakar 1* , I. Aini 2** , A.R. Omar 1, 2 and M. Hair Bejo 1 1 Biologics Laboratory, Faculty of Veterinary Medicine, 2 Institute Bioscience, University Putra Malaysia UPM, 43400 Serdang Selangor DE, Malaysia. *e-mail:mustydvm@gmail.com; **e-mail:aiini@admin.edu.my Received 11 January 2009, accepted 25 March 2009. Abstract The emergence of highly pathogenic avian influenza (HPAI) of Asian lineage and the subsequent spillover to other part of the globe and on going spread of Eurasian-Africa H5N1 epidemic into domestic, wild birds and human have generated unprecedented attention in recent times and threat of potential pandemic via the avian-human link. Historically, from 1878 through 1955, fowl plaque was described as a high mortality disease of poultry in many countries throughout Europe, Asia, North and South America and Africa and the etiology was proved to be a filterable virus. In the 1930s through the 1950s, fowl plaque disappeared as an endemic disease in most part of the world. In 1949, the first report of a low virulent disease in chickens caused by LPAI virus was reported. In 1955, the etiological of fowl plaque was determined to be influenza A virus, which subsequently was identified as the H7 subtype. In 1959, a “fowl plaque-like” outbreak was described in chickens, which was the first report of fowl plaque caused by a non-H7 AI virus, i.e. first fowl plaque outbreak from H5 subtype of AI virus. In 1961 the first wild birds infection and deaths were reported in common terns of South Africa. In 1966 and 1971, the first H5 and H7 LPAI viruses, respectively were identified; prior to this period, only HPAI viruses had H5 and H7 subtypes. In 1970, the AGID serological test was introduced, which allowed easy and rapid identification of AI virus-infected poultry flocks. In 1972, there was the first isolation of LPAI viruses in asymptomatic wild birds: ducks in the United State and shorebirds in Australia. In 1981, the term “highly pathogenic avian influenza” was accepted as standard nomenclature for fowl plaque and related synonyms. In 1983, LPAI virus was observed mutating to HPAI virus during LPAI field outbreak, and specific genomic changes were identified in the proteolytic cleavage site of the hemagglutinin responsible for the virulence change. In the late 1980s and early 1990s, molecular criteria were added to the definition for classifying an AI virus as HPAI. In 2002, there were the first reported infections and deaths in a wide variety of wild bird species from AI virus H5N1 HPAI virus. The primary goal of this review is to highlight the global situation of HPAI and provide baseline information to show the potential pandemic nature of the virus, so that control and prevention strategies can be improved. Key words: Highly pathogenic avian influenza (HPAI), H5N1, fowl plaque, LPAI virus, Global trend. www.world-food.net Journal of Food, Agriculture & Environment Vol.7 (2) : 10-19. 2009 WFL Publisher Science and Technology Meri-Rastilantie 3 B, FI-00980 Helsinki, Finland e-mail: info@world-food.net Introduction Avian influenza (AI) virus is a global virus that knows no geographic boundaries nor does it have any political agenda. AI viruses or evidence of their infection has been detected in seventeen taxonomic orders of birds irrespective of their agricultural or other anthropocentric systems on all the seven continents. These include Anseriformes (ducks, geese, swans); Casuariiformes (emu), Charadriiformes (turnstones, sandpipers, gulls, terns, puffins, guillemots); Ciconiiformes (herons, ibis); Columbiformes (doves); Falconiformes (raptors); Galliformes (chickens, turkeys, quail, pheasant, guineafowl, partridges); Gaviiformes (loons); Gruiformes (coots, moorhen); Passeriformes (mynahs, finches, weaverbirds); Pelecaniformes (cormorant); Piciformes (woodpecker); Podicipediformes (grebe); Procellariiformes (shearwater); Psittaciformes (parrots, cockatoos, parakeets); Rheiformes (rhea); Struthioniformes (ostrich) 37, 109, 128 . However, report of AI infections or disease in domestic and other birds vary with individual countries, regions and continents. The reported frequency of AI is greatly skewed by the availability of diagnostics, quantity of surveillance conducted, the type of birds and production sector tested, the time of year, geographic location, climatic conditions, and other undefined factors. Because influenza is an international efforts and cooperation 122 . Understanding the global nature of AI has to do with the recognition of the changing definition of AI infections and the diseases they cause, based on scientific development in diagnosis and the new knowledge in the ecology, epidemiological dynamics over the past 125 years. Three major events have changed the definition of avian influenza and thus impacted the reported frequency of AI in the world: (1) early diagnosis of fowl plaque in domestic poultry was based primarily on clinical features, lesions and animal studies; (2) recognition of LPAI viruses and their infections in domestic poultry based on serology and virus isolation; and (3) discovery of AI in asymptomatic wild birds reservoirs 27, 128 . Historically, AI is of relatively recent description in the poultry health literature with historical records reporting the first case of AI as a highly lethal, systemic disease of chicken in Italy during 1878, that is HPAI 90 . This systemic disease of chickens has most frequently been termed fowl plaque, fowl pest, but other names have been used, including pest aviaire, Geflügelpest, typus exudatious gallinarum, Brunswick bird plaque, Brunswick disease, fowl disease, fowl or birds grippe, and others 111, 112, 124 . The uniform