Epidemiology of Avian Influenza - 0 views
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Avian influenza (AI) is caused by specified viruses that are members of the family Orthomyxoviridae and placed in the genus influenzavirus A
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There are three influenza genera - A, B and C;
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Domestic fowl, ducks, geese, turkeys, guinea fowl, quail and pheasants are susceptible.
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Disease outbreaks occur most frequently in domestic fowl and turkeys. A particular isolate may produce severe disease in turkeys but not in chickens or any other avian species. Therefore, it would be impossible to generalize on the host range for avian influenza, for it will likely vary with the isolate. This assumption is supported by reports of farm outbreaks where only a single avian species of several species present on the farm became infected. Many species of wild birds particularly water birds and seabirds - are also susceptible, but infections in these birds are generally sub-clinical.
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athogenic strains could emerge and cause disease in domestic poultry in any country at any time without warning. In fact, outbreaks have occurred at irregular intervals on all continents.
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he most serious outbreaks in recent times have been reported in Hong Kong 1997-1998 and 2003, Chile 2002, The Netherlands 2003 and South East Asia 2004-2006.
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he incubation period is 3 to 5 days in general but may be longer. Maximal incubation period is 21 days as defined by the OIE Terrestrial Animal Health Code.
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Inactivated quality assured oil-emulsion vaccines have been demonstrated to be effective in reducing mortality, preventing disease, or both, in chickens and turkeys. These vaccines, however, may not prevent infection in some individual birds, and if infected could shed virulent virus. Nevertheless, the amount virus shed is considerable less than that of non-vaccinated and infected birds. It is imperative that the circulating antigenic avian influenza virus is known and the vaccine represent this antigenic strain, since there is no cross-protection among the 15 known HA subtypes.
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Birds that die of peracute disease may show minimal gross lesions, consisting of dehydration and congestion of viscera and muscles.
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The following diseases must be considered in the differential diagnosis of virulent AI: Other diseases causing sudden high mortality Newcastle disease infectious laryngotracheitis duck plague acute poisonings
