Avian Influenza 



Many strains of avian influenza (AI) virus exist worldwide and are capable of 

 producing many degrees of the disease that vary tremendously in virulence and 

 clinical signs. These viruses affect chickens, turkeys, pheasants, quail, ducks, geese, 

 and guinea fowl as well as a wide variet)' of free-flying species. Migratory waterfowl 

 have been shown to be a natural reservoir for AI. 



AI viruses can be classified in either low-pathogenicity or high-pathogenicity forms 

 based on the severity of the illnesses they produce. Most of the highly pathogenic AI 

 viruses fall under types H5 or H7; however, most AI infections, including those typed 

 as H5 or H7, are clinically of low pathogenicity. These typically produce few or no 

 clinical signs in affected birds. Sometimes the only evidence of this virus is a minor 

 increase in bird mortality. Aside from the possible mutation of low-pathogenicity 

 strains under field conditions into high-pathogenicity strains, the presence of 

 low-pathogenicity virus can also result in restrictions on exports and serious 

 repercussions on the production economy. APHIS works to keep AI from becoming 

 established in U.S. poultry populations. 



Identifying Infected Birds 



Birds infected with the AI virus may show one or more of the following signs: 



• Sudden death without clinical signs; 



• Lack of energy and appetite; 



• Decreased egg production or soft-shelled or misshapen eggs; 



• Swelling of head, comb, eyelid, wattles, and hocks; 



• Purple discoloration of wattles, comb, and legs; 



• Nasal discharge, coughing, and sneezing; 



• Incoordination; or 



• Diarrhea. 



Epidemiology 



AI can strike poultry quickly and spread rapidly from premises to premises. 

 Migratory waterfowl can introduce the disease to U.S. poultry. International visitors 

 or smuggled birds are also risk factors. Once introduced, the disease spreads from 

 bird to bird by direct contact or through contact with contaminated manure, 

 equipment, vehicles, crates, and the clothing or shoes of individuals who have 

 come in contact with the virus. The virus remains viable in the environment for 

 long periods, particularly at lower temperatures, and it can survive indefinitely in 

 frozen material. 



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