Updated: 22/04/2002

Highly pathogenic avian influenza

 Aetiology  Epidemiology  Diagnosis  Prevention and control  References 

AETIOLOGY

Classification of the causative agent

Virus family Orthomyxoviridae, genus Influenzavirus A, B. To date, all highly pathogenic isolates have been influenza A viruses of subtypes H5 and H7

Resistance to physical and chemical action

Temperature: Inactivation by 56C/3 hours; 60C/30 min
pH: Inactivated by acid pH
Chemicals: Inactivated by oxidising agents, sodium dodecyl sulphate, lipid solvents, -propiolactone
Disinfectants: Inactivated by formalin and iodine compounds
Survival: Remains viable for long periods in tissues, faeces and also in water


EPIDEMIOLOGY

Hosts

Transmission

Sources of virus

Occurrence

Apathogenic and mildly pathogenic influenza A viruses occur worldwide. Highly pathogenic avian influenza A (HPAI) viruses of the H5 and H7 HA subtypes have been isolated occasionally from free-living birds in Europe and elsewhere. Outbreaks due to HPAI were recorded in the Pennsylvania area, USA, in the years 1983-84. More recently outbreaks have occurred in Australia, Pakistan and Mexico. There is evidence that H5 viruses of low pathogenicity may mutate and become highly pathogenic. HPAI infections are very rarely seen, and should not be confused with viruses of low pathogenicity, which may also be of H5 or H7 subtypes

For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin

DIAGNOSIS

Incubation period is 3-5 days

Clinical diagnosis

Lesions

Chickens

The lesions in turkeys are similar to those in chickens, but may not be as marked. Ducks infected with HPAI and excreting the virus, may not show any clinical signs or lesions

Differential diagnosis

Laboratory diagnosis

Procedures

Identification of the agent

Serological tests

Samples

Identification of the agent

Serological tests

PREVENTION AND CONTROL

No treatment

Sanitary prophylaxis

In outbreaks

Medical prophylaxis

REFERENCES AND OTHER INFORMATION

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