Highly Pathogenic Avian Influenza in the US - US - This is a report via OIE on the recent outbreak of Highly Pathogenic Avian Influenza in the US.

Date of previous outbreak of highly pathogenic avian influenza in the United States of America reported to the OIE: 1984).

Emergency report

Information received on 23 February 2004 from Dr Peter Fernandez, Associate Administrator, Animal and Plant Health Inspection Service, United States Department of Agriculture (USDA), Washington, DC:

Date of the report: 23 February 2004.

Nature of diagnosis: laboratory.

Date of initial detection of animal health incident: 17 February 2004.

Estimated date of primary infection: 15 February 2004.

Outbreaks:

Location	No. of outbreaks
State of Texas, Gonzalez County	1

Description of affected population: chickens. No biosecurity measures had been applied on the affected production unit.

Total number of animals in the outbreak:

species	susceptible	cases	deaths	destroyed	slaughtered
avi	approx. 6,600	...	...	approx. 6,600	0

Diagnosis: the infection was detected under the routine State monitoring programme for avian influenza.

A. Laboratory where diagnosis was made: Texas Veterinary Medical Diagnostic Laboratory.

Further testing (DNA sequencing and pathogenicity studies) is being conducted at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa.

B. Diagnostic tests used: serological agar-gel immunodiffusion test and real-time PCR⁽¹⁾ testing.

C. Causal agent: avian influenza virus strain H5N2. Pathogenicity details are pending. While DNA sequence analysis shows a string of multiple basic amino acids at the haemagglutinin cleavage site, which is consistent with one of the OIE definitions of high pathogenicity (see Manual of Standards for Diagnostic Tests and Vaccines, OIE, 2000), the inoculation studies in 4- to 8-week-old chickens have not resulted in any unusual mortality.

Epidemiology:

A. Source of agent / origin of infection: unknown at this time.

B. Other epidemiological details:

- Birds raised on the premises were being sold to supply the live bird markets in metropolitan areas (Houston).

- Poultry premises within a 16-km radius of the index case are being sampled and tested. To date, the premises tested within this radius are negative for avian influenza.

Control measures:

- stamping-out;

- quarantine;

- movement control inside the country;

- screening;

- surveillance.

(1) PCR: polymerase chain reaction

Note by the OIE Animal Health Information Department: The USDA has confirmed that the H5N2 strain of avian influenza in a flock of chickens in Texas is highly pathogenic.

Source: Office International des Epizooties - 27th February 2004