Information received on 5 March 2003 from Dr Frederik H. Pluimers, Chief Veterinary Officer, Ministry of Agriculture, Nature Management and Fisheries, The Hague:

End of previous report period: 2 March 2003 (see Disease Information, 16 [10], 58, dated 7 March 2003).

End of this report period: 5 March 2003.

Nature of diagnosis: clinical and laboratory.

Date of initial detection of animal health incident: 28 February 2003.

Estimated date of first infection: 21 February 2003.

Outbreaks:

Description of affected population in the outbreaks: laying hens / free range poultry holdings.

Total number of animals in the outbreaks:

Diagnosis:

A. Laboratory where diagnosis was made: Central Institute for Animal Disease Control (CIDC), Lelystad.

B. Diagnostic tests used: virus isolation in embryonated fowl eggs, haemagglutination inhibition test.

C. Causal agent: Highly pathogenic avian influenza virus subtype H7. For outbreak No. 03/01, nucleotide sequencing has demonstrated the presence of multiple basic amino acids at the cleavage site of the haemagglutinin.

Epidemiology:

A. Source of agent / origin of infection: the type of strain isolated on one of the infected holdings and the fact that both of the holdings had free-housing facilities strongly suggests introduction via waterfowl.

B. Mode of spread: possibly by indirect contact with waterfowl.

Control measures during reporting period:

- quarantine, and movement control inside the country;

- stamping out;

- screening;

- zoning;

- Outbreak 03/01 and outbreak 03/02 were culled on 5 March 2003;

- All carcasses are being destroyed by incineration.

Source: OFFICE INTERNATIONAL DES EPIZOOTIES - 7th March 2003