Two consignments of birds, one warehouse, and a ticking clock

The tale of the dead parrot began at Heathrow airport in September when a consignment of 148 exotic birds destined for the pet trade arrived by air freight from the former Dutch colony of Surinam in South America.

Customs officials and border post inspectors at the airport's animal reception centre checked the consignment before sealing the bird crates ready for their transport by road to a private quarantine facility in Essex.

Although the crates containing the birds were sealed, they were not airtight and the birds could breathe fresh air freely during the three-hour journey around the M25 to their final destination.

On arrival in Essex, a private vet working for the Department for Food, Environment and Rural Affairs checked the seals on the containers before the birds were recaged in the licensed quarantine facility of the private importer, whose name has not been released.

That happened on 16 September, when the quarantine clock started. European regulations state that imported "captive" birds, which may in fact have been caught in the wild, have to be kept under lock and key for at least 30 days. But a week later the importer legally introduced a consignment of 216 exotic birds described as "soft bills", meaning they eat soft food rather than seeds, from Taiwan. Both consignments shared the same "air space".

Under the "co-terminus" quarantine rule, which allows birds from different parts of the world to be quarantined together, the 30-day clock had to be reset to zero so that all birds spent a full month in quarantine.

Defra officials are still trying to piece together exactly what happened during the next few weeks, but from the information available it appears that two birds died, one of them being the parrot that raised the initial alarm. The identity of the second bird - and even to which consignment it belonged - was still being assessed yesterday, Defra said.

However, tissue material from both dead birds was pooled together and tested for avian flu virus using a highly sensitive method, PCR, which is capable of detecting just one molecule of the virus.

The initial results, released on Friday was that one or both of the dead birds were infected with the H5 strain of avian flu. Further tests by the Veterinary Laboratories Agency in Weybridge, Surrey, identified it as the deadly H5N1 strain, and even matched it to a recent outbreak in Chinese ducks.

Thats indicated the parrot from Surinam was free of the virus when it arrived at Heathrow and became infected while it was in quarantine with the birds from Taiwan, which has reported avian flu in domestic poultry.

If none of the birds had died, the vet in charge would have tested "sentinel" birds - healthy chickens kept in the same facility - for avian flu virus before sanctioning their release to pet shops.

Testing each bird for avian flu is expensive and not normal, except for high-value birds. The Essex importer had opted for the cheaper method of using sentinel birds.

Defra officials are now trying to assess what symptoms if any were shown by the Taiwanese birds. Some of these birds also died in quarantine but as yet nobody is quite sure what they died of.

Virologists at the Veterinary Laboratories are "pooling" tissues samples from batches of the culled birds to test for the presence of the virus. It is their hypothesis that the soft bills from Taiwan were infected with the lethal H5N1 strain.