A mysterious disease hit waterfowl in west Iran, leaving thousands of dead birds, the cause is still unknown, the World Organization for Animal Health (OIE) said in Paris on Thursday.
"A high mortality has been observed among wild waterfowl in Poldasht (in West Azerbaijan province)" said the Paris-based organization on its website.
It noted that there was no pathological agent identified nor particular lesion appeared at the autopsy and that weakness and death are only signs of this affection.
The OIE said a total of 3,673 wild waterfowl had died since the phenomenon was found on Oct. 2, said the Iranian authorities, which have quarantined the region.
Iranian veterinary services are asked for test over bird flu research and further information about the disease.