Texas Veterinarian Helped Crack the Mystery of Bird Flu in Cows

The first calls that Dr. Barb Petersen received in early March were from dairy owners worried about crows, pigeons and other birds dying on their Texas farms. Then came word that barn cats — half of them on one farm — had died suddenly.

Within days, the Amarillo veterinarian was hearing about sick cows with unusual symptoms: high fevers, reluctance to eat and much less milk. Tests for typical illnesses came back negative.

Petersen, who monitors...