Stephen M. Kritsick, 42, veterinarian on "Good Morning America." Educated at Michigan State University and Angell Memorial Animal Hospital in Boston, Kritsick worked in New York's Henry Bergh Memorial Hospital of the ASPCA, the Animal Medical Center and the Bide-A-Wee Home Assn. He had also served as staff veterinarian and national spokesman for the Humane Society of the United States and, with the title of animal science editor, was a regular contributor to ABC's morning talk program. Kritsick was the author of the advice book "Dr. Kritsick's Tender Loving Cat Care" and the novel "Creature Comforts." On Sunday in Lexington, Mass., of AIDS.