LANCASTER, Pa. — They saved Petunia first. She was the second cow. Her brother Louie had died within hours of his birth. But over two harrowing, sleepless nights, the three researchers kept Petunia alive to wheel her from the barn to the veterinary hospital and inject her with a virus carrying new genes.
Petunia had a bovine form of maple syrup urine disease (MSUD), a life-threatening condition that is also unusually prevalent within the Mennonite community here. The goal wasn’t to save the 79-pound calf. That would be a bonus. The goal, for Kevin Strauss, was to prove that an MSUD gene therapy could work — that after two decades he could finally offer the desperate families who entered his medical clinic here a simple, one-time fix.
It worked. Today, Petunia is a feisty, 5-year-old, hay-munching, 1,500 pound heifer. Yet not a single one of Strauss’s patients has received the treatment that saved her life, not even in a clinical trial.

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