ABOVE: An electron microscope built in the 1960s
WIKIMEDIA COMMONS
Dead baby chicks from farms began arriving by the dozens at the vet labs of North Dakota Agricultural College in Fargo in 1930. Chicken farmers also brought in their sick chicks, many of which were gasping for air. Others were listless and seemingly depressed, with drooping wings and emaciated bodies. In 20 years of lab and field research, vets Arthur Schalk and Merle Hawn had never seen a chicken disease quite like this one. It ripped through poultry farms in North Dakota and Minnesota that year, killing tens of thousands of baby birds. Based on necropsies of the dead birds, the vets ruled out laryngotracheitis, commonly called the croup, as a cause of death (JAVMA, 78:413–22, 1931). In that disease, lesions appear in the windpipe, but in these chicks, tissue damage was found farther down, deep in the lungs. The ...
