Psittacosis (“Parrot Fever”)
Charles Armstrong’s next major investigative challenge, which also became
potentially life threatening for him, occurred in the winter of 1929-1930. He was still
engaged in the experimental study of the effects of vaccinia virus pneumonia and the
pathology of generalized vaccinia in rabbits with his colleague, pathologist Ralph D.
Lillie (1, 2). He also continued to formulate his hypothesis about the etiology of post-
vaccinal encephalitis (3). Dr. George W. McCoy, Director of the Hygienic Laboratory,
called upon Armstrong to study the new public health problem caused by infected parrots
and other psitticine birds (parakeets, cockateels, love birds and others). Armstrong was
able to identify initially that the agent did not grow on ordinary media for culturing
bacteria, that it was not filtered by the various size bacteriologic filters, that the tissues
and excreta from infected parrots were highly infectious for other healthy parrots,
laboratory animals and humans. On the basis of these observations he was able to
recommend highly effective quarantine provisions to prevent the importation of sick and
infectious parrots.
Ritter, a Swiss scientist, first described psittacosis in 1879 (4). Ritter reported the
disease after a Swiss family who kept parrots and finches experienced severe illness in 5
family members and 2 visitors 3 weeks after one of the birds died. Three of the
family/visitors died of their illnesses. Isolated reports of the disease occurred in the
world’s medical literature after Ritter’s report. In 1892 E. Nocard isolated an organism
from the wings of parrots during an outbreak in Paris. Nocard identified the organism as a