Recognition of fatal congenital toxoplasmosis in a new-born Negro infant in Memphis, Tennessee, provided an unusual opportunity for epidemiological study. Serological tests suggested that all members of the infant's family had been exposed to a common source of infection at a fairly recent date. Brain tissues from all available animals in the immediate neighborhood were inoculated into white mice in an attempt to isolate Toxoplasma. Parasites were recovered from 7 of 35 cats (20%); from 2 of 3 domestic ducks (67%); from 3 of 7 chickens (43%); from 1 of 16 pigeons (6%); and from 7 of 121 mice, Mus musculus (6%). Of 20 mice caught in the infected family's home, five were infected with Toxoplasma, while only two of 101 mice from neighboring homes were infected. One dog collected four blocks away contained parasites, but eight others taken within a half-mile radius of the patient's home were negative. No infections were found in 22 wild sparrows and cardinals. Since all vertebrates in the area, except the wild birds, showed some degree of infection with Toxoplasma organisms, it is suggested that toxoplasmosis should be regarded as a zoonosis in which man is only one of several normal vertebrate hosts.
Located at the University of Tennessee, School of Medicine, 874 Union Avenue, Memphis, Tennessee.