A note on the serology of sarcosporidiosis and toxoplasmosis.

Serological methods for the diagnosis of toxo-plasmosis have received considerable attention since the first authentic report of a fatal infection in a human infant (Wolf, Cowen, and Paige, 1939). The complement fixation reaction (Warren and Sabin, 1942) and the dye test (Sabin and Feldman, 1948) are now recognized as the two best methods of detecting the disease. Serological studies in sarcosporidiosis have not, however, been given the same amount of attention, although this infection has a much longer history than that of toxo-plasmosis. For example, organisms designated as sarcosporidial in nature were described in the laryngeal muscle cells of a human patient (Baraban and Saint Remy) as long ago as 1894. Similar aggregations have since been described in isolated human patients in the muscles of tongue, biceps, heart, etc., and these have usually been given the specific name of Sarcocystis lindemanni (Rivolta). The discovery that chronic toxoplasmic infections are often associated with the formation of " pseudocysts " containing large numbers of organisms not only in nervous tissue but in skeletal and heart muscle adds to the suspicion that some reported cases of sarcosporidiosis in man and animals might in fact be cases of toxo-plasmosis. Different investigators give different dimensions for these organisms. " Sarcosporidial spores " described in human infections range from 8 to 9 ,u long (Baraban and Saint Remy, 1894) to 4.25 p long (Darling, 1909, 1919). While it seems unlikely that organisms regularly of the first dimensions are Toxoplasma, suspicion arises in the case of smaller organisms. The issue is complicated by the fact that in some of these reports the " septa" and enclosing membrane associated with the more typical sarcosporidial cysts could not be demonstrated. Kean and Grocott (1945) concluded that in the absence of inoculation and serological studies the absolute identification of these two parasites is impossible. In October, 1951, Muhlpfordt used the Sabin-Feldman dye test in an endeavour to differentiate between infections of Toxoplasma and Sarcocystis. " Miescher's tubes " (sarcosporidial cysts) recovered from gullet muscles of sheep or goats were inoculated per os or intraperitoneally into guinea-pigs, rats, and hamsters, and the serum of these animals was tested by the dye test against toxoplasms. In all cases, preliminary tests made before the inoculation with sarcosporidia produced negative results, but after the infection was allowed to establish itself the animals reacted positively , thus suggesting that antibodies reacting with the toxoplasms were …