Plasmodium japonicum,P. juxtanucleare and P. nucleophilum in the Far East*

SYNOPSIS. Plasmodium japonicum and P. juxtanucleare are two very similar species of avian malaria parasites. The former was discovered in domestic fowl in Japan, and the latter in the same host species in Brazil; it has since been found in chickens in Uruguay, Mexico, and Ceylon. The present study, based on a Ceylon strain of P. juxtanucleare and slides from the Bamboo Partridge (Bambusicola thoracica sonorivox) of Taiwan indicates that the latter host is a natural reservoir of P. juxtanucleare, since this species appears to differ in no significant way from P. japonicum. Infection is common in the Bamboo Partridge (5 of 26 birds showed it), but it has not so far been found in any other avian species, although a total of 973 birds, belonging to 17 orders, 45 families, 110 genera, and 183 species, have been examined from this area. Since the younger stages of Plasmodium nucleophilum look very much like similar stages of P. juxtanucleare, they are compared. The older stages however are usually easily distinguishable, and the former species is so far known only from non-gallinaceous birds whereas the latter appears to be limited to gallinaceous ones.