A Revision of the Coccidia Parasitic in Man

Abstract

From a study of the organisms themselves, so far as this has been possible, and from an analysis of all accessible records relating to them, I conclude that there are four distinct species of coccidia which may parasitize man. These are: (1) Isospora hominis Rivolta, 1878 (emend.), discovered by Kjellberg in 1860. and recently investigated by Wenyon; (2) Eimeria wenyoni n.sp., a form discovered in 1915 by Wenyon; (3) Eimeria oxyspora n.sp., another new form, here described for the first time; (4) an undetermined species of Eimeria (?) which was discovered by Gubler in 1858. This last inhabits the human liver, whilst the three others probably live in the small intestine. Probably some seventy cases of infection with the Isospora have now been seen, mostly in persons who have been in the Near East; but the other parasites appear to be extremely rare, and little is known concerning their probable geographical distribution.All these parasites are probably peculiar to man. There is no evidence that any of them is or can be parasitic in any other host. The prevailing belief that the coccidia of man are identical with those of rabbits, cats, or dogs, is therefore unfounded. Furthermore, there is as yet no good evidence to show that man may harbour any species of coccidia other than the four just enumerated. All these forms, however, require fuller investigation. They are here briefly and incompletely described from the data at present available.There is at present no proof that the coccidia of man—with the probable exception of the species occurring in the liver—can produce a clinically recognizable pathological condition of “coccidiosis”: and as yet no method of treatment which will eradicate an infection with any species has been discovered.