C. Dobell 
185 
examined at a base hospital in Mesopotamia, they found seven infected with 
Isospora. Finally, O’Connor 1 has found nine more infected cases in Egypt and 
Sinai among British troops and natives, of whom he examined some 3800 in 
1916 and 1917. 
Castellani (1917) states that “coccidiosis is, comparatively speaking, 
common in the Balkans,” and mentions that he has seen “six cases, all in 
Macedonia.” It is possible that these too were Isospora infections, but in the 
absence of any further information it is impossible to ascertain what organisms 
he studied. 
Sangiorgi (1918) has quite recently described a case—a soldier suffering 
from nephritis—in which he believes he has found Isospora bigemina. The 
oocysts were found in the faeces, and bodies interpreted as schizogonic stages 
in the urine. It seems probable that this patient was really infected with 
I. hominis, though from the dimensions of the parasites—if they are correctly 
stated—this is doubtful. They can hardly have been I. bigemina, as the author 
believes. The “stages” found in the urine seem also open to question. 
It will thus be seen that about seventy cases of infection with Isospora 
hominis have now been definitely recorded: and to this list several doubtful 
cases, both ancient and modern, should possibly be added. It is noteworthy 
that all the infections recorded since 1915 have been found in men who had 
been in Egypt, Gallipoli, Salonika, or Mesopotamia: The “dysentery” cases 
invalided to England from Gallipoli in 1915 showed a fairly high percentage 
of infection with I. hominis —2-7 per cent, in Wenyon’s (1916) original series— 
but since then the infection has apparently disappeared in this country, even 
from among the same class of cases. At all events, I have not found the 
oocysts of Isospora in the faeces of any patients from Gallipoli or elsewhere 
since 1916, and inquiries which I have made of others have likewise failed to 
elicit a single case of infection in the patients invalided to this country during 
the last two years. 
In most of the cases infected with Isospora the infection appears to have 
been small and transitory. An extreme instance is a case studied by Dr 
Stevenson and myself (1917), in which the stools were examined—sometimes 
most exhaustively—on six occasions, and only a single oocyst was ever found. 
Heavy infections appear to be uncommon, but have been found by Wenvon 
(1916), Roche (1917), Cragg (1917), and O’Connor. Roche (1917) states that 
“as a rule these parasites disappeared within a few days, but in one patient 
they were found in daily examinations for three weeks.” 
Pathogenicity. There is, up to the present, no proof that /. hominis is a 
pathogenic parasite. Since it is, like all other coccidia, an organism which lives 
at the expense of the tissues of its host, it is clear that it may be able to produce 
a pathological condition: nevertheless, even in the most heavily infected cases, 
1 Capt. F. W. O’Connor, R.A.M.C., has very kindly permitted me to record this and other 
information (contained in the present section, and attributed to him) from his still unpublished 
work. 
