474 



PROTOZOOLOGY 



nucleus appears as a clear circular area; when the faecal specimen 

 is kept in a covered container at the room temperature, the proto- 

 plasmic mass divides into 2 spherical sporo blasts in about 24 hours 

 (Fig. 220, 3) each sporoblast develops in another 24 hours into a 

 spore (10-16m by T-lO/z) containing 4 sporozoites (4). Further 

 changes take place when the oocyst finds its way into the human in- 

 testine in contaminated food or water. 



/. hominis has been observed in widely separated regions, but 

 appears not to be of common occurrence. Magath (1935) reviewed 

 the reported cases up to 1935. As to its effect on the human host, 

 very little is known. Connal (1922) described the course of an acci- 

 dental oral infection by viable mature oocysts, as follows: The 



Fig. 220. Isospora hominis, X1150 (Kudo). 1, a young oocyst; 2, an 

 oocyst in which the protoplasmic mass has contracted; 3, an oocyst with 

 2 sporoblasts, one of which shows the division of content; 4, a mature 

 oocyst with 2 tetrazoic spores. 



incubation period was about six daA-s, the onset sudden, and the 

 duration over a month. The cure was spontaneous. The symptoms 

 were diarrhoea, abdominal discomfort, flatulence, lassitude, and loss 

 of weight. During the first three weeks of the illness no oocysts were 

 found, but then oocysts appeared in the stools for nine days. On the 

 10th day they were not seen, but reappeared on the 11th and 12th 

 days, after which the}' were not found again. The acute signs of ill- 

 ness abated within one week of the finding of the oocysts. The faeces 

 contained a large amount of undigested material, particularly fat 

 which gave it a thick oily consistency, showing signs of slow gaseous 

 formation. 7. hominis is to be considered as pathogenic to man 

 (coccidiosis) ; but although it gives rise to illness in some cases, the 

 coccidian causes no serious disturbances in most instances. 



/. higemina (Stiles) (Fig. 219, .s). In the gut of cat and dog; oocysts 

 10-14m by 7-9fi. 



