256 



KLOSSIELLA AND HEPATOZOON 



inflammatory reaction. No fatal infec- 

 tions have been reported. 



Klossiella cobayae Seidelin, 1914 

 occurs sporadically in the guinea pig 

 thruout the world. Each microgametocyte 

 forms 2 microgametes. Each sporont 

 forms 30 or more sporocysts, each of 

 which contains about 30 sporozoites. K. 

 cobayae is apparently non-pathogenic and 

 produces slight if any pathologic changes 

 in the kidney. However, it may be en- 

 countered in sections of the kidney or 

 other organs which are being examined 

 for something else, as C. C. Morrill and 

 I (unpublished) did in some guinea pigs at 

 the University of Illinois. 



FAMILY HEPATOZOIDAE 



In this family the zygote is active (an 

 ookinete), secreting a flexible membrane 

 which is stretched during development. 

 The life cycle involves 2 hosts, 1 of which 

 is vertebrate and the other invertebrate. 

 The parasites are found in the cells of 

 the circulatory system of vertebrates and 

 of the digestive system of invertebrates. 

 The oocysts are large and contain many 

 sporocysts, each with 4 to 12 or more 

 sporozoites. There is a single genus, 

 Hepatozoon. 



Genus HfPATOZOON Miller, 1908 



In this genus schizogony takes place 

 in the viscera of a vertebrate, and the 

 gametocytes are either in the leucocytes 

 or erythrocytes, depending on the species. 

 Fertilization and sporogony occur in a 

 tick, mite, louse, tsetse fly, mosquito or 

 other blood-sucking invertebrate, de- 

 pending again on the species. The micro- 

 gametocyte forms 2 microgametes. A 

 synonym of this generic name is Leucocy- 

 togregarina . 



Species of Hepatozoon have been 

 described from mammals, reptiles and 

 birds. They ai-e especially common in 

 rodents. 



The vertebrate hosts become infected 

 by eating the invertebrate hosts. The 



sporozoites are released in the intestine, 

 penetrate its wall and pass via the blood 

 stream to the liver, lungs, spleen or bone 

 marrow; different species prefer different 

 organs. The sporozoites enter the tissue 

 cells and become schizonts, which divide 

 by multiple fission to produce a number of 

 merozoites. There are several asexual 

 generations in the visceral cells, but their 

 number is known in only a few cases. The 

 last generation merozoites enter the blood 

 cells and become gamonts. These look 

 alike; presumably the female is a macro- 

 gamete and the male a microgametocyte, 

 but no evidence is available on this point. 



No further development takes place 

 until the parasites reach the alimentary 

 tract of the intermediate host. The ga- 

 monts then leave their host cells, asso- 

 ciate in syzygy, and the microgametocyte 

 forms 2 non-flagellate microgametes. 

 These are relatively large, but smaller 

 than macrogametes. One of them ferti- 

 lizes the macrogamete, and the resultant 

 ookinete penetrates the intestinal wall and 

 comes to lie in the haemocoel. Here it 

 grows considerably and becomes an oocyst. 

 Several nuclear divisions take place in the 

 sporont within the oocyst wall. The daugh- 

 ter nuclei migrate to its periphery, and 

 each one buds off to form a sporoblast, 

 leaving a large residual mass. The sporo- 

 blasts then form a wall around themselves, 

 becoming sporocysts. Sporozoites develop 

 in the sporocysts, their number depending 

 on the species. When the vertebrate host 

 ingests the invertebrate one, the oocysts 

 and sporocysts rupture in its intestine, 

 releasing the sporozoites. 



It is possible that trans-placental in- 

 fection may also occur, at least in some 

 species. At any rate, Clark (1958) found 

 a full-blown infection with H. i^riseisciuri 

 in a 36-hour-oId grey squirrel which had 

 been born in a mite-free environment. 



HEPATOZOON CAMS 

 (JAMES, 1905) 



Synonyms : Leucocylozoon cauls, 

 Hac'Diogyegarina caiiis, Haeniogregarina 

 yolundata, HacDiogregariiia chatloiii, 

 Hepatozoon felis . 



