In this family, the zygote is not motile. A typical oocyst is not formed, but a number of sporocysts each containing many sporozoites develop within a membrane which is perhaps laid down by the host cell. Each microgametocyte forms 1 to 4 non-flagellated microgametes. The life cycle involves a single host, gametogony and schizogony occurring in different locations. There is a single genus, Klossiella.
This genus has the characters of the family. Infection takes place by ingestion of sporulated sporocysts, and the sporozoites pass into the blood stream and enter the endothelial cells of the capillaries and arterioles of the kidneys, lungs, spleen and other organs. Here they turn into schizonts, and these then produce merozoites. There are probably several asexual generations.
Eventually some merozoites enter the epithelial cells of the convoluted tubules of the kidney, where they become gamonts and where gametogony and sporogony take place. A macrogamete and microgametocyte are found together in syzygy within a vacuole in the host cell. The microgametocyte divides to form 2 to 4 microgametes, one of which fertilizes the macrogamete. The resultant zygote (sporont or mother sporoblast) divides by multiple fission to form a number of sporoblasts. Each of these develops into a sporocyst containing 8 to 25 or more sporozoites. The sporocysts are enclosed within a membrane, but all authorities do not agree whether it is a true oocyst or simply the remnant of the host cell.
The sporocysts are released into the lumen of the kidney tubules by rupture of the host cell, and pass out in the urine.
Synonym: Eimeria utinensis (?).
Hosts: Horse, ass.
Geographic Distribution: Europe, Turkey, North America.
Prevalence: Unknown. This species has been encountered only in the course of histopathologic examinations of the kidney for some other reason. Baumann (1946) found it in the kidney of a horse from Hungary which had died of pneumonia, Seibold and Thorson (1955) found it in the kidney of a jackass in Alabama which had died of spinal injuries incurred while he was being roped. Akcay and Urman(1954) found it on histopathologic examination of the kidneys of 72 out of 117 donkeys in the course of an experiment on infectious anemia.
Morphology: The stages in the kidney are the only ones known. These are found in the epithelial cells lining the thick limbs of Henle's loops in the medullary rays. Schizonts and merozoites have not been recognized. The macrogametes and microgametocytes develop in syzygy. The latter form 4 microgametes (Baumann, 1946). After fertilization, the zygote grows to 38 to 46 by 32 to 39 u and produces a large number of sporoblasts by multiple nuclear fission followed by budding from a large, central residual mass. Each sporoblast develops into a sporocyst. The fully developed "oocysts" are thin-walled sacs 50 to 90 by 35 u containing as many as 40 ovoid sporocysts measuring 8 to 10 by 4 to 5 u. Each sporocyst contains 8 to 12 sporozoites. Seibold and Thorson (1955) found 40 sporocysts in a cross section of one of the largest sacs they saw, so there must have been many more actually present.
Pathogenesis: Apparently non-pathogenic.
Remarks: Pachinger (1886) described parasites resembling Eimeria falciformis in the kidneys of 3 horses. These were almost certainly K. equi. Selan and Vittorio (1924) described a parasite from the lungs and gall bladder of a horse in Italy which they called Eimeria utinensis. Their description was too poor to be sure what they actually saw, but it may perhaps have been a stage of K. equi.
Other species of Klossiella
Klossiella muris Smith and Johnson, 1902 is apparently fairly common in laboratory mice thruout the world, but has been reported only once in wild house mice. In the laboratory colonies in which it is found, 20 to 100% of the mice are infected. Each microgametocyte forms 2 microgametes. Each sporont forms 12 to 16 sporocysts, each of which contains about 25 to 34 banana-shaped sporozoites. K. muris is ordinarily non-pathogenic, altho in heavy infections the kidneys may have minute, greyish, necrotic foci over their entire surface, and the epithelium of the infected kidney tubules is destroyed (Smith and Johnson, 1902). Otto (1957) described a perivascular, follicular, lymphocytic infiltration in the region of the medullary cortex which he considered of diagnostic significance. There is no inflammatory reaction. No fatal infections 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 encountered 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.