MICROBIOLOGICAL REVIEWS, Dec. 1986, p. 458-483 Vol. 50, No. 4 0146-0749/86/040458-26$02.00/0 Copyright © 1986, American Society for Microbiology Cryptosporidium spp. and Cryptosporidiosis R. FAYER1* AND B. L. P. UNGAR2 Agricultural Research Service, Animal Parasitology Institute, Beltsville, Maryland 20705,1 and Laboratory of Parasitic Diseases, National Institute ofAllergy and Infectious Diseases, Bethesda, Maryland 202052 INTRODUCTION .................................. 458 THE ORGANISM .................................. 459 History ................................. 459 Classification .................................. 459 Host Specificity ................................. 460 Life Cycle.................................. 460 Morphology ..................................463 THE HOSTS .................................. 463 Infection in Fish and Snakes.................................. 463 Infection in Birds ................................. 464 Infection in Small Mammals ................................. 464 Mice .................................. 464 Rats .................................. 465 Rabbits .................................. 465 Guinea pigs.................................. 465 Cats .................................. 465 Dogs.................................. 465 Squirrels and raccoons .................................. 465 Infection in Large Mammals.................................. 465 Nondomesticated ruminants.................................. 465 Pigs.466...................................Horses .................................. 465 Sheep.................................. 466 Goats .................................. 466 Cattle ...................................466 Infection in Nonhuman Primates .................................. 467 Infection in Humans ................................. 467 History .................................. 467 Geographic distribution and prevalence .................................. 467 Age and sex distribution .................................. 470 Clinical features................................. 470 Pathological features .................................. 471 Transmission .................................. 472 Immune response .................................. 473 DIAGNOSIS .................................. 473 EXPERIMENTAL.................................. 475 Animal Models .................................. 475 Cross-Transmission .................................. 475 Virulence.................................. 475 Oocyst and Sporozoite Isolation................................. 475 Excystation .................................. 475 Cultivation.................................. 476 TREATMENT AND CONTROL ................................. 476 Treatment .................................. 476 Control ..................................477 ACKNOWLEDGMENTS.................................. 477 LITERATURE CITED.................................. 477 INTRODUCTION be rare and host specific, Cryptosporidium is now known to The genus Cryptosporidium identifies protozoan parasites be ubiquitous and to have many hosts. Once thought to be that grow and reproduce within epithelial cells of the respi- nonpathogenic, some isolates are now known to cause ratory and digestive organs of vertebrates. Once thought to severe illness. Although recognized and named in 1907, most information on its identification, clinical significance, epide- miology, and treatment has been obtained only within the * Corresponding author. past few years. 458 VOL. 50, 1986 CRYPTOSPORIDIUM SPP. AND CRYPTOSPORIDIOSIS 459 TABLE 1. Named species of Cryptosporidium Species Author Host C. agni Barker and Carbonell, 1974 Ovis aries (domestic sheep) C. ameivae Arcay de Peraza and Bastardo de San Jose, 1969 Ameiva ameiva (lizard) C. anserinum Proctor and Kemp, 1974 Anser anser (domestic goose) C. baileyi Current, Upton and Haynes, 1986 Gallus gallus (domestic chicken) C. bovis Barker and Carbonell, 1974 Bos taurus (ox) C. crotali Triffit, 1925 Crotalus confluens (snake) C. ctenosauris Duszynski, 1969 Costa Rican lizard C. cuniculus Inman and Takeuchi, 1979 Oryctolagus cuniculus (domestic rabbit) C. felis Iseki, 1979 Felis catis (domestic cat) C. garnhami Bird, 1981 Homo sapiens (man) C. lampropeltis Anderson, Dusynski, Marquardt, 1968 Lampropeltis calligaster (lizard) C. meleagridis Slavin, 1955 Meleagris gallopavo (turkey) C. muris Tyzzer, 1907 Mus musculus (domestic mouse) C. nasorum Hoover, Hoerr, Carlton, Hinsman and Ferguson, 1981 Naso literatus (fish) C. parvum Tyzzer, 1912 Mus musculus (domestic mouse) C. rhesi Levine, 1981 Macaca mulatta (rhesus monkey) C. serpentis Levine, 1981 Colubrid, crotalid, and boid snakes C. tyzzeri Levine, 1961 Gallus gallus (domestic chicken) C. vulpis Wetzel, 1938 Vulpes vulpes (European common fox) C. wrairi Vetterling, Jervis, Merrill, Sprinz, 1971 Cavia porcellus (guinea pig) This review summarizes recent publications that have interest that resulted in numerous case reports and surveys increased our knowledge about Cryptosporidium and its on a variety of domestic animals. biology and its veterinary and medical importance. The first cases of human cryptosporidiosis were reported in 1976 (175, 195), but relatively few were subsequently THE ORGANISM diagnosed until cryptosporidiosis was reported to be a life- History threatening infection in acquired immune deficiency syn- drome (AIDS) patients. Medical interest in the epidemiol- According to the American parasitologist E. E. Tyzzer ogy, diagnosis, and treatment of cryptosporidiosis increased (260), the first published description of a parasite resembling dramatically from that time to the present. Cryptosporidium, in the gastric epithelium of mice, was by Accumulation of veterinary and medical observations on Clark in 1895. In 1907, Tyzzer (259) himself clearly described clinical illness associated with severe cryptosporidiosis stim- a protozoan he frequently found in the gastric glands of ulated experimental studies, which seek to find a small laboratory but not wild mice. He offered the name animal model of disease, develop in vitro growth systems, Cryptosporidium muris but did not provide characteristics and test potential disinfectants and chemotherapeutic for establishing a new genus until 1910 (260). Using a agents. microscope with limited resolution, Tyzzer saw stages of asexual development, sexual development, and sporogony, Classification all of which he interpreted to be extracellular; he noted that oocysts left the body via the feces (259). In 1910, Tyzzer All species of Cryptosporidium are taxonomically classi- (260) described C. muris in greater detail, extended the host fied as shown in Table 2. Within the phylum Apicomplexa range, and suggested that sporozoites liberated from oocysts are several related genera referred to collectively as that had matured in the gastric glands might be a source of coccidia. These include Besnoitia, Caryospora, Eimeria, autoinfection. A second species, C. parvum, was identified and named TABLE 2. Taxonomic classification of Cryptosporidiuma by Tyzzer in 1912 (261). It was found in the small intestine (not the stomach) of laboratory mice and could be transmit- Classifi- Name Biological characteristics ted to other laboratory mice in which it also developed only cation in that location. He found similar organisms in the small Phylum Apicomplexa Apical complex with polar rings, intestine of a rabbit, but omitted the rabbit as a host in the rhoptries, micronemes, conoid, species description. and subpellicular microtubules Cryptosporidium sp. in cecal epithelia of chickens was Class Sporozoasida Locomotion of mature organisms by body flexion, gliding, or reported by Tyzzer in 1929 to be identical to C. parvum, but undulation in 1961 Levine named it C. tyzzeri to emphasize the chicken Subclass Coccidiasina Life cycle with merogony, game- host and then synonymized it with C. meleagridis in 1984 togony, and sporogony (152). Morbidity and mortality in avian cryptosporidiosis Order Eucoccidiorida Merogony present; in vertebrates was described by Slavin in 1955 in turkeys; he named this Suborder Eimeriorina Male and female gametes develop parasite C. meleagridis (240). independently Between 1968 and 1981, other species of Cryptosporidium Family Cryptosporidiidae Homoxenous with development in fish, reptiles, birds, and mammals were named on the just under surface membrane of without host harbored a host cell; oocyst sporo- assumption that each species separate cysts and with four sporozoites; species of Cryptosporidium (Table 1). microgametes without flagella Recognition of Cryptosporidium associated with bovine diarrhea by Panciera et al. in 1971 (200) initiated veterinary a From reference 154. 460 FAYER AND UNGAR MICROBIOL. REV. Frenkelia, Isospora, Sarcocystis, Toxoplasma, and Cryptosporidium. Twenty species of Cryptosporidium were TABLE 3. Transmission of Cryptosporidium infection among named according to the host in which the parasite was found host species via oocysts (Table 1). These recently have been reviewed by Levine (152) Oocyst Recipient Infection of and by Upton and Current (280). Several Cryptosporidium source species recipienta Citation(s) species must be considered invalid because the oocyst stage which was the basis for speciation has recently been identi- Cat Cat + 128 Human (+) 144, 155 fied as the sporocyst stage of Sarcocystis. These include C. Mouse 128 ameivae, C. ctenosauris, C. lampropeltis, C. crotali, and C. Guinea pig 128 vulpis. Recent cross-transmission studies (Table
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