Epidemiology of Cryptosporidium: transmission, detection and identification.

Cryptosporidium and cryptosporidiosis in man and animals

There has been an explosion of descriptions of new species of Cryptosporidium during the last two decades. This has been accompanied by confusion regarding the criteria for species designation, largely because of the lack of distinct morphologic differences and strict host specificity among Cryptosporidium spp. A review of the biologic species concept, the International Code of Zoological Nomenclature (ICZN), and current practices for Cryptosporidium species designation calls for the establishment of guidelines for naming Cryptosporidium species. All reports of new Cryptosporidium species should include at least four basic components: oocyst morphology, natural host specificity, genetic characterizations, and compliance with the ICZN. Altogether, 13 Cryptosporidium spp. are currently recognized: C. muris, C. andersoni, C. parvum, C. hominis, C. wrairi, C. felis, and C. cannis in mammals; C. baileyi, C. meleagridis, and C. galli in birds; C. serpentis and C. saurophilum in reptiles; and C. molnari in fish. With the establishment of a framework for naming Cryptosporidium species and the availability of new taxonomic tools, there should be less confusion associated with the taxonomy of the genus Cryptosporidium. The clarification of Cryptosporidium taxonomy is also useful for understanding the biology of Cryptosporidium spp., assessing the public health significance of Cryptosporidium spp. in animals and the environment, characterizing transmission dynamics, and tracking infection and contamination sources.

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Cryptosporidium Taxonomy: Recent Advances and Implications for Public Health

There has been an explosion of descriptions of new species of Cryptosporidium during the last two decades This has been accompanied by confusion regarding the criteria for species designation, largely because of the lack of distinct morphologic differences and strict host specificity among Cryptosporidium spp A review of the biologic species concept, the International Code of Zoological Nomenclature (ICZN), and current practices for Cryptosporidium species designation calls for the establishment of guidelines for naming Cryptosporidium species All reports of new Cryptosporidium species should include at least four basic components: oocyst morphology, natural host specificity, genetic characterizations, and compliance with the ICZN Altogether, 13 Cryptosporidium spp are currently recognized: C muris, C andersoni, C parvum, C hominis, C wrairi, C felis; and C cannis in mammals; C baileyi, C meleagridis, and C galli in birds; C serpentis and C saurophilum in reptiles; and C molnari in fish With the establishment of a framework for naming Cryptosporidium species and the availability of new taxonomic tools, there should be less confusion associated with the taxonomy of the genus Cryptosporidium The clarification of Cryptosporidium taxonomy is also useful for understanding the biology of Cryptosporidium spp, assessing the public health significance of Cryptosporidium spp in animals and the environment, characterizing transmission dynamics, and tracking infection and contamination sources

Cryptosporidium Taxonomy: Recent Advances and Implications for Public Health (Review)

Prior to the work of Cable and Hopp (J. Parasit. 40(6): 674.680, 1954) Neoechinorhynchus emydis (L e i d y, 1851) was the only recognized species of Acanthocephala in North American turtles. To date, a total of five species have been described. Of these, two species (Neoechinorbynchus pseudemydis Cable and Hopp, 1954, and N. emyditoides Fisher, 1960) were recovered from six of 12 Louisiana turtles (Pseudemys scripta elegans (Wied)) examined by Fisher (J. Parasit. 46(2): 257-266, 1960). He (1960) also found N. chrysemydis Cable and Hopp, 1954 in Pseudemys scripta subsp. The data pt .sented are results of studies conducted between the spring of 1965 and the summer of 1966. Seventynine turtles (48 female and 31 males) encompassing seven species (47 Pseudemys scripta elegans (Wied), three P. floridana hoyi (Holbrook), eight Chelydra serpentina serpentina (L.), eight Kinosternon subrubrum hippocrepis Gray, seven Terrapene carolina carolina (L.), five T. c. triunguis (Agassiz) and one Trionyx muticus (LeSueur) collected from Baton Rouge and vicinity were examined. This investigation revealed the presence of three species of Acanthocephala (Neoechinorhynchus pseudemydis, N. emyditoides, and N. chrysemydis) in Louisiana turtles and confirms Fisher’s (1960) work. Of the seven species of turtles examined, only P. s. e!egans (25 16 females and 9 males) and P. floridana hoyi (2 females) were positive with infection. Three of the 25 P. s. e!egans had mixed infection comprising three species of Neoechinorhynchus while seven had two species respectively. P. f!oridana hoyi represents a host record for N. chrysemydis;

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Myiasis in man and animals in the old world

The ultrastructure of Cryptosporidium muris, which parasitizes the stomach of mice, was studied by transmission electron microscopy. The entire development of the parasite occurred in the microvilli of the surface mucus cells in the gastric glands. The ultrastructural features of the attachment site of C. muris to the host cell differed remarkably from those of C. parvum and its closely related species, which parasitize the intestine of various animals. The size of C. muris was greater at almost every developmental stage than that of C. parvum. These findings confirmed that C. muris and C. parvum are distinct species. The mitochondria, subpellicular microtubules, and Golgi complex were demonstrated in detail. A small invagination in the meront and intravacuolar tubules were found in Cryptosporidium. The wall of each developing oocyst in the parasitophorous vacuole was composed of three layers: the outermost layer was considered to be a true oocyst wall, whereas the middle and innermost layers were assumed to develop into the sporocyst wall. The outermost layer was fragile and disintegrated as the oocyst matured. In excystation in vitro, a suture was seen in a thick layer of the two-layered sporocyst wall of an oocyst (sporocyst wall; see Discussion) that enveloped four sporozoites. The fine structure of the attachment site of the present species to the host cell appears to reveal a unique mode of hostparasite interaction in Cryptosporidium infection.

Ultrastructure of Cryptosporidium muris (strain RN 66) parasitizing the murine stomach.

Hard ticks taken from the Japanese serow, Capricornis crispus, in Yamagata Prefecture, Honshu, har- boured infective larvae of onchocercid filariae after incubation from the 22nd to the 158th day. Haemaphysalis flava and H. japonica contained one to eight filarial larvae; females, males and a nymph of the ticks were infected. The 44 infective larvae recovered were 612-1,370 lm long, and 11 of them, 930-1,340 lm long, were studied in detail. The larvae possessed the morphologic characteristics of the larvae of the genus Cercopithifilaria, namely an oesoph- agus with a posterior glandular part, no buccal capsule and a long tail with three terminal lappets. Five types (A to E) of infective larvae were identified based on the morphologic characteristics. While to date five species of Cercopithifilaria have been described from the Japanese serow, a specific identification of the larvae found in this study was generally not possible. Only type E larvae could be tentatively assigned to Cercopithifilaria tumidicervicata, as they had a cer- vical swelling similar to that of the adults of this species. A key for the identification of the five larval types is pre- sented. The study presents circumstantial evidences indicating that H. flava and H. japonica may transmit Cercopithifilaria spp. to Japanese serows. It also suggests the possibility that such filarial larvae will be found in hard ticks anywhere, because Cercopithifilaria is distributed worldwide, though this genus generally goes unnoticed, as its microfilariae occur in the skin, not in the blood, of host animals.

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Infective larvae of Cercopithifilaria spp. (Nematoda: Onchocercidae) from hard ticks (Ixodidae) recovered from the Japanese serow (Bovidae).

Babesia bovis, causative agent of cattle babesiosis, induces characteristic alterations on the membrane of infected erythrocytes. Elliptical protrusions measuring about 320 nm in long axis and about 160 nm in short axis appear on the membrane of infected erythrocytes, both in vitro and in vivo. Freeze-fracture demonstrated alignment of intramembrane particles (IMP) along the long axis of both the P and E faces of the protrusions. The number of IMP on the endoplasmic face increases, but the number of IMP on the protoplasmic face of the protrusions is not statistically altered from that of uninfected erythrocytes. In vitro, there are more protrusions per erythrocyte infected with the virulent form (low passage form) of B. bovis than with the avirulent form (high passage form). This suggests that the number of protrusions which appear on the membrane of infected erythrocytes may have a direct relationship to the virulence of the parasites. These protrusions may be attached to the capillary endothelial cells, which causes fatal cerebral babesiosis.

Structural alteration of the membrane of erythrocytes infected with Babesia bovis.

The human mAb 33G2 has high capacity to inhibit in vitro invasion of erythrocytes by Plasmodium falciparum merozoites and, thus, is of special interest with regard to protective immunity against the parasite. In order to obtain more information about asexual blood stage Ag of P. falciparum that are seen by this antibody, material from synchronized P. falciparum cultures was studied by immunofluorescence, immunoelectron microscopy, and immunoblotting. Reactivity was mainly confined to the membrane of infected erythrocytes. Soon after merozoite invasion the antibody stained the erythrocyte membrane. This membrane-associated staining faded during intracellular development of the parasites. Beginning about 18 h after invasion, a dotted pattern appeared which increased in strength with time and persisted to schizont rupture. Pf155/RESA was the major Ag recognized in immunoblots of parasites collected throughout the entire erythrocytic cycle, although other polypeptides also bound the antibody. Among these was a 260-kDa polypeptide found in late trophozoites and schizonts. The specificity of the antibody was analyzed with synthetic peptides corresponding to repeated sequences in the P. falciparum Ag Pf155/RESA, Pf11.1, and Ag332. Synthetic peptides related to Ag332 were the most efficient inhibitors of antibody binding in immunofluorescence studies and cell ELISA. A beta-galactosidase-Ag332 fusion protein was also efficient in reversing reinvasion inhibition caused by 33G2. These results define a family of cross-reactive P. falciparum Ag recognized by mAb 33G2 and suggest that Ag332 was its original target.

Shigehiko Uni

Papers

Ultrastructure of Cryptosporidium muris (strain RN 66) parasitizing the murine stomach.

Infective larvae of Cercopithifilaria spp. (Nematoda: Onchocercidae) from hard ticks (Ixodidae) recovered from the Japanese serow (Bovidae).

Structural alteration of the membrane of erythrocytes infected with Babesia bovis.

Reactivity of the human monoclonal antibody 33G2 with repeated sequences of three distinct Plasmodium falciparum antigens.

Hepatozoon ursi n. sp. (Apicomplexa: Hepatozoidae) in Japanese black bear (Ursus thibetanus japonicus).