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PubMed2002

Larval Gulf Coast ticks (Amblyomma maculatum) [Acari: Ixodidae] as host for Hepatozoon americanum [Apicomplexa: Adeleorina].

Laboratory-reared larval Gulf Coast ticks (GCTs) (Amblyomma maculatum) were exposed experimentally and found to acquire Hepatozoon americanum infection while feeding on parasitemic dogs. These ticks supported gamogonic and sporogonic development of the apicomplexan, and oocysts from newly molted nymphs were infectious for a dog. Other nymphs from this cohort that were allowed to feed on a blood-parasite naive sheep molted normally; the resulting adult ticks contained oocysts that were infectious for another dog. Merogonic development of H. americanum in the dogs and the resulting lesions/disease appeared similar, irrespective of whether infectious oocysts were derived from nymphal or adult ticks that acquired infection as larvae. In the system previously known, nymphal ticks acquire infection and adults harbor infective oocysts, which vertebrate hosts ingest. Given that larval A. maculatum can acquire infection and nymphs can harbor viable oocysts as demonstrated by this study, the potential variety of vertebrate hosts that can alternate with GCTs in maintaining an endemic cycle is considerably expanded.

Animals↗
PubMed2003

Characterization of S-adenosylmethionine synthetase in Cryptosporidium parvum (Apicomplexa).

The S-adenosylmethionine synthetase gene of the apicomplexan Cryptosporidium parvum (CpSAMS), an agent of diarrhea in immunocompromised and healthy humans and animals is described. CpSAMS is a single-copy, intronless gene of 1221 bp encoding a polypeptide of 406 amino acids with a molecular mass of 44.8 kDa. The gene is AT-rich (61.8%). CpSAMS was expressed in Escherichia coli TB1 cells as a fusion with maltose binding protein. The activity of the recombinant fusion was assayed, and was found to be inhibited by the methionine analog cycloleucine. In order to determine whether CpSAMS was differentially expressed during the life cycle of C. parvum, HCT-8 cells were infected with C. parvum and assayed over 72 h. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) confirmed the differential expression of CpSAMS.

Amino Acid Sequence↗
PubMed2001

Eimeria auratae n. sp. (Apicomplexa: Eimeriidae) infecting the lizard Mabuya aurata in Saudi Arabia.

Eimeria auratae n. sp. was described from the gall bladder of the lizard Mabuya aurata collected at Al-Hofuf village, eastern region, Saudi Arabia. Morphology of sporulated as well as non-sporulated oocysts were studied. Sporulated oocysts were ellipsoidal 22-31.5x13.5-21.8 (27.7x18.5) microm with smooth brownish-yellow bilayered wall, 1.1 (0.9-1.3) microm. Micropyle, polar granule and oocyst residuum were absent. Sporocysts were ellipsoidal 10.5-12.8x7.5-9 (11.8x8.5) microm. Sporocyst residuum was present but Stieda body was absent. Sporozoites were crescent-shaped, blunt at one end and slightly tapered at the other. Eimeria species from Scincidae were compared.

Animals↗
PubMed1983

Host cell invasion by Apicomplexa: an expression of the parasite's contractile system?

Recent studies on the motility of coccidian sporozoites have demonstrated a membrane-associated contractile system capable of moving certain intramembraneous components down the parasite surface propelling it forwards. The properties of this system resemble recorded observations on host cell invasion. In this study the invasive behaviour of Eimeria tenella and E. acervulina has been examined, with reference to the above findings, by light microscope and scanning and transmission electron microscopes. Known inhibitors of motility prevent invasion, though attachment appears unaffected. Invasion itself consists of 3 phases; attachment and orientation, induction of a parasitophorous vacuole and translocation of the parasite into the vacuole. Ultrastructural examination reveals a close membrane/membrane association maintained throughout invasion. From these results it is suggested that the parasite enters the parasitophorous vacuole by 'capping' the host/parasite junction down its body, so locomoting into the host cell. Such a model has two main advantages; it requires no additional modifications to either cell, and the specificity of membrane receptors would enable the one membrane-associated contractile system to be responsible for locomotion, antibody capping and host cell invasion.

Adhesiveness↗
PubMed1991

Characterization and immunolocalization of an oocyst wall antigen of Cryptosporidium parvum (Protozoa: Apicomplexa).

A monoclonal antibody (OW-IGO) raised against purified excysted oocysts of Cryptosporidium parvum reacted in an immunofluorescence assay with the oocyst wall. The corresponding antigen was localized by immunoelectron microscopy in fibrillous material present in the parasitophorous vacuole of developing macrogametes and in the wall of both single and double layered sporulating oocysts. Gold particles were also detected over electron-lucent vesicles of the macrogametes by immunoelectron microscopy. On Western blotting of C. parvum oocyst extracts, major bands at 250 and 40 kDa and several minor components were recognized by Mab OW-IGO. Almost complete abolition of Western blot reactivity occurred after periodate oxidation of oocyst antigen, suggesting that monoclonal antibody OW-IGO reacts with a carbohydrate epitope. Taken together, our results suggest that a fibrillous glycoproteinic material is released in the parasitophorous vacuole from electron-lucent vesicles during gametogenesis, and later condensed in the oocyst wall.

Animals↗
PubMed2001

Eimeria telekii n.sp. (Apicomplexa: Coccidia) from Lemniscomys striatus (Rodentia: Muridae): morphology, pathology and phylogeny.

Using a combination of morphological, life-cycle and molecular data, we describe a new apicomplexan parasite Eimeria telekii n.sp. from a striped grass mouse Lemniscomys striatus captured in Kenya. Oocysts are oval to spherical or ellipsoidal, 20.4 x 15.7 (15.5-25.0 x 12.0-20.0) microm with a colourless, smooth and bilayered wall. Sporocysts are ellipsoidal, 11.2 x 7.8 (10.0-12.0 x 7.0-9.0) microm with a small Stieda body and granular sporocyst residuum and contain 2 elongated, banana-shaped sporozoites with a single refractile body. Life-cycle, pathogenicity and host specificity of this parasite were studied in laboratory-bred Lemniscomys barbarus and BALB/c mice. Two asexual stages and the sexual phase took place within the enterocytes of the caecum and colon of L. barbarus but not in inoculated BALB/c mice. An infectious dose of 5000 oocysts caused severe clinical illness and mortality in 2/2 (100%) L. barbarus. Phylogenetic analysis of the small subunit rRNA gene of E. telekii and members of the genera Eimeria, Cyclospora and Isospora placed E. telekii within the eimerian rodent clade.

Animals↗
PubMed2002

Invasion, and short- and long-term survival of Babesia divergens (Phylum Apicomplexa) cultures in non-bovine sera and erythrocytes.

In order to explore the feasibility of producing a Babesia divergens live vaccine free of bovine material contaminants the parasite's ability to grow in human, sheep and horse erythrocytes and serum and serum-free medium was investigated. B. divergens was successfully maintained in bovine erythrocytes overlaid with serum-free HL-1 medium. Supplementation of the culture medium with bovine or sheep serum improved parasite growth (monitored by measuring parasitaemia and uptake of tritiated hypoxanthine) whereas horse and human sera reduced parasite growth. As assessed by Giemsa's stained and FITC-labelled blood smears, the parasite invaded all erythrocyte types. Polyparasitism was less common in sheep and horse erythrocytes than in bovine and human erythrocytes. Accole stages were observed in bovine, human and sheep but not in horse erythrocytes. Proliferation following invasion was higher in human but lower in horse and sheep erythrocytes compared with bovine erythrocytes. Long-term cultures of B. divergens reached similar peak parasitaemias in human, sheep and bovine erythrocytes. Attempts to establish long-term cultures in horse erythrocytes failed. These results suggest that B. divergens is not host specific at the level of host cell attachment and invasion. Instead, parasite survival appears to be decided once the organism has gained access into the cell.

Animals↗
PubMed2002

Chymotrypsin and neuraminidase treatment inhibits host cell invasion by Babesia divergens (Phylum Apicomplexa).

The process of host cell invasion by Babesia divergens is poorly understood and improved knowledge of the mechanism involved could lead to development of measures effective in disease prevention. The investigate parasite ligands on the erythrocyte surface, B. divergens cultures in bovine erythrocytes were transferred into enzyme-treated bovine, human, ovine and equine erythrocytes. Parasite invasion of bovine erythrocytes was not affected by trypsin treatment while treatment with alpha-chymotrypsin led to a reduction in parasite growth of 20-40%. Treatment of bovine and non-bovine erythrocytes with neuraminidase decreased their susceptibility to invasion by up to 97% implicating sialic acid as an important erythrocyte ligand for babesia, but the addition of either bovine or human N-acetylneuraminyl-lactose to B. divergens cultures in bovine erythrocytes had no inhibitory effect.

Animals↗
PubMed2003

Clotrimazole, ketoconazole, and clodinafop-propargyl inhibit the in vitro growth of Babesia bigemina and Babesia bovis (Phylum Apicomplexa).

We evaluated the growth inhibitory efficacy of the imidazole derivatives, clotrimazole (CLT) and ketoconazole (KC), and the herbicide clodinafop-propargyl (CP), in in vitro cultures of Babesia bovis and B. bigemina. Clotrimazole was effective in a dose range of 15 to 60 microM (IC50: 11 and 23.5 microM), followed by KC (50 to 100 microM; IC50: 50 and 32 microM) and CP (500 microM; IC50: 265 and 390 microM). In transmission electron microscopy, extensive damage was observed in the cytoplasm of drug-treated parasites. Combinations of CLT/KC, CLT/CP and CLT/KC/CP acted synergistically in both parasites. In contrast, the combination of KC/CP was exclusively effective in B. bovis, but not in B. bigemina.

Animals↗
PubMed2000

Population biology of Eimeria (Protozoa: Apicomplexa) in Apodemus sylvaticus: a capture/recapture study.

The first long-term (27 month) survey of single species of Eimeria occurring in a population of Apodemus sylvaticus in the UK showed that Eimeria apionodes, E. hungaryensis and E. uptoni occurred throughout the period whilst E. sp. E. was only found during 4 months. In first-captured animals, overall prevalence of Eimeria spp. was 73%: a figure higher than previously published, but possibly an underestimate. Multiple infections (2 or 3 species) occurred in 34% of first-capture infected animals, but without significant associations. There were no significant differences of prevalence rates between the sexes, nor between adults and juveniles, except for E. uptoni which was more common in juveniles than in adults. E. hungaryensis and E. uptoni probably occurred as near-continuous infections whilst E. apionodes occurred more intermittently but with no long-term total immunity. Monthly prevalence data indicated ongoing trends over the 27 months. Prevalences of E. apionodes indicated an annual cycle, lowest in January-May and with a peak in October-November, correlating positively with both the number of animals and the percentage of juveniles in the host population and also with the environmental relative humidity. There was no consistent pattern for E. uptoni and an annual cycle for E. hungaryensis was not apparent.

Age Factors↗
PubMed1999

Isospora automoli, a new coccidian parasite (Apicomplexa: Eimeriidae) from the buff-throated foliage-gleaner Automolus ochrolaemus and the olive-backed foliage-gleaner A. infuscatus from South America.

A new species of isosporan parasite is described from the faecal contents of the buff-throated foliage-gleaner Automolus ochrolaemus and the olive-backed foliage-gleaner A. infuscatus collected in the rainforests of eastern Ecuador. Sporulated oöcysts are subspherical to ovoidal, 23.4 x 21.3 (18-28 x 17-24) microns, colourless, with a smooth, double-layered wall with the inner layer darker and thinner; the shape-index (length/width) is 1.1 (1-1.22). Oöcysts contain one polar granule, but lack a micropyle and an oöcyst residuum. Sporocysts are ovoidal, 15.4 x 9.9 (14-17 x 8-11) microns, with a smooth single-layered wall and a small nipple-like Stieda body attached to a small, inconspicuous, acentric substieda body. Sporozoites are vermiform with one prominent posterior, refractile body (c. 4 x 5 microns), and a centrally located nucleus of equal size. Sporozoites are randomly arranged in the sporocysts with a subspherical sporocyst residuum composed of coarse granules.

Animals↗
PubMed2000

A survey on coccidian infection of Lake Biwa fishes in Japan, with the description of four new species of Goussia labbe, 1896 (Apicomplexa).

Thirty-two specimens of 11 freshwater fish species from Lake Biwa, Japan were surveyed for coccidian infections. Four fish species proved to be infected with apicomplexans belonging to the genus Goussia. Altogether, seven Goussia species were found. Oöcysts of four species inhabiting the intestinal epithelium were shed at the sporulated stage. Two other intestinal species left the fish unsporulated. A few relatively large and aged oöcysts of a further species were found in the renal tubules. The sporulated intestinal species were described as Goussia biwaensis n. sp., G. grygieri n. sp., G. nipponica n. sp. and G. wakabayashii n. sp.

Animals↗
PubMed2000

Isospora lutrae n. sp. (Apicomplexa: Eimeriidae), a new coccidium from the European otter Lutra lutra (L.) (Carnivora: Mustelidae) from Spain.

Parasitological examination of European otter originating from Extremadura, Spain revealed the presence of a new isosporan species. Oöcysts of Isospora lutrae n. sp. are spherical to subspherical, 31.2 (27.5-32) x 29.6 (28-31) microm and have a smooth wall c. 1 microm thick. Sporocysts are ellipsoidal, 18.2 (17-19) x 14.4 (14-16) microm and lack Stieda and substieda bodies. A spherical sporocyst residuum is present, consisting of granules scattered among the sporozoites. Sporozoites are spindle-shaped, 12.4 x 2.5 microm and have anterior and posterior refractile bodies. Based on its unique morphologic structure and host, I. lutrae is considered to be new.

Animals↗
PubMed2001

Five new species of coccidia (Apicomplexa: Eimeriidae) from Madagascan chameleons (Sauria: Chamaeleonidae).

Coprological examination of 19 Madagascan chameleons of the genera Furcifer and Brookesia revealed the presence of five new coccidian species. Isospora brygooi n. sp. from Furcifer pardalis has spherical to subspherical oöcysts with a slightly pitted wall, 20.7 (17-24.5) x 19.3 (16-23) microm and broadly ellipsoidal sporocysts, 12.2 (11.5-13) x 8.1 (8-8.5) microm, with Stieda and substieda bodies. Oöcysts of Eimeria glawi n. sp. from Furcifer pardalis are cylindrical to ellipsoidal, 27.7 (26-29.5) x 18.4 (17-19) microm, with ellipsoidal sporocysts, 7.3 (6.5-8) x 5.2 (5-5.5) microm. E. vencesi n. sp. described from F. pardalis has spherical to subspherical oöcysts, 14.3 (13-15.5) x 13.0 (12-13) microm, with small granules, one to three globular polar granules and ellipsoidal sporocysts, 7.3 (6.5-8) x 5.2 (5-5.5) microm. E. worthi n. sp., described from Furcifer oustaleti has spherical oöcysts, 17.9 (17.5-19.0) x 15.0 (14.5-16.0) microm without a polar granule and ellipsoidal to cylindroidal sporocysts, 8.2 (7.0-9.5) x 5.8 (5.0-6.5) microm. Oöcysts of E. brookesiae n. sp. from Brookesia decaryi are cylindrical, 25.6 (23-27) x 15.0 (13-16) microm with ellipsoidal sporocysts, 10.1 (9-11) x 6.9 (6-7) microm. Endogenous development of E. vencesi is confined to the intestine, while that of E. glawi occurs in the gall-bladder.

Animals↗
PubMed1998

Expression, purification, and biochemical characterization of a recombinant lectin of Sarcocystis muris (Apicomplexa) cyst merozoites.

The mature major microneme protein of Sarcocystis muris cyst merozoites, which is known as a dimeric lectin with high affinity to galactose and some of its derivatives, was expressed in Escherichia colias a histidine-tagged fusion protein. The recombinant polypeptide, which was recognized by a monoclonal antibody directed against the native lectin, was purified from inclusion bodies after solubilization and refolding, using a combination of metal chelate and lactose affinity chromatography. The apparent molecular mass of the refolded polypeptide as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoreses was 16 kDa, whereas gel filtration chromatography clearly demonstrated that the recombinant protein, like its native counterpart, exists as a homodimer of two non-covalently associated subunits. Inhibition of haemagglutination suggests that the combining site of the recombinant lectin recognizes N-acetyl-galactosamine as the dominant sugar, thus confirming the correct folding of the monosaccharide combining site in the renatured lectin. To the best of our knowledge, this work represents the first reported detailed characterization of a recombinant lectin from apicomplexan parasites, and may contribute to a better understanding of the process of host cell recognition and invasion by these obligate intracellular protozoa.

Animals↗
PubMed2002

The endogenous development of four new species of Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from Australian geckos.

Four new species of Isospora are described from Australian geckoes. Isospora gehyrae n. sp. from Gehyra cf. variegata in South Australia have 18.5-22.5 x 17.5-20.0 microm oöcysts with 10.0-12.5 x 7.5-9.0 microm sporocysts; endogenous stages develop in the host cell cytoplasm. Of the two species found in Heteronotia binoei from northern Queensland, Isospora cytoheteronotis n. sp., with oöcysts of 20.0-26.0 x 17.5-25.0 microm and sporocysts of 10.0-13.5 x 7.5-11.5 microm, undergoes endogenous development in its host cell cytoplasm, whereas I. nucleoheteronotis n. sp., with oöcysts of 17.5-22.5 x 17.5-21.5 microm and sporocysts of 9.0-12.5 x 6.5-10.0 microm, develops in the host cell nucleus. I. oedurae n. sp. from Oedura rhombifer in northern Queensland has oöcysts of 22.5-25.0 x 22.5-24.0 microm and sporocysts of 12.5-14.0 x 7.5-11.5 microm, and undergoes endogenous development in its host cell nuclei.

Animals↗
PubMed2004

Note on the Taxonomy of Frenkelia microti (Findlay & Middleton, 1934) (Apicomplexa: Sarcocystidae).

Based on biological, morphological and molecular data, species of Frenkelia Biocca, 1968 should be reclassified within the genus Sarcocystis Poche, 1913. This taxonomic change leads to the secondary homonymy of S. microti (Findlay & Middleton, 1934) n. comb. and S. microti Dubey, 1983. The recently suggested conspecificity and consequent synonymy of S. microti (Findlay & Middleton, 1934) and S. buteonis (Henry, 1932) is not really justifiable and thus S. microti (Findlay & Middleton, 1934) should be considered a valid species. S. jaypeedubeyi nom. nov. is, therefore, proposed as a nomen novum for S. microti Dubey, 1983 to alleviate the problem of this secondary homonymy.

Animals↗