Genus Isospora Research Articles

Phylogenetic position of a renal coccidium of the European green frogs, 'Isospora' lieberkuehni Labbé, 1894 (Apicomplexa: Sarcocystidae) and its taxonomic implications.

'Isospora' lieberkuehni, an unusual isosporoid renal coccidium that parasitizes the European water frog was isolated from the edible frog, Rana kl. esculenta, in the Czech Republic. Sequencing of the small-subunit (SSU) rRNA gene showed that it belongs to the family Sarcocystidae, being closely related to a clade comprising members of the subfamily Toxoplasmatinae. The position within Sarcocystidae correlates with the mode of excystation via collapsible plates as postulated by previous authors. Phylogenetic, morphological and biological differences between 'Isospora' lieberkuehni and the other Stiedabody-lacking members of the genus Isospora justify separation of this coccidium on a generic level. Hyaloklossia Labbé, 1896 is the oldest available synonym and is herein re-erected. The original definition of the genus Hyaloklossia is emended based on recent observations.

Temporal variation in shedding of coccidial oocysts: implications for sexual-selection studies

Studies of the effects of parasites on the sexual ornamentation and behavior of animals are becoming increasingly common. A potential difficulty in many studies of this type is the accurate assessment of parasite prevalence within a population and of the parasite burden of individual hosts. We present data that illustrate how a simple factor such as the time of day at which samples are collected can drastically alter the results of parasite assessments. House finches (Carpodacus mexicanus) infected with coccidians of the genus Isospora shed oocysts in their feces predominantly during the late afternoon. The importance of recognizing such circumstances (e.g., diurnal periodicity) is discussed in the light of possible negative effects on studies of host-parasite relationships.

An Eimeriid Origin of Isosporoid Coccidia with Stieda Bodies as Shown by Phylogenetic Analysis of Small Subunit Ribosomal RNA Gene Sequences

Morphological and life cycle features of the tissue cyst-forming coccidia have been difficult to interpret in devising taxonomic classifications for the various genera. In this study, we amplified the full small subunit rRNA gene sequence of Isospora robini McQuistion and Holmes, 1988, and the partial sequence of Isospora gryphoni Olsen, Gissing, Barta, and Middleton, 1998 by PCR. Both of these species vary from Isospora species of mammals in having Stieda bodies on the sporocysts. The sequences were cloned and sequenced and were incorporated into an alignment with other Isospora species lacking Stieda bodies as well as with other coccidia. Maximum parsimony analysis of these sequences produced a single most parsimonious tree that placed I. robini and I. gryphoni in a clade containing various other eimeriid species. The Isospora species lacking Stieda bodies were in the sarcocystid clade. Similar results were found by maximum likelihood analysis. These findings indicate that the genus Isospora as defined by several authors is polyphyletic. Taxonomic changes to the genus Isospora would have to incorporate the 2 major clades found by molecular phylogenetic analysis. Isospora species with Stieda bodies should be classified in the family Eimeriidae, whereas those without Stieda bodies should remain in the family Sarcocystidae.

Cyclospora: An Enigma Worth Unraveling

In part, Cyclospora cayetanensis owes its recognition as an emerging pathogen to the increased use of staining methods for detecting enteric parasites such as Cryptosporidium. First reported in patients in New Guinea in 1977 but thought to be a coccidian parasite of the genus Isospora, C. cayetanensis received little attention until it was again described in 1985 in New York and Peru. In the early 1990s, human infection associated with waterborne transmission of C. cayetanensis was suspected; foodborne transmission was likewise suggested in early studies. The parasite was associated with several disease outbreaks in the United States during 1996 and 1997. This article reviews current knowledge about C. cayetanensis (including its association with waterborne and foodborne transmission), unresolved issues, and research needs.

Phylogenetic analysis of coccidia based on 18S rDNA sequence comparison indicates that Isospora is most closely related to Toxoplasma and Neospora.

The phylogenetic relationships and taxonomic affinities of coccidia with isosporan-type oocysts have been unclear as overlapping characters, recently discovered life cycle features, and even recently discovered taxa, continue to be incorporated into biological classifications of the group. We determined the full or partial 18S ribosomal RNA gene sequences of three mammalian Isospora spp., Isospora felis, Isospora ohioensis and Isospora suis, and a Sarcocystis sp. of a rattlesnake, and used these sequences for a phylogenetic analysis of the genus Isospora and the cyst-forming coccidia. Various alveolate 18S rDNA sequences were aligned and analyzed using maximum parsimony to obtain a phylogenetic hypothesis for the group. The three Isospora spp. were found to be most closely related to Toxoplasma gondii and Neospora caninum. This clade in turn formed the sister group to the Sarcocystis spp. included in the analysis. The results confirm that the genus Isospora does not belong to the family Eimeriidae, but should be classified together with the cyst-forming coccidia in the family Sarcocystidae. Furthermore, there appear to be two lineages within the Sarcocystidae. One lineage comprises Isospora and the Toxoplasma/Neospora clade which share the characters of having a proliferative phase of development preceding gamogony in the definitive host and an exogenous phase of sporogony. The other lineage comprises the Sarcocystis spp. which have no proliferative phase in the definitive host and an endogenous phase of sporogony.

Isospora ptyodactyli n. sp. (Apicomplexa: Eimeriidae), a new coccidian parasite of the fan-footed gecko Ptyodactylus puiseuxi Boutan, 1893 (Reptilia: Gekkonidae) from Jordan

Faecal samples from 17 fan-footed geckoes Ptyodactylus puiseuxi Boutan were examined for coccidian parasites. Five geckoes (29%) were found to be passing oocysts of the genus Isospora Schneider. Comparison with other members of the genus Isospora indicates that the coccidian found represents a new species. Sporulated oocysts of I. ptyodactyli n. sp. are spherical or subspherical, 22.1 (19.0–24.0) × 21.2 (18.0–23.0) µm, with a shape-index (length/width) of 1.04; and a smooth and bilayered oocyst wall, 1.0–1.5 µm thick. A micropyle, oocyst residuum and polar granule are absent. The sporocysts are ellipsoidal, 12.2 (11.0–14.0) × 8.0 (7.5–9.0) µm, with a shape index of 1.5 (1.4–1.9). Stieda and substieda bodies are present, the Stieda body being knob-like and the substieda body spherical to subspherical. A sporocyst residuum is present and composed of numerous granules of different size scattered among the sporozoites. The sporozoites are vermiform, with a slightly granulated surface appearance, and are arranged head to tail within the sporocyst. Most oocysts have still to sporulate when excreted; sporulation was completed within 12 h at 25 °C. Endogenous development occurs inside the nuclei of enterocytes in the small intestine.

Biology of Isospora spp. from humans, nonhuman primates, and domestic animals.

Coccidial parasites of the genus Isospora cause intestinal disease in several mammalian host species. These protozoal parasites have asexual and sexual stages within intestinal cells of their hosts and produce an environmentally resistant cyst stage, the oocyst. Infections are acquired by the ingestion of infective (sporulated) oocysts in contaminated food or water. Some species of mammalian Isospora have evolved the ability to use paratenic (transport) hosts. In these cases, infections can be acquired by ingestion of an infected paratenic host. Human intestinal isosporiasis is caused by Isospora belli. Symptoms of I. belli infection in immunocompetent patients include diarrhea, steatorrhea, headache, fever, malaise, abdominal pain, vomiting, dehydration, and weight loss, blood is not usually present in the feces. The disease is often chronic, with parasites present in the feces or biopsy specimens for several months to years. Recurrences are common, Symptoms are more severe in AIDS patients, with the diarrhea being more watery. Extraintestinal stages of I. belli have been observed in AIDS patients but not immunocompetent patients. Treatment of I. belli infection with trimethoprim-sulfamethoxazole usually results in a rapid clinical response. Maintenance treatment with trimethoprim-sulfamethoxazole is needed because relapses often occur once treatment is stopped.

Biology of Isospora spp. from humans, nonhuman primates, and domestic animals.

Coccidial parasites of the genus Isospora cause intestinal disease in several mammalian host species. These protozoal parasites have asexual and sexual stages within intestinal cells of their hosts and produce an environmentally resistant cyst stage, the oocyst. Infections are acquired by the ingestion of infective (sporulated) oocysts in contaminated food or water. Some species of mammalian Isospora have evolved the ability to use paratenic (transport) hosts. In these cases, infections can be acquired by ingestion of an infected paratenic host. Human intestinal isosporiasis is caused by Isospora belli. Symptoms of I. belli infection in immunocompetent patients include diarrhea, steatorrhea, headache, fever, malaise, abdominal pain, vomiting, dehydration, and weight loss, blood is not usually present in the feces. The disease is often chronic, with parasites present in the feces or biopsy specimens for several months to years. Recurrences are common, Symptoms are more severe in AIDS patients, with the diarrhea being more watery. Extraintestinal stages of I. belli have been observed in AIDS patients but not immunocompetent patients. Treatment of I. belli infection with trimethoprim-sulfamethoxazole usually results in a rapid clinical response. Maintenance treatment with trimethoprim-sulfamethoxazole is needed because relapses often occur once treatment is stopped.

Isospora atrata N. Sp. (Apicomplexa, Eimeriidae): a New Coccidium Isolated from Carduelis atrata (Passeriformes, Fringillidae)

ABSTRACT Large numbers of coccidian oocysts belonging to the genus Isospora were obtained from the intestinal contents of 98 Carduelis atrata imported into Italy from South America during the months of August through December 1994. The oocysts are sub‐spherical and average 21 × 20.3 μm (19.4–23.5 μm × 18.5–22 μm), have a bilayered wall, and an oval polar granule (rarely two). The sporocysts are elliptical and measure 18.8 μm × 10.3 μm (17.5–18.94 μm × 9.5–11.0 μm). The Stieda body protrudes slightly from the end of the sporocyst. A large sporocyst residuum is present, consisting of many granules that may be in a compact mass or scattered. Since this Isospora sp.does not resemble any other species of Isospora previously described from birds of the genus Carduelis, it has been named Isospora atrata n. sp. after the host. Disseminated asexual stages were found in mononuclear cells derived from formalin‐fixed post mortem material, suggesting this coccidian may represent an Atoxoplasma‐like parasite. Four coccidia‐free Serinus canarius L. cohabitated for a long period (4 mo) with infected C. atrata but oocysts were never found in the stool of these birds.

Cognitive decline in geriatric chronic schizophrenic patients: evidence for a neurodegenerative process?

The domestic pigeon, Columba livia domestica, is reared for meat production, as a pet, or for racing. Few reports have characterized the parasitic protists from the genus Isospora isolated from Columbiformes. We detected Isospora-like oocysts from C. livia reared for racing. The oocyst contained two sporocysts, and each sporocyst included four sporozoites. The sporulated oocysts (n = 4) were spherical; their mean diameters were 25.6 (24.0–27.2) × 24.7 (23.4–26.0) μm. Micropyles, polar granules, and oocyst residuum were absent. The mean length and width of the sporocysts (n = 8) were 19.5 (18.5–20.5) and 11.2 (10.2–12.1) μm, respectively. Stieda and sub-Stieda bodies were observed. Single-oocyst PCR revealed two different 18S rRNA gene sequences and one 28S rRNA gene sequence in a single oocyst of Isospora sp. Based on a phylogenetic analysis of the 18S rRNA gene, the two sequences made a group which fell within a cluster of known avian Isospora species. A tree based on the 28S rRNA gene sequence indicated that sequences from the pigeon Isospora sp. fell within a cluster of avian Isospora species. Both trees failed to clarify the phylogenetic relationships among the avian Isospora species due to limited resolution. Because the morphological description of Isospora sp. is based on only four oocysts, Isospora sp. is not proposed as a novel species here. This is the first description of Isospora sp. isolated from the domestic pigeon C. livia.

Studies on isosporosis in dogs. I: Isolation and sporulation of Isospora ohioensis.

Based on the morphologic characteristics of oocysts of the genus Isospora, we have demonstrated that I. ohioensis is a relatively common Isospora species in dogs which are resident in Chonbuk province, Korea. The prepatent period of I. ohioensis was four days. The size of the unsporulated oocysts in fresh stool specimens was 22.9 x 19.8 microns (R = 1.16). The size of the contracted sporonts was 17.4 x 16.3 microns (R = 1.06). By 96 hours, sporulation is complete and the ratio of length/width was constant relatively. And the sizes of oocysts and sporocysts were 22.8 x 20.5 microns (R = 1.11) and 15.0 x 10.8 microns (R = 1.39), respectively. At this time it is most reliable for the measurements of oocyst sizes of I. ohioensis to provide with the identifiable clues against the others. It is therefore recommended that the clinical fecal specimens suspected of isosporosis should first be incubated and aerated for 96 hours before a definitive parasitological diagnosis can be reached. These and other observations contribute to the understanding of the biological characteristics and laboratory and clinical diagnosis of isosporosis.

Description of Two New Species of Coccidia (Apicomplexa: Eimeriorina) from Flat-Headed Snakes, Tantilla gracilis (Serpentes: Colubridae) and Reclassification of Misnomer Species within the Genera Isospora and Sarcocystis from Snakes

Two new species of coccidia were recovered from the feces of flat-headed snakes, Tantilla gracilis, from Texas and Arkansas, U.S.A. Oocysts of Caryospora gracilis n. sp. are spherical or subspherical, 23.7 x 22.5 (21-25 x 21-24) #m, with a thick, bilayered wall and a shape index (length/width) of 1.06 (1.00-1.12). A micropyle is absent, but an oocyst residuum and polar granule are present. Sporocysts are ovoidal, 17.1 x 12.7 (1518 x 11-13.5) ,im, with Stieda and substieda bodies. The sporocyst shape index is 1.34 (1.29-1.40). Oocysts of Isospora wilsoni n. sp. are spherical, rarely subspherical, 17.2 x 17.0 (15-19 x 14.5-19) Aim, with a thick, bilayered wall and a shape index of 1.01 (1.001.11). A micropyle, oocyst residuum, and polar granule are absent. Sporocysts are ovoidal, 10.9 x 8.4 (10.5-12 x 8-9) ,im, with Stieda and substieda bodies and a shape index of 1.30 (1.24-1.40). In addition to these new coccidia, a check-list of the coccidian genera Isospora and Sarcocystis representing species misidentified from snakes, which places most members within the genus Sarcocystis, is presented. The flat-headed snake, Tantilla gracilis, ranges from southwestern Illinois, Missouri, and eastern Kansas to southern Texas and Coahuila, Mexico (Conant & Collins, 1991). This small, secretive snake prefers rocky hillsides and is found most often in sandy soils associated with limestone. Prey include centipedes, insect larvae, and various invertebrates (Conant & Collins, 1991). Little is known of the biology of snakes in the genus Tantilla and only a few taxonomic and natural history studies have been published (see Wilson, 1982, 1983, 1987). Coccidia never have been reported from any member of the genus, but our studies revealed two undescribed species that we report below as new. MATERIALS AND METHODS Between March and August 1991, 12 flat-headed snakes were captured alive by hand from various localities in Arkansas and Texas, U.S.A. Snakes were ' We thank the Texas Parks and Wildlife Department and Arkansas Game and Fish Commission for scientific collecting permits SPR-0390-027 and 831 to C.T.M. and S.E.T., respectively. We also thank Dr. James R. Dixon for providing specimens of T. gracilis from Llano County, Texas. TRANS. AM. MICROSC. SOC., 111(1): 50-60. 1992. ? Copyright, 1992, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.112 on Wed, 29 Jun 2016 04:50:26 UTC All use subject to http://about.jstor.org/terms VOL. 111, NO. 1, JANUARY 1992

Ultrastructure of Sarcocystis Sporocysts from Passerine Birds and Opossums: Comments on Classification of the Genus Isospora

Sporocysts were obtained from the feces of opossums (Didelphis virginiana) which had been fed muscles of passerine birds (Molothrus ater and Cassidix mexicanus) infected with Sarcocystis. Sporocysts were examined by phas microscopy and scanning and transmission electron microscopy. Ridges on the surface of the sporocysts outlined four plates. Thin sections of the sporocyst wall showed thickened regions and gaps interpreted as cross sections of the ridges. The sporocyst wall has four major layers with a thick, granular inner layer which resembles the inner layer of sporocysts of related species. Excystation structures are discussed as a basis for classifying disporocystic coccidia to correlate with Frenkel's (1977) life cycle classification of this group.

The Sarcosporidia (Protozoa, Sporozoa): Life Cycle and Fine Structure

Publisher Summary Sarcosporidia have adapted their life cycle to the “predator–prey” relationship existing between their hosts. Some carnivores may be final hosts of several sarcocystis species and omnivores may be involved as intermediate as well as final hosts in the life cycles of different sarcosporidian species. Sporocysts or sporulated oocysts shed in the faeces of the final host must always be ingested by the intermediate host. The oocysts and sporocysts of the sarcosporidian life cycles are morphologically identical with those of the genus isospora, and thus, sarcocystis has been classified as isospora species. However, there are four differences: (1) the Sarcosporidia have an obligatory two-host cycle, (2) schizogony has two phases: an extraintestinal multiplication followed by cyst formation mostly within the muscles of the intermediate host, (3) in Sarcosporidia, no schizogonic multiplication occurs in the gut wall of the final host or in cell culture, and (4) in Sarcosporidia, oocysts are excreted fully sporulated; single sporocysts are often observed in the faeces of the final host because of the rupture of the extremely fine oocyst wall.

Prevalência de Isospora em cães de diferentes áreas da cidade do Rio de Janeiro

Foi examinado um total de 222 cães, sendo que 197 eram cães de rua apreendidos nas áreas suburbanas e rurais do Rio de Janeiro e 25 eram animais de estimação, mantidos em residências (apartamentos) nas zonas Centro e Sul da cidade. Do total de 197 cães de rua, foram encontrados 49 (24,87%) parasitados por coccidios do gênero Isospora, sendo que 6 deles (3,04%) eram parasitados por I. canis e 43 (21,83%) por I. rivolta. Nos 43 casos de parasitismo por I. rivolta foi encontrada nas fezes uma alta percentagem de esporocistos livres com 4 esporozoitos (35 casos, representando 81,4%). As fezes foram coletadas diretamente do reto e a técnica empregada para o exame do material foi a centrífugo-flutuação em sulfato de zinco. Entre os 25 cães de estimação não foi encontrado nenhum caso de parasitismo por Isospora sp. Os valores médios para os diâmetros maior e menor das formas de Isospora sp. encontradas foram de 38,63μ x 31,93μ. para oocistos de I. canis; 23μ x 18,94μ. para oocistos de I. rivolta e, 19,94μ x 10,05μ para os esporocistos de I. rivolta, encontrados livres nas fezes. Não foi diagnosticado nenhum caso de I. bigemina. Entre todos os casos positivos foram encontrados apenas 3 casos de infecção maciça nos animais. Nos 3 casos, tratavam-se de animais jovens parasitados por I. rivolta. O teste estatístico de diferença de proporções demonstrou que o sexo e a idade dos animais não tiveram influência na maior ou menor percentagem de cães positivos para Isospora sp, na presente casuística.

Eimeria palustris sp. n. and Isospora hammondi sp. n. (Coccidia: Eimeriidae) from the Marsh Rice Rat, Oryzomys palustris (Harlan)

Eimeria palustris sp. n. and Isospora hammondi sp. n. are described from the marsh rice rat, Oryzomys palustris, from Alabama. The ellipsoidal oocysts of E. palustris measure 19 to 28 by 16 to 21 /L (mean 23.7 by 18.1 u), and sporocysts are 12 to 15 by 7 to 9 A (mean 13.6 by 7.5 4). A polar granule is present, but an oocyst residuum is absent. Prepatent and patent periods averaged 3.3 and 4.7 days, respectively. The ovoid oocysts of I. hammondi measure 24 to 30 by 16 to 21 ,u (mean 27.1 by 18.9 a/), and sporocysts are 13 to 18 by 11 to 15 A (mean 16.0 by 11.9 I/). The oocysts lack a micropyle, oocyst residuum, polar granule, and Stieda bodies. Prepatent and patent periods averaged 5.3 and 3.5 days, respectively. This is the first report of prepatent and patent periods of an Isospora species from a rodent. Nineteen marsh rice rats, Oryzomys palustris (Harlan), were trapped in the Tuskegee National Forest, Macon County, Alabama, and examined for coccidia at the Regional Parasite Research Laboratory, ARS, USDA, Auburn, Alabama. Nine of these animals harbored coccidian oocysts. Two species of coccidia were distinguished-one of the genus Eimeria and one of the genus Isospora. Both are previously undescribed and are described herein as new

Cell Culture of Isospora from the English Sparrow, Passer domesticus domesticus

Coccidia of the lacazei group of the genus Isospora were cultured in vitro. Isospora from the English sparrow, Passer domesticus domesticus, developed in primary cultures of embryonic chick and canary cells grown in Leighton tubes in medium 199, Hanks' base with 10% calf serum. When sporozoites were added to tubes containing chick or canary cells, trophozoites were first observed at 3 hr, immature schizonts with refractile globules and mature schizonts at 24 hr, and immature schizonts without refractile globules at 48 hr. Evidence that at least 2 asexual generations developed is presented. Mature schizonts accounted for 66% of the total developing parasites in chick cells on day 5 and for approximately 90% of the total parasites in canary cells on days 4, 5, and 6. Many more parasites developed in canary cells than in chick cells. The first cultivation of a coccidian in cell culture was reported by Patton (1965), who grew asexual stages of a chicken coccidian, Eimeria tenella, in monolayers of a variety of cells. He observed the development of at least one asexual generation. Doran and Vetterling (1967a, b, 1968) cultured other Eimeria species from turkeys and chickens in a variety of cells through at least one cycle of asexual development. Hammond and Fayer (1968) reported growing second-generation schizonts of Eimeria bovis, a parasite of cattle, in an embryonic bovine tracheal cell line and summarized their work and the work of others in cultivation of Eimeria in vitro. Development of sexual stages in cell culture was first reported by Strout and Ouellette (1969), who obtained development of mature macroand microgametes in primary chick embryonic kidney cells inoculated with sporozoites of E. tenella. More recently Doran (1970) reported development of the same parasite from sporozoites to viable oocysts in cell cultures prepared so that cell aggregates were abundant. Although species of the coccidian genus Eimeria have previously been grown in cell cultures by several investigators there is only one report of cultivation of an Isospora in vitro (Sheffield and Melton, 1970). These workers cultured asexual stages of Toxoplasma gondii from sporozoites obtained from an Isosporalike oocyst from cats. Other workers have demonstrated that T. gondii can be transmitted by an oocyst resembling Isospora bigemina found Received for publication 9 December 1969. in cats (Frenkel et al., 1970; Hutchison et al., 1970). The present paper reports the first cultivation in vitro of an Isospora of the lacazei group from English sparrows (Passer domesticus domesticus). MATERIALS AND METHODS Cells for culture were obtained by trypsinization of 10-day-old chick embryos and 9to 13-day-old canary embryos. Both types of cells were suspended in growth medium 199 in Hanks' balanced salt solution with 10% calf serum, penicillin (100 units/ml), streptomycin (100 ,/g/ml), and phenol red (0.02 g/liter). Leighton tubes containing 10.5by 35-mm cover slips were each inoculated with 0.8 ml of a cell suspension containing 1.6 X 10' cells. Isospora oocysts were obtained from feces of English sparrows trapped on the Galveston campus of the University of Texas Medical Branch. Sparrows were maintained in air-conditioned quarters and fed chick starter mash. Clean newspapers were placed on the floor of the cages between 2 PM and 3 PM. Water was poured on the papers to prevent drying of feces passed in the night. Feces were collected as soon as possible the next morning since most of the oocysts are passed between 3 PM and 11 PM (Boughton, 1933). Approximately 2 parts of 2.5% (w/v) potassium dichromate were mixed with 1 part of feces in a Waring blender for 1 min, strained through 2 layers of gauze, and poured into petri dishes in layers not over 5 mm deep. After 6 days at room temperature, fecal mixtures were pooled, diluted with an equal volume of water, and stored in the refrigerator until needed. Measurements were made on oocysts collected and sporulated as above using an ocular micrometer at a magnification of 400 X. Oocysts were recovered from fecal mixtures by a flotation method similar to that described by Doran and Farr (1962) except that the flotation solution contained 180 g cane sugar mixed with water to make 1 liter (sp gr 1.08). Oocysts were

Toxoplasma gondii: the oocyst, sporozoite, and infection of cultured cells.

The infective form of Toxoplasma gondii fouind in cat feces is an oocyst wihich, when sporutlated, resembles that of the genus Isospora in havinig two sporocysts. Sporozoites obtained by artificial excystation of the oocyst are infective for monkey kidney cell cultures. Ultrastructural characteristics of sporozoites resemble those seen previously in proliferative stages of Toxoplasma gondii.

Coccidian-like nature of Toxoplasma gondii.

Specific pathogen-free domestic cats were fed with tissue cysts containing Toxoplasma gondii. In two infected cats large numbers of oocysts were produced in the faeces; no oocysts were observed in the faeces of the uninfected control cat. Five days after the feeding of the toxoplasms profuse schizogonic and gametogonic stages were observed in the epithelial cells of the small intestine of one infected cat. A single schizont was observed in an intestinal epithelial cell of a second cat six days after being fed the tissue cysts. There was no evidence of schizogony or gametogony in the uninfected control cat. The stages observed in the intestinal epithelium are identical with those of the well-known endogenous cycles of coccidian parasites. The appearance of these stages, together with the nature of the oocyst, indicates that T. gondii is a coccidian parasite closely related to the genus Isospora.

Isospora boughtoni n. sp. from the American Opossum, Didelphis virginiana

Examinations of the opossum, Didelphis virginiana, from the vicinity of Athens, Georgia, have shown them to be parasitized by an undescribed coccidian of the genus Isospora. The only coccidian reported in the literature from a marsupialian host was named Eimeria macropodis by Wenyon and Scott in 1925 from Bennett's wallaby, Macropus bennetti, in the Zoological Gardens of London, England. In one opossum minutely examined, the upper small intestine for a length of four inches below the stomach was filled with a bloody mass containing numerous fully-sporulated o6cysts. There was a very heavy infection of gametocytes, schizonts and fully-sporulated o6cysts, each developing above the nucleus of its host-cell in the epithelial and subepithelial tissues. The outer cells of the villi were sloughed off into the lumen of the intestine.