Description of a new Eimeria sp. and associated lesions in the kidneys of double-crested cormorants (Phalocrocorax auritus)

A new Eimeria sp. is described as the cause of an outbreak of renal coccidiosis in double-crested cormorants (Phalacrocorax auritus) in Georgia. Sporulated oocysts were spherical to subspherical and measured 16.1 x 16.5 (13.8-18 x 14-19) microm, with an average length-width ratio of 1:1. Oocyst wall was thin (1 microm), greenish, and pitted on the outer surface. Micropyle, micropylar cap, Stieda body, and polar bodies were absent. Small oocyst residuum (4-8 granules) was usually absent but occasionally present. Sporocysts were oval and measured 6.6 x 9.3 (6-7 x 8-10.5) microm, with an average length-width ratio of 1:1.4. A sporocyst residuum was present, located in between sporozoites, and was composed of numerous granules of unequal size. A small refractile body was present in each sporozoite. Collecting duct and distal renal tubular epithelial cells were distended by large oocysts in their cytoplasm, and many oocysts were present in the lumen of dilated tubules. Various stages of meronts, gamonts, and developing oocysts were present in other renal tubular epithelial cells. Multiple infections of parasitized cells were frequently observed, with cells containing up to 12 gamonts or developing oocysts. The importance of this Eimeria sp. on double-crested cormorant populations is not known. But in this case, significant lesions and mortality were associated with infection.     

Isolation and identification of Cryptosporidium from various animals in Korea. II. Identification of Cryptosporidium muris from mice

Each of SPF mice(Scl: ICR strain, 3-week-old males) was inoculated with 5 x 10(4) oocysts of Cryptosporidium by stomach tube. The oocysts were large type one which was previously isolated from Korean mice, and passaged in 3-week-old SPF mice. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of developmental stages the stomach of the mice was examined by transmission electron microscopy (TEM) at 4 weeks post-inoculation. The prepatent period for 6 mice was 5.6 days post-inoculation on the average, and the patent period was 63.2 days. The number of oocysts discharged per day from the mice reached peak on day 36.6 post-inoculation on the average. A large number of oocysts were found in fecal samples obtained from inoculated mice on days 30-50 post-inoculation. C. muris was larger than C. parvum at almost every developmental stages, the size difference being 1.4 times in oocysts, 2.4 times in sporozoites, 1.6 times in merozoites, and 1.5 times in microgametes. The ultrastructural features of the attachment site of C. muris to the mucus cells were remarkably different from those of C. parvum and its closely related species. The anterior projection of the protozoa (C. muris), the outer aspect of which was surrounded by a thick filamentous process of the host cell, has not been reported at any developmental stages of C. parvum or its closely related species. The size of the oocysts of strain RN 66 was larger than that of Korean mice origin. The above results reveal that the large type Cryptosporidium of Korean mice origin is identified as Cryptosporidium muris and this type was named as C. muris (strain MCR).     

In vitro interaction between persisting oocysts of Cryptosporidium parvum and murine resident peritoneal macrophages. I. Effect of parasite on macrophage capability for oxidative burst

Cryptosporidiosis in an opportunistic infection which poses a significant threat to the immunodeficient patients (including people with AIDS). The aim of the present work was to study whether oxidative burst, known as a nonspecific immune response of macrophages, may be modulated in vitro by persisting oocysts of a coccidian pathogen Cryptosporidium parvum. Live oocysts of C. parvum engulfed by murine perithoneal macrophages may persist within the phagosomes and retain their initial morphology for about 7 days following oocyst injection into macrophage monolayer. A short-term interaction of adherent macrophages with C. parvum oocyst suspension for 5-15 min caused oxidative burst in these macrophages. After a while, the intensity of this oxidative burst smoothly decreased to vanish within the following 2-6 h oocyst-macrophage cultivation. Dead oocysts caused no oxidative burst in macrophages. Co-cultivation of macrophages with oocysts for 1.0-1.5 days led to the appearance of macrophages, which had oocysts both contacting the cell surface and existing inside the phagosomes. In these macrophages the oxidative burst in response to the addition of a chemotactic peptide (fMLP) was considerably higher than in uninfected control cells. During a 1-4 day co-cultivation, the degree of oxidative burst caused by fMLP in macrophages containing only phagocytosed oocysts did not differ from that in the non-infected (oocyst-free) control. The data obtained enable us to propose that the products of oxidative burst in macrophages, formed in response to the interaction with C. parvum oocysts, do not kill the oocysts. These can survive for a long time in the phagosomes of macrophages. Such a long persistence of oocysts in phagosomes does not affect the capability of macrophages for oxidative burst in response to the action of fMLP.     

Chemical and physical factors affecting the excystation of Cryptosporidium parvum oocysts.

Cryptosporidium parvum oocysts were examined to ascertain excystation requirements and the effects of gamma irradiation. Oocysts and excysted sporozoites were examined for dye permeability and infectivity. Maximum excystation occurred when oocysts were pretreated with acid and incubated with bile salts, and potassium or sodium bicarbonate. Pretreatment with Hanks' balanced salt solution or NaCl lowered excystation; however, this effect was overcome with acid. Sodium ions were replaceable with potassium ions, and sodium bicarbonate was replaceable with sodium phosphate. Oocysts that received 200 krad irradiation excysted at the same rates as nonirradiated oocysts (95%), the excystation rates were lowered (50%) by 2,000 krad, and no excystation was observed by 5,000 krad. No differences were observed between the propidium iodide (PI) permeability of untreated oocysts and oocysts treated with 200 krad, while 92% of oocysts were PI positive after 2,000 krad. Most of the sporozoites exposed to 2,000 krad were not viable as indicated by the dye permeability assay. The oocysts irradiated with 200 and 2,000 krad infected cells, but no replication was observed. The results suggest that gamma-irradiated oocysts may still be capable of excystation and apparent infection; however, because the sporozoites could not reproduce they must not have been viable.     

The suppressive effect of Mekabu fucoidan on an attachment of Cryptosporidium parvum oocysts to the intestinal epithelial cells in neonatal mice

The present study was done to investigate the effects of fucoidan and de-sulfated fucoidan isolated from the sporophyll of Undaria pinnatifida on the C. parvum adhesion to the cultured human intestinal cells and on the C. parvum infection in neonatal mice. The C. parvum adhesion to human Intestinal 407 cells was significantly suppressed by a low dose (1 micro g/ml) of Mekabu fucoidan (1 micro g/ml) (approx. 20.5 oocysts, p<0.0001), but not by de-sulfated fucoidan (approx. 138.2 oocysts), as compared with that (approx. 121.0 oocysts) of phosphate-buffered saline (PBS). The in vivo experiments presented here revealed that C. parvum oocysts in the fucoidan-treated mice was reduced nearly one fifth (approx. 5.4x10(4) oocysts, p<0.02) of the total number of oocysts (approx. 3.0x10(5)) in mice treated with PBS, but no significant effect of de-sulfated fucoidan was observed. These results show that (i) fucoidan effectively inhibits the growth of C. parvum in mice; and (ii) the ester sulfate of fucoidan is an active site to prevent the adhesion of C. parvum to the intestinal epithelial cells. Finally, we concluded that fucoidan might inhibit cryptosporidiosis through the direct binding of fucoidan to the C. parvum-derived functional mediators in the intestinal epithelial cells in neonatal mice.     

Development of Plasmodium berghei ookinetes to young oocysts in vitro.

The mosquito stage of Plasmodium berghei was cultivated in vitro, with special attention to ookinete transformation into early oocyst. The ookinetes were obtained by in vitro culture of gametocytes taken from infected mice, purified by density gradient of metrizoic acid or a lymphocyte separation medium, and incubated either in acellular culture or in co-cultivations with mosquito cells. In acellular culture, the ookinetes were found to aggregate with each other and transformed from banana to round shapes. Their inner pellicular membranes and subpellicular microtubules partially disappeared, indicating that development to early oocyst had occurred. Co-cultivation wtih Aedes albopictus cells (C6/36 clone) revealed that ookinetes transformed into early oocyst in the medium, or invaded the cells and then transformed to early oocysts within the cell cytoplasm as well. However all of these transformed cells failed to develop further, i.e., neither deposition of the oocyst capsule nor nuclear division was observed. Many ookinetes which failed to penetrate the Aedes cells were phagocytized within three days of culture. A significant difference between invaded and transformed oocysts and phagocytized ookinetes was seen in that the former lacked vacuole membrane. Co-cultivation with Toxorhynchites amboinensis cells (TRA-284-SFG clone) permitted transformation of ookinetes into early oocysts in the medium as in the acellular culture, but no ookinete invasion nor phagocytosis by the cell was observed.     

The effect of lectins on Cryptosporidium parvum oocyst in vitro attachment to host cells

The influence of lectins on Cryptosporidium parvum oocyst agglutination and on attachment to both fixed Madin Darby Canine Kidney (MDCK) cells and fixed HCT-8 (human colorectal epithelial) cells was examined. Oocyst cell wall characteristics were examined by transmission electron microscopy. Lectin-free oocysts were shown to adhere equally to both MDCK cells and HCT-8 cells. In MDCK cells, the addition of 1-25 microg/ml Codium fragile lectin, 10 microg/ml Maclura pomifera lectin, 10 microg/ml Helix pomatia lectin, and 10-200 microg/ml Artocarpus integrifolia lectin significantly increased attachment to at least 1 of the cell cultures as compared to oocysts incubated without any lectin. The lectin-enhanced attachment was reversed by co-incubation of lectin treated-oocysts with 250 mM of each specific sugar (for a given lectin). In agglutination assays, concentrations as low as 0.5 microg/ml of C. fragile, M. pomifera, and A. integrifolia lectin agglutinated oocysts within 60 min. Finally, in TEM samples, colloidal gold conjugated-lectins from A. integrifolia, C. fragile, H. pomatia, and M. pomifera attached to oocysts, and this could be competitively inhibited by a lectin-specific sugar. This suggests that C. parvum oocysts are highly reactive to N-acetyl galactosamine-binding lectins and that the presence of N-acetyl-galactosamine containing molecules on oocysts can potentially help in oocyst attachment to host cells.     

Capture and retention of Cryptosporidium parvum oocysts by Pseudomonas aeruginosa biofilms

The association of Cryptosporidium oocysts with biofilm communities can influence the propagation of this pathogen through both environmental systems and water treatment systems. We observed the capture and retention of C. parvum oocysts in Pseudomonas aeruginosa biofilms using laboratory flow cells. Biofilms were developed in two different growth media using two different strains of P. aeruginosa, a wild-type strain (PAO1) and a strain that overproduces the exopolysaccharide alginate (PDO300). Confocal laser-scanning microscopy was used in conjunction with image analysis to assess the structure of the biofilms prior to introducing oocysts into the flow cells. More oocysts were captured by the biofilm-coated surfaces than the abiotic glass surface in both media. There was no significant difference in capture across the two strains of P. aeruginosa biofilm, but the fraction of oocysts captured was positively related to biofilm roughness and surface-area-to-volume ratio. Once captured, oocysts were retained in the biofilm for more than 24 h and were not released after a 40-fold increase in the system flow rate. We believe the capture and retention of oocysts by biofilm communities can impact the environmental transmission of C. parvum, and this interaction should be taken into consideration when predicting the migration of pathogens in the environment.     

Improving the rate of infectivity of Cryptosporidium parvum oocysts in cell culture using centrifugation.

Centrifugation was evaluated as a method to improve infectivity assays of Cryptosporidium parvum in cell culture using the focus detection method, an immunofluorescence-based method for detecting infectious C. parvum oocysts in vitro. Human ileocecal adenocarcinoma (HCT-8) cells were grown for 48 hr on 13-mm cover slips in 24-well microtiter plates and infected with bleach-treated C. parvum oocysts. Plates were centrifuged at 228 g for 10 min and incubated at 37 C for 5, 12, 18, 24, and 48 hr. Foci of infection were stained by immunofluorescence and enumerated using epifluorescent microscopy. Results were compared to noncentrifuged controls. Foci in centrifuged samples could be enumerated after 18 hr. According to most probable number (MPN) analysis, the number of infectious oocysts estimated at 48 hr (13,326 infectious oocysts) was reached by 18 hr in centrifuged samples. After 48 hr, there was no significant difference (P < 0.05) between centrifuged and noncentrifuged samples enumerated by number of foci or the MPN of infectious oocysts. Centrifugation may expedite detection during C. parvum infectivity assays. Furthermore, multiwell plate formats are more cost effective than traditional chamber slides.     

Storage Polysaccharide in Coccidial Sporozites after Excystation and Penetration of Cells

SYNOPSIS. Eimeria acervulina, E. necatrix , and E. meleagrimitis sporozoites were examined for carbohydrates by cytochemical methods during dormancy, after excystation, and after penetration of cells. The only carbohydrate found was amylopectin, a homogeneous polymer of glucose. It was distributed in 3 regions: (a) in front of the anterior refractile globule, (b) around the nucleus, and (c) behind the posterior refractile globule. The relative amounts decreased after excystation and penetration of cells until only small amounts remained around the nucleus. The quantity of amylopectin decreased following excystation from 30.0-36.7 to 9.4-13.3 μg glucose/10⁶ oocysts. Over a 6 yr period of storage at 4 C, there was a decrease in the quantity of amylopectin in dormant sporozoites of E. acervulina from 33.3 μg glucose/10⁶ oocysts at 3 mos to 1.5 μg at 6 years. Coincidentally, 3 month- and 1 year-old oocysts of E. acervulina produced patent infections in chicks with a dosage of 5 × 10⁴ oocysts, but only a few of the oocysts that had been stored for 2 years were infective; a dosage of 2 × 10⁶ oocysts was necessary to produce a patent infection. Oocysts which had been stored 6 years did not produce a patent infection.
It was concluded that amylopectin is the energy source for excystation and subsequent penetration of cells. Small amounts of amylopectin are used during dormancy and, when the content in the sporozoite falls below a certain level, the sporozoites lack sufficient energy to infect cells.     

Eimeria cicaki sp. n. and Isospora thavari sp. n. from the house lizard Gehyra mutilata Boulenger in Malaysia.

Oocysts and endogenous stages of new species of Eimeria and Isospora from the house lizard, Gehyra mutilata, are described. The ellipsoid to subspherical 2-layered oocysts of E. cicaki averaged 24.0 X 21.0 mum. Polar granules are present. Micropyle and oocyst residuum are absent. Ellipsoid sporocysts average 12.2 X 9.0 mum. A sporocyst residuum is present, but the Stieda body is absent. Endogenous stages are in epithelial cells of the small intestine. The subspherical single-layered oocysts of I. thavari average 23.8 X 22.8 mum. The polar granule is present; micropyle and oocyst residuum are absent. Ellipsoid sporocysts average 12.8 X 9.4 mum. Stieda body and sporocyst residuum are present. There are endogenous stages in epithelial cells of the small intestine.     

Goussia girellae n. sp. (Apicomplexa: Eimeriorina) in the opaleye, Girella nigricans

Goussia girellae n. sp. is described from the opaleye fish, Girella nigricans. Merogonic stages were observed in the apices of intestinal epithelial cells, in the lamina propria, and in extra-intestinal sites including liver, gills, and spleen. Gamonts were observed in the intestinal epithelial cells. Only unsporulated oocysts were detected in the intestine, and sporulation occurred when feces containing oocysts were incubated for 48 h in seawater at 21 degrees C. Oocysts are elongated (24.8 x 14.7 micron) with a wall about 200 nm thick and have no residuum, micropyle, or polar granule. Sporocysts are ellipsoid (8.5 x 4.5 micron), have a thin two-layered wall approximately 30 nm thick, and consist of two valves joined by a suture. Although moribund opaleye were also infected with Gyrodactylus sp., Cryptobia sp., Cardicola sp., and epitheliocystis organisms (chlamydia), all fish were heavily infected with G. girellae and morbidity was thus attributed to the coccidium.     

Identification of Cryptosporidium oocysts in river water.

Water samples were collected from four rivers in Washington State and two rivers in California and examined for the presence of Cryptosporidium oocysts. Oocyst-sized particles were concentrated from 20-liter samples of water by membrane filtration, centrifugation, and differential sedimentation. The particle concentrate was then deposited on a 25-mm-diameter membrane filter for oocyst identification by indirect immunofluorescence assay. The identification procedure had a limit of detection of about five oocysts per liter. Cryptosporidium oocysts were found in each of 11 river water samples examined. Concentrations ranged from 2 to 112 oocysts per liter. The finding of Cryptosporidium oocysts in all samples examined from six western rivers is noteworthy in light of recent reports indicating that Cryptosporidium sp. is a significant agent of human and animal disease. This finding suggests that waterborne oocysts of this parasite are more important than was previously recognized. More detailed studies are needed to define geographical and temporal distribution, to assess the viability of waterborne oocysts, and to determine the importance of water as a means of transmission.     

Sporogonic development of Leucocytozoon smithi.

The sporogonic development of Leucocytozoon smithi in its black fly vector was studied by light and electron microscopy and was compared with that of other haemosporidians. Within 18 to 24 h after ingestion of gametocytes by black flies, ookinetes passing through the midgut epithelium were observed. Intracellular migration of ookinetes resulted in the apparent disruption and degeneration of host cells. Intercellular migration also occurred as was evidenced by the presence of ookinetes between midgut cells. Transformation of ookinete to spherical oocyst occurred extracellularly in three different sites. Although most oocysts were found between the host cell basal membrane and the basal lamina, large numbers also were found attached to the external surface of the basal lamina, projecting into the hemocoel. Ectopic development of oocysts in the midgut epithelium between cells was observed much less frequently than development on the basal side of the midgut. The oocyst wall of dense granules, believed to be of parasite origin, was distinguishable from the basal lamina of the host's midgut epithelium. As in other Leucocytozoidae, the cytoplasm of the oocyst differentiated into a single sporoblastoid from which 30-50 sporozoites were formed. Beginning on the third day post infection, elongation of segregated dense sporoblastoid material associated with pellicle thickening led to the formation of the finger-like sporozoite buds which projected into the oocyst cavity. Sporozoites within mature oocysts and salivary glands were structurally similar to sporozoites as described for other haemosporidians.     

Failure to propagate Cryptosporidium spp. in cell-free culture

The successful propagation of Cryptosporidium parvum in cell-free culture medium was recently reported. To investigate whether this phenomenon could be broadened to include other C. parvum isolates, as well as Cryptosporidium hominis, we attempted to propagate 3 isolates in cell-free medium under reported culture conditions. Cryptosporidium oocysts from C. parvum strains Moredun (MD) or IOWA or C. hominis strain TU502 were added to media containing coagulated newborn calf serum. The cultures were sampled at various times throughout a 45 (IOWA) or 78 (MD, TU502)-day period and were microscopically examined for various life stages of Cryptosporidium. Cell-free cultures harvested on days 45 and 68 postinoculation were tested for in vitro infectivity on Madrin-Darby bovine kidney cells. In vivo infectivity testing was performed using either infant or 2-wk-old immunosuppressed C57BL mice with cell-free cultures harvested on days 52 and 78. Fecal and gut samples collected from mice were examined by modified acid-fast staining. Data from wet mounts, electron microscopy, and in vitro and in vivo infectivity testing showed that the original oocysts did not complete their life cycle and produce new, viable, infectious oocysts in cell-free culture. Thus, we conclude that this is not a universal phenomenon or readily accomplished.     

The life cycle of Cryptosporidium baileyi n. sp. (Apicomplexa, Cryptosporidiidae) infecting chickens

The life cycle and morphology of a previously undescribed species of Cryptosporidium isolated from commercial broiler chickens is described. The prepatent period for Cryptosporidium baileyi n. sp. was three days post oral inoculation (PI) of oocysts, and the patent period was days 4-24 PI for chickens inoculated at two days of age and days 4-14 for chickens inoculated at one and six months of age. During the first three days PI, most developmental stages of C. baileyi were found in the microvillous region of enterocytes of the ileum and large intestine. By day 4 PI, most parasites occurred in enterocytes of the cloaca and bursa of Fabricius (BF). Mature Type I meronts with eight merozoites first appeared 12 h PI and measured 5.0 x 4.9 micrometers. Mature Type II meronts with four merozoites and a large granular residuum first appeared 48 h PI and measured 5.1 x 5.1 micrometers. Type III meronts with eight short merozoites and a large homogeneous residuum first appeared 72 h PI and measured 5.2 x 5.1 micrometers. Microgamonts (4.0 x 4.0 micrometers) produced approximately 16 microgametes that penetrated into macrogametes (4.7 x 4.7 micrometers). Macrogametes gave rise to two types of oocysts that sporulated within the host cells. Most were thick-walled oocysts (6.3 x 5.2 micrometers), the resistant forms that passed unaltered in the feces. Some were thin-walled oocysts whose wall (membrane) readily ruptured upon release from the host cell. Sporozoites from thin-walled oocysts were observed penetrating enterocytes in mucosal smears. The presence of thin-walled, autoinfective oocysts and the recycling of Type I meronts may explain why chickens develop heavy intestinal infections lasting up to 21 days. Oocysts of C. baileyi were inoculated orally into several animals to determine its host specificity. Cryptosporidium baileyi did not produce infections in suckling mice and goats or in two-day-old or two-week-old quail. One of six 10-day-old turkeys had small numbers of asexual stages only in the BF. Four of six one-day-old turkeys developed mild infections only in the BF, and sexual stages of the parasite were observed in only one of the four. All seven one-day-old ducks and seven two-day-old geese developed heavy infections only in the BF with all known developmental stages present.     

Isolation of amylopectin granules and identification of amylopectin phosphorylase in the oocysts of Eimeria tenella.

Amylopectin granules were purified from Eimeria tenella oocysts following digestion with sodium dodecyl sulfate and pronase. The oval granules had a uniform size of 0.5 X 0.7 mum, and consisted of only glucose polymers. alpha-Amylase treatment yielded 235 nmoles of maltose from the granules from 10(6) unsporulated oocysts and 93 nmoles maltose from those from 10(6) sporulated oocysts. Amylopectin phosphorylase activity was detected in the cytoplasm of unsporulated oocysts of E. tenella. It had a specific activity of 13 U/mg protein in crude extracts, and a pH optimum of 6.0. The Km values determined were 9.1 mM for glucose-1-phosphate and 5.6 mM for glucose end groups in potato amylopectin. Enzyme activity declined at a linear rate during sporulation, sporulated oocysts containing less than 8% of the activity of unsporulated oocysts. No amylase-type activity was found in the parasite.     

Cryptosporidium scophthalmi n. sp. (Apicomplexa: Cryptosporidiidae) from cultured turbot Scophthalmus maximus. Light and electron microscope description and histopathological study

Cryptosporidium scophthalmi n. sp. is described from the turbot Scophthalmus maximus L., sampled from different farms on the coast of NW Spain. The parasite was found mainly in the intestinal epithelium and very seldom in the stomach. Oocysts were almost spherical, with 4 naked sporozoites and a residuum, and measured 3.7-5.03 x 3.03-4.69 microm (mean 4.44 x 3.91) (shape index 1.05-1.34, mean 1.14). Sporulation was endogenous, as fully sporulated oocysts were found within the intestinal epithelium, lumen and faeces. Merogonial and gamogonial stages were in the typical extracytoplasmic position, whereas sporogonial stages were deep within the epithelium. Oocysts and other stages of C. scophthalmi comply with most of the diagnostic features of the genus Cryptosporidium, but differ from all hitherto described species. Ultrastructural features, including the characteristic feeding organelle, were mainly comparable with those of other Cryptosporidium species. Mitochondria were frequently observed in sporozoites. Infection prevalence was very variable, and juvenile fish were most frequently and intensively parasitised. External clinical signs were not detected, although some fish showed intestinal distension at necropsy. The marked histopathological damage occurring in severe infection includes distension of epithelial cells by large vacuoles, containing clusters of oocysts, and can lead to sloughing of epithelial cell remnants and oocysts or even detachment of intestinal mucosa. An inflammatory reaction involving leucocyte infiltration was sometimes observed.     

The Life Cycle of Cryptosporidium baileyi n. sp. (Apicomplexa, Cryptosporidiidae) Infecting Chickens

ABSTRACT. The life cycle and morphology of a previously undescribed species of Cryptosporidium isolated from commercial broiler chickens is described. The prepatent period for Cryptosporidium baileyi n. sp. was three days post oral inoculation (PI) of oocysts, and the patent period was days 4–24 PI for chickens inoculated at two days of age and days 4–14 for chickens inoculated at one and six months of age. During the first three days PI, most developmental stages of C. baileyi were found in the microvillous region of enterocytes of the ileum and large intestine. By day 4 PI, most parasites occurred in enterocytes of the cloaca and bursa of Fabricius (BF). Mature Type I meronts with eight merozoites first appeared 12 h PI and measured 5.0 × 4.9 μm. Mature Type II meronts with four merozoites and a large granular residuum first appeared 48 h PI and measured 5.1 × 5.1 μm. Type I meronts with eight short merozoites and a large homogeneous residuum first appeared 72 h PI and measured 5.2 × 5.1 μm. Microgamonts (4.0 × 4.0 μm) produced 16 micro-gametes that penetrated into macrogametes (4.7 × 4.7 μm). Macrogametes gave rise to two types of oocysts that sporulated within the host cells. Most were thick-walled oocysts (6.3 × 5.2 μm), the resistant forms that passed unaltered in the feces. Some were thin-walled oocysts whose wall (membrane) readily ruptured upon release from the host cell. Sporozoites from thin-walled oocysts were observed penetrating enterocytes in mucosal smears. The presence of thin-walled, autoinfective oocysts and the recycling of Type I meronts may explain why chickens develop heavy intestinal infections lasting up to 21 days. Oocysts of C. baileyi were inoculated orally into several animals to determine its host specificity. Cryptosporidium baileyi did not produce infections in suckling mice and goats or in two-dayold or two-week-old quail. One of six 10-day-old turkeys had small numbers of asexual stages only in the BF. Four of six one-day-old turkeys developed mild infections only in the BF, and sexual stages of the parasite were observed in only one of the four. All seven one-day-old ducks and seven two-day-old geese developed heavy infections only in the BF with all known developmental stages present.     

Gibbsia archiuli (Apicomplexa, Eucoccidiorida) n. g., n. sp. from the Millipede Archiulus moreleti

ABSTRACT. Gibbsia archiuli n. g., n. sp. (Eucoccidiorida, Adeleidae) is named for the apicomplexan protozoon described by Gibbs (1952) from the blood cells of the South African garden millipede Archiulus moreleti. Merogony, gamogony, and sporogony all take place in the host's blood cells. The oocysts contain four sporocysts, each with one sporozoite. The microgametes are not flagellated.