New observations on first-generation merogony of Eimeria tuskegeensis in Sigmodon hispidus

First-generation development of Eimeria tuskegeensis was evaluated using light microscopy. Sporozoite-shaped meronts containing a prominent refractile body were observed in small intestinal cells of an experimentally infected cotton rat at 24 h post inoculation (PI). Mature spherical or subspherical meronts containing crescent-shaped merozoites were observed at 36 h PI. Refractile bodies were observed in some of these merozoites. Sporozoite-shaped meronts that were isolated from host intestinal cells and inoculated onto human fetal lung cell cultures penetrated the cultured cells by 2 h PI. A mature, subspherical, first-generation meront containing seven merozoites was observed at 9 h PI in cell culture, indicating that sporozoite-shaped meronts isolated from the host retained their infectivity.     

Early Development of Eimeria Papillata (Apicomplexa: Eimeriidae) In the Mouse

ABSTRACT Early development of Eimeria papillata (Apicomplexa) in the mouse was evaluated using Nomarski interference-contrast and brightfield microscopy. Sporozoite-shaped meronts, which were motile and contained a large posterior refractile body and a smaller anterior refractile body, were observed entering and leaving host cells in the jejunum of an experimentally infected mouse at 26 h post inoculation (HPI). However, early developmental stages were not observed in tissue of the duodenum, ileum, cecum and colon. the mean length and width of these meronts (n = 20) were 12.0 μm and 3.7 μm, respectively. Spherical or subspherical meronts containing crescent-shaped merozoites were observed at 36 HPI.     

Early development of Eimeria papillata (Apicomplexa: Eimeriidae) in the mouse

Early development of Eimeria papillata (Apicomplexa) in the mouse was evaluated using Nomarski interference-contrast and brightfield microscopy. Sporozoite-shaped meronts, which were motile and contained a large posterior refractile body and a smaller anterior refractile body, were observed entering and leaving host cells in the jejunum of an experimentally infected mouse at 26 h post inoculation (HPI). However, early developmental stages were not observed in tissue of the duodenum, ileum, cecum and colon. The mean length and width of these meronts (n = 20) were 12.0 microns and 3.7 microns, respectively. Spherical or subspherical meronts containing crescent-shaped merozoites were observed at 36 HPI.     

Development of the Swine Coccidium Eimeria debliecki Douwes, 1921 in Mammalian Cell Cultures1

Sporozoites of Eimeria debliecki entered human fetal lung and porcine kidney cells grown in cultures and underwent one merogenous cycle, terminating in the production of second-generation trophozoites. Sporozoites were intracellular 1 h post-inoculation (PI) and developed into sporozoite-shaped meronts at 40 h PI. These meronts, one of which was motile, had from two to ten nuclei. Sporozoite-shaped meronts then developed into elongate or spheroidal meronts with 10 to 24 nuclei by two days PI. Ten to 26 first-generation merozoites were formed by budding from the meront surface. Mature first-generation merozoites were most numerous three days PI. Most meronts had ruptured and released nonmotile merozoites into the culture medium by four days PI. Merozoites that were not released became rounded and developed into second-generation trophozoites. Refractile bodies were present in all developmental stages. No further development was observed five through eight days PI.     

Development of the swine coccidium Eimeria debliecki Douwes, 1921 in mammalian cell cultures

Sporozoites of Eimeria debliecki entered human fetal lung and porcine kidney cells grown in cultures and underwent one merogenous cycle, terminating in the production of second-generation trophozoites. Sporozoites were intracellular 1 h post-inoculation (PI) and developed into sporozoite-shaped meronts at 40 h PI. These meronts, one of which was motile, had from two to ten nuclei. Sporozoite-shaped meronts then developed into elongate or spheroidal meronts with 10 to 24 nuclei by two days PI. Ten to 26 first-generation merozoites were formed by budding from the meront surface. Mature first-generation merozoites were most numerous three days PI. Most meronts had ruptured and released nonmotile merozoites into the culture medium by four days PI. Merozoites that were not released became rounded and developed into second-generation trophozoites. Refractile bodies were present in all developmental stages. No further development was observed five through eight days PI.     

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.     

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.     

Development of Caryospora simplex (Apicomplexa: Eimeriidae) from Sporozoites to Oocysts in Human Embryonic Lung Cell Culture1

Leighton tubes containing monolayers of human embryonic lung cells were inoculated with 70,000 or 30,000 sporozoites of the viperid coccidium Caryospora simplex and examined at 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18 days post-inoculation (PI). By day 1 PI, sporozoites had penetrated cells and were within parasitophorous vacuoles. Most sporozoites became spherical and then underwent karyokinesis several times between days 2 and 6 PI. Mature Type I meronts were found on days 6–16 PI and contained 8 to 22 short, stout merozoites. Mature Type II meronts were present on days 10–18 PI and contained 8 to 22 long, slender merozoites. Developing gamonts (undifferentiated sexual stages) were observed on days 14 and 16 PI. Mature micro- and macrogametes and thin-walled unsporulated oocysts were present on days 16 and 18 PI. Attempts to sporulate oocysts in tissue culture medium or in a 2.5% (w/v) aqueous solution of K₂Cr₂O₇ at 25/°C and 37°C were unsuccessful; only a few oocysts developed to the contracted sporont stage. Four Swiss-Webster mice injected intraperitoneally with merozoites obtained from Leighton tubes on day 10 PI did not acquire infections. This is the second coccidium reported to complete its entire development, from sporozoite to oocyst, in cell culture.     

Development and Ultrastructure of First-Generation Meronts of Sarcocystis cruzi in Calves Fed Sporocysts from Coyote Feces*

SYNOPSIS. The development of Sarcocystis cruzi Hasselmann (syn. S. fusiformis Railliet) meronts was studied in seven 7- to 10-day-old calves killed 4, 7, 11, 15, 22, 25 and 28 days postinoculation (DPI) with 5 × 10⁷ sporocysts from feces of coyotes. No meronts were found 4 and 7 DPI. Young and intermediate meronts with 1–16 nuclei were found in endothelial cells of arteries in mesenteric lymph nodes, but not in kidneys 11 DPI. Mature meronts were noted in endothelial cells of arteries, arterioles, or capillaries of many organs of calves killed 15 to 25 DPI. No first-generation meronts were found 28 DPI. By electron microscopy, all stages of the first-generation merogony were found free within the host cell cytoplasm and not within a parasitophorous vacuole. The appearance of intranuclear spindles preceded the formation of merozoites by endopolygeny. Mature meronts measured 41.0 × 17.5 (34–50 × 15–24) μm, contained ～ 100–350 merozoites, and had 2 to 4 relatively small residual bodies, 2.8 μm in diameter. Merozoites measured 6.3 × 1.5 (5.5–7 × 1 μm) and contained most of the organelles characteristically found in coccidian merozoites. Micropores were observed in merozoites, but not in young and intermediate meronts. Merozoites were seen free in the lumen of blood vessels, in intracellular areas, and free within the host cell cytoplasm.     

Development of Caryospora simplex (Apicomplexa: Eimeriidae) from sporozoites to oocysts in human embryonic lung cell culture

Leighton tubes containing monolayers of human embryonic lung cells were inoculated with 70,000 or 30,000 sporozoites of the viperid coccidium Caryospora simplex and examined at 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18 days post-inoculation (PI). By day 1 PI, sporozoites had penetrated cells and were within parasitophorous vacuoles. Most sporozoites became spherical and then underwent karyokinesis several times between days 2 and 6 PI. Mature Type I meronts were found on days 6-16 PI and contained 8 to 22 short, stout merozoites. Mature Type II meronts were present on days 10-18 PI and contained 8 to 22 long, slender merozoites. Developing gamonts (undifferentiated sexual stages) were observed on days 14 and 16 PI. Mature micro- and macrogametes and thin-walled unsporulated oocysts were present on days 16 and 18 PI. Attempts to sporulate oocysts in tissue culture medium or in a 2.5% (w/v) aqueous solution of K2Cr2O7 at 25 degrees C and 37 degrees C were unsuccessful; only a few oocysts developed to the contracted sporont stage. Four Swiss-Webster mice injected intraperitoneally with merozoites obtained from Leighton tubes on day 10 PI did not acquire infections. This is the second coccidium reported to complete its entire development, from sporozoite to oocyst, in cell culture.     

The endogenous stages of Eimeria utahensis (Protozoa: Eimeriidae) in the kangaroo rat, Dipodomys ordii

The endogenous life cycle of Eimeria utahensis is described from experimentally infected kangaroo rats, Dipodomys ordii. The endogenous asexual cycle consisted of 4 generations of meronts. First-generation meronts were concentrated in the anterior third of the small intestine. The succeeding generations of meronts and the sexual stages were concentrated in the middle third of the small intestine. First-generation meronts had a mean diameter of 9.7 micrometer and contained 12 to 16 merozoites. Second-generation meronts had a mean diameter of 8.0 micrometer and contained 12 to 16 merozoites and a residual body. Third-generation meronts had a mean diameter of 12.4 micrometer and contained 4 to 8 merozoites. Fourth-generation meronts had a mean diameter of 8.6 micrometer and contained 16 to 24 merozoites. Young gamonts were located in epithelial cells of the crypts of the small intestine. Shortly after the parasites entered the epithelial cells, the infected cells became displaced into the lamina propria, and most of the mature gamonts were in this location. The nuclei of host cells containing young sexual stages became greatly elongated and flattened. A few young gamonts were seen in cells in which the host cell nuclei were dividing. During development, nuclei of microgamonts became arranged on the periphery of numerous compartments. Only one type of wall-forming body could be distinguished in the macrogamonts.     

Ultrastructural Study of Schizogony in Eimeria callospermophili*

SYNOPSIS The development of 1st generation schizonts of Eimeria callospermophili was studied with cell cultures and with experimentally infected host animals, Spermophilus armatus. Sporozoite-shaped schizonts each had 5-10 nuclei and all of the organelles of the sporozoite; each nucleus had a nucleolus and an associated Golgi apparatus. In stages immediately preceding merozoite formation, an intranuclear spindle apparatus with conical polar areas were observed near the outer margin of each nucleus. Two centrioles, each having 9 single peripheral tubules and one central tubule, were observed near each pole in some specimens. Merozoite formation began internally, with anlagen of 2 merozoites developing near each nucleus. The inner membrane of the merozoites first appeared as 2 dense thickenings adjacent to the polar cones and centrioles; subpellicular microtubules appeared simultaneously. Two anterior annuli and the conoid formed between the 2 thickenings. Vesicles, possibly of Golgi origin, were located next to the forming inner membrane. As the forming merozoites underwent elongation, a rhoptries anlage, a Golgi apparatus, refractile bodies, and mitochondria were incorporated into each. Sporozoite-shaped schizonts with merozoite anlagen transformed into spheroid or ovoid schizonts; at this time the conoid, rhoptries, micronemes, and the inner membrane of the pellicle gradually disappeared; several small refractile bodies were formed from the larger one. When development was about 1/3 complete, the immature merozoites began to grow outward from the surface of the schizont. In this phase of development, the single surface membrane of the schizont became the outer membrane of the merozoite's pellicle, and additional organelles, including the nucleus, were incorporated. Finally, the merozoites became pinched off, leaving a residual body. Development in cell cultures and host tissues was similar. This type of schizogony, previously undescribed in Eimeria, is compared with corresponding stages of development in other species of Eimeria and Sporozoa.     

The asexual pre-cyst development of Sarcocystis tenella in experimentally infected specific pathogen-free lambs

Twenty-two lambs raised under sporozoa-free conditions were infected at weaning with 0.25–2.0 million Sarcocystis tenella sporocysts obtained from dogs and then necropsied at intervals between 1.3 h and 41 days post-inoculation (dpi). Fixed and frozen sections from 47 different tissues from each lamb were examined respectively by a variety of histochemical stains and by indirect fluorescent-antibody staining. The remnants of excysted sporocysts were found within the gastro-intestinal tract between 1.3 h and 3 dpi. No enteric proliferative stage of the parasite was detected. First-generation meronts (schizonts) were detected from 6 to 19 dpi within the endothelial cells of arterioles in most organs and tissues. The meronts were undifferentiated from 6 to 9 dpi but were mature in appearance from 12 to 19 dpi (measuring 22.3 × 13.4 μm and containing 18–28 merozoites). Second-generation meronts were detected from 21 to 34 dpi within the endothelial cells of capillaries throughout the entire body. They were undifferentiated from 21 to 23 dpi but appeared mature from 25 to 34 dpi (measuring 15.2 × 10.6 μm and containing 18–38 merozoites). Several smaller meronts were then detected at 36 dpi within cells of the mononuclear phagocytic system. They were all mature in appearance (measuring 7.4 × 5.1 μm and containing 6–9 merozoites) and are thought to have formed facultatively following the incorporation of some second-generation merozoites into phagocytic cells. Only developing cysts were then detected at 41 dpi throughout the cardiac and skeletal musculature. Elements in both first- and second-generation merozoites stained markedly with haematoxylin and eosin, periodic acid-Schiff's, alkaline Giemsa-colophonium and basic fuchsin stains. However, only second-generation meronts and developing cysts exhibited strong specific reactions with the fluorescent-antibody stain.     

Observations on the endogenous stages of Eimeria crandallis in domestic lambs (Ovis aries)

Lambs reared coccidia-free were inoculated orally with various numbers of sporulated oocysts of E. crandallis and were killed between 1 and 22 days after inoculation; tissues were examined histologically. Sporozoites were seen 1, 2 and 3 days after inoculation (DAI) in crypt epithelial cells in the mid-jejunum. Infected cells migrated into the lamina propria where the parasite within them developed into a firstgeneration meront containing about 250,000 merozoites at 10 DAI. A second generation of meronts was seen at 10–12 DAI, each containing up to about 10 merozoites, situated mainly at the bases of crypts in the jejunum and ileum but also in the caecum. From 11 DAI pro-gamonts were seen which were enveloped by the host cell nucleus and which divided in synchrony with the host cell for an undetermined number of generations. Mature gamonts began to develop from them by 16 DAI. Oocyst output began at 16 DAI and rose to a peak at about 22 DAI. Up to 10⁸ oocysts were produced per oocyst inoculated. They showed wide variation in size and colour.     

Development and ultrastructure of first-generation meronts of Sarcocystis cruzi in calves fed sporocysts from coyote feces

The development of Sarcocystis cruzi Hasselmann (syn. S. fusiformis Railliet) meronts was studied in seven 7- to 10-day-old calves filled 4, 7, 11, 15, 22, 25 and 28 days postinoculation (DPI) with 5 x 10(7) sporocysts from feces of coyotes. No meronts were found 4 and 7 DPI. Young and intermediate meronts with 1-16 nuclei were found in endothelial cells of arteries in mesenteric lymph nodes, but not in kidneys 11 DPI. Mature meronts were noted in endothelial cells of arteries, arterioles, or capillaries of many organs of calves killed 15 to 25 DPI. No first-generation meronts were found 28 DPI. By electron microscopy, all stages of the first-generation merogony were found free within the host cell cytoplasm and not within a parasitophorous vacuole. The appearance of intranuclear spindles preceded the formation of merozoites by endopolygeny. Mature meronts measured 41.0 x 17.5 (34-50 x 15-24) microgram, contained approximately 100-350 merozoites, and had 2 to 4 relatively small residual bodies, 2.8 microgram in diameter. Merozoites measured 6.3 x 1.5 (5.5-7 x 1 microgram) and contained most of the organelles characteristically found in coccidian merozoites. Micropores were observed in merozoites, but not in young and intermediate meronts. Merozoites were seen free in the lumen of blood vessels, in intracellular areas, and free within the host cell cytoplasm.     

A Comparison of Endogenous Development of Three Isolates of Cryptosporidium in Suckling Mice1

ABSTRACT. Suckling mice were used as a model host to compare the endogenous development of three different isolates of Cryptosporidium: one from a naturally infected calf, one from an immunocompetent human with a short-term diarrheal illness, and one from a patient with acquired immune deficiency syndrome (AIDS) and persistent, life-threatening, gastrointestinal cryptosporidiosis. After oral inoculation of mice with oocysts, no differences were noted among developmental stages of the three isolates in their sites of infection, times of appearance, and duration, morphology, and fine structure. Sporozoites excysted within the lumen of the duodenum and ileum, penetrated into the microvillous region of villous enterocytes, and developed into type I meronts with six or eight merozoites. Type I merozoites penetrated enterocytes and underwent cyclic development as type I meronts or they became type II meronts with four merozoites. Type II merozoites did not exhibit cyclic development but developed directly into sexual forms. Microgamonts produced £16 small, bullet-shaped microgametes, which were observed attaching to and penetrating macrogametes. Approximately 80% of the oocysts observed in enterocytes had a thick, two-layered wall. After sporulating within the parasitophorous vacuole, these thick-walled oocysts passed through the gut unaltered and were the resistant forms that transmitted the infection to a new host. Approximately 20% of the oocysts in enterocytes consisted of four sporozoites and a residuum surrounded only by a single oocyst membrane that ruptured soon after the parasite was released from the host cell. The presence of thin-walled, autoinfective oocysts and recycling of type I meronts may explain why a small oral inoculum can produce an overwhelming infection in a suitable host and why immune deficient persons can have persistent, life-threatening cryptosporidiosis in the absence of repeated oral exposure to thick-walled oocysts.     

Complete Development of Isospora suis of Swine in Chicken Embryos1

Development of the swine coccidium, Isospora suis, in embryonated chicken eggs is described. The allantoic cavities of eight-to-ten-day-old white Leghorn embryos were inoculated with either 100,000 or 200,000 sporozoites. Developmental stages morphologically similar to those found in the intestines of piglets were present in the endodermal layer of the chorioallantoic membrane (CAM), beginning three days post inoculation (PI). No stages were found in the mesodermal or ectodermal layers of the CAM and none were observed in heart, lung, liver, or spleen. Type I meronts and merozoites were found on days 3 through 10 PI. Type II meronts and merozoites were found days 4 through 10 PI. Mature microgamonts, macrogamonts, and oocysts were found on days 7 through 10 PI. Oocysts appeared to be retained in the endodermal cells and in ovo sporulation did not occur. Attempts to sporulate CAM-derived oocysts were not successful. Isospora suis was not pathogenic for embryos under the conditions of this study. This study represents the first fully documented report of complete development of a mammalian coccidium in chicken embryos.     

Complete development of Cryptosporidium parvum in host cell-free culture

The present study describes the complete in vitro development of Cryptosporidium parvum (cattle genotype) in RPMI-1640 maintenance medium devoid of host cells. This represents the first report in which Cryptosporidium is shown to multiply, develop and complete its life cycle without the need for host cells. Furthermore, cultivation of Cryptosporidium in diphasic medium consisting of a coagulated new born calf serum base overlaid with maintenance medium greatly increased the total number of Cryptosporidium stages. Type I and II meronts were detected giving rise to two morphologically different merozoites. Type I meronts, which appear as grape-like clusters as early as 48 h post culture inoculation, release merozoites, which are actively motile, and circular to oval in shape. Type II meronts group in a rosette-like pattern and could not be detected until day 3 of culturing. Most of the merozoites released from type II meronts are generally spindle-shaped with pointed ends, while others are rounded or pleomorphic. In contrast to type I, merozoites from type II meronts are less active and larger in size. Sexual stages (micro and macrogamonts) were observed within 6-7 days of culturing. Microgamonts were darker than macrogamonts, with developing microgametes, which could be seen accumulating at the periphery. Macrogamonts have a characteristic peripheral nucleus and smooth outer surface. Oocysts at different levels of sporulation were seen 8 days post culture inoculation. Cultures were terminated after 4 months when the C. parvum life cycle was still being perpetuated with the presence of large numbers of excysting and intact oocysts. Culture-derived oocysts obtained after 46 days p.i. were infective to 7- to 8-day-old ARC/Swiss mice. The impact of C. parvum developing in cell-free culture is very significant and will facilitate many aspects of Cryptosporidium research.     

The life cycle and pathogenicity of coccicium Eimeria nocens (Kotlán, 1933) in domestic goslings

Twenty-four 10-day-old, artificially reared, coccidia-free goslings (Anser cygnoides var. domestica) were inoculated orally with 1.0x10(5)-1.0x10(6) sporulated oocysts of Eimeria nocens, and killed at intervals from 30 to 336 hr postinoculation (PI). Parts of the visceral organs, including intestines, kidney, liver, gallbladder, and spleen from inoculated goslings, were fixed and sectioned. The life cycle of E. nocens and histologic changes during infection were examined microscopically. The results showed that at least 3 generations of meronts developed in the endogenous stage of the life cycle of E. nocens. Two types of meronts were found. The first completed maturation at 54 to 78 hr PI. These meronts were the first generation, with each forming about 12 merozoites. The second completed maturation at 102 to 240 hr PI. These meronts were the second or third generations, with each meront forming about 24 merozoites. Development of gamonts began at about 198 hr after infection. The prepatent period was 9 days and discharge of oocysts continued for 4 days. Sporulation of oocysts occurred in 60-72 hr at 25 C. Eimeria nocens invaded the posterior jejunum, ileum, caecum, rectum, and cloaca. Developmental stages were localized within the epithelial cells of villi and crypts, and in lamina propria. Marked histological changes, including desquamation and necrosis of intestinal epithelium, submucosal edema, hemorrhages, infiltration of inflammatory cells, and villous atrophy, were seen during the periods of late merogony, gamogony, and oocyst shedding. They were most pronounced in the ileum and the regions nearby. The infected goslings showed severe diarrhea, bloody feces, anorexia, emaciation, and even death, suggesting that E. nocens is highly pathogenic for goslings.     

In vitro cultivation of meronts of Sarcocystis cruzi

Several established cell lines were tested for their ability to support in vitro development of meronts of Sarcocystis cruzi. Sporozoites penetrated bovine monocytes (BM), bovine pulmonary artery endothelial cells (CPA), Madin-Darby bovine kidney cells and mouse macrophages, but developed to meronts in BM and CPA only. Sporozoites developed to large meronts that contained approximately 180-350 merozoites, whereas merozoites formed small meronts with 50-100 merozoites. Mature large meronts were present at 18-86 days after inoculation (DAI) in BM and at 16-72 DAI in CPA. Small meronts were present at 23-115 and 23-91 DAI in BM and CPA. Considerably more merozoites developed in CPA than in BM. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that merozoites harvested at 36 and 48 DAI each had 1 unique protein as well as numerous common proteins.