The Life Cycle of Eimeria vermiformis Ernst,Chobotar and Hammond, 1971 in the Mouse Mus musculus1

SYNOPSIS. The life cycle of Eimeria vermiformis from the mouse Mus musculus is described from experimental infections. The prepatent period was 7 days, and the patent period 7–22+ days. Endogenous stages were in the lower 2/3 of the small intestine. Two generations of schizonts were found. Mature 1st generation schizonts, seen 4 days after inoculation, were 16–25 × 9–16 μ and had long vermiform merozoites. Mature 2nd generation schizonts were first seen 5 days after inoculation. They were 8–18 × 7–14 μ (mean 11.2 × 13.1 μ). Mature microgametocytes, 17–32 × 12–25 μ, were present 6 days after inoculation. Macrogametes with plastic granules were found at the same time. The life cycle of E. vermiformis is compared with those of other species of Eimeria from Mus.     

Eimeria bateri Bhatia,Pandey and Pande, 1965 from the Hungarian Quail Coturnix c. coturnix in the United States and Its Attempted Transmission to the Chicken**

SYNOPSIS. Eimeria bateri Bhatia, Pandey, Pande, 1965 is described from the Hungarian quail Coturnix c. coturnix for the first time in the U.S. Its oocysts are either ellipsoidal or ovoid, 14–28 by 12–19 μ with a mean of 20.5 by 15.3 μ. Its sporocysts are elongate ovoid, with a Stieda body, 8–12 by 6–9 μ with a mean of 10.3 by 7.5 μ. Two coccidia-free chicks 8 days old were inoculated with 50,000 oocysts each of E. bateri, but patent infections did not occur. This coccidium is therefore presumably host-specific.     

Endogenous Cycle of the Swine Coccidium Eimeria debliecki Douwes, 1921*

SYNOPSIS. A pure strain of Eimeria debliecki (University of Illinois strain A) established from a single oocyst was used to determine the endogenous cycle. Young parasite-free pigs 2 weeks to 3 months old were used throughout the study. The endogenous cycle was found to take place in the small intestine where the parasites were located in the distal portion of the striated simple columnar epithelial cells of the villi. The first generation schizonts were found in only the jejunum (15% of small intestine). The second generation schizonts and gametes occurred in the jejunum and ileum (70% of small intestine), a slight posterior progression occurring with each stage. The entire cycle required 6.5 days. The schizogonous cycle comprised 2 generations. The first generation schizonts required 2.5 days to reach maturity, measured 8-12 μ, contained 16 merozoites measuring 12-15 μ and had a polar residual mass. The second generation schizonts required 2 days to reach maturity, measured 13-16 μ, contained 32 rotund merozoites measuring 6–8 μ, and had only a few granules of residual material. Gametogony took place in 1.5 days. The macrogametes measured 12-16 μ, and the microgametocytes measured 9-14 μ with microgametes measuring 5–6 μ.     

Development of Eimeria auburnensis in Cell Cultures

SYNOPSIS. Monolayer established cell line cultures of bovine kidney (Madin-Darby) and human intestine (Intestine 407), as well as embryonic bovine tracheal and embryonic spleen cell line cultures were inoculated with E. auburnensis sporozoites and observed for a maximum of 22 days. Mature 1st generation schizonts developed in the kidney, tracheal and spleen cells. In the intestine cells, trophozoites were seen in 3 of 4 experiments, but schizonts were not found. Sporozoites penetrated cells, beginning within a few minutes after inoculation. Penetration was usually accomplished within 10 seconds, and the body of the sporozoite underwent a slight constriction as it passed thru the host cell membrane. Some sporozoites left cells. Numerous intracellular sporozoites were observed in kidney, tracheal and spleen cultures. Crescent bodies were seen in the parasitophorous vacuole as early as 1 day after inoculation. At this time, the nuclei of most intracellular sporozoites had changed from vesicular to compact. Beginning 4 days after inoculation, enlarged sporozoites and parasites having a sporozoite shape, but with 2-5 nuclei, were frequently seen. These enlarged sporozoites and sporozoite-shaped schizonts evidently transformed into trophozoites and spheroidal schizonts by means of lateral outpocketings. Few trophozoites were seen. More immature schizonts developed in kidney cells than in the other cell types. The numbers of mature schizonts observed in kidney and tracheal cells were similar, but development occurred less consistently in the latter. Few immature and mature schizonts developed in spleen cells. Mature schizonts, first seen 9 days after inoculation, were considerably smaller than those reported from calves. Some motile merozoites were seen; evidently no development beyond these occurred. The nucleus and nucleolus of host cells were enlarged; this enlargement was not as pronounced as in infections in calves. Multiple host cell nuclei were frequently observed. Degenerative changes in the cultured cells and in the parasites usually occurred, beginning 9-17 days after inoculation; these were more pronounced in the spleen cells than in the others.     

Development of Eimeria alabamensis from Cattle in Mammalian Cell Cultures*

SYNOPSIS. Monolayer primary cultures of cells from bovine embryonic intestine (BEInt), kidney (BEK), spleen (BES), and thyroid (BETy) and cell line cultures of embryonic bovine trachea (EBTr) and synovium (BESy) as well as established cell line cultures of bovine kidney (Madin-Darby, MDBK), human intestine (Int 407) and Syrian hamster kidney (BHK) were inoculated with freshly excysted sporozoites of Eimeria alabamensis and observed for 4–5 days. Sporozoites penetrated all cell types; during the 1st 24 hr, intracellular sporozoites, trophozoites and binucleate schizonts were seen in all cell cultures. Mature schizonts were more numerous in BES and MDBK cells than in the others. Large schizonts, 14.2 (11–18.5) by 10.2 μ (8.5–11), with 6–14 short, stubby merozoites (each with 2 refractile bodies) occurred at 2 and 3 days in all cells except BESy, Int 407, and BHK. Small schizonts, 9.7 (5.5–13) by 6 μ (5–8.5), with 6–10 long, slender merozoites (each with 2 refractile bodies) were found 3 days after inoculation in all cell types. At 4 days, some intracytoplasmic merozoites and a few intranuclear 2nd generation trophozoites were found. After 4 days post-inoculation, intracellular parasites were rarely seen and these were apparently degenerate. Development within the host cell nucleus, the normal site of development in the host animal, was observed infrequently in cell cultures. Intranuclear sporozoites, found no earlier than 2 days after inoculation, developed similarly to those in the cytoplasm, and small intranuclear schizonts with 6–10 merozoites (each with 2 refractile bodies) occurred after 3 days in culture.     

Development of Eimeria callospermophili and E. bilamellata from the Uinta Ground Squirrel Spermophilus armatus in Cultured Cells*

SYNOPSIS. Cell lines or established cell lines of bovine, ovine or human origin and primary cells from whole embryos of groundsquirrels were used in a study of the in vitro development of Eimeria callospermophili and E. bilamellata from the Uinta ground squirrel, Spermophilus armatus. Monolayers in Leighton tube cultures were inoculated with sporozoites of either of these 2 species and examined with phase-contrast microscopy at various intervals. After such examination, coverslips were fixed in Schaudinn's or Zenker's fluid and variously stained. E. callospermophi sporozoites penetrated cells and underwent development to mature 1st generation schizonts in most cell types. At different times after inoculation, both species formed sporozoite-shaped schizonts, which later became spheroidal. Intracellular movements of sporo zoite-shaped schizonts of E. callospermophili were observed and such schizonts penetrated cells when freed by mechanical disintegration of the host cells. Merozoites were formed at the periphery of the schizont in both species. Mature 1st generation schizonts of E. callospermophili, with 6–14 merozoites, were first seen 15 hr after inoculation; the corresponding values for E. bilamellata were 12–27 merozoites and 4 days. Merozoites of both had anterior and posterior refractile bodies. Exposure to a trypsin-bile solution stimulated motility in merozoites of E. callospermophili. Second generation trophozoites and immature schizonts of E. callospermophili were seen in cultures of primary cells of whole ground-squirrel embryos 20–24 hr and 44–48 hr, respectively, after inoculation of sporozoites.     

Eimeria colchici sp. nov. (Protozoa: Eimeriidae), the Cause of Cecal Coccidiosis in English Covert Pheasants

SYNOPSIS. Eimeria colchici sp. n. is described from English pheasants Phasianus colchicus. It has cocysts measuring 19–33.5 (27.4) by 13–21 (16.7) μ, having both micropyle and polar granule. The large 1st and 2nd generation schizonts occur in the glands of the small intestine, 3rd generation schizonts occur deep in the glands of the ceca, and gametocytes occur in the epithelial cells of the ceca. The prepatent period is 6 days. In young pheasants the parasite causes coccidiosis characterized by formation of white cores in the ceca. Mortality is high in experimental infections. Zoalene (0.0125%) in the feed almost completely suppressed the infection; Amprolium (0.0125%) also gave good control, but sulfaquinoxaline (0.0125%) was not so effective. Sulfaquinoxaline, Saquadil and Sulfamezathine in the drinking water controlled mortality, but treatment had to be applied early to avoid weight losses.     

Comparative Development of Eimeria tenella from Sporozoites to Oocysts in Primary Kidney Cell Cultures from Gallinaceous Birds

Eimeria tenella completed its endogenous life cycle in primary cultures of kidney cells from 2- to 3-week-old-chickens, guinea fowl, partridges, pheasants, quail, and turkeys. Similarity in percentage of infection at 4 hr suggested that sporozoites entered cells from all birds in equal numbers. Development was better, however, in chicken cells in that the percentage of survival and of developmental stages during the first 2 days were greater, developmental stages occurring after 2 days usually were found earlier, mature 2nd-generation schizonts and oocysts were larger, and oocyst production was far greater than in nonhost cells. Multinucleate macrogametes, which sometimes reached sizes 3–4 times greater than normal oocysts, are reported for the first time.     

Life Cycle of Isospora canis Nemeséri, 1959 in the Dog*

The life cycle of I. canis Nemeséri, 1959 was studied in experimentally infected dogs. Freshly sporulated oocysts were ovoid and 34–40 × 28–32 μm. The endogenous stages were found directly beneath the epithelium of the distal portion of the small intestinal villi. Most of the endogenous stages were in the lower 1/3 of the small intestine, but occasionally they were found in other portions of the small intestine. Three asexual generations were present. First-generation schizonts were 16–38 × 11–23 μm and contained 4–24 merozoites; mature 1st-generation merozoites were 8–11 × 3–5 μm. First-generation schizogony lasted up to 7 days after inoculation. Second-generation schizonts were 12–18 × 8–13 μm and contained up to 12 merozoites which were 11–13 × 3–5 μm. Second-generation schizogony was present on postinoculation days 6 and 7. Third-generation schizonts were formed by nuclear division of 2nd-generation merozoites. Most 2nd-generation merozoites underwent nuclear division without leaving the parasitophorous vacuole of the 2nd-generation schizont. Mature 3rd-generation schizonts were 13–38 × 8–24 μm and contained 6–72 merozoites. Third-generation merozoites were 8–13 × 1–3 μm. Third-generation schizogony was present on days 6–8 after inoculation. Mature macrogametes were 22–29 × 14–23 μm. Mature microgametocytes were 20–38 × 14–26 μm. Gametes were present on postinoculation days 7–10. Oocysts were present in tissue sections on postinoculation days 8–10 and 12. The prepatent period was 9–11 days.     

Life Cycle and Host Specificity of Eimeria larimerensis Vetterling, 1964, from the Uinta Ground Squirrel Spermophilus armatus1

SYNOPSIS. Eimeria larimerensis was found in 5 species of ground squirrels and the white-tailed prairie dog. The hosts included Spermophilus armatus from Utah and Montana, S. variegatus from Utah, S. tridecemlineatus from Wyoming, S. lateralis from Utah, S. beecheyi from California and Cynomys leucurus from Wyoming. Oocysts were not present in fecal samples of S. richardconi from Montana, S. lateralis from California or S. columbianus from Washington. This coccidium could not be experimentally transmitted to S. richardsoni; however, patent infections were established in S. armatus, S. lateralis, and S. variegatus. No infections were found after inoculation of least chipmunks (Eutamius minimus), Mongolian gerbils (Meriones unguiculatus), or laboratory rats even tho excystation occurred in these animals. Resistance to infection did not develop during repeated experimental infections of S. armatus, S. lateralis, or S. variegatus. No outward signs of coccidiosis were seen in any of the experimentally infected animals. In experimentally infected S. armatus, the prepatent period was 5 days, and the patent period lasted 3–7 (mean 6.5) days. The endogenous stages were located in the epithelial cells of the jejunum and ileum. Mature 1st-generation schizonts, 1st seen 2.5 days after inoculation, contained 16–32 merozoites. Mature 2nd generation schizonts were present 3.5 days after inoculation and contained 22–46 merozoites of a larger size than those of the 1st generation. Gametocytes were 1st seen 3.5 days after inoculation and developing oocysts were present 4 days after inoculation. Macrogametes contained eosinophilic granules which coalesced to form the oocyst wall. Formation of the macrogametes took place around cytoplasmic masses within the microgametocytes.     

Cultivation of Eimeria tenella in Japanese quail embryos (Coturnix coturnix japonica).

Complete development of Eimeria tenella in Japanese quail embryos was observed. Sporozoites were inoculated into the allantoic cavity of 7-day-old Japanese quail embryos (Coturnix coturnix japonica), after which the infected embryos were incubated at 41 C. In the chorioallantoic membrane mature first generation schizonts, mature second generation schizonts, and gametes were detected at 48 hr postinoculation of sporozoites (PI), 84 hr PI, and 126 hr PI, respectively. Mature gametes and zygotes were found at 132 hr PI, and oocysts were detected at 138 hr PI. Mortality of embryos increased with increment of inoculum size of sporozoites. LD50 was 1.7 x 10(2) sporozoites. Oocyst production was also dependent on inoculum size. Oocysts harvested from embryos sporulated. The oocysts were inoculated into 13-day-old chickens, and oocysts, capable of sporulating normally, were recovered from ceca 7 days after inoculation.     

The Development of First Generation Schizonts of Eimeria bovis*

SYNOPSIS. In young first generation schizonts of E. bovis, the nuclei appeared to have a random distribution. In calves killed 8 days after inoculation some of the schizonts had the nuclei arranged in a single layer at the periphery, with a few infoldings of this layer into the interior. In further development, such ingrowths of the nuclear layer resulted in the formation of compartments of varying size. In schizonts of calves killed 12 days after inoculation spherical or ellipsoidal bodies (blastophores), about 5–20 μ in diameter with a single peripheral layer of nuclei were formed. Merozoites developed as radial outgrowths from the blastophores, leaving residual bodies of variable size, which later disappeared. The response of the host cell to the presence of the schizont was characterized by marked growth of both the nucleus and cytoplasm. The nucleolus became greatly enlarged, and the chromatin was distributed in relatively fine granules. In the host cell cytoplasm, 2 concentric layers were observed; the inner was more dense than the outer. After growth of the schizont was completed its host cell was stretched into a thin covering layer about 1 μ thick. In some schizonts, the host cell disintegrated, and the schizont was then invaded by eosinophils, macrophages and other cells, which eventually destroyed the merozoites.     

The Life Cycle of Isospora felis Wenyon, 1923, a Coccidium of the Cat*

SYNOPSIS. A pure strain of Isospora felis derived from a single oocyst was used to study the endogenous cycle. One and a half to two-month-old laboratory-reared, coccidia-free kittens were used thruout the study. The endogenous stages occurred in the epithelial cells of the distal parts of the villi in the ileum and occasionally duodenum and jejunum. All stages lay above the host cell nucleus. There were 3 asexual generations. The 1st generation schizonts were 11–30 by 10–23 μ when mature and contained 16–17 banana-shaped merozoites 11–15 by 3–5 μ. They became mature in 96 or sometimes in 120 hours. The 1st generation merozoites entered new host cells, rounded up and formed 2nd generation schizonts. These formed within themselves 2–10 or more spindle-shaped bodies resembling 1st generation merozoites in shape and size. These were 2nd generation merozoites. They were uninucleate 120 hours after inoculation, but by 144 hours they became larger, multinucleate and some lost their elongate shape and became ovoid. They were then 3rd generation schizonts. They were 12–16 by 4–5 μ. Each formed up to 6 or more banana-shaped merozoites 6–8 by 1–2 μ. The 3rd generation schizonts and merozoites developed within the same host cell and parasitophorous vacuole as the 2nd generation schizonts and merozoites. Mature schizonts containing only 3rd generation merozoites appeared 144 hours after inoculation, were most abundant 168 hours after inoculation, and might be present as late as 216 hours after inoculation. They were 14–36 by 13–22 μ and contained 36 to more than 70 merozoites. The 3rd generation merozoites entered the sexual cycle. The mature microgametocytes were 24–72 by 18–32 μ and contained a central residuum and a large number of microgametes 5–7 by 0.8 μ with 2 posteriorly-directed flagella. The mature macrogametes were 16–22 by 8–13 μ. Gametogony occurred 144–216 hours after inoculation. The prepatent period was 168–192 hours and the patent period 10–11 days. Peak oocyst production occurred on the 6th day of the patent period.     

Life Cycles of Leucocytozoon dubreuili Mathis and Leger, 1911 and L. fringillinarum Woodcock, 1910 (Haemosporidia: Leucocytozoidae)*

SYNOPSIS The development of Leucocytozoon dubreuili and L. fringillinarum was studied on successive days in simuliid and avian hosts. Sporogony of both parasites is completed in at least 5 species of sylvatic Simuliidae in a minimum of 4-5 days at 21 C. The pattern of development of the 2 species is similar but the size of the oocysts and the number of sporozoites differ. Sporozoites of L. dubreuili and L. fringillinarum were injected into uninfected robins (Turdus m. migratorius) and grackles (Quiscalus quiscula versicolor), respectively. Hepatic biopsies were performed on some of the injected birds. These and others were killed at intervals following inoculation and their tissues examined to detect stages of schizogony. Blood and macerated tissues from birds injected with sporozoites were transferred to uninfected birds to determine whether asexual stages would develop in the latter as a result of the inoculations. The 1st asexual cycle of L. dubreuili is completed in hepatic parenchymal cells in a minimum of 84 hr. Merozoites produced by the hepatic schizonts apparently follow one of 3 courses: invade hepatic parenchymal cells to initiate another cycle; penetrate blood cells and become gametocytes; penetrate tubular cells of the kidneys and grow into renal schizonts. The minimum prepatent period in infections with L. fringillinarum is 76 hr. The 1st asexual cycle occurs in hepatic parenchymal cells and in tubular cells of the kidney. A schizogonic cycle is completed in a minimum of 72 hr in the former and 96 hr in the kidney. Merozoites from the primary hepatic schizonts apparently give rise to (a) gametocytes; (b) secondary hepatic schizonts; (c) renal schizonts. Thus the schizogonic cycles of L. dubreuili and L. fringillinarum differ from each other and from those of L. simondi in ducks.     

Pre-Erythrocytic Development and Associated Host Responses to Haemoproteus meleagridis (Haemosporina: Haemoproteidae) in Experimentally Infected Domestic Turkeys12

ABSTRACT. Two generations of pre-erythrocytic schizogony occurred in skeletal and cardiac muscle of domestic turkeys infected with sporozoites of Haemoproteus meleagridis. First generation schizonts reached maturity approximately five days post-inoculation (DPI) and developed in capillary endothelial cells and myofibroblasts. The schizonts ranged from 12 to 20 μm in diameter and produced long (5–6 μm), slender merozoites. Early second generation schizonts were first detected in capillary endothelial cells between 5 and 8 DPI. They were cylindrical and ranged in size from 5 to 8 μm in diameter and up to 28 μm in length. Second generation schizonts which reached maturity by 17 DPI were surrounded by a thick, hyaline wall and were packed with numerous spherical merozoites less than 1 μm in diameter. Mature megaloschizonts were fusiform, ranged from 30 to 113 μm in diameter, and extended as much as 465 μm along the long axis of muscle fibers. Merozoites developed as buds from cytomeres that formed between 8 and 14 DPI. Infected turkeys developed a moderate to severe myositis within 5 DPI and were lame in one or both legs. The myositis was associated with the necrosis of scattered groups of muscle fibers. Muscle fibers surrounding mature megaloschizonts were swollen and hyaline. Megaloschizonts were surrounded occasionally by fibroblasts and infiltrates of mononuclear cells. The morphology and site of development of mature megaloschizonts of Haemoproteus meleagridis are contrasted with those of other avian haemosporidians.     

In vitro Development of First-Generation Schizonts of Eimeria canadensis (Bruce, 1921)*†

SYNOPSIS. In vitro development of Eimeria canadensis from cattle was studied in monolayer cultures of various bovine cell lines grown on coverslips in Leighton tubes. Excysted sporozoites were used for inoculation of the cell cultures. Sporozoites entered the host cells within a few minutes, but apart from a reduction in the number of refractile bodies, changed little in appearance during the first 9 days. Beginning at 91/2 days postinoculation, sporozoites developed into sporozoite-shaped schizonts or, less frequently, transformed into trophozoites. Sporozoite-shaped schizonts with as many as 8 nuclei were observed transforming into spheroid schizonts. At 111/2 days, intermediate schizonts had a characteristic single mass of refractile granules and 60–80 nuclei. Deep invaginations, which resulted in the formation of several blastophores, usually occurred when schizonts had about 100 nuclei. Merozoites were formed as a result of radial outgrowth from the surface of spheroid schizonts as well as of blastophores. Mature merozoites were seen 1st after 13 days.     

A New Method for Intraerythrocytic Cultivation of Malaria Parasites (Plasmodium coatneyi and P. falciparum)

SYNOPSIS. Infected blood (from the rhesus monkey with P. coatneyi or an Aotus trivirgatus monkey with P. falciparum) was placed in a special vial equipped with an overflow tube 2–3 mm above the bottom of the vial. A slow flow (50 ml per day) of culture medium was maintained over the settled layer of red cells. In favorable experiments both species of parasites went thru 2 cycles of development without addition of fresh erythrocytes. so that late schizonts and young rings were present after 4 as well as after 2 days of incubation. There was, however, no increase in total parasite number.     

Life Cycle and Host Specificity of Eimeria callospermophili Henry, 1932 From the Uinta Ground Squirrel Spermophilus armatus*

SYNOPSIS. Eimeria callospermophili was found in 6 species of ground squirrels and the white-tailed prairie dog. The hosts included Spermophilus armatus from Utah and Montana, S. richardsoni from Montana and Wyoming, S. beecheyi from California, S. lateralis and S. variegatus from Utah, and S. tridecemlineatus and Cynomys leucurus from Wyoming. Infections were generally transmissible from each species of ground squirrel to S. armatus and S. richardsoni. Oocysts from C. leucurus caused infections in S. armatus and S. richardsoni. No infections were found after inoculation of E. callospermophili oocysts into least chipmunks (Eutamius minimus), Mongolian gerbils (Meriones unguiculatus), or laboratory rats; however, excystation occurred in these animals. Resistance to infection did not develop in S. armatus, S. richardsoni, or S. variegatus, but did occur after 5 or more infections in S. lateralis. Eimeria callospermophili had little or no effect on the host in S. armatus, S. lateralis, or S. variegatus, but caused bloody diarrhea in severely infected individuals of S. richardsoni. The oocysts had an oocyst residuum consisting of several distinct bodies, which later coalesced to form a large homogeneous body. Each sporozoite had an unusually large refractile body. In experimentally infected specimens of S. armatus the prepatent period and patent period lasted for 5 and 9 days, respectively. Mature 1st-generation schizonts, first seen 2 days after inoculation, had 8–12 merozoites. Mature 2nd-generation schizonts, first seen 3 days after inoculation, had an average of 18 merozoites which were smaller than those of the 1st generation. Mature gametes were 1st seen 4 days after inoculation. Mature microgametocytes were only slightly larger than mature macrogametes.     

Life Cycle of Hammondia hammondi (Apicomplexa: Sarcocystidae) in Cats

Hammondia hammondi and Toxoplasma gondii are feline coccidians that are morphologically, antigenically, and phylogenitically related. Both parasites multiply asexually and sexually in feline intestinal enterocytes, but H. hammondi remains confined to enterocytes whereas T. gondii also parasitizes extra‐intestinal tissues of the cat. Here, we studied multiplication of H. hammondi in feline intestine and compared with T. gondii cycle. Five parasite–free cats were inoculated orally with tissue cysts and free bradyzoites from skeletal muscles of gamma interferon gene knockout mice and killed at 1, 3, 4, 6, and 7 d later. At 1 and 3 d post inoculation (DPI), numerous individual intracellular bradyzoites were detected in histological sections of small intestine. At 4 DPI only schizonts were found and they were located in enterocyte cytoplasm above the host cell nucleus. At 6 and 7 DPI both schizonts and gamonts were seen and they were located in enterocytes. Ultrastucturally, schizogonic and gametogonic development of H. hammondi was similar to T. gondii. However, in H. hammondi merozoites rhoptries were longer, and coiled and contained more micronemes than in T. gondii. Ultrastructural development is illustrated in detail.     

Intralymphocytic schizonts associated with an initial infection of Saurocytozoon tupinambi in Tupinambis teguixin

An initial natural infection of Saurocytozoon tupinambi in a juvenile Tupinambis teguixin from Venezuela was studied for 131 days following capture of the host. Intralymphocytic parasites appeared in this sequence: small uninucleate and binucleate stages (days 1–31 and again on day 41); schizonts with 3–102 nuclei (days 8–14 and 29–35); immature gametocytes (days 29–35) and apparently mature gametocytes of Saurocytozoon tupinambi from day 41. Maximum parasitemia of trophozoites and binucleate schizonts occurred on day 4 when 11% of lymphocytes were infected. Maximum parasitemia by larger schizonts occurred on day 8 at 0.13% of lymphocytes, while maximum gametocytemia was found on day 49 with 16.4% of lymphocytes parasitized. Two types of schizonts were observed: intralymphocytic and the same type free of host cells, and fragments of varying size which may have been torn from capillary endothelium.Due to presence of concurrent infection by a small Plasmodium species, identity of intralymphocytic asexual stages with S. tupinambi cannot be established. Presence of asexual and sexual stages in the same type of host cells (lymphocytes and close derivatives), sequential appearance of trophozoites, schizonts and gametocytes over a period of 40 days, and correlated fluctuations in lymphocyte density suggest they are conspecific, and that Saurocytozoon, which has a plasmodiid type of sporogony may prove to further differ from leucocytozoids by presence of an asexual cycle in circulating blood cells.