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Feces containing Isospora suis oocysts were collected from naturally- and experimentally-infected pigs from four different areas of the United States. The unsporulated oocysts were cleaned, concentrated, mixed with 2.5% aqueous potassium dichromate solution, poured into petri dishes to a depth of 5 mm, and incubated at 25 degrees C. The oocysts were examined with a microscope at 12 h intervals and the stages of sporulation present were counted. Although a few oocysts were completely sporulated after 12 h of incubation, in most fecal samples the majority of the oocysts were not completely sporulated until 24 or 36 h. In the present study, the sporulation time of I. suis oocysts was considered to be less than or equal to 48 h. There were no major differences in the sporulation times of I. suis oocysts from the different sources.

Macrogametes of Eimeria ferrisi occurred in epithelial cells of the cecum and colon of Mus musculus and were studied by electron microscopy. Young stages were identified as macrogamonts by the presence of wall-forming bodies. At first an outerlimiting membrane and remnants of the inner membrane complex of the former merozoite pellicle were present; the latter was later lost but in mature macrogametes 3 limiting membranes were observed. Type II wall-forming bodies appeared before type I; the former developed in expanded cisternae of the endoplasmic reticulum whereas the latter were smaller in size and appeared in the ground substance of the cytoplasm. After formation of the oocyst wall the bodies of the 2 types were no longer visible. The presenceodies of the 2 types were no longer visible. The persistence of micronemes in mature macrogametes and the presence of numerous layers of rough endoplasmic reticulum during wall formation have not been previously reported.

Results of a program designed to control neonatal porcine coccidiosis on a total confinement, farrow-to-finish swine farm are reported. The control program consisted of washing, phenol disinfection, and steam cleaning of farrowing houses and treatment of sows with amprolium HCl before and after farrowing. Before initiation of the control program, 88.9% of the sows examined in the farrowing house were negative for coccidian oocysts, 9.9% were positive for Eimeria spp, and 1.2% were positive for Isospora suis. Most pigs nursing on sows before initiation of the control program had diarrhea at 5 to 10 days of age, which led to dehydration and weight loss. Morbidity was high, and mortality was moderate. Composite fecal samples from these litters were all positive (100%) for I suis. After initiation of the control program, 99.6% of the sows examined in the farrowing house were negative for coccidian oocysts and 0.4% were positive for Eimeria spp. Clinical signs of coccidiosis were rarely present in nursing pigs examined after the control program was initiated; however, I suis was still present in 19.8% of the composite fecal samples from pigs examined. An association between oocyst production in sows and I suis infections in pigs was not found in the present study. Oocysts of Eimeria spp were not found in the feces from the pigs.

The development of the macrogamete of Eimeria mivati Edgar and Seibold 1964 was studied with the electron microscope. Development of the young gamont was characterized by a loss of organelles such as the apical complex, subpellicular microtubules, rhoptries and micronemes, followed by an increase in micropores, mitochondria, rough endoplasmic reticulum (rER), and Golgi complexes. Nuclear detachment bodies and canaliculi were present in maturing macrogamonts. Amylopectin was first observed as small electron-dense rod-like bodies that eventually became large electron-transparent bodies. Type II wall-forming bodies developed in the cisternae of the rER. Type I wall-forming bodies appeared shortly thereafter in close association with numerous Golgi complexes. Many small vesicles located between the cisternae of the rER and the Golgi complexes formed what appeared to be a secretory pathway whereby protein formed in the cisternae and, modified by the Golgi complex, may produce the type I wall body material. The outer wall of the oocyst developed between two distal membranes on the surface of the macrogamete. Although the actual mechanism of deposition of the wall material was not seen, it was probably by some secretory process. Wall-forming bodies did not fuse.

Anthelmintic activities of 22,23-dihydroavermectin B1 (comprised to greater than or equal to 95% 22,23-dihydroavermectin B1a and less than or equal to 5% 22,23-dihydroavermectin B1b) against gastrointestinal nematodes in calves were evaluated in 2 controlled experiments. Infective larvae of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, and C punctate were given to 11-week-old calves and Oesophagostomum radiatum had been given 21 days earlier to allow all larvae to attain adulthood at the same time. Each experiment had 4 groups of 5 calves each. Treatment was given to the calves at 14 weeks of age, and 7 to 8 days after treatment, the calves were necropsied. In experiment 1, group 1 control calves had a geometric mean of 11,054 nematodes; groups 2, 3, and 4 calves (at 14 weeks of age) given 22,23-dihydroavermectin B1 orally at doses of 50, 100, or 200 microgram/kg had reductions of 73.5%, 97.3%, and 99.7%, respectively. In experiment 2, group 5 control calves had a geometric mean of 18,897 nematodes; groups 6, 7, and 8 calves given 22,23-dihydroavermectin B1 subcutaneously at doses of 50, 100, or 200 microgram/kg had reductions of 74.6%, 95.3%, and 98.8%, respectively.

The in vitro excystation of sporozoites of Isospora suis Biester 1934 is described. Sporocysts of I. suis lack a Stieda body. Upon incubation in 0.75% sodium taurocholate or in 0.25% trypsin + 0.75% sodium taurocholate excystation solutions, sporozoites were released by separation of the sporocyst wall into four plates. Occasionally, the sporocyst wall did not separate completely but opened partially and released the sporozoite. At the time of excystation, sporozoites were short and broad but became elongated after 5 to 10 min in the excystation fluids. Elongate sporozoites measuring 11.7 x 3.8 micrometers, had a pointed anterior end and a nucleus located in the posterior half of the cell. Living sporozoites exhibited gliding movements, side-to-side flexion, and probed with their anterior ends. Incubation in 5.25% sodium hypochlorite removed the oocyst walls from most oocysts. Sporozoites did not excyst from sporocysts that were released during treatment with sodium hypochlorite.

Anthelmintic activities of albendazole were evaluated in a controlled experiment. Forty calves experimentally infected with gastrointestinal nematodes were allotted to 4 groups. Calves in group 1 were used as nonmedicated controls; calves in groups 2, 3, and 4 were given (by oral route) a suspension containing albendazole at dose concentrations of 2.5, 5.0, and 7.5 mg/kg of body weight on the 35th day after administration of infective nematode larvae. In groups 2, 3, and 4 calves, average overall reductions (based on geometric means) were 77.1, 93.6, and 98.1%, respectively. These reductions were highly significant (P less than 0.01) in calves given doses of 5.0 and 7.5 mg/kg, and were significant (P less than 0.05) in calves given the 2.5-mg/kg dose. Ostertagia ostertagi, Trichostrongylus axei, Cooperia onchophora, Cooperia punctata, and Oesophagostomum radiatum removals at the 5.0- and 7.5-mg/kg dose levels were all highly significant (P less than 0.01); whereas, removals of Haemonchus contortus were not significant, even at the 7.5-mg/kg dose level.

A species of porcine coccidia, Isospora suis, when inoculated into piglets, produced diarrhea, dehydration, weight loss and death. Gross lesions were characterized by a fibrino-necrotic membrane within the jejunum and ileum. Villous atrophy and variable erosion, often with an adhered necrotic membrane, were seen microscopically. Asexual and sexual stages of I. suis were seen within the intestinal epithelium and oocysts were recovered from the feces. The severity of clinical disease and lesions were dose-related.

Thirty calves 12 weeks of age raised under essentially parasite-free conditions were used to determine the effects of Cooperia punctata and Eimeria bovis (in single and combination infections) on mucosal alkaline phosphatase activities at 8 locations in the small intestine. In experiment 1, 5 calves infected with C punctata 3 weeks previously had highly significant (P less than 0.01) reductions in mucosal alkaline phosphatase activities compared with those in 5 noninfected control calves. These reductions were greatest in the 2 locations of the intestine closest to the pylorus. Infected calves had a mean of 44,356 C punctata adults present. In experiment 2, 5 calves infected with E bovis 2 weeks previously had significant (P less than 0.05) reductions in mucosal alkaline phosphatase activities compared with those in 5 noninfected control calves. These reductions were present in the caudal half of the intestine. Numerous 1st-generation E bovis schizonts were present in the caudal third of the intestine. In experiment 3, 5 calves infected with C punctata and E bovis of the same durations as in experiments 1 and 2 had highly significant (P less than 0.01) reductions in mucosal alkaline phosphatase activities in the cranial half of the intestine compared with those in the controls. These reductions were much larger than in either of the monospecific infections (experiments 1 and 2). A mean of 31,968 adult C punctata were recovered from the infected calves, and numerous E bovis schizonts were observed in the caudal third of the intestine.

Developmental stages of Caryospora simplex were found in connective tissue of the cheek, tongue, and nose of Swiss-Webster and C57 BL/6 mice (Mus musculus) from 8 through 70 days after oral inoculation with 50,000 or 250,000 oocysts, or 60,000 free sporocysts of the same species obtained from an Ottoman viper, Vipera xanthina xanthina. The earliest developmental stages were seen on day 8 post-inoculation (PI) and consisted of two types of meronts and gamonts (undifferentiated sexual stages). Gamonts, microgametocytes, macrogametes, and unsporulated oocysts were found on days 10 and 12 PI. Fully sporulated, thin-walled oocysts containing eight sporozoites surrounded by a thin sporocyst membrane were first seen 12 days PI. Monozoic cysts (caryocysts) were first seen 12 days PI and appeared fully viable throughout the duration of the study, 70 days PI. Four mice injected intra-peritoneally with 150,000 free sporozoites and killed 12 days PI contained unsporulated and sporulated oocysts in connective tissues of the cheek, tongue, and nose, suggesting that sporozoites may be carried to the site of infection via the lymphatic/circulatory system. Four cotton rats, Sigmodon hispidus, inoculated orally with 250,000 oocysts all had unsporulated and sporulated oocysts of C. simplex in connective tissue of the cheek, tongue, and nose when killed on day 12 PI, indicating extraintestinal development in the secondary host is not species specific. This is the first report of a heteroxenous coccidium with both asexual and sexual development in the primary (predator) and secondary (prey) hosts.

Oocysts of Isospora suis were not found in any of 77 fecal samples from sows on farms with a history of neonatal coccidiosis. Oocysts of Isospora suis were found in 1 of 172 fecal samples from farms without a history of neonatal coccidiosis. Oocysts of Eimeria spp were found in 81.8% of the sows from farms with a history of neonatal coccidiosis and in 94.8% of the sows from farms without a history of neonatal coccidiosis. Oocysts of Isospora spp from birds were encountered as a pseudoparasite in several fecal samples.

The microgamogony of Eimeria ferrisi from experimentally infected mice was investigated with the electron microscope. Microgamonts were recognizable by the presence of peripherally arranged nuclei and the presence of single or paired centrioles between each nucleus and the limiting membrane of the parasite. Often an intranuclear centrocone directed toward the centriole was present. Differentiation of the microgamete began when elevations of the limiting membrane, which indicated the commencement of flagellar development, appeared above the centrioles. This event was accompanied by the segregation of nuclear content into a dense osmiophilic portion and an electron-pale portion. Then followed a gradual protrusion of the dense portion of the nucleus and developing flagella into the parasitophorous vacuole. A dense ring developed at the base of the differentiating microgamete, resulting in the formation of a stalk which was occupied by the residual portion of the nucleus. Fully developed microgametes became detached and occupied the parasitophorous vacuole along with residual cytoplasm. Microgametes had an anterior perforatorium, a dense elongate nucleus, with an anteriorly positioned mitochondrion in a small groove of the nucleus. Usually two flagella were present but one microgamete appeared to have three. Polysaccharide first appeared when differentiation was in progress and increased until large numbers of granules were present in the microgamont cytoplasm.

Anthelmintic activities of fenbendazole were evaluated in a controlled experiment. Forty calves artificially infected with gastrointestinal nematodes were allotted to 4 groups. Calves in group 1 were used as nonmedicated controls; the other calves were given (orally) fenbendazole at the dose level of 5 mg/kg in the forms of a suspension (group 2), medicated feed to individual calves (group 3), and medicated feed to the group (group 4). These treatments were given on day 35 after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 99.5%, 99.7%, and 99.6%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes present in the calves were Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia onchophora, C punctata, and Oesophagostomum radiatum.

Cryptosporidiosis is reported in a healthy 25-year-old male. Clinical symptoms include 1 day of nausea and low-grade fever and 9 days of diarrhea, followed by 3 days of constipation. Oocysts of Cryptosporidium sp. were present in sugar flotations of the first fecal sample collected 56 hours after onset of the symptoms and in daily fecal samples collected through day 12 of the illness. Oocysts of the human isolate of Cryptosporidium sp. were morphologically indistinguishable from those obtained from naturally and experimentally infected calves. After 1 week of sporulation at room temperature, oocysts from the human and from calves contained four sporozoites and a spherical residuum. When inoculated orally, sporulated Cryptosporidium sp. oocysts of human and of calf origin produced indistinguishable infections in suckling mice and rats and in adult mice.

Four of 5 meadow jumping mice (Zapus hudsonius) captured had in their feces a previously undescribed species of Eimeria which is named Eimeria zapi sp. n. The sporulated oocysts measured 21.7 (19.5-24.0) x 20.3 (17.5-23.0) micrometer. The single-layered oocyst wall was 1.5 micrometer thick, rough, pitted and appeared clear-to-amber. Usually 2 polar granules could be seen. An oocyst residuum was not observed. Each sporocyst averaged 16.0 (12.5-18.0) x 9.7 (7.5-11.5)micrometer. A substiedal body was present. The sporocyst residuum consisted of a membrane-enclosed packet of 15 to 20 granules. This is the first species of Eimeria to be described from the genus Zapus.

Anthelmintic efficacy of ivermectin (greater than or equal to 80% 22,23-dihydroavermectin B1a and less than or equal to 20% 22,23-dihydroavermectin B1b) was evaluated in a controlled experiment against immature nematodes. Twenty calves raised to about 8 weeks of age under nematode-free conditions were allocated into 4 groups. Infective larvae of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, Oesophagostomum radiatum, and Dictyocaulus viviparus were given orally to each calf on a staggered schedule 6 to 14 days before treatments. The drug was given subcutaneously when the nematodes were in the early 4th stage of development, and the calves were killed 23 or 24 days later. Group 1 nonmedicated control calves had a geometric mean of 25,102 nematodes; groups 2, 3, and 4 calves given ivermectin at dose rates of 50, 100, or 200 micrograms/kg had reductions of 88.2%, 98.0%, and 99.8%, respectively.

Sporogony of Isospora suis of swine is described. Unsporulated oocysts were collected immediately after defecation, mixed in 2.5% potassium dichromate solution, incubated at various temperatures, examined at different time intervals, and classified as to stage of development. The uninucleate sporont underwent nuclear division and became binucleated, and then divided to form two round, uninucleate sporoblasts. Binucleate sporoblasts elongated to form binucleate sporocysts, each of which then gave rise to four sporozoites. Sporulation was completed within 56 hr at 20 C, 40 hr at 25 C, 16 hr at 30 C, and 12 hr at 37 C. No sporulation occurred at 4, 40, 42, 45, or 50 C. The thermal death point was between 37 and 40 C.

Infection with cryptosporidium occurred in 12 immunocompetent persons who had direct contact with the feces of infected calves during three unrelated outbreaks of calf cryptosporidiosis. Nine of the twelve subjects had diarrhea and abdominal cramps that lasted 1 to 10 days. Infections were diagnosed and monitored by detection of oocysts in feces, with a modified Sheather's flotation technique and phase-contrast microscopy. Oocysts of cryptosporidium were isolated from calves but not from other animals with which these subjects had been in contact. Oocysts of cryptosporidium were also detected during repeated examinations of feces from two immunodeficient patients with persistent cryptosporidiosis. An apparently identical infection was transmitted to calves and mice, using oocysts from infected calves and human beings. Oocysts from an immunodeficient person also produced infections in kittens, puppies, and goats. This study shows that cryptosporidium may produce a moderate self-limited illness in immunocompetent persons, which contrasts sharply with the prolonged severe diarrhea in immunocompromised patients who contract cryptosporidiosis. Calves with diarrhea should be considered a potential source of human infection, and immunocompromised persons should avoid contact with such animals.

Over a 2-year period involving a total of 168 Angus cows and their calves, 2 studies were conducted to evaluate the effect of once-daily suckling on cow reproduction, calf growth, and gastrointestinal parasitism. Experiment I compared 2 restricted suckling (RS) groups with 1 normal suckling (NS) group. Each group consisted of 24 cows with their calves (24 cows-calves/group = 24 cows and 24 calves/group). In the RS groups, suckling by the calves was restricted to once a day for 45 days, and then the calves were allowed to suckle normally throughout the remainder of the experiment. In the NS group, the calves suckled normally throughout the experiment. Experiment II compared 2 groups of RS cow-calves (24 cow-calves/group) with 2 groups of 24 NS cow-calves/group. In experiment I, there were no differences (P less than 0.05) in pregnancy rate or in the average number of nematode eggs/g of feces (epg) between the cows from the 2 treatment groups. The RS calves consistently had higher epg counts than did the NS calves during the 45 days of RS (169 vs 62 epg, P less than 0.05) and from the time of their return to pasture until weaning (266 vs 186 EPG, P = 0.27). The RS calves also had a higher average coccidia oocyst count during the RS period only. In experiment II, RS cows had a higher pregnancy rate (87.6% vs 66.0%, P less than 0.05) and a shorter postpartum interval (83 vs 101 days, P less than 0.05) than did NS cows.(ABSTRACT TRUNCATED AT 250 WORDS)

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 efficacy of salinomycin for treatment of experimental Eimeria bovis infections was evaluated. In experiment 1, 18 calves were placed into four groups. Group 1 calves were nonmedicated controls; groups 2, 3, and 4 calves were given salinomycin (0.33, 0.66, and 1.00 mg/kg of body weight, respectively) in daily oral divided doses starting 2 or 3 days prior to E bovis inoculations and continuing until postinoculation day (PID) 21. Calves treated with 0.66 and 1.00 mg/kg (groups 3 and 4) passed substantially fewer oocysts than did control calves (group 1) or calves treated with 0.33 mg/kg (group 2). Group 1 control calves had typical signs of severe E bovis infections, whereas signs of infection in medicated calves were almost nonexistant. Experiment 2 was conducted as before, with 15 calves. Group 5 calves were nonmedicated controls; groups 6, 7, and 8 calves were treated with 0.5, 1.0, and 2.0 mg/kg, respectively. All group 8 calves and three of four group 7 calves had nearly complete suppression of oocyst excretions. The severity of the disease in the group 5 control calves was not as extensive as it was in group 1 control calves. In experiment 3, 16 calves were used. Group 9 calves were nonmedicated controls, whereas other calves were given salinomycin (2.0 mg/kg) during PID 3 to 7 (group 10), PID 8 to 12 (group 11), and PID 13 to 17 (group 12). Salinomycin therapy in group 2 calves resulted in substantial reductions in oocyst excretions and clinical signs.

Eimeria gruis Yakinoff and Matschoulsky 1935, Eimeria reichenowi Yakimoff and Matschoulsky 1935, and an Adelina species are described from sandhill cranes in the United States. E. gruis was found in the feces of 11 of 14 Florida sandhill cranes (Grus canadensis pratensis) and 62 of 72 greater sandhill cranes (G. c. tabida) from Florida, 5 of 14 greater sandhill cranes from Arizona, and 4 of 16 lesser sandhill cranes (G. c. canadensis) from Texas. E. reichenowi was found in the feces of 12 of 14 Florida sandhill cranes and 66 of 72 greater sandhill cranes from Florida, 4 of 14 greater sandhill cranes from Arizona, and 5 of 16 lesser sandhill cranes from Texas. Adelina sp. was found in the feces of 3 of 14 Florida sandhill cranes and 2 of 72 greater sandhill cranes from Florida. The Adelina species is considered to be a spurious parasite of the cranes.

Attempts were made to produce repeatable infections with Eimeria wyomingensis in 2- to 4-wk-old calves. From 0.2 million to 10 million sporulated oocysts, or sporocysts from 1 million sporulated oocysts were given orally to 50 calves. Several regimens of flumethasone and dexamethasone at excessive dosage levels were given to some to the oocyst-inoculated calves. Nine of 10 calves given flumethasone and one of 12 calves given dexamethasone treatments died. Of the 41 calves which survived past post-inoculation day 21, 32 had patent infections. The prepatent period in the 32 infections was 13 to 15 (mean 14.2) days and the patent period was 1 to 7 (mean 3.6) days. More fecal oocysts were excreted by calves given sporulated oocysts than those given sporocysts. Calves given corticosteroids passed fewer oocysts than nontreated calves.

Anthelmintic activity of albendazole against adult Dictyocaulus viviparus was evaluated in a controlled experiment. Calves were raised nematode-free to approximately 8 weeks of age and were each given 4,000 infective 3rd-stage larvae. Twenty calves with patent parasitisms were allotted to 2 groups of 10 calves each. Calves in group 1 were used as nonmedicated controls, and calves in group 2 were given albendazole in paste formulation at the dosage concentration of 7.5 mg/kg of body weight on the 30th day after administration of infective larvae. At necropsy, nonmedicated control calves had a total of 308 adult D viviparus, whereas the albendazole-treated calves had 11, for an average efficacy of 96.4%. These reductions were statistically highly significant (P less than 0.01). At necropsy, none of the treated calves was passing 1st-stage C viviparus larvae in their feces, whereas control calves were passing an average of 46 larvae/10 g of feces.

Two established tall fescue pastures were used in a 4-year study of the relationship between the level of gastrointestinal parasitism in cattle and the level of nitrogen fertilization of the pasture. One pasture was fertilized with 224 kg of NH4NO3/ha each year and served as the control. A second pasture, referred to as the low-fertilized (LF) pasture, was fertilized with N at 84 kg/ha the first year and 74 kg/ha in each of the next 3 years. Both pastures were stocked with Angus cows (2.5/ha) and their calves. Rectal fecal samples obtained every 6 weeks from 10 cows and as many calves as possible in each pasture were examined for nemotode eggs and coccidia oocysts. Two calves from each group were slaughtered at the end of each of the last 3 years to determine the numbers and species of parasites. Cows had significantly lower egg counts than did the calves. Egg counts did not differ between the two groups of cows, but the control cows had higher average weights than the cows on the LF pasture. Control calves had significantly lower egg counts than the calves on the LF pasture, but only slightly higher mean adjusted 205-day weights. At necropsy, significantly fewer worms were recovered from the controls (17,977) than from the LF-pastured calves (52,332). Cooperia oncophora was the predominant species. The level of coccidia infection did not differ between the two groups of cows and calves. The greater availability of forage in the control than in the LF pasture probably was responsible for the lower level of parasitism in the control calves and for the greater weight gains made by the control cows and calves.

Anthelmintic activities of the B1a fraction of avermectin were evaluated in a controlled experiment. Twenty 12-week-old calves artificially infected with gastrointestinal nematodes were allotted to four groups. Calves in group 1 were used as nonmedicated controls; other calves in groups 2, 3, and 4 were given (orally) B1a avermectin at dosage levels of 50, 100, and 200 microgram/kg of body weight, respectively. These treatments were given 35 days after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 98.6%, 98.7%, and 98.4%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes in the calves were Haemonchus contortus. Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, and Oesophagostomum radiatum.

Oocysts of Eimeria bukidnonenisis and E. wyomingensis were found to be morphologically similar, and could be reliably differentiated only by measurements. Pyriform oocysts of E. bukidnonensis measured 43 to 51 by 30 to 35 mum (mean 47.4 by 33.0 mum); sporocysts were 18 to 21 by 9 to 11 mum (mean 19.6 by 9.8 mum). Micropyle present; polar granule, oocyst residuum, and sporocyst residuum absent. Oocyst wall of 2 layers, 3.5 mum thick, and dark brown. Pyriform oocysts of E. wyomingensis measured 36 to 44 by 26 to 30 mum (mean 39.9 by 28.3 mum); sporocysts were 17 to 20 by 8 to 10 mum (mean 18.7 by 8.6 mum). Micropyle present; polar granule, oocyst residuum, and sporocyst residuum absent. Oocyst wall of 2 layers, 2.5 mum thick, and colored brown. The width of the oocyst was the most reliable criterion for differentiating the 2 species.

Endogenous stages of Eimeria tuskegeensis were studied in experimentally infected cotton rats, Sigmodon hispidus. Almost all parasites were located on the basilar side of the nucleus in epithelial cells on the sides and tips of villi of the small intestine. The endogenous cycle consisted of three generations of schizogony followed by gametogony. First-, second-, third-generation schizonts could be distinguished by time of appearance, size and shape of the schizont, and number, size, shape, and arrangement of merozoites. Immature gametogonous stages appeared to 84 hr postinoculation (PI) and developed into mature microgametocytes and macrogametes by 96 hr PI. Microgametocytes had a mono-centric type of development. Intermediate macrogametes had small, basophilic wall-forming bodies and mature macrogametes had large, eosinophilic wall-forming bodies. It was not possible to determine whether these were two distinct types of wall-forming bodies or whether they were different stages of a single type. Two nuclei were seen in the host's epithelial cells parasitized by schizonts, microgematocytes, macrogametes, and oocysts. This binucleate condition was apparently parasite-induced.

Seven of 12 calves given 10(6) Eimeria wyomingensis sporulated oocysts had sexual stages of the parasite when examined at necropsy. Clinical signs of coccidiosis were not observed in any calf. Sexual stages were located in host cells in the lamina propria of the villi in the terminal small intestine. Infected host cells underwent nuclear and cytoplasmic hypertrophy. Immature microgamonts usually had folded cytoplasm and an overall spherical to elongate shape. Mean length and width +/- SEM of immature microgamonts were 43.3 +/- 1.6 by 29.0 +/- 1.1 micron. Mature microgamonts contained hundreds of microgametes, lacked visible cytoplasmic folds, and measured 52.8 +/- 4.7 by 43.0 +/- 4.2 micron. Macrogamonts were spherical to ovoid and had a large nucleus and prominent nucleolus. Immature macrogamonts without visible wall-forming bodies measured 16.0 +/- 0.5 by 13.3 +/- 0.2 micron. Mature macrogamonts had 3-8-micron eosinophilic wall-forming bodies and measured 24.6 +/- 0.7 by 19.6 +/- 0.8 micron. Oocysts were ovoid and had a 2-3-micron-thick eosinophilic oocyst wall. A micropyle was present in appropriately sectioned oocysts. Oocysts measured 27.7 +/- 1.7 by 19.3 +/- 0.8 micron. The sexual stages of E. wyomingensis are compared to those described previously for species of Eimeria infecting the bovine small and large intestines.

The endogenous development of Isospora suis Biester 1934 is described in piglets inoculated with 150,000 or 200,000 sporulated oocysts. Endogenous stages developed within villous epithelial cells throughout the small intestine. Two distinct types of meronts were seen in tissue sections. Type I meronts, which were seen at 3 days postinoculation, were binucleate, elongate, and 10.5 by 4.7 micron. They produced two to 14 Type I merozoites per parasitophorous vacuole. Type I merozoites were 10.0 by 3.6 micron. They produced two to 14 Type I merozoites per parasitophorous vacuole. Type I merozoites were 10.0 by 3.6 micron. Type II meronts, which were seen at 4 days postinoculation, were elongate and contained three to 12 nuclei. Type II meronts were 11.4 by 5.3 micron, and one to four were found per parasitophorous vacuole. Type II merozoites were 6.3 by 2.1 micron, and three to 16 were found per parasitophorous vacuole. The peak of asexual development occurred 4 days postinoculation. Fully developed microgamonts, macrogamonts, and oocysts were seen 5 days postinoculation. The prepatent period was 5 days, and the patent period was 5 to 8 days. No extraintestinal stages were seen.

For two consecutive years, determinations were made of the prevalence and abundance of coccidian oocysts from crossbred beef calves raised on Bahia grass pastures in the coastal plain area of Georgia. Of the 534 fecal samples collected during the survey, 461 (86.3%) contained one or more species of coccidian oocysts. The total mean oocysts per gram of feces (OPG) was significantly different (P less than 0.10) between the two years. Thirteen species of Eimeria were found during both years of the survey. Eimeria bovis was the most prevalent species found in the survey; E. ellipsoidalis, however, had the greatest number of OPG. Eimeria bukidnonensis, E. pellita, and E. brasiliensis were the least prevalent species and also had the lowest numbers of OPG. Only one clinical case of coccidiosis was seen. A nine-month-old calf had E. zuernii coccidiosis; it excreted E. zuernii oocysts in several fecal samples before the clinical disease appeared.

The schizogony of Eimeria ferrisi was studied in experimentally infected Mus musculus. Developmental stages occurred in epithelial cells of the cecum and colon. During transformation of invasive stages into schizonts the inner membrane complex of the pellicle, the conoid, subpellicular microtubules and micronemes gradually disappeared. The micropore, however, seemed to persist. Dividing nuclei had eccentric intranuclear spindles consisting of microtubules which extended between 2 centrocones, in close relationship with centrioles. During the last nuclear division anlagen of merozoites appeared as extensions on the surface of schizonts. The outer single membrane of the schizont became the outer membrane of the merozoite pellicle. Cytoplasmic organelles, typical of eimerian merozoites were incorporated into the developing merozoites. Finally the merozoite became detached leaving behind a residual cytoplasm. Fully developed merozoites had a 3-layered pellicle, the outer single unit membrane was continuous around the merozoite with the inner complex having interruptions at the anterior and posterior poles and at the micropores. Thirty-two subpellicular microtubules, originating at the anterior polar ring extended to the posterior region of each merozoite. The apical complex consisted of a conoid, preceded by 2 rings and surrounded by a polar ring. Two rhoptries were present having club-shaped terminal ends and slender ductules in the conoid region. Some merozoites had enlarged rhoptries, with the distal vesical appearing dense and osmiophilic. The Golgi complex, endoplasmic reticulum, mitochondria, polysaccharide granules were similar to those seen in other eimerian merozoites.

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.

Eighteen calves about 3 months old were inoculated with 3,000 Dictyocaulus viviparus infective larvae. Three groups of 6 calves each were formed. Thirteen days after inoculations, 3 of the 6 group 1 control calves were given vehicle subcutaneously (SC) and the group 2 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Thirty-five days after inoculation, the remaining 3 calves in group 1 were given vehicle SC and the group 3 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Necropsies were performed 42 days after inoculations. A total of 474 D viviparus was recovered from the group 1 control calves, whereas none was recovered from the calves treated when the nematodes were in the 4th stage of development (group 2) or adult stage (group 3).