Identification of outer oocyst wall proteins of three Cryptosporidium (Apicomplexa: Cryptosporidiidae) species by 125I surface labeling

Autoradiography of oocyst wall surface proteins of three Cryptosporidium spp. revealed common bands at 285 to 290, 145 to 148, 120, 57, and 32 kilodaltons (kDa). Cryptosporidium baileyi and C. muris share proteins at 180, 100, 80 to 81, 29, and 18 to 19 kDa; C. baileyi and C. parvum share one protein at 46 to 47 kDa; and C. muris and C. parvum share a protein at 67 to 69 kDa. Additional protein bands, each unique to one species, were also observed.

Controlled dosage titration of febantel paste in naturally parasitized cattle

A controlled anthelmintic trial was conducted to determine the efficacy of febantel paste (45.5%) at dosages of 2.5, 5.0, 7.5, and 10.0 mg/kg in calves harboring natural gastrointestinal nematode infections. Dosages of 5.0, 7.5 and 10.0 mg of febantel/kg of body weight were greater than 96% effective in removing adults of Haemonchus contortus, Ostertagia spp, Cooperia spp, and Oesophagostomum radiatum. The 2.5 mg/kg dosage was considered suboptimal because of low efficacy against Ostertagia and Cooperia spp. Efficacies against Trichostronglylus axei, Trichuris spp, Bunostomum phlebotomum, and Stronglyloides papillosus were difficult to determine because fewer numbers of these nematodes were recovered. Efficacies of febantel paste against immature bovine parasites ranged from 83.62% to 97.72%.

Caryospora uptoni and Frenkelia sp.-like coccidial infections in red-tailed hawks (Buteo borealis)

The feces from 16 red-tailed hawks (Buteo borealis) were examined by fecal flotation for the presence of coccidial oocysts or sporocysts. Oocysts of Caryospora uptoni were found in five (31%), sporocysts of a Frenkelia sp.-like coccidium were found in eight (50%), and mixed infections with both species of coccidia were found in three (19%) red-tailed hawks. Neither oocysts nor sporocysts were found in six (38%) red-tailed hawks. Sexual stages of C. uptoni were found in the duodenum and jejunum of a naturally infected red-tailed hawk. Sexual stages were located in enterocytes on the distal three-fourths of the villi. This study shows that over 60% of red-tailed hawks may be passing coccidial oocysts/sporocysts in their feces and provides morphological information for diagnosing C. uptoni infections in histological sections.

Serial transmission of Caryospora bigenetica Wacha and Christiansen, 1982 (Apicomplexa: Eimeriidae) between different species of rodents

Transmission of Caryospora bigenetica by cannibalism between cotton rats, between cotton rats and mice, and between mice was demonstrated. All experimental animals developed swollen muzzles and scrota 8 days after ingestion of infected tissues. Infections were confirmed by light microscopy of fresh tissue smears. Tissues of cannibalized animals contained caryocysts that, after ingestion by the next host, released sporozoites that underwent merogony, gamogony, sporogony, and caryocyst formation in dermal tissues. This study demonstrates that C. bigenetica can be transmitted by predation between species of rodents and that, in the recipient host, asexual and sexual reproduction occur before caryocysts appear.

Determination of homovanillic acid, 5-hydroxyindoleacetic acid and pressure in the cerebrospinal fluid of collie dogs following administration of ivermectin

Twelve adult Collie dogs were studied to determine the effects of ivermectin on neurotransmitter metabolites released from the brain into the cerebrospinal fluid (CSF) and on CSF pressure. Ten of the 12 Collies were given ivermectin orally at a concentration of 200 micrograms/kg body weight. Three of these 10 Collies showed clinical signs of ivermectin-induced toxicosis which progressed into a state of unresponsive recumbency in 2 dogs. Cerebrospinal fluid pressures and neurotransmitter metabolite concentrations in cisterna magna CSF were analysed 49 to 50 hours after administration of ivermectin in 6 of the 10 treated dogs, and in the 2 untreated control Collies. Cerebrospinal fluid pressures were within normal limits in all dogs. However, compared to the CSF concentrations in the 2 untreated and 3 non-reactive Collies, the 2 ivermectin-reactive Collies still in recumbency had elevated CSF concentrations of homovanillic acid (HVA), a metabolite of dopamine, and 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin. These findings suggest an association between altered neurotransmission and severe ivermectin-induced neurological abnormalities. No evidence of elevated intracranial pressure was found.

Experimental infections in domestic ducks with Cryptosporidium baileyi isolated from chickens

Oral inoculation of 13 ducks (Anas platyrhynchos) with 1 x 10(6) Cryptosporidium baileyi oocysts produced patent infections but no clinical signs of disease. Intratracheal inoculation of 13 ducks with 1 x 10(6) C. baileyi oocysts produced only mild clinical signs of respiratory disease, no deaths, and gross lesions of airsacculitis in only three ducks. The distribution of developmental stages of C. baileyi in ducks was similar to that observed in experimentally infected chickens and turkeys. Results of this study indicate that ducks are more resistant to experimentally induced respiratory cryptosporidiosis caused by C. baileyi than are chickens and turkeys.

Inactivation of Giardia lamblia and Giardia canis cysts by combined and free chlorine

Free chlorine and a combined organic N-chloramine (3-chloro-4,4-dimethyl-2-oxazolidinone, compound 1) were compared for efficacy as disinfectants against an admixture of cysts of Giardia lamblia and Giardia canis in water solution under a variety of test conditions; variables were pH, temperature, and water quality. In general, compound 1 was found to reduce the giardial excystation in the solutions at lower concentration or shorter contact time at a given total chlorine concentration than did free chlorine.

Fatal Caryospora bigenetica (Apicomplexa: Eimeriidae) infections in cotton rats, Sigmodon hispidus

Four groups of cotton rats, Sigmodon hispidus, were shown to be suitable secondary hosts for the viperid coccidium, Caryospora bigenetica, following oral inoculation of a mixture of oocysts and sporocysts. Swelling of the face, ears, and scrota and hemorrhagic ears were the predominant clinical signs and some cotton rats died in 3 of 4 experiments. Developmental stages of C. bigenetica were found in connective tissue components of the ear, nose, cheeks, anal skin, scrotum, and penile sheath of all cotton rats in which these tissues were examined. Additionally, developmental stages of C. bigenetica were found in connective tissue components of the following tissues examined from some cotton rats: tongue, lung, testicle, epididymis, rectum, base of the tail, footpad, and bone marrow. The present study shows that C. bigenetica can be pathogenic for cotton rats and demonstrates many new anatomic sites for developmental stages of this parasite in the secondary host.

Effect of broiler chicken age on susceptibility to experimentally induced Cryptosporidium baileyi infection

Clinical signs of respiratory tract disease were observed in chickens that were inoculated intratracheally with 1 x 10(6) oocysts of Cryptosporidium baileyi at 2 or 14 days of age (10 chickens/group), but not in chickens inoculated at 28 or 42 days of age (10 chickens/group). Orally inoculated chickens in all age groups (10 chickens/group) did not develop clinical signs of disease. Orally and intratracheally inoculated chickens in all age groups were infected, as determined by the finding of cryptosporidia in tissue sections of the trachea, bursa of Fabricius, and cloaca, and by the recovery of oocysts from their feces. Chickens inoculated at 2 and 14 days of age excreted oocysts for a longer period and had greater numbers of cryptosporidia in their tissues, compared with chickens inoculated at 28 and 42 days of age.

Comparison of serologic tests for detection of antigen in canine heartworm infections

In 30 random-source dogs, we determined sensitivity and specificity of 5 serologic tests for detection of canine heartworm antigens. Seventeen of the dogs were infected naturally with adult Dirofilaria immitis, and 4 of the infected dogs were amicrofilaremic. The ability of the serologic tests to predict whether a dog was infected or uninfected (overall test accuracy) ranged from 73 to 97%. Sensitivity was not affected by circulating D immitis microfilariae, but was markedly influenced by the number of adult D immitis present. False-positive reactions were rare and were not associated with intestinal parasites or Dipetalonema reconditum microfilariae. Modifications of some of the test procedures were necessary to maximize test accuracy and reproducibility. These modifications and other technical details might limit the usefulness of some of the tests in a veterinary practice.

Cultivation of Cryptosporidium baileyi: studies with cell cultures, avian embryos, and pathogenicity of chicken embryo-passaged oocysts

Sporozoites of Cryptosporidium baileyi did not undergo development in primary cell cultures from either avian or mammalian hosts, or in mammalian cell lines. Oocysts of C. baileyi produced infections resulting in complete development to sporulated oocysts in chicken embryos and embryos of 8 other avian species examined. Inoculation of 4 X 10(5) oocysts was not pathogenic for avian embryos as evidenced by the lack of gross lesions or death. Oocysts obtained after C. baileyi had been passaged 10 times (first experiment) or 20 times (second experiment) in chicken embryos still caused clinical respiratory disease and gross airsacculitis when inoculated intratracheally into 2-day-old broiler chickens. Oocysts that had been passaged 10 times in chicken embryos were similarly pathogenic for 4-day-old turkeys after intratracheal inoculation.

Further characterization of the biology of Hammondia heydorni

Hammondia heydorni oocysts, recovered from the diarrheic feces of a dog suffering from corticosteroid toxicosis, were sporulated and characterized morphometrically. Sporulated H. heydorni oocysts were administered to three dogs, five goats, a calf and three guinea pigs, and tissues from these inoculated animals fed to coccidia-free dogs to determine species susceptibility to H. heydorni. Morphometric characteristics of H. heydorni oocysts were similar to previous descriptions. Oocysts were not excreted in the feces of dogs inoculated with oocysts. Dogs fed tissues from goats killed 14, 28 or 42 days after inoculation (d.a.i.) with oocysts excreted H. heydorni oocysts in their feces after consuming goat tissues. Dogs fed tissues from a calf killed at 28 d.a.i., and from goats killed 21 and 56 d.a.i., did not excrete oocysts in their feces. Developmental stages of H. heydorni were not observed in histologic sections of tissues from any of the animals.

Caryocyst-like host cell formation by Caryospora duszynskii (Apicomplexa: Eimeriidae) in human fetal lung cell cultures

Sporozoites of the coccidium, Caryospora duszynskii, penetrated human fetal lung cell cultures but did not undergo asexual or sexual multiplication during a 29-day observation period. Beginning three days postinoculation (PI), infected host cells lost their normal elongated fibroblast-like shape and became ellipsoidal in appearance and resembled caryocysts. These caryocyst-like infected cells were observed from 3 through 29 days PI. Sporozoites remained viable throughout the study as evidenced by motility of extracellular sporozoites in infected human fetal lung cell cultures. Results of this in vitro study suggest that some species of Caryospora may form caryocysts in secondary hosts without undergoing asexual or sexual multiplication in these hosts.

Prevalence of Sarcocystis odocoileocanis from white-tailed deer in Alabama and its attempted transmission to goats

Sarcocysts of Sarcocystis odocoileocanis were found in tissue sections of hearts and tongues examined by light microscopy from 30 (88%) of 34 white-tailed deer (Odocoileus virginianus). Hearts were infected less often (13 of 34, 38%) than were tongues (30 of 34, 88%). Sarcocysts of Sarcocystis odoi were not observed in the white-tailed deer examined. A gray fox (Urocyon cinereoargenteus) excreted sporocysts after consuming tongues of white-tailed deer infected with S. odocoileocanis. Two goats inoculated with either 50,000 or 500,000 sporocysts of S. odocoileocanis isolated from the gray fox did not have sarcocysts in tissue sections of the heart, tongue, diaphragm, or esophagus when examined 122 days postinoculation. Dogs fed these tissues from control or inoculated goats did not pass sporocysts in their feces. The present study demonstrates: (1) a high prevalence of S. odocoileocanis infection in white-tailed deer in Alabama, and (2) that goats are not suitable intermediate hosts for S. odocoileocanis.

Experimental Cryptosporidium parvum infections in opossums (Didelphis virginiana)

Five nursing opossums (Didelphis virginiana) were each inoculated with 5 x 10(6) Cryptosporidium parvum oocysts of calf origin. Following inoculation, endogenous stages of C. parvum were observed in the ileum, cecum, and colon of these opossums. Two of three noninoculated pouch mates acquired infections during the study based on examinations of feces and tissue sections of all eight opossums. Mild diarrhea was observed in four of seven opossums harboring C. parvum, although none died as a result of the infection. Under the conditions of this study, C. parvum appeared to be only mildly pathogenic for opossums.

Whipworms and intestinal threadworms

Whipworms (genus Trichuris) parasitize the lower bowel of humans, domestic animals, and wild animals. The species of Trichuris that are important in small animal practice are T. vulpis in the dog and T. campanula and T. serrata in the cat. Intestinal threadworms (Strongyloides stercoralis in the dog and S. tumefaciens in the cat) parasitize the small intestine. The identification of whipworms and threadworms, their life cycles, and the diagnosis, treatment, and control of infection are discussed in this article.

Anatrichosoma sp infection in a dog

Embryonated, double-operculated eggs were observed during routine examination of a fecal specimen from a 5-month-old dog. Similar eggs were found on a skin scraping of a raised, flaking, erythematous nodule on the dorsal midline in the lumbar region. Eggs were identified as being similar to those of Anatrichosoma spp. After surgical excision, histologic examination of the nodule revealed nematodes with morphologic features consistent with those of Anatrichosoma spp.

Frenkelia sp.-like infection in the small intestine of a red-tailed hawk

Developmental stages of a Frenkelia sp.-like coccidium were observed in tissue sections of the duodenum, jejunum, and ileum of a naturally infected red-tailed hawk (Buteo jamaicensis borealis) that died and was examined at necropsy. Developmental stages were located in the lamina propria of these tissues. Thirty sporulated sporocysts measured 11.1 X 8.1 microns in tissue sections. Four sporozoites were present in each sporulated sporocyst. The coccidial infection was not a contributing factor in the death of this red-tailed hawk.

Cryptosporidium baileyi: effects of intra-abdominal and intravenous inoculation of oocysts on infectivity and site of development in broiler chickens

Developmental stages of Cryptosporidium baileyi were observed on the epithelium of the larynx, trachea, primary and secondary bronchi, air sacs, bursa of Fabricius, and cloaca of 12 chickens inoculated intra-abdominally with oocysts. All 12 birds inoculated intra-abdominally developed clinical signs of respiratory disease and had gross lesions of airsacculitis at necropsy. Developmental stages of C. baileyi and clinical signs of disease were not observed in 12 chickens inoculated intravenously with oocysts. The response of chickens to intra-abdominal inoculation of oocysts was similar to responses recorded following intratracheal inoculation of oocysts in previous studies.

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.

Efficacy of fenbendazole-medicated feed blocks against gastrointestinal nematode infections in calves

An anthelmintic trial was conducted to determine the efficacy of fenbendazole (FBZ) incorporated into two types of feed blocks given daily for 3 or 10 days to calves naturally parasitized with gastrointestinal nematodes. Each treated calf consumed 5 mg of FBZ/kg of body weight. The FBZ was greater than 99% effective in removing adults of Haemonchus contortus, Ostertagia ostertagi, O lyrata, Cooperia punctata, C pectinata, C onchophora, Trichostrongylus axei, Bunostomum phlebotomum, and Oesophagostomum radiatum. Fenbendazole was also greater than 99% effective against immature nematodes recovered from the small intestine, which were thought to be mainly Cooperia spp. Efficacy was similar for FBZ in each of the two types of feed block carriers and for the 3- and 10-day regimens. Calves readily consumed feed blocks containing FBZ and did not have adverse reactions to FBZ.

Experimental Eimeria debliecki infections in nursing and weaned pigs

Three litters of six, 3-day-old nursing pigs were inoculated via a stomach tube with 8.0 X 10(5), 1.6 X 10(6) or 5.0 X 10(6) sporulated oocysts of Eimeria debliecki and four groups of six, 4-week-old weaned pigs were inoculated with 8.0 X 10(5), 1.6 X 10(6), 5.0 X 10(6) or 1.0 X 10(7) sporulated oocysts of E. debliecki to determine its pathogenicity. Clinical coccidiosis or deaths did not result from infections. Infections were confined to the jejunum and occasionally the duodenum. Microscopic lesions of mild to moderate villous atrophy were observed in one nursing pig given 5.0 X 10(6) oocysts and three weaned pigs given 1.6 X 10(6), 5.0 X 10(6) and 1.0 X 10(7) oocysts and examined 5 days post-inoculation. Pathogenic bacteria or viruses were not demonstrated in any pigs. Results of this study indicate that E. debliecki is not a cause of neonatal or weaning diarrhea in pigs.

Development of Isospora suis from pigs in primary porcine and bovine cell cultures

Sporozoites of Isospora suis penetrated and developed by endodyogeny in primary porcine kidney (PPK) and primary fetal bovine kidney (PFBK) cell cultures. Motile merozoites and binucleate Type I meronts were observed in both types of cultured cells. Multinucleate Type II meronts developed in PPK cell cultures only. These multinucleate meronts were always found singly, were nonmotile and did not form merozoites.

Experimental Cryptosporidium baileyi infections in chickens and turkeys produced by ocular inoculation of oocysts

Developmental stages of Cryptosporidium baileyi were observed on the conjunctival epithelium of 3 of 14 chicks and none of 7 turkeys following ocular inoculation of oocysts. No clinical signs of disease were observed in chicks or turkeys. All 14 chicks had developmental stages of C. baileyi in the cloaca, whereas 4 of the 7 turkeys were infected at this site.

Anthelmintic efficacy of ivermectin in naturally parasitized cats

Ivermectin was administered per os [( PO]; n = 15) or subcutaneously [( SC]; n = 3) to naturally parasitized cats at 10 (n = 6), 100 (n = 6), or 300 (n = 6) micrograms/kg of body weight. Nontreated control cats were given sterile isotonic saline solution PO (n = 5) or SC (n = 1). Qualitative fecal examinations were performed on each cat 1 day before treatment and 14 days after treatment. Cats were euthanatized 14 days after treatment, at which time parasites from the gastrointestinal tracts were recovered, identified, and enumerated. Lungs and urinary bladders were examined histologically or by digestion (lungs only) for Capillaria spp and/or Aelurostrongylus abstrusus. Ivermectin was effective in removing Ancylostoma spp at all doses, but removal of Toxocara cati required 300 micrograms of ivermectin/kg. Efficacies against A abstrusus, Capillaria spp, and Physaloptera spp could not be determined definitively. Ivermectin had no effect on Dipylidium caninum, Hydatigera taeniaeformis, Spirometra mansonoides, or Isospora spp. Adverse reactions were not observed in cats given ivermectin PO; however, 3 cats given ivermectin SC reacted as though they experienced pain at the injection site.

Experimental cryptosporidiosis in broiler chickens

Seven-day-old conventional broilers were inoculated either orally or intratracheally (IT) with 2.5 X 10(5), 5.0 X 10(5), or 2.0 X 10(6) oocysts of Cryptosporidium baileyi (32 birds for each dosage level per group; 192 birds total). Thirty-two birds served as unninoculated controls. Mean weekly weight gain and feed conversion were determined during a 5-week period. Carcass pigment was graded using a Roche Color Fan. Fecal oocysts were calculated from random cage samples 6, 8, 11, 13, 15, 18, 20, 22, and 25 days after inoculation (DAI). Effects of C. baileyi on immune responses were examined for Newcastle disease virus-hemagglutination inhibition (NDV-HI) antibody, infectious bursal disease virus-enzyme-linked immunosorbent assay (IBDV-ELISA) antibody titers and delayed hypersensitivity (DH) in half of the birds in each group. Disease or death from cryptosporidiosis did not result from oral inoculation of C. baileyi. Signs of respiratory disease, consisting of rales, sneezing, and dyspnea were observed in all IT-inoculated birds 7 to 21 DAI. Seven deaths occurred in the IT-inoculated groups 14 to 21 DAI. At necropsy, lung parenchyma was gray, firm, and wet in the ventral region. Air sacs contained a foamy, white to gray, mucoid fluid. Histologic lesions in the air sacs and bronchi were epithelial hyperplasia, discharge of mucocellular exudate to the mucosal surface, thickening of the mucosa by cellular infiltrates, loss of cilia, and dilation of mucous glands. Weight gains for IT-inoculated birds were lower (P less than .05) than controls from 14 to 21 DAI, although weight gains for the 5-week period were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemoprophylaxis of cryptosporidiosis in chickens, using halofuginone, salinomycin, lasalocid, or monensin

Chemoprophylaxis of Cryptosporidium baileyi infections was attempted by feeding 4 groups of chicks diets containing 3 mg of halofuginone/kg of feed, 60 mg of salinomycin/kg, 75 mg of lasalocid/kg, or 110 mg of monensin/kg. Rations were fed 5 days before oral or intratracheal inoculation with oocysts and were continued for 20 days. None of the drugs prevented C baileyi infections. Clinical signs of respiratory tract disease and gross lesions of airsacculitis were observed in intratracheally inoculated birds in all treatment groups and nonmedicated controls. Orally inoculated birds did not develop clinical signs of infection. Pathogenic bacteria were not isolated from the respiratory tract systems of any chicks. Halofuginone delayed the establishment of infections of the bursa of Fabricius and cloaca, but not of the trachea.

In vitro excystation of Cryptosporidium baileyi from chickens

Release of sporozoites from the oocysts of Cryptosporidium baileyi is described from Nomarski interference-contrast microscopy. Just prior to excystation, the four sporozoites became motile and rearranged themselves within the oocyst. The sporozoites were then rapidly expelled through an opening that formed in the oocyst wall, and the residuum was either released or retained within the oocyst. Excysted sporozoites were crescent shaped and measured 5.0-9.0 microns X 1.0-1.6 micron (mean = 6.8 X 1.1 microns). Excystation occurred when sodium taurocholate or a mixture of trypsin and sodium taurocholate was present in the incubation medium. High levels of excystation occurred at 37 degrees or 40 degrees C, but excystation did not occur at 4 degrees C. The ability of biles from two avian and two mammalian hosts to produce excystation of C. baileyi was also studied. After a 2-h incubation at 40 degrees C, the percentages of excystation were 69.5% in goat bile, 45.0% in pig bile, 33.0% in chicken bile, and 34.5% in turkey bile.

Experimentally induced infections in turkeys with Cryptosporidium baileyi isolated from chickens

Oocysts of Cryptosporidium baileyi isolated from chickens were inoculated by different routes into 3 groups of turkey poults. Intratracheal inoculation of oocysts produced clinical signs of respiratory tract disease, deaths, and gross lesions of airsacculitis. Parasites developed in the microvillous border of the nasopharynx, larynx, trachea, bronchi, and air sacs. Oral and intracloacal inoculations of oocysts caused no deaths or clinical signs of disease, but did produce patent infections. Respiratory tract infections limited to the nasopharynx, larynx, and trachea occurred in 3 orally inoculated poults. Respiratory tract infections were not observed in intracloacally inoculated poults. The mode of inoculation did not influence the distribution of C baileyi in the digestive tract. The cloaca was parasitized in 100% of the birds with intestinal infections, and the bursa of Fabricius was parasitized in 72.7%.

Comparative efficacies of ivermectin, febantel, fenbendazole, and mebendazole against helminth parasites of gray foxes

Anthelmintic efficacies of ivermectin, febantel, fenbendazole, and mebendazole were compared in 45 adult gray foxes (Urocyon cinereoargenteus) naturally infected with helminth parasites. Fecal specimens were examined one week before treatment and one week and 3 weeks after treatment with each anthelmintic, using a sucrose flotation technique. Compared with pretreatment, fewer foxes in all groups were infected with helminths one week and 3 weeks after treatment. Ivermectin, febantel, and fenbendazole more effectively eliminated helminths than did mebendazole. Parasites found were Ancylostoma sp, Capillaria aerophila, and Aelurostrongylus abstrusus and/or Filaroides osleri.

Caryospora uptoni n. sp. (Apicomplexa: Eimeriidae) from red-tailed hawks (Buteo jamaicensis borealis)

Oocysts of Caryospora uptoni n. sp. were described from the feces of red-tailed hawks, Buteo jamaicensis borealis. Sporulated oocysts were spherical or subspherical and measured 28.1 by 26.4 micron. The oocyst wall was composed of a yellowish outer layer and brownish inner layer and was about 1.5 micron thick. Neither micropyle, polar granules, nor oocyst residuum were present. A single, spherical sporocyst 18.2 by 17.9 micron was present; a Stieda body was absent. A spherical eccentrically located sporocyst residuum was present in many sporocysts, but it degenerated to form a dispersed granular residuum in other sporocysts. Eight randomly arranged sporozoites, 12.6 by 4.2 micron, were present in each sporocyst; they contained a centrally or slightly posteriorly located nucleus.

Host specificity of Cryptosporidium sp. isolated from chickens

The host specificity of Cryptosporidium sp. infecting chickens was evaluated by oral inoculation of oocysts into 6 different species of neonatal rodents, adult nude mice (athymic), neonatal conventional and gnotobiotic pigs, turkeys, muscovy ducks and bobwhite quail. Examinations of tissue sections, ileal mucosal smears, fecal flotations and stained feces failed to reveal any infections in the mammalian species examined. Oocysts were observed in the feces, and developmental stages were observed in tissue sections, of turkeys and muscovy ducks but not bobwhite quail. This study indicates that Cryptosporidium sp. infections in avian species are probably not a zoonotic threat to humans.

Experimental Cryptosporidium infections in chickens: oocyst structure and tissue specificity

Oocysts of an avian isolate of Cryptosporidium were used to inoculate 21 chicks orally and 7 chicks intratracheally to determine the tissue specificity of this organism. Oocysts were passed in the feces 4 to 5 days after inoculation. Oocysts (6.8 by 5.0 microns) were fully sporulated and they were passed for at least 17 days by infected chicks. The mode of inoculation did not influence the distribution of cryptosporidia within the digestive tract. Cryptosporidia were found in the cloaca (100%), bursa of Fabricius (95.7%), terminal portion of the colon (26.1%), and cecum (4.3%) of chicks that were positive for developmental stages. Of 21 chicks inoculated orally, 4 had cryptosporidia in their trachea, whereas 6 of 7 chicks inoculated intratracheally had cryptosporidia in the trachea, bronchi, and air sacs. Cryptosporidium was found in the ducts of the salivary glands and nasal turbinates of chicks inoculated intratracheally that had clinical signs of respiratory tract disease. None of the chicks died or had intestinal disease.

Evaluation of three formulations of fenbendazole (10% suspension, 0.5% pellets, and 20% premix) against nematode infections in cattle

Anthelmintic efficacies of 3 formulations of fenbendazole were evaluated in cattle naturally parasitized with nematodes: a 10% oral suspension, 0.5% pellets as a top dressing on feed, and a 20% premix. All formulations of fenbendazole were greater than 99% effective in removing adults of Haemonchus contortus, Ostertagia spp, Cooperia spp, and Oesophagostomum radiatum. Fenbendazole was greater than 96% effective in removing adults of Strongyloides papillosus and greater than 85% effective in the removal of Trichuris sp. Fenbendazole was greater than 96% effective against immature nematodes, which were thought to be primarily Cooperia spp. Adverse reactions were not observed in calves treated with the 3 formulations of fenbendazole.

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.

Anthelmintic activity of ivermectin against immature gastrointestinal nematodes of sheep

Twenty-four lambs of mixed breeding with mixed experimental infections of Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, and T colubriformis were allotted to 4 groups. One group (control) was given the vehicle propylene glycol, and the others were given 100, 200, or 300 micrograms of ivermectin/kg of body weight by mouth. Twelve days after treatment, the sheep were necropsied. The compound was greater than 99% effective against immature stages of 4 nematode species at all dosages, except at the 100 micrograms/kg dosage, where efficacy was 96% against H contortus.

Pathological changes and immunity associated with experimental Eimeria vermiformis infections in Mus musculus

Pathological changes and immunity induced by Eimeria vermiformis (Ernst, Chobotar & Hammond, 1971) were studied in outbred Swiss mice inoculated with 5000, 10,000, 20,000, or 40,000 oocysts. Cross immunity to E. ferrisi was also studied. In the case of E. vermiformis, mortality was dose dependent; most deaths were observed in the intermediate-dose groups. Most deaths also correlated with peak oocyst output. Histopathologic changes consisted of an early neutrophil and mononuclear cell infiltration in the small intestine. Later, villus atrophy and crypt hyperplasia caused a decrease in the villus-crypt ratio. During the acute phase (8-10 days after inoculation), villus tips were eroded and parasites with necrotic debris filled the cryptal and intestinal lumina. Vacuolar changes were observed in epithelial cells of the small intestine. Neither parasites nor significant pathological changes were observed in extra-intestinal organs. Mice were totally immune to reinfection with E. vermiformis 30 and 105 days after inoculation. Cross immunity was not observed between E. vermiformis and E. ferrisi.

Clinical and histologic observations of actively induced resistance to Eimeria ferrisi Levine and Ivens, 1965 (Protozoa: Eimeriidae) in the mouse (Mus musculus)

Actively induced resistance to Eimeria ferrisi was studied clinically and histologically in Mus musculus. Results indicated that a partial resistance to challenge was obtained. Initially infected animals had severe symptoms of coccidiosis but the symptoms diminished as the infections progressed. Previously infected mice had only slight symptoms of infection when challenged. Challenge doses produced severe coccidiosis in the non-immune controls although none died. Six mice died at peak patency during the immunizing inoculations. Histologic examination indicated that parasite numbers were reduced in resistant animals. The reduction appeared greatest during late sexual development. Tissues from resistant animals showed little evidence of damage and appeared to contain an increased amount of lymphoid tissue. Tissues from non-immunized mice killed after challenge were heavily infected and contained extruded blood, mucous, and cellular debris in the gut lumen. Considerable destruction of host epithelial cells occurred. The observations are discussed and compared to other coccidial immunity studies.