The thickness of the crystal mush on the floor of the Bushveld magma chamber.

The thickness of the crystal mush on magma chamber floors can be constrained using the offset between the step-change in the median value of dihedral angles formed at the junctions between two grains of plagioclase and a grain of another phase (typically clinopyroxene, but also orthopyroxene and olivine) and the first appearance or disappearance of the liquidus phase associated with the step-change in median dihedral angle. We determined the mush thickness in the Rustenburg Layered Suite of the Bushveld Complex at clinopyroxene-in (in Lower Main Zone) and magnetite-in (in Upper Zone). We also examined an intermittent appearance of cumulus apatite in Upper Zone, using both the appearance and disappearance of cumulus apatite. In all cases, the mush thickness does not exceed 4 m. These values are consistent with field observations of a mechanically rigid mush at the bases of both magnetitite and chromitite layers overlying anorthosite. Mush thickness of the order of a few metres suggests that neither gravitationally-driven compaction nor compositional convection within the mush layer is likely to have been important processes during solidification: adcumulates in the Bushveld are most likely to have formed at the top of the mush during primary crystallisation. Similarly, it is unlikely either that migration of reactive liquids occurs through large stretches of stratigraphy, or that layering is formed by mechanisms other than primary accumulation.

Ultrastructure of trichocysts in Hematodinium spp. infecting Atlantic snow crab, Chionoecetes opilio.

Trichocyst morphology and development were explored using transmission electron microscopy in Hematodinium spp. isolated directly from Atlantic snow crab (Chionoecetes opilio) hemolymph and from in vitro cultures. Appearance of trichocysts defines the initiation of a morphological transition in the parasites life cycle from vegetative stage to the transmission stage. Trichocysts within sporonts were found in distinct clusters near the nucleus in close apposition to the Golgi. As cells transitioned to more mature dinospores however, trichocysts were found randomly distributed throughout the cytoplasm. Clusters contained both primordial and maturing trichocysts at various stages indicating an asynchronous development. The random distribution of mature trichocysts suggests deployment to the cell membrane for future extrusion. Mature trichocysts of Hematodinium spp. appeared structurally similar to trichocysts from photosynthetic dinoflagellates. Hematodinium spp. trichocysts differed by the presence of peripheral tubules associated with novel cuboidal appendages in the apical region rather than a network of central electron dense fibres as found in photosynthetic dinoflagellates. Additionally, the trichocyst membrane of Hematodinium spp. was in close apposition to the square crystalline core. Trichocyst expulsion was not observed during our study which along with features of development and maturation within Hematodinium life stages should provide insight into proposed roles in host attachment or defense that could further our understanding of the mechanisms of pathogenesis and transmission of the parasite.

Overview of "bumper car" disease--impact on the North American lobster fishery.

Recent (1993) landings of American lobsters (Homarus americanus) were valued at $294 million (Can.) in Canada and $213 million (Can.) in the United States. However, post-harvest losses are estimated at $50-75 million (10-15%) annually. The lobster fishery is one of the few remaining viable traditional fisheries in eastern North America. "Bumper car" disease of lobsters, caused by the scuticociliate Anophryoides haemophila, can cause significant losses in coldwater impoundments. Apparently epidemics now occur more frequently and with greater severity; surprisingly the epidemiology and economic impacts of "bumper car" disease are not well documented. The ciliate A. haemophila is easily maintained in a cell-free, chemically defined, seawater-based medium at 5 degrees C. Cultured ciliates require longer and more parasites to kill lobsters than those transmitted by intrahaemocoelic injection from lobster-to-lobster. Regardless of source of ciliates, the larger the inoculum, the more rapid the death of lobsters. The pathogenesis of "bumper car" disease is unknown. Horizontal transmission could occur across the thin cuticle of gills or via wounds in the exoskeleton present during moulting of lobsters. Because ciliates are initially sequestered in lobster tissues for an extended period, they are detectable sooner by histological examination of tissues than by direct examination or culture of haemolymph. Additional to indirect fluorescent antibody testing and immunoperoxidase staining of tissues, utilizing monoclonal antibodies prepared to sonicated ciliates, the parasites are readily detected with oligonucleotide probes based on ssu-rDNA of A. haemophila. The prevalence of A. haemophila should be re-evaluated. Ciliates sequester in gill, heart and muscle tissues. Several disinfectants and chemotherapeutants, licensed in North America for veterinary use in food-producing animals, are efficacious against A. haemophila in vitro. A definition of healthy vs ciliate-infected lobsters is being prepared, based on haematology and clinical chemistry of haemolymph. Our novel bar-coded labelling system for aquatic organisms facilitates experimental design and randomization protocols of lobsters. The model of "bumper car" disease will aid study of health and infectious disease processes of lobsters and other crustaceans.

Isolation of the Lyme disease spirochete, Borrelia burgdorferi, from Ixodes dammini (Acari: Ixodidae) collected on Prince Edward Island, Canada.

Studies were undertaken to monitor for the presence of Borrelia burgdorferi, the etiologic agent of Lyme disease, on Prince Edward Island, Canada. Gut contents were removed for culturing from seven engorged ticks collected in 1991-1992 including five Ixodes dammini (Spielman, Clifford, Piesman & Corwin) and two I. scapularis (Say) removed from a dog that had recently traveled to the southern United States. B. burgdorferi was recovered from one I. dammini that had been removed from a cat in Charlottetown in October 1991. The cat had not traveled off the island. Immunofluorescent antibody (IFA) studies on sera from 75 dogs, 7 cats, and 8 white-tailed deer (Odocoileus virginianus) collected on Prince Edward Island between 1989 and 1992 revealed one reactor with an IFA titer > or = 1:256. The reactor was a dog with a history of travel to the United States. This report documents the first isolate of B. burgdorferi in Atlantic Canada, possibly because of the introduction of I. dammini on migratory birds. Serological studies do not indicate widespread occurrence of B. burgdorferi on Prince Edward Island.

Use of proteinase K in the excystation of Sarcocystis cruzi sporocysts for in vitro culture and DNA extraction.

Proteinase K was used for the cleaning of Sarcocystis cruzi (Apicomplexa) sporocysts prior to excystation. Bovine pulmonary endothelial cell cultures inoculated with the excysted sporozoites remained free of bacterial contamination for the duration of the experiment and had high yields of merozoites. The excysted sporozoites also yielded genomic DNA that could be labelled efficiently with 32P dATP by the random priming method.

Development of genomic probes to Sarcocystis cruzi (Apicomplexa).

A genomic library of Sarcocystis cruzi sporozoite DNA was constructed in bacteriophage lambda gt10. Recombinant phages containing insert DNA were selected by growth on Escherichia coli strain C600 hflA150. Of 14 clones examined, 11 contained DNA inserts ranging in size from approximately 1.45 kilobase (kb) to 6.18 kb. Insert DNA from four of these clones specifically hybridized to 32P-labelled S. cruzi merozoite DNA. One of these insert DNA, clone SL41, was selected and labelled with 32P. This probe did not hybridize with the other ten DNA inserts nor with bovine cellular DNA, but it hybridized with sporozoite, merozoite and bradyzoite DNA preparations. The SL41 probe could detect merozoite DNA in as little as 17 ng total DNA. Genomic probes detecting developmental stages of Sarcocystis spp. could provide an improved means is diagnosis of acute bovine sarcocystosis.

Use of genomic DNA probes for the diagnosis of acute sarcocystosis in experimentally infected cattle.

Two clones of 1.4 and 4.33 kilobase pairs (kbp) DNA inserts, were selected from a Sarcocystis cruzi sporozoite genomic library constructed in bacteriophage lambda gt10. These clones strongly hybridized with sporozoite and merozoite DNA and were evaluated as probes for detection of merozoite DNA in clinical samples. Of five calves in the experiment, four were each orally dosed with approximately 200,000 S. cruzi sporocysts; one calf served as non-infected control. Subsequently, blood was collected from the calves twice weekly for 3.5 months and fractionated into buffy coats, polymorphonuclear cells, and plasma. Total cellular DNA extracted from these fractions was dot blotted on nylon membranes and hybridized with the probes radiolabeled with [alpha-32P]dATP. The probes detected merozoites on Day 22 post infection in the buffy coats and intermittently from Day 25-39 in the granulocyte fraction. Parasitemia (i.e. merozoites in blood) was also detected by indirect fluorescent antibody technique (IFAT) and direct microscopy, Diagnosis of sarcocystosis in cattle using genomic DNA probes by dot blot hybridization provides an alternative method of detecting parasitemia that is more rigorous than the other two tests (IFAT, direct microscopy) which rely on morphology of the merozoite and visualization by the examiner. As probes detected merozoite DNA in the granulocyte fraction, polymorphonuclear cells may be involved in the pathogenesis of S.cruzi; however this hypothesis requires further study.

Cryptosporidiosis in the respiratory tract of turkeys in Saskatchewan.

Developmental stages of Cryptosporidium sp. (Protozoa: Cryptosporiidae) were observed in tracheal epithelium of two groups of turkey poults from a farm in central Saskatchewan. Lesions associated with the parasite included excess mucus, epithelial hyperplasia and metaplasia and necrosis, and macrophage and heterophil infiltration in thickened lamina propria. Infection with the parasite was confirmed by histologic and ultrastructural examination of tracheal tissues.

Use of injectable potassium chloride for euthanasia of American lobsters (Homarus americanus).

Potassium chloride (KCl: 330 mg/ml) was assessed as an euthanasia agent in American lobsters (Homarus americanus). Two groups of 10 lobsters (408.2 to 849.9 g) were maintained at 11.9 to 12.1 degrees C ('warm') and 1.5 to 2.5 degrees C ('cold') to evaluate the possible effect of ambient temperature on response to KCl. Death was defined as time of cardiac arrest, as viewed and measured by use of ultrasound. The KCl solution was injected (100 mg of KCl/100 g of body weight) at the base of the second walking leg to flood the hemolymph sinus containing the ventral nerve cord with potassium. Disruption of this 'central nervous system' was immediate, followed by cardiac arrest within 60 to 90 seconds. Group median ( +/- SD) baseline heart rate was 42 +/- 14 'warm' and 36 +/- 5 'cold' beats per minute. Time until cardiac arrest ranged from 35 to 90 (57 +/- 18) seconds in the 'warm' group and from 40 to 132 (53 +/- 34) seconds in the 'cold' group. There was no significant difference between group medians for either parameter. Histologic lesions were limited to mild to moderate acute degeneration, characterized by cell swelling, loss of contraction bands, and occasional mild cytoplasmic vacuolation of skeletal muscle at the injection site. Injectable KCl solution was an effective, reliable method for euthanasia of H. americanus.

Response of American lobsters Homarus americanus to infection with a field isolate of Aerococcus viridans var. homari (Gaffkemia): survival and haematology.

American lobsters Homarus americanus were inoculated with a field isolate of the Gram-positive bacterium Aerococcus viridans var. homari, causative agent of gaffkemia, at 1 x 10(6), 1 x 10(4) or 1 x 10(2) colony forming units (CFU) kg(-1) or with sterile 3% NaCl and maintained at 10 or 15 degrees C until they died or were euthanised. Progression of disease in individual animals was monitored daily by total haemocyte count (THC) and haemolymph culture. Post-mortem examinations were performed on all lobsters. Effects of both ambient temperature and infective dose on survival time were observed. Marked bacteraemia occurred in all mortalities. Haemocytopenia (THC < 10 x 10(9) cells l(-1)) preceded death in most, but not all, mortalities.

Estimated prevalence of Aerococcus viridans and Anophryoides haemophila in American lobsters Homarus americanus freshly captured in the waters of Prince Edward Island, Canada.

The Canadian lobster industry holds lobsters Homarus americanus in captivity for various periods to supply markets with live product year-round. Mortality during holding results in considerable losses, estimated at 10 to 15 % yr(-1) by the industry. This study examined the prevalence of Anophryoides haemophila and Aerococcus viridans, causative agents of 'bumper car' disease and gaffkemia, respectively, in lobsters freshly captured in the waters of Prince Edward Island during the spring and fall fishing seasons of 1997. A total of 116 lobsters were sampled in the spring, and 138 in the fall. A. haemophila was not detected in the spring, while the prevalence was 0.72 % in the fall with a 95% confidence interval (CI) of 0.02 to 3.97% and an overall prevalence of 0.39% (95% CI: 0.01 to 2.17%). The prevalence of A. viridans was estimated at 6.9% (95% CI: 3.0 to 13.14%) in the spring, 5.8% in the fall (95% CI: 2.54 to 11.10%), and 6.30% overall (95% CI: 3.64 to 10.03%). Because of the reduced interest in food of diseased lobsters, and compromised metabolism in the case of gaffkemia, these prevalence estimates are likely underestimates of the true prevalence of gaffkemia and 'bumper car' disease in the wild populations of lobster around Prince Edward Island.

Description of the goose coccidium Eimeria stigmosa (Klimes, 1963), with evidence of intranuclear development.

Oocysts of Eimeria stigmosa isolated from a wild juvenile lesser snow goose (Anser caerulescens caerulescens) were used in experimental infections of laboratory-reared geese. The structure of oocysts is described; a peculiar bumpy surface and a calyx-like thickening around the micropyle are illustrated by scanning electron microscopy. Experimentally infected geese had reduced feed intake and passed blood in their feces. Six days post-inoculation (p.i.) oocysts were passed for about 24 hr. Oocyst production was not increased in dexamethasone-treated geese. Complete sporulation of oocysts occurred after about 3.5 days. Developmental stages in lesser snow geese were occasionally present throughout the intestine, but were concentrated at Meckel's diverticulum, and at foci in the ileum and colon. Meronts were found 2, 3 and 4 days p.i. and gamonts and developing oocysts were observed 4, 5 and 5.5 days p.i. All endogenous stages of E. stigmosa were present in the nucleoplasm of enterocytes, primarily at the apical half of villi. Nuclear hypertrophy occurred in infected cells and nuclei containing gamonts were enlarged up to 4 times their normal size. Mild lesions were observed in the intestine of infected geese. Patent infections were established in lesser snow, Canada (Branta canadensis) and domestic (Anser anser domesticus) geese, but oocysts were not passed by inoculated ducks.

Effects of the protozoan parasite Sarcocystis rauschorum on open-field behaviour of its intermediate vertebrate host, Dicrostonyx richardsoni.

Behaviour and activity levels were measured in varying lemmings experimentally infected with the heteroxenous parasite, Sarcocystis rauschorum to test the hypothesis that the parasite alters behaviour of this intermediate host and thereby increases probability of transmission to the definitive host, the snowy owl (Nyctea scandiaca). Measures of short-term activity levels on a running wheel indicated no effect of the parasite, either directly, or indirectly as a result of illness. We observed behaviour of infected lemmings placed in an "open field" (arena). Lemmings would increase their susceptibility to predators if they spent more time away from cover, used crypsis (stationary postures) less, spent more time exploring (especially in unfamiliar areas), or responded inappropriately to threats from predators. We found that only exploratory activity showed significant change after infection. The frequency of exploratory activity increased and became disassociated from the usual fear response. This may increase the lemmings' susceptibility to aerial predation. The mechanism for this effect is unknown, but neurological lesions have been observed. The examination of the modes of transmission of the S. rauschorum parasite within lemming populations and of a possible fecundity compensation strategy adopted by the lemmings, and their relevance to population control, are suggested as areas for future study.

Ultrastructural development of the sarcocyst of Sarcocystis rauschorum (Apicomplexa: Sarcocystidae) in the varying lemming Dicrostonyx richardsoni.

The development of the sarcocyst of Sarcocystis rauschorum in its intermediate host was studied. Lemmings were orally administered sporocysts of S. rauschorum obtained from snowy owls (Nyctea scandiaca). Beginning at 9 days postinoculation (DPI) and at various intervals to 84 DPI, skeletal muscle tissue taken from the infected lemmings was examined by electron microscopy. At 9 DPI the sarcocysts contained few metrocytes and the cyst wall was flat. The metrocytes underwent endodyogeny, and within a few days the cyst wall of the rapidly growing sarcocyst developed numerous tubulovesicular invaginations into the electron-dense layer, and the wall had a few irregular infoldings. By 21 DPI, banana-shaped bradyzoites appeared, and by 84 DPI the mature cysts were filled with bradyzoites in groups subdivided by septa and by deep infoldings of the cyst wall. The fine structure of the wall remained simple throughout maturation, with no conspicuous invagination or protrusion. The sarcocyst produced in response to S. rauschorum is unlike those from many species of Sarcocystis, which have complex walls that change markedly as the sarcocysts mature; however, its simple appearance is similar to other species that have rodents as intermediate hosts and raptorial birds as definitive hosts.

In vitro excystation of Sarcocystis capracanis, Sarcocystis cruzi and Sarcocystis tenella (Apicomplexa).

Improved rates of in vitro excystation of sporozoites from sporocysts of Sarcocystis capracanis, Sarcocystis cruzi, and Sarcocystis tenella were obtained by pretreating sporocysts with an aqueous sodium hypochlorite (NaOCl) solution followed by incubation in excysting fluid (EF). After pretreatment with NaOCl, sporocysts were washed 4 times in Hanks' balanced salt solution and then incubated in various EF (pH 7.4) at 38.5 C in 5% CO2-95% air. Maximum rates of excystation (free sporozoites/(sporozoites in sporocysts + free sporozoites) X 100) for all 3 species of Sarcocystis occurred at 4 hr after incubation in EF. These rates were 17% for S. capracanis after incubation in EF containing 2% trypsin + 10% caprine bile; 90% for S. cruzi in 2% trypsin + 10% bovine bile; and 20% for S. tenella in 2% trypsin + 10% caprine bile. Only a 40% excystation rate occurred in sporocysts of S. cruzi that had been stored previously for 14 days in aqueous potassium dichromate. Excysted sporozoites of S. capracanis, S. cruzi, and S. tenella penetrated and developed to mature meronts in bovine pulmonary artery endothelial cells or bovine monocytes.

Ascariasis, respiratory diseases and production indices in selected Prince Edward Island swine herds.

The levels of production, ascarid burden and respiratory disease were measured on 15 purposively selected swine herds, and the relationships between the various measures of ascarid burden were examined. On each farm 30 randomly selected pigs were weighed and rectal fecal samples were collected at approximately 11, 15, 19 and 22 weeks of age, and at slaughter. Fecal ascarid-egg counts and duration of infection were combined to calculate a composite measure of ascarid burden called "lifetime burden". At the abattoir the carcass weight and levels of anteroventral pneumonia, atrophic rhinitis, and liver lesions were recorded for each hog. The number of ascarids in the small intestines were counted. Study hogs were marketed at an average of 189 +/- 22 days. The average dressed carcass weight was 77.0 +/- 5.9 kg and the mean average daily gain was 0.519 +/- 0.071 kg/day. The percent of hogs with ascariasis varied widely among farms, no matter what measure of ascariasis was used; the percent with intestinal ascarids at slaughter ranged from 0% to 96%, the percent that shed ascarid eggs during their lifetime ranged from 0% to 100%, and the range for hogs with liver lesions ranged from 27% to 100%. Of the hogs slaughtered, 82% had milk spot lesions, 32% shed ascarid eggs during their lifetime and 35% had intestinal ascarids. The latter had an average of 12 intestinal ascarids. Anteroventral pneumonia occurred in 55% of the slaughtered hogs and 9% had atrophic rhinitis scores of five. The percent of hogs per farm with pneumonia ranged from 17% to 96%. The percent of hogs per farm with atrophic rhinitis scores of five ranged from 0% to 57%.

Diplotriaena tricuspis (Fedtschenko, 1874) (Nematoda: Diplotriaenoidea) in crows (Corvus brachyrhynchos Brehm) wintering in Ontario.

Two hundred and eleven of 4404 (4.8%) crows (Corvus brachyrhynchos) collected in the winters of 1976-77 and 1977-78 in Essex County, southwestern Ontario, were infected with Diplotriaena tricuspis (Fedtschenko, 1874) Henry and Ozoux, 1909. Prevalence of potentially patent infections was only 2.6%, however, as crows often had nematodes of a single sex only. Intensity was 4.0 (1-74) and was similar in both male and female crows of all age groups. Intensity tended to be higher in young-of-the-year crows than yearlings and adults.

An epizootic of besnoitiosis in captive caribou (Rangifer tarandus caribou), reindeer (Rangifer tarandus tarandus) and mule deer (Odocoileus hemionus hemionus).

Besnoitia sp. was diagnosed in two caribou (Rangifer tarandus caribou) which died of pneumonia at the Assiniboine Park Zoo (Winnipeg, Manitoba, Canada) in 1983. During the following 3 yr besnoitiosis spread to an isolated herd of caribou, to mule deer (Odocoileus hemionus hemionus) and to reindeer (Rangifer tarandus tarandus). Reduction of exposure to biting insects appears to have reduced the transmission of besnoitiosis within the reindeer herd. The morbidity rate was approximately 82% in caribou and 67% in mule deer over the age of 2 mo. Most animals with clinical signs were euthanized; this precluded an estimation of the disease-related mortality rate. Twenty-eight caribou, 10 mule deer and three reindeer have been euthanized or died as a result of this epidemic. Attempts to artificially transmit the disease to potentially susceptible intermediate and definitive hosts were unsuccessful.

Experimental transmission of Sarcocystis sp. (Protozoa: Sarcocystidae) between the shoveler (Anas clypeata) duck and the striped skunk (Mephitis mephitis).

Muscle containing macroscopic cysts of Sarcocystis sp. from naturally infected wild shoveler (Anas clypeata) ducks was fed to two captive striped skunks (Mephitis mephitis). The skunks passed sporocysts in their feces beginning 19 and 22 days post-infection, and continued to pass small numbers of sporocysts sporadically to 63 and 51 days post-infection, respectively. Sporocysts from the skunks were administered orally to four laboratory-reared shovelers. No cysts were found in ducks examined 56 and 84 days post-infection. One duck examined at 85 days post-infection had many microscopic cysts in its skeletal muscle. The remaining duck had numerous small macroscopic cysts in muscle at 154 days post-infection. A skunk fed muscle from this duck began to pass sporocysts on day 18 post-infection. All cysts in muscle (natural and experimental infection) had irregular cauliflower-like projections of the primary cyst wall.