Quantitative genetics of disease resistance in vaccinated and unvaccinated Atlantic salmon (Salmo salar L.)

Furunculosis (Aeromonoas salmonicida) is an important disease in Atlantic salmon (Salmo salar) farming. Vaccination and selective breeding for increased resistance to the disease on the basis of challenge tests of unvaccinated fish are used as complementary prophylactic methods. An important issue is whether genetic predisposition to infection is consistent across vaccinated and unvaccinated fish. Hence, the main objective of this study was to determine the magnitude of the genetic associations (correlations) between resistance to furunculosis in vaccinated and unvaccinated fish, and to estimate the magnitude of the correlation of resistance to furunculosis with resistance to the viral diseases infectious pancreatic necrosis (IPN) and infectious salmon anaemia (ISA). Sub-samples of unvaccinated and vaccinated salmon from 150 full-sib families were subjected to separate cohabitation challenge tests. Substantial genetic variation was found in resistance to furunculosis in both the unvaccinated (heritabilities of 0.51 ± 0.05) and vaccinated (0.39 ± 0.06) fish. However, the genetic correlation between resistance to furunculosis in the two groups was low (0.32 ± 0.13), indicating a weak genetic association between resistance in the two groups. Hence, the current selection strategy on the basis of challenge tests of unvaccinated fish is likely to produce low genetic improvement in resistance to furunculosis under field conditions, where fish are vaccinated with an effective vaccine. Evidence was found of significantly favourable genetic associations of resistance to furunculosis in unvaccinated (but less so for vaccinated) fish with resistance to both IPN and ISA (unvaccinated fish), indicating that vaccination 'mask' genetic associations between resistance to different diseases.

A sequential threshold cure model for genetic analysis of time-to-event data

In analysis of time-to-event data, classical survival models ignore the presence of potential nonsusceptible (cured) individuals, which, if present, will invalidate the inference procedures. Existence of nonsusceptible individuals is particularly relevant under challenge testing with specific pathogens, which is a common procedure in aquaculture breeding schemes. A cure model is a survival model accounting for a fraction of nonsusceptible individuals in the population. This study proposes a mixed cure model for time-to-event data, measured as sequential binary records. In a simulation study survival data were generated through 2 underlying traits: susceptibility and endurance (risk of dying per time-unit), associated with 2 sets of underlying liabilities. Despite considerable phenotypic confounding, the proposed model was largely able to distinguish the 2 traits. Furthermore, if selection is for improved susceptibility rather than endurance, the error of applying a classical survival model was nonnegligible. The difference was most pronounced for scenarios with substantial underlying genetic variation in endurance and when the 2 underlying traits were lowly genetically correlated. In the presence of nonsusceptible individuals, the method provides a novel and more accurate tool for utilization of time-to-event data, and has also been proven successful when applied to zero-inflated longitudinal binary data.

Molecular and epidemiological investigations of cryptosporidiosis in Cuban children

Molecular and epidemiological studies of Cryptosporidium infections amongst 28 Cuban children (aged 2-8 years) with diarrhoea are described. As few of the younger infected children but most of the older infected children had been breastfed, short-term protection from maternal antibodies passed to infants during breastfeeding may result in a lack of cryptosporidial infection in infancy. This protection of breastfeeding children may, however, result in such children developing less anti-Cryptosporidium immunity of their own (than their bottle-fed counterparts), so that, by school age, the children who had been breastfed are those most likely to be found infected. In the present study, in contrast with the observations made during a previous study of cryptosporidiosis in Cuban children, vomiting was rare (7%) whereas abdominal pain was common (57%). These differences in expression of symptoms between studies may be age-related. As seen in other studies from similar countries, including those of the Caribbean and Latin America, C. hominis was found to predominate, the results of the successful molecular analyses revealing 10 C. hominis infections but no C. parvum. Subgenotyping (at the gp60 locus) indicated that the C. hominis infections included a wide range of subtypes, with isolates from three subtype families (Ia, Ib and Id) being detected.

Giardia infections in Cuban children: the genotypes circulating in a rural population

Stool samples containing Giardia duodenalis cysts were collected from 95 primary-school children in central Cuba, and preserved by storing at -20 degrees C in 70% ethanol. Clinical data were collected for each child. Although 57% of the children were asymptomatic, the remaining 43% each reported between one and three symptoms. Following cyst quantification and isolation, molecular analyses were attempted on all cyst isolates, with the focus on the parasite's beta-giardin and glutamate-dehydrogenase (gdh) genes. Unfortunately, the cyst-preservation procedure appeared to have a deleterious effect on the cysts, since genotyping data could only be obtained for 20 of the 95 isolates. These data indicated, however, an approximately equal distribution between assemblage A (nine isolates) and assemblage B (11 isolates). Children found to be excreting relatively large numbers of cysts were more likely to be symptomatic than children who were excreting fewer cysts, and children with Giardia isolates from assemblage B were more likely to have symptomatic infections than children with isolates from assemblage A. Although considerable sequence variability was seen in the assemblage-B isolates, the assemblage-A isolates were relatively genetically homogeneous. This is the first publication from the Caribbean in which the Giardia genotypes circulating within the population have been identified, the first from the Americas providing information on associations between clinical presentation and the assemblage of the infecting Giardia, and the first to indicate that levels of cyst excretion may have clinical significance.

Family association between immune parameters and resistance to Aeromonas hydrophila infection in the Indian major carp, Labeo rohita

Seven innate immune parameters were investigated in 64 full-sib families (the offspring of 64 sires and 45 dams) from two year-classes of farmed rohu carp (Labeo rohita). Survival rates were also available from Aeromonas hydrophila infection (aeromoniasis) recorded in controlled challenge tests on a different sample of individuals from the same families. Due to strong confounding between the animal additive genetic effect and the family effects (common environmental+non-additive genetic), reliable additive (co)variance components and hence heritabilities and genetic correlations could not be obtained for the investigated parameters. Therefore, estimates of the association of challenge test survival with the studied immune parameters were obtained as product moment correlations between family least square means. These correlations revealed statistically significant (p<0.05) negative correlations of survival with bacterial agglutination titre (-0.48), serum haemolysin titre (-0.29) and haemagglutination titre (-0.34); and significant positive correlation with ceruloplasmin level (0.51). The correlations of survival to aeromoniasis with myeloperoxidase activity, superoxide production and lysozyme activity were found to be not significantly different from zero (p>0.05). Assuming that the negatively correlated candidate traits are not favourable as indirect selection criteria, the results suggest that ceruloplasmin level could potentially be a marker for resistance to aeromoniasis in rohu. The use of this immune parameter as an indirect selection criterion for increased resistance to aeromoniasis in rohu will, however, require that the parameter shows significant additive genetic variation and a significant genetic correlation with survival. Further studies are therefore needed to obtain a reliable heritability estimate for ceruloplasmin and its genetic correlation with survival from aeromoniasis.

Development and use of a pepsin digestion method for analysis of shellfish for Cryptosporidium oocysts and Giardia cysts

Investigation of shellfish for Cryptosporidium oocysts and Giardia cysts is of public health interest because shellfish may concentrate these pathogens in their bodies, and because shellfish are frequently eaten raw or lightly cooked. To date, the methods used for the analysis of shellfish for these parasites are based on those originally designed for water concentrates or fecal samples; the reported recovery efficiencies are frequently relatively low and the amount of sample examined is small. Here, we describe the development and use of a pepsin digestion method for analyzing shellfish samples for these parasites. The conditions of the isolation method did not affect subsequent parasite detection by immunofluorescent antibody test, and allowed examination of 3-g samples of shellfish homogenate, with recovery efficiencies from blue mussel homogenates of between 70 and 80%, and similar recoveries from horse mussel and oyster homogenates. Although exposure of the parasites to the conditions used in the technique affected their viability, as assessed by vital dyes, the maximum reduction in viability after 1-h incubation in digestion solution was 20%. In a preliminary survey of shellfish collected from the Norwegian coast, Cryptosporidium oocysts were detected in blue mussel homogenates in 6 (43%) of 14 batches and Giardia cysts in 7 (50%) of these batches. However, this relatively high occurrence, compared with other surveys, may be due to the higher recovery efficiency of the new method, and the relatively large sample size analyzed. A more comprehensive study of the occurrence of these parasites in shellfish would be of pertinence to the Norwegian shellfish industry.

First record of natural Tritrichomonas foetus infection of the feline uterus

Tritrichomonas foetus was found in the uterus of a cat with pyometra and in the faeces of three other cats in the same household, one of which had chronic diarrhoea. This is the first report of a feline uterine infection with T. foetus and also the first time T. foetus has ever been diagnosed in animals in Norway. The diagnosis was made by microscopic examination and sequencing studies.

The potential for acquiring cryptosporidiosis or giardiosis from consumption of mung bean sprouts in Norway: a preliminary step-wise risk assessment

The current work evolved from a microbial survey of fruits and vegetables conducted in Norway between 1999 and 2001. This survey found that mung bean sprouts were more likely to be contaminated with Cryptosporidium and Giardia than the other produce included in the survey. To support this observation and to demonstrate to public health officials that this might be a risk warranting further attention, a simple risk assessment was initiated. Assuming that 60,000 people in Norway consume a single serving of bean sprouts per week, and contamination levels are similar to those found in the survey, it was calculated that there could be in the order of 20 cases of Giardia or Cryptosporidium infection per 100,000 population attributable to consumption of mung bean sprouts. A number of assumptions were made for the calculations, including parasite factors (e.g. viability, genotype), product factors (e.g. extent of product contamination) and host factors (e.g. composition and extent of consumer group). These assumptions and areas of uncertainty, where further data would improve the risk assessment, are highlighted throughout. Not only does the risk assessment identify new areas of research, but it also demonstrates how risk assessment can be used as a tool to try to influence public health surveillance.

Full scale validation of helminth ova (Ascaris suum) inactivation by different sludge treatment processes

The Norwegian sewage sludge regulation requires disinfection (hygienisation) of all sludges for land application, and one of the criteria is that disinfected sludge should not contain viable helminth ova. All disinfection processes have to be designed and operated in order to comply with this criterion, and four processes employed in Norway (thermophilic aerobic pre-treatment, pre-pasteurisation, thermal vacuum drying in membrane filter presses and lime treatment) have been tested in full scale by inserting semipermeable bags of Ascaris suum eggs into the processes for certain times. For lime treatment supplementary laboratory tests have been conducted. The paper presents the results of the experiments, and it could be concluded that all processes, except lime treatment, could be operated at less stringent time-temperature regimes than commonly experienced at Norwegian plants today.

Occurrence of parasites on fruits and vegetables in Norway

Between August 1999 and January 2001, samples of various fruits and vegetables obtained within Norway were analyzed by published methods for parasite contamination. Neither Cyclospora oocysts nor Ascaris (or other helminth) eggs were detected on any of the samples examined for these parasites. However, of the 475 samples examined for Cryptosporidium oocysts and Giardia cysts, 29 (6%) were found to be positive. No samples were positive for both parasites. Of the 19 Cryptosporidium-positive samples. 5 (26%) were in lettuce, and 14 (74%) in mung bean sprouts. Of the 10 Giardia-positive samples, 2 (20%) were in dill, 2 (20%) in lettuce, 3 (30%) in mung bean sprouts, 1 (10%) in radish sprouts, and 2 (20%) in strawberries. Mung bean sprouts were significantly more likely to be contaminated with Cryptosporidium oocysts or Giardia cysts than the other fruits and vegetables. Concentrations of Cryptosporidium and Giardia detected were generally low (mean of approximately 3 [oo]cysts per 100 g produce). Although some of the contaminated produce was imported (the majority, if sprouted seeds are excluded), there was no association between imported produce and detection of parasites. Crvptosporidium oocysts and Giardia cysts were also detected in water samples concerned with field irrigation and production of bean sprouts within Norway. This is the first time that parasites have been detected on vegetables and fruit obtained in a highly developed. wealthy country, without there being an outbreak situation. These findings may have important implications for global food safety.

Factors affecting recovery efficiency in isolation of Cryptosporidium oocysts and Giardia cysts from vegetables for standard method development

While recently published techniques for recovering parasites from fruits and vegetables demonstrate a marked increase in efficiency and utility, there is still scope for further improvement in developing a standard method, particularly with difficult, but important, sample matrices such as bean sprouts. Herein, a number of parameters used in published techniques are investigated more closely. While sample size reduction may improve recovery efficiency because of a range of factors, it is important to keep the sample large enough for detection of low-level contamination. Age of sample is also important, and samples should be as fresh as possible. Elution procedures may contribute to losses of Giardia and should be more thoroughly investigated. Improved immunomagnetic separation techniques currently coming onto the market also have the potential to increase recovery efficiency substantially, even with difficult samples such as aged bean sprouts. However, merely increasing magnetic strength of the capturing magnet does not affect recovery efficiency, which must be reliant on a superior bead system, buffering system, or both.

Occurrence of Cryptosporidium oocysts and Giardia cysts in raw waters in Norway

AIMS

This paper reports the first investigation into the occurrence of Cryptosporidium and Giardia in Norwegian raw water sources.

METHODS

Between June 1998 and October 1999, 408 raw water samples, collected from 147 different sites across Norway, were analysed for these parasites. Analysis was based upon US EPA Method 1623.

RESULTS

In 305 samples (75%), parasites were not detected. In 55 samples (13.5%), Cryptosporidium only was detected. In 38 samples (9%), Giardia only was detected. In 10 samples (2.5%) both Cryptosporidium and Giardia were detected. Of the sites sampled, parasites were not detected at 100 (68%) of them, Cryptosporidium only was detected at 20 (13.5%). Giardia only was detected at 11 (7.5%), and both Cryptosporidium and Giardia were detected at 16 (11%). Concentrations of parasites were low; usually one cyst/oocyst detected per 10 litres of water.

CONCLUSIONS

Significant associations were demonstrated for these samples between the detection of these parasites and (a) turbidity > or =2.0 NTU, and (b) high numbers of domestic animals within the catchment area. No association between seasonality and the occurrence of these parasites could be detected. The results are discussed in relation to other studies and the potential public health implications for Norway.

Isolation of Cyclospora oocysts from fruits and vegetables using lectin-coated paramagnetic beads

Published techniques for recovering parasites from fruit and vegetables are generally inadequate, with low and variable recovery efficiencies. Herein, we describe an improved method for analyzing fruit and vegetables for Cyclospora oocysts. The technique includes washing procedures, sonication, and separation using lectin-coated paramagnetic beads. Identification is by microscopy (differential interference contrast and fluorescence). Oocyst recovery efficiencies from mushrooms, lettuce, and raspberries were approximately 12%. Recovery efficiencies from bean sprouts were approximately 4%. Although no significant difference in recovery efficiency could be detected between samples processed using the lectin-coated beads and samples processed without this procedure, distinct advantages were apparent when the lectin-coated beads were used. A considerably smaller, cleaner final volume remained for microscopy, which increases the sensitivity of the technique and reduces operator time.

Isolation and enumeration of Giardia cysts, cryptosporidium oocysts, and Ascaris eggs from fruits and vegetables

Published techniques for recovering parasites from fruit and vegetables are generally inadequate, with low and variable recovery efficiencies. Here we describe an improved methodology for analyzing fruit and vegetables for Giardia cysts, Cryptosporidium oocysts, and Ascaris eggs. The method includes washing procedures, sonication, and, for Giardia and Cryptosporidium, immunomagnetic separation. Identification is by immunofluorescence (Giardia and Cryptosporidium) or brightfield microscopy (Ascaris). Recovery efficiencies from lettuce, Chinese leaves, and strawberries were found to be approximately 67% for Giardia, 42% for Cryptosporidium, and 72% for Ascaris. Recovery efficiencies from bean sprouts tended to be more variable and lower. This could be due to material removed with the parasites during the washing procedures, which, in turn, appeared related to the age of the bean sprouts. It is therefore recommended that fruit and vegetables should be as fresh as possible when analyzed for parasites.

Effect of sample holding time on recovery of Cryptosporidium oocysts and Giardia cysts from water samples

U.S. Environmental Protection Agency methods for analysis of water for Cryptosporidium and Giardia stipulate maximum sample holding times which are not always practical to comply with. A spiking experiment indicated that holding times of up to 2 weeks had no significant effect on recovery of these parasites from 10-liter samples of raw water in plastic carboys.

Definition of animal breeding goals for sustainable production systems

What we do is determined by the way we "view" a complex issue and what sample of issues or events we choose to deal with. In this paper, a model based on a communal, cultural, or people-centered worldview, informed by a subjective epistemology and a holistic ontology, is considered. Definitions and interpretations of sustainable agriculture are reviewed. Common elements in published definitions of sustainable agriculture and animal production among those who seek long-term and equitable solutions for food production are resource efficiency, profitability, productivity, environmental soundness, biodiversity, social viability, and ethical aspects. Possible characteristics of future sustainable production systems and further development are presented. The impact of these characteristics on animal breeding goals is reviewed. The need for long-term biologically, ecologically, and sociologically sound breeding goals is emphasized, because animal breeding determined only by short-term market forces leads to unwanted side effects. Hence, a procedure for defining animal breeding goals with ethical priorities and weighing of market and non-market values is suggested. Implementation of non-market as well as market economic trait values in the aggregate genotype, as suggested, may allow for breeding programs that contribute to sustainable production systems. Examples of breeding goals in salmon, cattle, and pigs are given, and the resulting genetic responses are evaluated with respect to economic profit (or costs) and other criteria of sustainability. Important prerequisites for breeding programs for sustainable production are appropriate governmental policies, awareness of our way of thinking, and a more communal worldview informed by a subjective epistemology and a holistic ontology.

Intestinal parasites in swine in the Nordic countries: multilevel modelling of Ascaris suum infections in relation to production factors

In Denmark, Finland, Iceland, Norway and Sweden, 413 sow herds were randomly selected for sampling. Faeces from pigs of 7 age groups/categories were examined for helminth eggs (11,233 individual samples), and an accompanying questionnaire was completed at each visit. In total, 1138 pigs on 230 farms were found to be positive for Ascaris suum. Considerable differences in the occurrence of A. suum could be observed directly for several of 20 independent variables at the herd or category level. However, given that univariate analyses may be severely affected by confounding of covariates resulting in spurious inference, additional multivariate analyses were undertaken. An ordinary logistic regression on Ascaris positive/negative farms showed that Denmark had the highest frequency of infected herds, while Iceland and Finland had the lowest frequencies and that herds using 'late weaning' and 'Class 2' drugs (pyrantel, levamisole) were most often infected. Because many herds were found to be totally negative for A. suum, mixed hierarchical logistic-normal regression models (both the penalized quasi-likelihood and the Markov Chain Monte Carlo methods) were developed for both a full (all herds) and a reduced (the 230 infected herds) data set using either a cut-off of > 0 eggs per gram (epg) or > 200 epg to counter for false-positive egg counts. Estimates for identical models, but where the animal level variance was constrained to the binomial assumption, were also calculated. Significant covariates were robust to model development with 'Age group', 'Country', 'Weaning age', 'Water system' and simple interactions between the latter two and 'Age group' being significantly associated with the occurrence of A. suum, while all variables concerning anthelmintic drug, anthelmintic strategy, floor type, bedding, dung removal, washing and disinfection were not. These findings are discussed in the light of the complex relationship between A. suum and its pig host.

Adult Dirofilaria repens in a subcutaneous granuloma on the chest of a dog

A 10-year-old, 9 kg, intact male crossbred dog was treated for nasal mites with milbemycin oxime using a dose of 1 mg/kg bodyweight orally, three times at 10-day intervals. One month after the initiation of this treatment a subcutaneous nodule developed on the sternum of the dog. The nodule was removed and found to contain a single, 82 mm long, thread-like nematode. Several exotic parasites were suspected as possibilities because the dog had been imported to Norway from South Africa. Microfilariae were not detected in the blood and heartworm antigen tests were negative. The worm was identified morphologically as an adult, female Dirofilaria repens. This is the first report of D repens from Norway. The case is of interest because of the differential diagnostic problem it posed and because infestation was recognised following treatment of another parasitic condition with a broad-spectrum, antiparasitic drug. In addition, the case provides a reminder of the necessity to be aware of geographical differences in disease occurrence which can produce unexpected disease in non-endemic areas as a consequence of increased international travel with pets.

Intestinal parasites in swine in the Nordic countries: prevalence and geographical distribution

In Denmark (DK), Finland (FIN), Iceland (I), Norway (N), and Sweden (S), 516 swine herds were randomly selected in 1986-1988. Individual faecal analyses (mean: 27.9 per herd) from eight age categories of swine showed that Ascaris suum, Oesophagostomum spp., Isospora suis, and Eimeria spp. were common, while Trichuris suis and Strongyloides ransomi-like eggs occurred sporadically. Large fatteners and gilts were most frequently infected with A. suum with maximum prevalences of 25-35% in DK, N and S, 13% in I and 5% in FIN. With the exception of the remarkably low A. suum prevalence rates in FIN, no clear national differences were observed. Oesophagostomum spp. were most prevalent in adult pigs in the southern regions (21-43% in DK and southern S), less common in the northern regions (4-17% adult pigs infected), and not recorded in I. I. suis was common in piglets in DK, I, and S (20-32%), while < 1% and 5% were infected in N and FIN, respectively. Eimeria spp. had the highest prevalences in adult pigs (max. 9%) without clear geographical differences. I. suis and Eimeria spp. were recorded for the first time in I, and I. suis for the first time in N.

Scarcity of gamma delta T cells in intestinal epithelia containing coccidia despite general increase of epithelial lymphocytes

Lymphocytes of intestinal epithelia were examined in lambs experimentally infected with coccidia. Fourteen conventional, coccidia-free 3-week-old lambs of the Dala breed were given either 250,000 (eight lambs in experiment 1) or 100,000 (six lambs in experiment 2) sporulated oocysts of Eimeria ovinoidalis (> 99.9% pure) via a stomach tube. Nine lambs (five in experiment 1 and four in experiment 2) of the same age served as uninoculated controls. The infected lambs developed diarrhea and dehydration between days 10 and 13 after infection. Intestinal specimens were collected 10-20 days after inoculation. A heavy multifocal infection of the epithelium comprising schizonts, gamonts, and oocysts resulted, with changes being most pronounced in the large intestine and the terminal part of ileum. Lesions included villous atrophy, villous fusions, and crypt hyperplasia. Computer-assisted morphometric analysis was applied to immunoperoxidase-stained sections for quantification of intraepithelial T cell subsets and included the distal jejunum of lambs of experiment 1. A significant increase in the epithelial area of the distal jejunum occupied by CD8+ lymphocytes was found in the infected lambs as compared with uninfected controls (18.3% versus 3.7%). The increased presence of CD8+ cells may be of significance in the intestinal immune response to ovine coccidiosis. A moderate, overall increase was also found for the gamma delta lymphocytes in the jejunal epithelium. Examination of the ileum of infected lambs of both experiments showed a scarcity of gamma delta cells (0.4% of epithelial area) in stretches of epithelium infected by coccida as compared with adjacent noninfected epithelium (4.0% of epithelial area).(ABSTRACT TRUNCATED AT 250 WORDS)

Chemoprophylaxis of coccidiosis in lambs with a single oral dose of toltrazuril

The prophylactic efficacy of a single oral dose of toltrazuril against coccidiosis (mixed Eimeria infections) in naturally infected lambs was evaluated in two experiments. Toltrazuril at 20 mg kg-1, given on Day 7 or Day 10 after turnout on pasture, proved to be highly efficacious in preventing clinical coccidiosis under Norwegian conditions. Toltrazuril reduced the oocyst output to very low levels, prevented the development of diarrhoea and improved weight gain during the first 4-5 weeks after treatment. Treatment on Day 7 was superior to treatment on Day 10 with respect to improving weight gain and preventing the development of soft faeces. Lambs treated with toltrazuril on Day 7 seemed to be as immune as untreated lambs to natural reinfections with coccidia later in the grazing season. In one of the experiments, natural infections with the nematode Nematodirus battus produced a coccidiosis-like disease in some lambs simultaneously with the outbreak of coccidiosis.

Effects of leucocyte extract, levamisole and sulphadimidine on natural coccidial infections (Eimeria spp.) in young lambs

The efficacy of leucocyte extract (LE) and sulphadimidine in preventing coccidiosis in naturally infected lambs on pasture was evaluated in 3 separate experiments, whereas the prophylactic effect of levamisole was studied in 1 of the experiments. LE prepared from ewes immune to coccidia (Eimeria spp.) was administered either intravenously or intraperitoneally to young lambs 7, 5, or 2 days before they were turned out on pastures contaminated with coccidia. In all experiments, LE failed to transfer protective immunity to the lambs against the first coccidial infection on pasture. The LE preparations used apparently had an immunosuppressive effect, which resulted in more severe clinical signs of coccidiosis in the recipients. The lambs given LE showed a higher incidence of diarrhoea, a poorer weight gain, a higher mortality, and a higher oocyst output than the untreated control lambs. In lambs treated with sulphadimidine at 200 mg/kg on days 12, 13, and 14 after turnout there was a reduced severity of the coccidial infections in all experiments. The sulphadimidine-treated lambs had better weight gains and passed fewer oocysts than the controls during the third and fourth week after turnout, but some of them developed diarrhoea. Lambs treated with levamisole at 2 mg/kg 2 days before turnout, at turnout, and 2 days after turnout were more severely affected by the first coccidial infection on pasture than the controls.

To study the lambs’ immunity against a heavy challenge infection with coccidia as compared with their immunity against the natural reinfection on pasture, some of the lambs from the original groups (untreated, sulphadimidine-treated, LE-treated) were each inoculated with 2 mill. Eimeria spp. oocysts about 6 weeks after turnout. The oocyst counts of the challenged lambs, except the LE-treated lambs, increased to a new peak 19–20 days after challenge. The challenge infection caused a softening of the faeces and a marked depression in weight gain in all challenged groups of lambs, mainly between days 10 and 17 after challenge. The lambs were thus only partially immune to coccidia after the first coccidial infection on pasture. The lambs treated with either LE or sulphadimidine in connection with the first coccidial infection on pasture were not appreciably more susceptible to the challenge infection than the untreated lambs.

Scanning electron microscopy of the sarcocysts of six species of Sarcocystis from reindeer (Rangifer tarandus tarandus)

Sarcocysts belonging to six species of Sarcocystis were isolated from the musculature of reindeer and examined by scanning electron microscopy (SEM) to reveal their surface morphology. Sarcocysts of S. grueneri had thin, strip-like surface processes, cysts of S. rangi had long hair-like processes, and cysts of S. tarandivulpes had short, knob-like processes interconnected by microfolds. Cysts of S. hardangeri had prominent, slanting linguiform processes, whereas the cysts of both S. tarandi and S. rangiferi had upright finger-like surface projections. The processes of S. rangiferi were thicker and longer than those of S. tarandi. SEM of the cysts of these species corroborated and supplemented previous descriptions of their surface morphology, which were based on transmission electron microscopy.

Circumstantial evidence of an extracellular (epicellular) localization of developmental stages of Cryptosporidium

Goccidian parasites of the genus Cryptosporidium have been reported in a variety of host species. Within the host, developmental stages of Cryptosporidium occur on the luminal surface of epithelial cells of the gastrointestinal and/or respiratory tract. The developing organisms are covered by an envelope of uniform thickness, consisting of 2 unit membranes and an intervening thin cytoplasmic layer. When observed in thin sections, the enveloped organisms appear to rest on a dense band (layer), on the surface of the host cells.

Efficacy of toltrazuril in the prevention of coccidiosis in naturally infected lambs on pasture

The efficacy of toltrazuril (Bay Vi 9142) in preventing ovine coccidiosis due to an infection acquired immediately after turnout on pasture was evaluated by comparing the faecal consistency, weight gain, and oocyst output of treated and untreated lambs in 3 trials. The lambs were either given a single treatment with toltrazuril at 15 or 20 mg/kg, or they were given a dose of 10 mg/kg on 2 separate days. A single treatment with toltrazuril at 20 mg/kg on day 10 after turnout on pasture almost completely prevented coccidiosis in 2 trials. In a third trial the acute phase of a severe Nematodirus battus infection coincided with the outbreak of coccidiosis, and thus partly masked the clinical effect of the anticoccidial treatment. In lambs treated with toltrazuril at 15 mg/kg on day 10 after turnout, the coccidial infection caused a softening of the faeces, but the lambs were not severely affected by the coccidia. In lambs given a dose of 10 mg/kg of toltrazuril twice, either on days 10 and 11 after turnout, or on days 10 and 20, the coccidial infection caused a softening af the faeces, including some cases of diarrhoea. Oocyst production due to the initial coccidial infection on pasture was markedly reduced by all treatments with toltrazuril. The reduction was most pronounced after a dose of 20 mg/kg. Lambs treated with single doses of 15 or 20 mg/kg of toltrazuril had a better weight gain than the untreated controls in 2 of the trials. Lambs treated with toltrazuril on day 10 after turnout were partially resistant to the coccidial reinfection acquired immediately after treatment, and they had a similar level of immunity as the untreated controls to the subsequent reinfection on pasture.

Ultrastructure of the cysts of Sarcocystis grueneri from cardiac muscle of reindeer (Rangifer tarandus tarandus)

Cysts of Sarcocystis grueneri from cardiac muscle of reindeer (Rangifer tarandus) in Norway were examined by transmission electron microscopy. The limiting unit membrane of the cyst proper formed regularly spaced invaginations into the cyst at numerous sites coinciding with interruptions in the underlying osmiophilic layer. The primary cyst wall formed numerous strip-like, sinuous protrusions, which were 30-40 nm thick, 150-300 nm wide and up to 4.5 microns long, and were running in parallel with the surface of the cyst. Generally the protrusions were arranged in several closely spaced layers compressed against the cyst. The nature and arrangement of the protrusions render them undetectable by light microscopy. Cyst ground substance divided the interior of the cyst into compartments containing typical sarcosporidian metrocytes and cystozoites. The cysts of S. grueneri from reindeer were ultrastructurally similar to cysts reported from red deer, roe deer and moose by other workers. The possibility that these cervids are hosts for a common Sarcocystis species is discussed.

Ultrastructure of the cysts of Sarcocystis tarandivulpes from skeletal muscle of reindeer (Rangifer tarandus tarandus)

The cysts of S. tarandivulpes were found to be limited by a unit membrane which has been called the cyst membrane. The surface of the cysts was covered by closely packed and hexagonally arranged knob-like protrusions. The protrusions were 0.6–1.2 μm long and had an elliptical cross section. At the base of and between the bases of the protrusions the cyst mem brane was raised into low anastomosing folds which delineated shallow compartments. Between the folds the cyst membrane formed small vesicle-like invaginations into the cyst. On the apical part of the protrusions the cyst membrane had a smooth contour and was underlined by 2 layers of electron-dense material. Cyst ground substance divided the interior of the cyst into compartments containing either metrocytes or cystozoites. Cystozoites undergoing endodyogeny were present among the nondividing cystozoites. Some new terms were introduced to denote structures at the border of the cyst. The old terms are reviewed and the structural resemblance between S. tarandivulpes and S. odocoileocanis from Odocoileus virginianus is discussed.

The domestic reindeer (Rangifer tarandus) from northern Norway as intermediate host for three species of Sarcocystis

Sections of skeletal and cardiac muscle of reindeer from northern Norway were examined for sarcocysts by light microscopy. In skeletal muscle 3 different types of cysts were demonstrated; thick-walled macroscopic cysts surrounded by a fibrillar layer (Type 1), thick-walled microscopic cysts (Type 2) and thin-walled microscopic cysts (Type 3). In cardiac muscle only thin-walled cysts of type 3 were found. The 3 different types of cysts are considered to be cysts of 3 different species of Sarcocystis infecting the reindeer.

Dogs and foxes fed muscular tissue from reindeer started shedding Sarcocystis sporocysts measuring 13.9×10.2 µm and 14.4×10.4 µm, respectively, after a prepatent period of 11–17 days. Dogs and foxes are considered to be definitive hosts for Sarcocystis sp. with type 3-cysts. The original descriptions of Sarcocystis grueneri are critically reviewed and found to be inadequate. By comparing the size, cyst wall morphology and location of the cysts in the present investigation with those of the original papers, it is found that Sarcocystis sp. with type 3-cysts in all likelihood is identical with Sarcocystis grueneri. The name Sarcocystis grueneri is retained and assigned to the Sarcocystis sp. with type 3-cysts in cardiac and skeletal muscle of reindeer.

The dog (Canis familiaris), the silver fox (Vulpes vulpes) and the blue fox (Alopex lagopus) are recorded as definitive hosts for Sarcocystis grueneri.

The fox as definitive host for Sarcocystis sp. Gjerde, 1984 from skeletal muscle of reindeer (Rangifer tarandus). With a proposal for Sarcocystis tarandivulpes n. sp. as replacement name

Skeletal muscle of 5 wild reindeer was examined for sarcocysts and used for experimental infection of 6 foxes. Skeletal and cardiac muscle of another reindeer were only examined for sarcocysts. The skeletal muscle of all animals was infected with Sarcocystis sp.. In 2 of the animals cysts of S. hardangeri were also present. The single heart examined contained only cysts of S. grueneri.

Four foxes given skeletal muscle containing apparently only cysts of Sarcocystis sp., started shedding Sarcocystis sporocysts, measuring on average 13.6×9.8 µm, after a prepatent period of 10–12 days. Two foxes given skeletal muscle containing cysts of both Sarcocystis sp. and S. hardangeri shed similar sporocysts, measuring on average 13.5×9.7 µm, after a prepatent period of 10–12 days.

Based on the results from the present and previous investigations, Sarcocystis sp. is considered to have foxes (Vulpes vulpes and Alopex lagopus) and dogs (Ganis familiaris) as definitive hosts, becoming the second species of Sarcocystis with a known reindeer/Canidae life cycle. The name Sarcocystis tarandivulpes n. sp. is proposed as a replacement name for Sarcocystis sp. Gjerde, 1984 from skeletal muscle of reindeer.

Sarcocystis infection in wild reindeer (Rangifer tarandus) from Hardangervidda in southern Norway: with a description of the cysts of Sarcocystis hardangeri n. sp

Fresh preparations of micro-isolated sarcosysts from skeletal muscle of 5 wild reindeer were examined by light microscopy. Slender, spindelshaped cysts measuring 821 × 60 µm, and having short knob-like cyst wall protrusions were found in all animals. In 1 animal cysts different in structure from the cysts of the 4 previously known Sarcocystis spp. of reindeer were found, These cysts are considered to be cysts of a new Sarcocystis sp. of reindeer, for which the name Sarcocystis hardangeri has been proposed.

S. hardangeri n. sp. had macroscopic, ovoid to cylindrical cysts measuring 1667 (900–2570) × 819 (450–1575) µm. The cysts were surrounded by a 8–10 µm thick layer of fibrillar material. After removal of this layer, relatively few and irregularly spaced, slanting protrusions became visible. The 20–30 µm long protrusions were tongue-like, and were lying close to the surface of the cyst.

Cysts of S. grueneri, S. rangiferi and S. tarandi were not demonstrated in the 5 wild reindeer examined.

Sarcocystis hardangeri and Sarcocystis rangi n. sp. from the domestic reindeer (Rangifer tarandus) in northern Norway

Fresh preparations of microisolated sarcocysts from striated muscle of several domestic reindeer from northern Norway were examined by light microscopy. In cardiac muscle, cysts of S. grueneri were found. In skeletal muscle, cysts of S. rangiferi, S. tarandi and S. tarandivulpes were found in all samples examined. In the abdominal muscles of some reindeer, one or two other types of cysts were found.

Cysts of one type were macroscopic in size, and ovoid to cylindrical in shape. The cysts were surrounded by a 8–12 µm thick layer of fibrous material, and measured 1682×910 µm. The cysts had relatively few and irregularly distributed, 20–35 µm long, and 3–5 µm wide, linguiform cyst wall protrusions, which could only be seen after removal of the fibrous layer. These cysts were classified as cysts of S. hardangeri, a species previously described from wild reindeer in southern Norway.

Cysts of the other type were long and slender, measuring 5460–12700 (8994 ± 2575) × 95–280 (180 ± 50) µm. The cysts had numerous very fine, flexible, hair-like cyst wall protrusions, which were 8–10 [xm long and less than 0.5 µm thick. These cysts are considered to belong to a new Sarcocystis species of reindeer, for which the name Sarcocystis rangi n, sp. is proposed. The reindeer is recorded as the intermediate host for 6 different species of Sarcocystis.

The raccoon dog (Nyctereutes procyonoides) as definitive host for Sarcocystis spp. of reindeer (Rangifer tarandus)

A raccoon dog (Nyctereutes procyonoides; Family: Canidae), was given cardiac muscle of reindeer infected with S. grueneri, and started shedding Sarcocystis sporocysts 10 days post feeding. The sporocysts measured 13.9 (12.4–15.7) × 10.1 (9.2–11.2) µm, and were excreted for at least 16 days. The raccoon dog is thus an additional definitive host for S. grueneri (Yakimoff & Sokoloff, 1934) Gjerde, 1984.

Another raccoon dog was given skeletal muscle infected with 4 species of Sarcocystis, none of which was S. grueneri. The raccoon dog started shedding Sarcocystis sporocysts on day 10 post feeding, and excreted sporocysts for at least 16 days. The sporocysts measured 14.0 (12.3–15.6) × 10.1 (9.2–11.2) µm, and are considered to be sporocysts of S. tarandivulpes Gjerde, 1984.

This is the first record of the raccoon dog as an experimental definitive host for Sarcocystis.

A light microscopic comparison of the cysts of four species of Sarcocystis infecting the domestic reindeer (Rangifer tarandus) in northern Norway

Fresh preparations of micro-isolated sarcocysts from skeletal and cardiac muscle of 12 reindeer were examined by light microscopy. On the basis of cyst structure and cyst wall structure 4 Sarcocystis spp. could be differentiated. New names have been proposed for 2 previously unnamed Sarcocystis spp. of reindeer, and S. grueneri has been redefined.

S. rangiferi n. sp. had macroscopic cysts in skeletal muscle measuring 2106×403 µm. The cyst wall protrusions were finger-like and measured 13.2×6.7 µm. The cysts were surrounded by a layer of fibrillar material.

S. tarandi n. sp. had micro- to macroscopic cysts primarily in skeletal muscle, but a few cysts were found in the heart of one animal. In skeletal muscle the cysts measured 999×75µm; in the heart the cysts were shorter and wider. The cyst wall protrusions were fingerlike and measured 9.2×2.2 µm.

S. grueneri had micro- to macroscopic cysts in cardiac muscle measuring 581×137 µm. The cyst wall was thin and relatively smooth with no visible protrusions.

Sarcocystis sp. had micro- to macroscopic, slender cysts in skeletal muscle measuring 916×64 µm. The cyst wall had tightly packed, short, knob-like protrusions. The cysts of this species were previously classified as cysts of S. grueneri.

Release of growth promotors from mononuclear human blood cells by LPS, lectins and lithium, as tested in the mouse CFU-C assay

Medium (MCM, 20% human serum), conditioned for 24 h by mononuclear human blood cells, had no colony-forming ability when tested in the mouse CFU-C assay. However, when combined with L-CSF, which predominantly generates macrophage colonies, MCM increased the colony number and size. Even more significant was the increased cellularity with a striking shift towards granulocyte production. Some human sera induced GIF formation without additives, but mostly LPS was required. After heat inactivation, all sera became dependent on LPS to yield an active MCM. Lithium, PHA, Con A and PMW also stimulated GIF formation, which itself depended upon protein synthesis. Heat inactivation of LPS and serum did not reduce their ability, in combination, to yield an active MCM. However, when serum and LPS were mixed before heat treatment, the ability to induce GIF production was abolished, but could be restored by adding intact LPS. This may indicate that LPS exerts its effect by combining with a serum factor yielding a heat-sensitive complex. However, even in the absence of serum, LPS had a stimulatory effect when used in large concentrations, but still the MCM was less active than MCM with serum.