Agar gel immunodiffusion test for the detection of bovine leukemia virus antibodies: lack of trans-Atlantic standardization.

Two agar gel immunodiffusion (AGID) kits for the serodiagnosis of bovine leukemia virus (BLV) were imported from Europe and were compared with North American kits. The BLV AGID kits from North America and from Europe differed significantly. The punches were different, as were the pattern distribution in the agar of the reference and the test sera, resulting in differences in the reading of the immunoprecipitation lines. Based on the testing of 1200 serum samples from cattle, the European kits gave a good correlation with the American kits, as indicated by their respective kappa values. However, the European kits were found to be less sensitive when evaluated against weakly positive samples from field specimens or following a dilution trial. Only 65% and 50% of the weakly positive samples detected by the American kit #1 were detected by the European kits #2 and #3, respectively. The American kit was also capable of detecting BLV antibodies in 45% of strongly positive samples diluted 1/50 in negative sera, while antibodies were detected in only 15% of the samples with the European kit #2 and in none of the samples with the European kit #3. False negatives were also detected with the European kits. Among the false negatives, the degree of expected reactions was weak (European kit #2) or of varying degrees of positivity (European kit #3). Besides the differences in format and performance, the BLV-AGID kits in Europe are evaluated with the National Standard Serum E4 while a proficiency panel composed of a quadruplicate set of 10 reference sera is used in Canada to monitor the kits. Based on the overall observations, we noted a lack of standardization between the BLV-AGID kits used in North America and in Europe.     

Inter- and intra-provenances variations in seed size and seedling characteristics of Khaya senegalensis A. Juss in Burkina Faso

Within- and between-provenance variations in seed and seedling traits of Khaya senegalensis A. Juss were studied at INERA in Burkina Faso. Nursery grown seedlings from four provenances in Burkina Faso were used for the study. The studies revealed significant variability in all traits evaluated. Seed length and weight significantly varied among provenances and families within provenances, where Bopiel and Koyenga had the highest mean values. Height and root collar diameter of 1 year old seedlings significantly varied among families within provenances. Except leaf biomass ratio and carbon isotope ratio which varied significantly among provenances but not among families within provenances, all other seedling biomass traits—total plant biomass, stem biomass ratio, leaf biomass ratio, root biomass ratio, root shoot ratio, specific leaf area, and leaf area ratio were significantly affected by provenances and families within provenances. The magnitude of variation due to family effect ranged from 65 to 93 % for seed size traits, and from 4.5 to 17.8 % for seedling characters. Estimates of family heritability were moderate to high (0.67–0.95) for seed traits, but low to moderate (0.19–0.59) for seedling characters, indicating that much of the total variation in seed traits is due to the genetic effect. The two most prominent provenances, Koyenga and Bopiel, with higher seed size and greater seedling growth could be considered for an eventual K. senegalensis improvement program in Burkina Faso.     

Copper,iron, zinc and tannin concentrations throughout the digestive tract of tropical goats and sheep fed a high-fibre tannin-rich diet

The dry season in tropical regions urges livestock to feed on nutritionally very poor diets. It has not been explored how tropical sheep—assumed grazers—and tropical goats—intermediate browsers—cope with a high-fibre tannin-rich diet. This study was designed to determine the effects of a high-fibre and tannin-rich diet on the flow of important microminerals iron (Fe), zinc (Zn) and copper (Cu) throughout the digestive tract of tropical sheep and goats. The feeding trial was set up with twelve adult male animals, six sheep with mean body weight (BW) of 30.3 ± 1.6 kg and six goats with mean BW of 26.4 ± 2.2 kg. The feed consisted of 36% leaves of Millettia ferruginea, 61% hay and 3% concentrate and was offered at 3% of BW (all on dry matter (DM) basis). The total faecal collection was carried out for 7 consecutive days. At the end of the experimental period, the animals were slaughtered to collect liver and digesta samples from the gastrointestinal tract. Feed, digesta and faecal samples underwent analysis of Fe, Zn, and Cu and total tannins (TT). Goats had significantly higher reticulum Cu concentrations expressed on DM as compared to sheep. Faecal Cu concentrations were higher for goats compared to sheep. Reticulum and colon digesta Zn levels were higher in goats than sheep. Abomasum and colon Fe levels were higher in sheep than goats when expressed on DM. These results suggest differences in feed intake, micromineral absorption, secretion and excretion between sheep and goats, pointing to a divergent mineral metabolism as an adaptation to the challenge of a dry season diet having very low nutritive value.     

Immunity-related genes and gene families in Anopheles gambiae

We have identified 242 Anopheles gambiae genes from 18 gene families implicated in innate immunity and have detected marked diversification relative to Drosophila melanogaster. Immune-related gene families involved in recognition, signal modulation, and effector systems show a marked deficit of orthologs and excessive gene expansions, possibly reflecting selection pressures from different pathogens encountered in these insects' very different life-styles. In contrast, the multifunctional Toll signal transduction pathway is substantially conserved, presumably because of counterselection for developmental stability. Representative expression profiles confirm that sequence diversification is accompanied by specific responses to different immune challenges. Alternative RNA splicing may also contribute to expansion of the immune repertoire.     

Arctic seabirds transport marine-derived contaminants

Long-range atmospheric transport of pollutants is generally assumed to be the main vector for arctic contamination, because local pollution sources are rare. We show that arctic seabirds, which occupy high trophic levels in marine food webs, are the dominant vectors for the transport of marine-derived contaminants to coastal ponds. The sediments of ponds most affected by seabirds had 60 times higher DDT, 25 times higher mercury, and 10 times higher hexachlorobenzene concentrations than nearby control sites. Bird guano greatly stimulates biological productivity in these extreme environments but also serves as a major source of industrial and agricultural pollutants in these remote ecosystems.     

Using isotopic tracers in lake sediments to assess atmospheric transport of lead in Eastern Canada

The isotopic composition of lead pollution in the environment provides information as to the source of emission. The ²⁰⁶Pb/²⁰⁷Pb ratio for Canadian industrial emissions (1.153±0.005) is significantly less than U.S. industrial emissions (1.213±0.008) making it possible to determine the relative contributions of emissions from both countries within Eastern North America by means of a simple isotopic mixing model. Profundal sediments in lakes chronicle contaminant inputs and are therefore useful monitors of environmental pollution. Surface sediment from 32 sediment cores across Quebec and Ontario, Canada were analyzed for ²⁰⁶Pb^/207Pb to ascertain the relative proportions of Pb emission from Canada and the U.S.A. Data show that U.S. contributions to the total lead burden in surficial sediments across much of southern Quebec and Ontario are often in excess of 50%. Local sources were particularly important in the Eastern Township region of Quebec which lies 200 km south east of the city of Montreal. The results are discussed in relation to the major sources of industrial lead emissions in North America.     

The effect of anti-neoplastic drugs on murine acquired immunodeficiency syndrome

The murine acquired immunodeficiency syndrome (MAIDS) is associated with proliferation of target cells that have been infected by a defective retrovirus. To control the growth of this primary neoplasia, virus-inoculated mice were treated with anti-neoplastic drugs. Paradoxically, cyclophosphamide, which is also immunosuppressive, was very effective in preventing the appearance and progression of the disease, in restoring a normal T cell function, and in depleting the number of infected target cells. This result suggests that the proliferating infected target cells were responsible for the immunodeficiency.     

Effect of Deinking Paper Sludge Compost On Nutrient Uptake and Yields of Snap Bean And Potatoes Grown in Rotation

The paper industry in Canada faces a challenge of economically sound and environmentally safe disposal of massive amounts of residues. A field study was conducted in 1996 and 1997 to evaluate the effects of application of a compost derived from a mixture of deinking paper residues and poultry manure (DSPC) on P and K uptake, and yields of snap bean (Phaseolus vulgaris L. cv. Centralia), and potato (Solanum tuberosum L. cv. Gold Rush). The experiment was conducted on a Tilly silt loam (Gleyed Humo-Ferric Podzol) located in Sainte-Croix de Lotbinière, Québec, Canada. The DSPC was applied in the spring 1996 at 0, 14, 28 and 42 Mg ha^?1 on a dry matter basis, and supplemented or not with mineral fertilizer (MF) at 0, 60, 120 and 180 kg P₂O₅-K₂O ha^?1. In 1997, P fertilizer was applied in subplots at 0, 100, 200 and 300 kg P₂O₅ ha^?1. Snap bean yield increased significantly with DSPC and MF application. Apparent P and K recoveries from MF by snap bean decreased with DSPC or MF rate. In combination with DSPC, P and K recoveries from MF by snap bean were smaller at all rates than those with no DSPC. Based on nutrient uptake, P and K in DSPC were more available than in MF. Potato yield in the following year was not significantly influenced by the previous treatments nor by supplemental P fertilizer added in the second year. This experiment indicates that compost derived from a mixture of deinking papermill sludges and poultry manure is a potential source of P and K for crops and will increase crop yields in the application year.     

Enzyme-linked immunosorbent assay for the diagnosis of bovine leukosis: comparison with the agar gel immunodiffusion test approved by the Canadian Food Inspection Agency.

Four commercially available bovine leukemia virus (BLV)-ELISA kits from Europe or the United States were compared to the agar gel immunodiffusion (AGID) test officially approved by the Canadian Food Inspection Agency (CFIA). A total of 1200 cattle serum samples were used. Three ELISA kits based on the envelope glycoprotein (gp51) gave an excellent correlation with the AGID test. The kappa values were 0.998, 0.984, and 0.986 for the ELISA kits #1, #2, and #3, respectively. The ELISA kit based on the p24 core protein was found to be less sensitive than the officially approved AGID test and detected 5.13% of false negatives. Forty BLV AGID strongly positive serum samples were diluted. Based on the dilution experiment, the gp51 ELISA kits were found to be more sensitive than the AGID test kits. They were capable of detecting antibodies in samples diluted up to 1/5000 (kit #1), 1/20 800 (kit #2) and 1/4000 (kit #3), whereas the AGID kit was only capable of detecting antibodies in samples diluted up to 1/100. Based on these observations, the gp51 BLV-ELISA was recognized as an official test method for the serodiagnosis of bovine leukosis in Canada.     

Prevalence of and carcass condemnation from maedi-visna,paratuberculosis and caseous lymphadenitis in culled sheep from Quebec,Canada

We determined the prevalence of lung and mammary gland lesions associated with maedi-visna (MV) infection, the prevalence of paratuberculosis (PTB), and the prevalence and lesions distribution of caseous lymphadenitis (CL) in culled sheep. Total of 451 ewes and 34 rams were selected randomly from two slaughterhouses in Quebec, Canada. MV serostatus was determined by recombinant ELISA test. PTB diagnosis was based on characteristic histological lesions in the terminal ileum, ileocecal lymph node and/or ileocecal valve and CL by gross detection of abscesses and isolation of Corynebacterium pseudotuberculosis. Seroprevalence of MV was 44% (95% CI: 40, 48). Seropositivity increased with age and was higher in ewes than in rams. The percentages of lung and mammary gland lesions in seropositive sheep were 14 and 40%, respectively, but mammary gland lesions lack specificity. The prevalence of PTB was 3% (95% CI: 2, 5). PTB increased with age and was lower among sheep with abscesses. The prevalence of CL was >/=21% (95% CI: 17, 24). The most-prevalent site of caseous lymphadenitis lesions was the thoracic cavity. The risk of carcass condemnation was significantly associated with region, body score and abscesses. Only the presence of abscesses was associated with an increase in trimming of carcasses.