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Pododermatitis is a disease of concern for mink breeders in Canada and worldwide, as it causes discomfort and lowers the breeding rates on farms affected by the disease. Unfortunately, the etiology and pathogenesis of pododermatitis are still unknown. In this study, we compared Staphylococcus spp. and Streptococcus canis isolates from healthy mink with isolates from animals with pododermatitis on 2 farms in Ontario. Almost all hemolytic Staphylococcus spp. isolated were shown to be Staphylococcus delphini Group A by 16S ribosomal ribonucleic acid (rRNA) sequence analysis and polymerase chain reaction (PCR). Pulsed-field gel electrophoresis (PFGE) did not reveal any S. delphini or S. canis clonal lineages specifically associated with pododermatitis, which suggests that these bacteria do not act as primary pathogens, but does not dismiss their potential roles as opportunistic pathogens. While S. delphini and S. canis were the most prevalent bacterial pathogens in mink pododermatitis, they were also present in samples from healthy mink. Arcanobacterium phocae is occasionally isolated from pododermatitis cases, but is difficult to recover with conventional culture methods due to its slow growth. A quantitative real-time PCR was developed for the detection of A. phocae and was tested on 138 samples of footpad tissues from 14 farms. The bacterium was detected only in pododermatitis-endemic farms in Canada and was at higher concentrations in tissues from infected footpads than in healthy tissues. This finding suggests that A. phocae is involved in the pathogenesis of pododermatitis.

La pododermatite est une maladie qui préoccupe les éleveurs de visons au Canada et ailleurs dans le monde, étant donné qu'elle cause un inconfort et diminue les taux de reproduction dans les fermes où la maladie est retrouvée. Malheureusement, l'étiologie et la pathogénie de la pododermatite sont encore inconnues. Dans la présente étude nous avons comparé des isolats de Staphylococcus spp. et Streptococcus canis provenant de visons en santé à ceux provenant d'animaux avec pododermatite de deux fermes en Ontario. Presque tous les isolats hémolytiques de Staphylococcus spp. ont été identifiés comme étant des S. delphini Groupe A par analyse des séquences de l'ARN ribosomal (ARNr) 16S et par réaction d'amplification en chaîne par la polymérase (PCR). L'analyse par électrophorèse en gel à champs pulsés (PFGE) n'a pas permis de mettre en évidence pour S. delphini ou S. canis de lignées clonales associées spécifiquement à la pododermatite, ce qui suggère que ces bactéries n'agissent pas en tant qu'agents pathogènes primaires, mais ne diminue pas pour autant leur rôle potentiel comme agents pathogènes opportunistes. Malgré le fait que S. delphini et S. canis étaient les bactéries pathogènes les plus prévalentes dans les cas de pododermatite chez le vison, elles étaient également présentes dans des échantillons provenant de visons en santé. Arcanobacterium phocae est isolé occasionnellement de cas de pododermatite, mais il est difficile de l'isoler en utilisant des méthodes conventionnelles de culture étant donné sa croissance lente. Une épreuve PCR quantitative en temps réel fut développée pour la détection d'A. phocae et fut testée sur 138 échantillon de tissus des coussinets plantaires provenant de 14 fermes. La bactérie fut détectée seulement de fermes canadienne où la pododermatite était endémique et se retrouvait en plus grande concentrations dans les tissus de coussinets plantaires infectés comparativement à des tissus sains. Ces résultats suggèrent qu'A. phocae est impliqué dans la pathogénie de la pododermatite.(Traduit par Docteur Serge Messier).

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A previously described multiplex PCR was evaluated for the identification and prevalence of Eimeria species in market-age commercial chicken flocks in Ontario. The multiplex PCR based on species-specific RAPD-SCAR markers was able to distinguish six available laboratory strains of Eimeria species (E. tenella, E. maxima, E. necatrix, E. mitis, E. acervulina, and E. brunetti) and E. tenella, E. maxima and E. acervulina in unknown field samples, including multiple infections in single reactions. No backyard (0/77) and 20/360 market-age commercial chickens were oocyst-positive using standard fecal flotation methods. PCR identified E. tenella alone (9/360, 2.5%), E. maxima alone (5/360, 1.38%), E. maxima plus E. tenella (5/360, 1.38%) and E. acervulina alone (1/360, 0.27%) in market-age commercial broilers. This is probably the first time the multiplex PCR has been evaluated in poultry establishments in Canada and illustrates the value of the tool in coccidiosis epidemiology on commercial farms.

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Marek's disease virus (MDV), which is the causative agent of Marek's disease (MD), is shed by infected chickens and transmitted to other chickens through the respiratory route. Experimental reproduction of MD has been commonly done either by intra-abdominal inoculation of cell-associated MDV or by exposure to MDV-infected 'seeder' chickens. The former method does not mimic the natural route of MDV infection, whereas the latter method suffers from lack of uniformity in the timing and amount of virus transmission from seeder chickens to susceptible birds. The aim of the present study was to establish an infection model of MDV that mimics the natural route of infection. Here we report that when chickens were exposed for 20 min to aerosols (particle size 1.91 microm) of cell-free MDV suspensions containing 1280 plaque-forming units/ml, which were generated using a nebulizer, pathological and clinical signs of MD were observed in 95%-100% of the aerosol-exposed chickens by 21 days post-infection (dpi). Chickens that were exposed to aerosols and sampled at 1, 2, 3, 10, and 21 dpi showed MDV replication as early as 1 dpi in lungs as well as in other tissues such as spleen and bursa of Fabricius. This infection model will facilitate the studies directed to elucidate MDV-host interaction at the site of virus entry.

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Infectious bronchitis (IB) is an economically important viral disease with worldwide distribution. Every country with an intensive poultry industry has infectious bronchitis virus (IBV). The virus rapidly spreads from bird to bird through horizontal transmission by aerosol or ingestion. Sentinel bird studies were carried out in southern Ontario and IBV has been isolated from layer flocks. Genetic analysis of the S1 region of the strains showed that they were not vaccine related. The pathogenicity of selected Ontario variants of IBV isolates was studied and the subsequent work was to determine the degree of protection against field isolates provided by a commonly used vaccine MILDVAC-Ma5 in Ontario. The protection was evaluated by challenging immunized chickens with the respiratory (IBV-ON1) and nephropathogenic (IBV-ON4) viruses. The mean vaccine efficacy for IBV-ON1 was 66.7% indicating that a Massachusetts serotype vaccine would provide some protection against IBV field isolates.

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Infectious bronchitis (IB) is one of the important viral diseases of chickens, and in spite of regular vaccination, IB is a continuous problem in Canadian poultry operations. In an earlier study using sentinel chickens we determined the incidence of infectious bronchitis virus (IBV) in Ontario commercial layer flocks. The objective of this study was to determine the pathogenicity of 5 nonvaccine-related IBV isolates recovered from the sentinel birds. The clinical signs, gross, and histological lesions in specific pathogen-free chickens indicated that all 5 isolates caused mild lesions in the respiratory tract. An important finding of this study was the significantly lower average daily weight gain among virus-inoculated groups of chickens during the acute phase of infection. Based on sequences of part of the S1 gene IBV-ON2, IBV-ON3, and IBV-ON5 formed a cluster and they were closely related to strain CU-82792. IBV-ON4 had 98.7% identity with the strain PA/1220/9, a nephropathogenic variant.

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Induction of immune response as characterised by expression of cytokine genes in the spleen following immunization of pre- and post-hatch chickens with herpesvirus of turkeys (HVT) vaccine was studied. The pattern of expression of IFN-gamma and IL-10 genes in pre-hatch immunized chickens was different from that observed in post-hatch HVT immunized chickens. This expression pattern of cytokine genes was associated with significantly higher HVT transcripts in pre-hatch immunized chickens than in post-hatch immunized chickens. In conclusion, HVT immunization in chickens, irrespective of the age of immunization, stimulates host response characterised by the expression of cytokine genes, such as IFN-gamma and IL-10 in the spleen. However, the age of immunization appears to influence the temporal pattern of IFN-gamma and IL-10 expression as well as replication of HVT.

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