Journal of veterinary medicine. B, Infectious diseases and veterinary public health最新文献

In order to assess the efficacy of a two-step vaccination protocol with respect to foetal protection against transplacental infections with bovine virus diarrhoea virus (BVDV) with special attention to BVDV-2 seronegative heifers were vaccinated with an inactivated BVDV-1 vaccine and boostered with a modified live BVDV-1 vaccine after 4 weeks. A second group was left unvaccinated as control. Between days 30 and 120 of pregnancy the heifers of both groups were intranasally challenged with a mixture of BVDV-1 and -2. All heifers of the vaccinated group gave birth to nine clinically healthy, seronegative (precolostral) and BVDV-free calves. In contrast in the control group four BVDV viraemic underdeveloped calves were born. Additionally, one calf was stillborn and another viraemic calf was not viable and died 2 days after birth. All six calves of the control group were viraemic with BVDV-2. This study demonstrated for the first time that two-step vaccination of breeding cattle with a modified live BVDV vaccine 4 weeks after application of an inactivated BVDV vaccine was capable of providing a foetal protection against transplacental infection with BVDV-2.

Patterns of Mycoplasma hyopneumoniae (Mh) infections were investigated in five clinically infected herds and in five herds subclinically infected with Mh. In the clinically infected herds, housing and management conditions were good whereas these conditions were poor in the subclinically infected herds. In each herd, serum antibodies against Mh were detected in pigs of different ages and nasal swabs were taken for Mh detection using nested PCR (nPCR). The percentage of seropositive pigs in the clinically infected herds increased from 8% in pigs of 9 weeks to 52% in pigs of 18 weeks and seroconversion was most shown between 12 and 15 weeks. In the subclinically infected herds, the percentages increased from 2 to 24% and most of the pigs became seropositive between 15 and 18 weeks. The percentage of nPCR positive pigs at 6 weeks was 16 and 0% in the clinically and subclinically infected herds, respectively. The results demonstrate that the seroprevalences were higher in the clinically infected herds and that most of the pigs became infected with Mh at a younger age. It can be concluded that additional factors different from housing and management, like differences among Mh strains, may determine the infection pattern of Mh and the clinical course of the infection.

The aim of this trial was to evaluate the effect of in-feed doxycycline (DOXY) on the control of ileitis in weaned piglets. On a farm with a previous history of ileitis outbreaks, 288 piglets at the age of weaning (25 +/- 2 days old) were divided into four experimental groups, each group comprising three pens with 24 piglets in each pen. Non-medicated animals served as negative control (NC) group, whereas groups DOXY-50, DOXY-125 and DOXY-250 received doxycycline via feed at 50, 125 and 250 ppm, respectively. Therapy lasted for 14 days followed by an observation period of 28 days. In conclusion, administration of doxycycline at a dose rate of 125 or 250 ppm had beneficial effect compared with the NC group. in terms of the reduction of diarrhoea prevalence, the enhancement of growth performance and the reduction of prevalence of Lawsonia intracellularis in the intestine, as shown either by the PCR method or by specific histopathological examinations. Treatment with 250 ppm of doxycycline for a fortnight interval post-weaning seems to be beneficial leading to better growth rates of piglets not only during treatment period, but also throughout the whole nursery phase.

A polymerase chain reaction (PCR) assay was developed to differentiate meat of Ceylon spotted deer (Axis axis ceylonensis), Ceylon hog deer (A. porcius oryzus), Ceylon sambhur (Cervus unicolor unicolor) and barking deer (Muntiacus muntijak malabaricus) from meat of cattle, goat, buffalo, pig, dog and sheep. A set of primers was designed according to the sequence of the mitochondrial cytochrome b gene of C. elaphus canadensis and by PCR amplification about 450 bp band was observed for all four animal species and these primers were not cross reacted with DNA of other animal species tested in the study under the tested reaction conditions. A band of 649 bp size was observed for all animal species when DNA was amplified with the universal primers and that indicated the presence of mitochondrial DNA in the samples. Further, the results indicated that this technique was sensitive enough to differentiate rotten meat, at least 5 days after the killing of an animal. Under these PCR conditions, the DNA of bacteria, which is involved in decomposition of meat, was not amplified with both universal and specific primers. However, the method was not sensitive enough in differentiating cooked meat of these species. Slaughtering of these four wild animal species is banned, but the animals are being killed illegally. Lack of meat identification methods has been identified as one of the major constraints to implement legal procedures and conserve biodiversity in the country.

The role of Staphylococcus aureus and coagulase-negative staphylococcal exosecretions was tested for its ability to elicit in vitro proliferation of bovine blood lymphocytes, which we determined by means of the 3H-thymidine proliferation assay and by flow cytometry. Exosecretions of 32 field strains of S. aureus isolated from bovine udder infection and one of each of S. intermedius (M2), S. hyicus (M5), S. xylosus (M6) and S. chromogenes (M10) were used. Of the 32 S. aureus bacterial exosecretions, only 14 stimulated bovine mononuclear cells to proliferate. A high degree of association was found when the proliferation indexes were compared with the virulence as determined by intracisternal inoculation. All the six S. aureus strains that were categorized as highly virulent and that were tested in the proliferation assay exhibited a proliferation index > 20, whereas the five S. aureus strains that were categorized as low did not stimulate at all. Cells treated with media or Columbia broth supplemented with 0.1% D-glucose, yeast extract, and 0.5% NaCl (CBs) did not exceed 15% of the T-cells double positive with CD25+, whereas incubation with Con A activated the T-cells to display CD25+ up to 90%. Cells treated with one of the exosecretions that stimulated bovine mononuclear cells to proliferate, stimulated CD3+ and CD4+ T-cells to exhibit CD25+ receptor significantly higher (P < 0.05) than that found in media and CBs treatments, but lower than those found in Con A treatments. The exosecretions that did not stimulate mononuclear cells to proliferate also did not activate T-cells to exhibit CD25+ receptor. Con A activated 74% out of the total CD8+ to exhibit ACT2 receptor and 50% out of the total CD4+ to exhibit ACT3 receptor. A few but not all of the exosecretions that activated the CD25 receptor on T-cells also activated the ACT3 receptor on CD4+ cells.

To evaluate the efficacy of an ivermectin controlled-release capsule (CRC), which delivers 1.6 mg ivermectin per day intraruminally for 100 days to sheep weighing 40-80 kg (IVOMEC Maximizer CR Capsule for adult sheep, Merial), against small lungworms two studies with 48 naturally infected adult female Merino Landrace sheep were conducted. The sheep were allocated by restricted randomization based on bodyweight to untreated controls or received an ivermectin CRC. Eight sheep per group were necropsied 35, 70 or 105 days post-treatment. Lungworms were recovered by dissection or peptic digestion of the lungs. Baermann/Wetzel technique was used for faecal lungworm larval counts at weekly intervals. The efficacy of treatment was 100% against Dictyocaulus filaria and Protostrongylus rufescens (P < 0.05) at each necropsy day. The efficacy against Protostrongylus brevispiculum, Cystocaulus ocreatus and Neostrongylus linearis increased from 35 to 105 days after administration of the CRC and was found to be 100% (P < 0.01), 96.6% (P < 0.01) or 99% (P < 0.01), respectively, at 105 days post-treatment. The reductions of Muellerius capillaris counts varied and were 96.2% (P < 0.05) at 70 days post-treatment and 44.6% (P > 0.1) at 105 days post-treatment. Faecal lungworm larvae disappeared nearly completely from at least 3 weeks after the ivermectin CRC administration for all protostrongylid species including M. capillaris so that pasture infectivity will be subsequently significantly reduced.

Analysis of the partial bovine leukaemia virus (BLV) env gp51 gene sequences obtained from three BLV strains isolated in three different regions of Brazil was carried out. The Brazilian BLV env gp51 sequences were compared with seven other corresponding sequences of BLV strains isolated in different countries and with consensus sequence as well. The obtained data point on qualitative and quantitative differences among the analysed strains as far as the occurrence of single point mutations is concerned. Two Brazilian strains show significantly higher mutation rate than other analysed strains. Amino acid analysis did not show, however, any substantial changes of the primary protein structure coded by well conserved region of BLV env gp51 gene. Based on the obtained data, the putative dendogram image of possible phylogenetic relations among the studied BLV strains is presented as well.

Chicken anaemia virus (CAV) was detected in the bursa of Fabricius of a 4-week-old chicken obtained from an outbreak of acute infectious bursal disease in Bangladesh. Repeated attempts to grow this virus in MDCC-MSB1 cells were not successful. A full-length PCR amplicon of the genome of this strain, designated as BD-3 CAV, was cloned and sequenced. The complete nucleotide sequence and the deduced amino acid sequence were compared with those of 12 other CAV strains. The genetic analysis of the amino acid sequences of VP1 indicated the possible existence of genetic groups among CAV strains, as BD-3 CAV along with four other strains (CIA-1, L-028, Isolate 704 and TR-20) formed a distinct lineage. These strains have four signatory amino acids in VP1, such as 75I/T, 97L, 139Q and 144Q, out of which the latter two are located in a small hydrophilic peak.

Chemiluminescent immunoassay (CLIA) was applied in the screening of swine meat juice samples obtained from different laboratories in Germany, using the indirect enzyme linked immunosorbent assay (ELISA) as test for comparison. Out of the 1350 samples tested, 987 were found acceptable for validation of results. A good level of agreement between the two tests was obtained with a kappa value of 0.824 at 20% cut-off and 0.798 at 40% cut-off. At 20% and 40% cut-off levels, a sensitivity of 96.2% and 97.3%, respectively, and a specificity of 94.6% and 95.1%, respectively, were demonstrated between CLIA and ELISA. The detecting lipopolysaccharide (LPS) antigen was tested for specificity and a cross-reaction with two Escherichia coli and Yersinia strains was found when tested with ELISA. This reaction was not observed in CLIA, possibly because of the broader measurement spectrum of this test, which allows a more distinctive definition of immunologic reactions. The same explanation can be given for the increased number of meat juice samples which were positively detected only in ELISA but not in CLIA. Because of the wide detection range in CLIA, a normalization scheme was necessary to obtain reproducible results in this test system. The samples positively classified in screening were further tested for reciprocal titres in both test systems, and a higher correlation between screening and titration results was obtained for CLIA. Based on the results of this study, CLIA can be used as a reference method in detecting Salmonella antibodies in the meat juice of slaughter pigs.

The in vitro susceptibilities of 128 isolates of east1 + Escherichia coli from pre-weaned and post-weaned pigs with diarrhoea were tested with nine commonly used anti-microbial agents by an agar dilution minimal inhibitory concentration (MIC) procedure according to National Committee for Clinical Laboratory Standards guidelines. For the isolates from preweaned and post-weaned pigs, most of them were susceptible to low concentrations (MIC90) of tetracycline (4 and 2 microg/ml), ceftiofur (2 and 2 microg/ml), and colistin (4 and 2 microg/ml). Marked resistance was found in others.