Cross protection studies on Bordetella bronchiseptica in mice using an intracerebral challenge model.

Protective activities of heat-inactivated (60 degrees C for 30 min) merthiolate preserved Bordetella bronchiseptica and B. pertussis bacterins were compared in intraperitoneally immunized mice challenged intracerebrally (i.p./i.c.) or intraperitoneally (i.p./i.p.). In the i.p./i.c. assay (Kendrick test), a B. pertussis bacterin protected mice against challenge with B. pertussis 18-323, as well as against phase I cytotoxic and non-cytotoxic strains of B. bronchiseptica. A B. bronchiseptica bacterin, prepared from a phase I cytotoxic strain, gave protection against two phase I B. bronchiseptica strains, irrespective of their cytotoxin-production. A non-cytotoxic phase I strain of B. bronchiseptica elicited protection against the homologous strain only. Neither cytotoxic nor non-cytotoxic B. bronchiseptica strains protected mice challenged with B. pertussis 18-323. Vaccines prepared from phase III strains of B. bronchiseptica were not protective at all against any of the challenge strains. No such differences in the protective activities of the bacterins could be detected by the i.p./i.p. method. They seem to cross-protect equally well. The results indicate that the Kendrick test may be useful in testing potency of different B. bronchiseptica bacterins.     

Plasma lipopolysaccharide elevations in cattle associated with early-stage infection by Fasciola hepatica

Fasciolosis is an endemic zoonotic parasitic disease with significant impacts on human health and both animal health and production. Early post-infection impacts on the host remain unclear. The objective of this study was to determine the changes, if any, to levels of endotoxin in cattle plasma in response to early-stage infection with Fasciola hepatica. Thirty-six (36) commercial bred cattle were experimentally infected with approximately 400 viable metacercariae. Plasma lipopolysaccharide (endotoxin) levels were examined on 24 occasions from 0 h before infection to 336 h after infection using the Limulus Amoebocyte Lysate chromogenic end point assay and compared with that of six (6) uninfected control animals. Peak lipopolysaccharide levels in infected animals were reached at 52 h after infection and returned to pre-infection levels at time 144 h after infection. Infected animals had significantly elevated lipopolysaccharide levels between 24 and 120 h after infection when compared to uninfected animals. The mean change in endotoxin units (EU)/mL over time after infection was statistically significant in infected animals. Elevations of lipopolysaccharide occurred in all infected animals suggesting a possible repeatable and titratable endotoxemia conducive to therapeutic agent model development.     

Kinetics of the reaction of the first metabolite of fenitropan with some low molecular weight thiols

2-Nitro-I-phenylpropen-3-yl acetate (NPPA), the first metabolite of the fungicide fenitropan, reacted readily with glutathione in aqueous ethanol solutions at room temperature, producing at least two products. The first reaction step, which is believed to be a bimolecular nucleophilic (Michael) addition, had a strongly pH-dependent reaction rate. Second-order rate constants were calculated for the reactions of NPPA at pH 4 with glutathione and with some other low molecular weight thiols. Nucleophilic reactivity of the reacting thiolate anions is linearly related to the pK_a values of the thiols. However, as the concentration of thiolate anion is also determined by the thiol pK_a, there is no simple relationship between second-order rate constants and thiol pK_a. Thus the blocking rate of the various essential sulphydryl groups in fungi by NPPA is determined by the sulphydryl pK_a values and the ambient pH value.     

Monensin toxicity in preruminant dairy heifers

Four-to six-week-old calves from a seasonal dairy herd in North Western Tasmania were presented for veterinary attention due to the occurrence of sudden deaths. Necropsy examination of one of the calves revealed several small pale foci of 1 cm diameter on the epicardium. Mortalities were found to be caused by monensin that was added to the milk diet as part of a vitamin/mineral commercial premix that also controlled coccidiosis. No cases of monensin toxicity in preruminant calves have been previously documented, although there have been numerous reports in older cattle and other species.     

Complications after implantation of a modular total hip prostheses compared with fixed head prostheses

164 total hip prostheses of different manufacturers were implanted over an 8-year period. Clinical records were evaluated with a complication rate of 29.0% (42 of 145 joints) or 31.7% (39 of 123 dogs). The complications encountered in dogs that received the modular hip prosthesis (Biomécanique, Bretigny-sur-orge, France) amounted to 16.3% (15 of 92), dogs that received a fixed head prosthesis (5 different manufactures) had 39% complications (28 of 72). Although the complication rate was influenced by different surgeons (n = 5) with different system predelictions and a different learning curve it was obvious that luxations (n = 6 of 10) and stem fractures (n = 5) more often occurred with the fixed head prosthesis systems. These stem fractures might be due to implant material failure or due to improper cementation followed by fatigue material failure. Femur fracture or infection were encountered with both prosthesis systems.     

Virulence and lienotoxicity of Bordetella bronchiseptica in mice

Whole-cell suspensions (WCSs) and cell-free sonicated extracts (SEs) of seven Bordetella bronchiseptica strains were studied for lethality and lienotoxicity in mice. Lethality was assessed after intravenous and intracerebral inoculation, and lienotoxicity by splenic atrophy after intravenous inoculation. The strains represented phase I isolates with or without cytotoxin production, their phase III subcultures and a phase IV variant. The lethality and lienotoxicity of the SEs were in close positive correlation with cytotoxin production. The WCSs of all phase I strains were lethal, irrespective of their cytotoxin- and lienotoxin-producing ability. The only difference was that cytotoxic phase I strains caused splenic atrophy while the noncytotoxic phase I strain induced splenic hypertrophy in the surviving mice. The WCSs of phase III and IV variants were non-lethal and caused splenic hypertrophy even though all but one of them showed some cyto- and lienotoxic activity when their SEs were tested. The results indicate that B. bronchiseptica possesses two different mouse lethal factors: one seems to be identical with the cytotoxin, the other is associated with cell integrity and viability and, presumably, propagation in vivo. It also follows from the results that only the SEs are suitable for accurate determination of the lienotoxin-producing ability of B. bronchiseptica.