Stress echocardiography in warmblood horses: comparison of dobutamine/atropine with treadmill exercise as cardiac stressors

The purpose of this study was to determine whether the combination of dobutamine and atropine causes cardiac stress equivalent to treadmill exercise. Therefore, electrocardiography and echocardiography were performed on 10 warmblood horses before, during, and after different cardiac stress tests. Stressors consisted of a standardized treadmill exercise and combined administration of dobutamine (7.5 microg/kg/min) and atropine (5 microg/kg). Maxima heart rates were achieved during the treadmill exercise (175 +/- 10 bpm). After exercise, a rapid decrease in heart rate was observed. Subsequently, a stress echocardiography for which a heart rate >100 bpm was required could only be performed within 1 minute after exercise. The mean heart rate during echocardiography was 136 +/- 8 bpm after exercise. The combination of dobutamine and atropine also resulted in a significant increase in heart rate, up to 141 +/- 20 bpm. Maxima heart rate was significantly higher during the treadmill exercise, but the decrease in heart rate was significantly slower after dobutamine and atropine administration. Over a period of 7.9 minutes, the mean heart rate was 123 +/- 8 bpm during dobutamine and atropine administration. Consequently, the combination of both drugs offered sufficient time for detailed examinations. Overall, echocardiographic examination identified a decrease in left ventricular (LV) dimensions, an increase in LV wall thickness, and a decrease in stroke volume after the treadmill exercise and during pharmacologic stress testing compared with baseline. Changes in echocardiographic variables generally were more pronounced during dobutamine and atropine administration. Similar to stress echocardiography in humans, in horses the combination of dobutamine and atropine is useful to produce an increase in heart rate comparable with what is achieved with exercise but without the need of increasing dobutamine dosage.     

Mycoplasma hominis ssp. associated endocarditis with myocardial necrosis in an alpaca (Vicugna pacos) in Manitoba in 2011

Severe endocarditis with myonecrosis, moderate to severe pleural and pericardial effusions, and mild ascites were found on necropsy in 3 alpacas. Mycoplasma hominis ssp. was detected on polymerase chain reaction (PCR) of fresh affected endocardial tissue in 1 alpaca.     

Comparison of some cardiopulmonary effects of etorphine and thiafentanil during the chemical immobilization of blesbok (Damaliscus pygargus phillipsi)

ObjectiveTo determine the cardiopulmonary effects of etorphine and thiafentanil for immobilization of blesbok.Study designBlinded, randomized, two-way crossover study.AnimalsA group of eight adult female blesbok.MethodsAnimals were immobilized twice, once with etorphine (0.09 mg kg^–1) and once with thiafentanil (0.09 mg kg^–1) administered intramuscularly by dart. Immobilization quality was assessed and analysed by Wilcoxon signed-rank test. Time to final recumbency was compared between treatments by one-way analysis of variance. Cardiopulmonary effects including respiratory rate (?_R), arterial blood pressures and arterial blood gases were measured. A linear mixed model was used to assess the effects of drug treatments over the 40 minute immobilization period. Significant differences between treatments, for treatment over time as well as effect of treatment by time on the variables, were analysed (p < 0.05).ResultsThere was no statistical difference (p = 0.186) between treatments for time to recumbency. The mean ?_R was lower with etorphine (14 breaths minute^–1) than with thiafentanil (19 breaths minute^–1, p = 0.034). The overall mean PaCO₂ was higher with etorphine [45 mmHg (6.0 kPa)] than with thiafentanil [41 mmHg (5.5 kPa), p = 0.025], whereas PaO₂ was lower with etorphine [53 mmHg (7.1 kPa)] than with thiafentanil [64 mmHg (8.5 kPa), p < 0.001]. The systolic arterial pressure measured throughout all time points was higher with thiafentanil than with etorphine (p = 0.04). The difference varied from 30 mmHg at 20 minutes after recumbency to 14 mmHg (standard error difference 2.7 mmHg) at 40 minutes after recumbency. Mean and diastolic arterial pressures were significantly higher with thiafentanil at 20 and 25 minute measurement points only (p < 0.001).ConclusionsBoth drugs caused clinically relevant hypoxaemia; however, it was less severe with thiafentanil. Ventilation was adequate. Hypertension was greater and immobilization scores were lower with thiafentanil.     

Local and systemic immune responses following infection of broiler-type chickens with avian Metapneumovirus subtypes A and B

Infections with avian Metapneumovirus (aMPV) are often associated with swollen head syndrome in meat type chickens. Previous studies in turkeys have demonstrated that local humoral and cell-mediated immunity plays a role in aMPV-infection. Previous experimental and field observations indicated that the susceptibility of broilers and their immune reactions to aMPV may differ from turkeys. In the presented study local and systemic immune reactions of broilers were investigated after experimental infections with subtypes A and B aMPV of turkey origin. Both virus subtypes induced a mild respiratory disease. The recovery from respiratory signs correlated with the induction of local and systemic aMPV virus-neutralizing antibodies, which began to rise at 6 days post infection (dpi), when the peak of clinical signs was observed. In a different manner to the virus neutralizing (VN) and IgG-ELISA serum antibody titres, which showed high levels until the end of the experiments between 24 and 28 dpi, the specific IgA-ELISA and VN-antibody levels in tracheal washes decreased by 10 and 14 dpi, respectively, which may explain the recurring aMPV-infections in the field. Ex vivo cultured spleen cells from aMPV-infected broilers released at 3 and 6 dpi higher levels of IFN-γ after stimulation with Concanavalin A as compared to virus-free birds. In agreement with studies in turkeys, aMPV-infected broilers showed a clear CD4+ T cell accumulation in the Harderian gland (HG) at 6 dpi (P<0.05). In contrast to other investigations in turkeys aMPV-infected broilers showed an increase in the number of CD8alpha+ cells at 6 dpi compared to virus-free birds (P<0.05). The numbers of local B cells in the Harderian gland were not affected by the infection. Both aMPV A and B induced up-regulation of interferon (IFN)-γ mRNA-expression in the nasal turbinates, while in the Harderian gland only aMPV-A induced enhanced IFN-γ expression at 3 dpi. The differences in systemic and local T cell and possibly natural killer cell activity in the HG between turkeys and chickens may explain the differences in aMPV-pathogenesis between these two species.     

Isolation and characterization of atypical Riemerella columbina strains from pigeons and their differentiation from Riemerella anatipestifer

Riemerella columbina (RC) and Riemerella anatipestifer (RA) belong to the genus Riemerella within the family Flavobacteriaceae. While RA is a well-described pathogen of waterfowl and other avian species, only little is known about RC. Previous work reporting the isolation of RC from internal organs of clinically diseased pigeons suggested a potential pathogenic role in this avian species. In this study we examined pharyngeal swabs collected from pigeons and found RC to be widely distributed also among healthy birds. Further characterization of 81 RC-isolates revealed several atypical strains, which differed from all previously described RC-isolates by the lack of aesculin-hydrolysis activity (17 isolates) or by expression of yellow or orange pigmentation (6 isolates). Sequence analysis of the 16S rRNA and outer membrane protein A (ompA) gene supported the affiliation of these strains to the species RC. Aesculin-hydrolysis negative isolates were found to be biochemically indistinguishable from RA. We demonstrated that bacterial fingerprinting using matrix assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI–TOF MS) analysis is useful for the identification and differentiation of RC and RA.