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peer reviewed | OBJECTIVE: To evaluate the hemodynamic effects of dobutamine hydrochloride (0.5 microg/kg of body weight/min) in halothane-anesthetized horses. ANIMALS: 6 adult Thoroughbred horses. PROCEDURE: Anesthesia was induced by use of romifidine (100 microg/kg) and ketamine (2.2 mg/kg), IV. Anesthesia was maintained by halothane (end-tidal concentration 0.9 to 1.0%). Aortic, left ventricular, and right atrial pressures were measured, using catheter-mounted strain gauge transducers. Cardiac output (CO), velocity time integral, maximal aortic blood flow velocity and acceleration, and left ventricular preejection period and ejection time were measured from aortic velocity waveforms obtained by transesophageal Doppler echocardiography. Velocity waveforms were recorded from the femoral vessels, using Doppler ultrasonography. The time-averaged mean velocity and early diastolic deceleration slope (EDDS) were measured. Pulsatility index (PI) and volumetric flow were calculated. Microvascular perfusion was measured in the semimembranosus muscles by laser Doppler flowmetry. Data were recorded 60 minutes after induction of anesthesia (control) and at 15 and 30 minutes after start of an infusion of dobutamine (0.5 microg/kg/min). RESULTS: Aortic pressures were significantly increased during the infusion of dobutamine. No change was observed in the indices of left ventricular systolic function including CO. Femoral arterial flow significantly increased, and the PI and EDDS decreased. No change was observed in the femoral venous flow or in microvascular perfusion. CONCLUSIONS AND CLINICAL RELEVANCE: At this dosage, dobutamine did not alter left ventricular systolic function. Femoral blood flow was preferentially increased as the result of local vasodilatation. The lack of effect of dobutamine on microvascular perfusion suggests that increased femoral flow is not necessarily associated with improved perfusion of skeletal muscles

peer reviewed | OBJECTIVE: To assess in vivo blood oxygen binding in double-muscled calves and dairy calves with conventional muscle conformation. ANIMALS: 58 dairy and 48 double-muscled calves. PROCEDURE: Calves were classified as neonatal (24 hours old) or older calves (2 to 26 days old). Venous and arterial blood samples were collected, and hemoglobin concentration, pH, PCO2, and PO2 were determined. Blood oxygen equilibrium curves (OEC) under standard conditions were constructed, and the oxygen exchange fraction (OEF) and the amount of oxygen released at the tissue level by 100 ml of blood (OEF Vol%) were calculated. RESULTS: In each breed, partial pressure of oxygen at 50% saturation of hemoglobin (P50) under standard conditions was significantly higher in older than in neonatal calves, indicating a right shift in OEC with age. Venous P50 was significantly lower in neonatal double-muscled calves than in neonatal dairy calves, but arterial and venous P50 were significantly higher in older double-muscled calves than in older dairy calves. In double-muscled, but not in dairy, calves, OEF was significantly higher in older than in neonatal calves. In neonatal calves, OEF Vol% was not significantly different between breeds, but OEF Vol% was significantly higher in older double-muscled calves than in older dairy calves. CONCLUSIONS AND CLINICAL RELEVANCE: The lower OEF in neonatal double-muscled calves, compared with dairy calves, could contribute to the higher sensitivity of double-muscled calves to hypoxia. Blood oxygen affinity decreased with age, but OEF and OEF Vol% were unchanged with age in dairy calves, whereas they increased with age in double-muscled calves

peer reviewed | OBJECTIVE: To use Doppler ultrasonography and single-fiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride. ANIMALS: 6 healthy adult horses. PROCEDURE: Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measure relative microvascular perfusion at a single site in the semimembranosus muscles. Phenylephrine or dobutamine was then administered to decrease or increase femoral arterial blood flow, and changes in blood flow and microvascular perfusion were recorded. RESULTS: Administration of phenylephrine resulted in significant decreases in femoral arterial and venous blood flows and cardiac output and significant increases in mean aortic blood pressure, systemic vascular resistance, and PCV. Administration of dobutamine resulted in significant increases in femoral arterial blood flow, mean aortic blood pressure, and PCV. Significant changes in microvascular perfusion were not detected. CONCLUSION AND CLINICAL RELEVANCE: Results suggest that Doppler ultrasonography and single-fiber LDF can be used to study blood flows in the hind limbs of anesthetized horses. However, further studies are required to determine why changes in femoral arterial blood flows were not associated with changes in microvascular perfusion

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.

Four calves were exposed via aerosol to 1 of 2 strains of foot-and-mouth disease virus. Two animals received virus derived from an infectious clone virus (A12-IC) and 2 received virus derived from the same clone but which lacked the leader coding region (A12-LLV2) that codes for a protein responsible for turning off host protein synthesis. Animals were euthanized at 24 and 72 h post exposure. Cattle receiving A12-IC had a rapid course of disease with more virus in tissues while A12-LLV2-infected cattle did not develop clinical signs of disease. Formalin-fixed, paraffin-embedded tissue sections were probed with digoxigenin-labeled riboprobes corresponding to the coding sequence for bovine interferon (IFN) alpha and IFNbeta. Staining for IFNalpha mRNA was noted in mononuclear cells of the lungs of all animals and in respiratory lymph nodes of cattle receiving A12-IC. Staining for IFNbeta mRNA was confined to bronchiolar epithelium and present only in the animals infected with A12-IC. Inability of the A12-LLV2 virus to achieve levels of spread seen with A12-IC may be related to translation of IFNalpha in A12-LLV2-infected cells, which renders adjacent cells less susceptible to productive infection.

This is the first extensive survey of metazoan parasites (particularly of the roundworm Baylisascaris procyonis) from the intestines of raccoons in British Columbia. The sample collected in 1997-1998 consisted of 82 raccoons that had been sick or had been killed accidentally by automobiles. Fifteen parasite taxa were found: 3 nematodes, 9 digenetic trematodes, 2 acanthocephalans and 1 cestode. Ten of these parasites constitute new host records for raccoons, including 4 digenetic trematodes that have been reported in marine birds and mammals on the Pacific Coast of North America. Baylisascaris procyonis infected 61% of the raccoons with a mean intensity of 27. The high rate of infection indicates a large potential for environmental contamination and, thus, human and animal exposure to infectious eggs. Prevention of larva migrans is discussed, particularly for people in contact with raccoons in wildlife rehabilitation centers.

Cells infected with bovine coronavirus (BCV) were solubilized with Triton X-100 to yield a cell lysate (CL) antigen having high hemagglutinating (HA) titers. The antigen gave high HA titers using rat erythrocytes, suggesting that it contained large amounts of hemagglutinin esterase (HE) antigen. The CL antigen, combined with an oil adjuvant, was tested for protective and antibody-inducing activities in cattle. Four groups (2 cattle/group) of cattle were inoculated with CL antigen having HA titers of 16 000, 4000, 1000, and 250. Another group served as untreated controls. Two intramuscular inoculations were given at an interval of 3 wk. The animals were challenged with virus 1 wk after the second inoculation. The groups immunized with the CL antigen having an HA titer of 4000 or 16 000 produced hemagglutination inhibition (HI) antibody titers of > 320 and serum neutralizing (SN) antibody titers of > 1280. These groups of animals showed no clinical abnormalities after challenge. In the groups immunized with CL antigen at an HA titer of 1000 or 250, HI antibody titers were 40 to 160 and SN titers were 80 to 640. The cattle with HI antibody titers of > or = 160 and the SN titers of > or = 640 showed no clinical signs, but the cattle with the HI antibody titer < 80 and the SN antibody titer < 160 developed watery diarrhea and fever after challenge. These results indicate that CL antigen with high HA titer induces antibody production in cattle that provides effective protection against winter dysentery.