2016 ACVIM Forum Research Abstract Program

Data was analyzed using the statistical software program Sig-maPlot version 12.3. To analyze flow cytometry and RT-PCR data for differences between PPID and non-PPID horses, t-tests were performed. To analyze lymphocyte proliferation data at various concentrations of Con A stimulation, two-way analysis of variance with repeated measures was performed. No significant differences between PPID and non-PPID horses were found for any of the immune measures examined including flow cytometry, RT-PCR, and proliferation data (P > 0.05). These results indicate that the immunosuppression associated with PPID does not appear to be due to differences in PBMC proliferation or cytokine production when comparing aged PPID horses with aged non-PPID horses. Thus, more research is warranted to further understand the immunological mechanisms responsible for immunosuppression and susceptibility to opportunistic infections in the PPID horse. False positive results may occur when testing horses for antibodies against Corynebacterium pseudotuberculosis by synergistic hemolysis inhibition (SHI). In small ruminants, ELISA tests based on exotoxin and cell wall antigens have greater accuracy than SHI in diagnosis of caseous lymphadenitis. The purpose of this study was to compare the detection of C. pseudotuberculosis antibodies in equine serum by SHI and a small ruminant ELISA test that uses exotoxin and cell wall antigens. Sera from 7 ponies experimentally infected with C. pseudotuberculosis were analyzed by both tests. Correlation and agreement were calculated by Pearson and Kappa coefficients, respectively. Receiver operating characteristic analysis was used to obtain the optimal cut-off value for the calculated ELISA score (Patient optical density/Negative control optical density x 100). Antigen reactivity to the sera was evaluated by immunoblotting. When SHI titers ≥1:128 were considered a positive result, the optimal ELISA score cut-off to determine positive status was 106%, with 73% sensitivity and 72% specificity with respect to SHI. Correlation between both tests was strong [r = 0.904; (95%CI 0.472-0.986, P = 0.005)]. Agreement in determining positive status was poor (Kappa=0.439; (95%CI 0.226-0.652). Correlation and agreement were strong in 3/7 ponies, but weak in 4/7. Immunoblot showed a band 13.4 times more intense in infected compared to pre-infected sera corresponding with the exotoxin antigen, but only non-specific reactivity with the cell wall antigen. The use of this ELISA test in horses is not recommended. Development of an ELISA test with specific antigens from C. pseudotuberculosis biovar equi is needed. Macrolide-induced anhidrosis is a concern in foals treated for Rhodococcus equi pneumonia. Because sweating in horses is caused by activation of b2-adrenergic receptors on sweat glands, it was of interest to evaluate responses to IV epinephrine in foals given erythromycin. Four pony-cross foals were treated for 3 days prior to epinephrine infusion with either erythromycin (25 mg/kg orally, 3 times daily) or a control preparation according to a 2-period randomized masked design. Epinephrine was given by CRI over 10 minutes at 0.5 lg/kg/minute and the following data were collected before and at intervals for 180 minutes after onset of infusion: sweat (absorbed into absorbent pads), heart and respiratory rates, systemic arterial BP, pupil size, PCV, plasma protein, and blood glucose concentration. Cardiac rhythm was monitored continuously by ECG.