Sangeeta Rao

Control of EHV-1 viremia and nasal shedding by commercial vaccines.

Equine herpesvirus-1 is a cause of outbreaks of abortion and neurological disease. The pathogenesis of both these diseases depends on establishment of viremia. An experiment was performed to determine the protective efficacy of two commercially available vaccines used with an optimized 3-dose vaccination regime: a modified-live viral (MLV) and a high antigen load killed vaccine licensed for abortion control. The study design was a blinded, randomized challenge trial. Three groups of 8 yearling ponies received one of three treatments: MLV vaccine (Rhinomune, Boehringer Ingelheim Vetmedica, Inc.); killed vaccine (Pneumabort-K, Pfizer Animal Health); or a placebo (control group). Three vaccinations were administered at intervals of 27 and 70 days followed by challenge infection 24 days later. Clinical disease after challenge was significantly reduced in both vaccine groups; the reduction was greater in the MLV vaccine group. Nasal shedding was reduced by at least 1-2 logs in both vaccine groups. The number of days of viremia was significantly reduced in the killed vaccine group only. This study demonstrated that both commercial vaccines significantly suppressed EHV-1 disease and nasal viral shedding, and one vaccine suppressed days of viremia.

Evaluation of immune responses following infection of ponies with an EHV-1 ORF1/2 deletion mutant

Equine herpesvirus-1 (EHV-1) infection remains a significant problem despite the widespread use of vaccines. The inability to generate a protective immune response to EHV-1 vaccination or infection is thought to be due to immunomodulatory properties of the virus, and the ORF1 and ORF2 gene products have been hypothesized as potential candidates with immunoregulatory properties. A pony infection study was performed to define immune responses to EHV-1, and to determine if an EHV-1 ORF1/2 deletion mutant (ΔORF1/2) would have different disease and immunoregulatory effects compared to wild type EHV-1 (WT). Infection with either virus led to cytokine responses that coincided with the course of clinical disease, particularly the biphasic pyrexia, which correlates with respiratory disease and viremia, respectively. Similarly, both viruses caused suppression of proliferative T-cell responses on day 7 post infection (pi). The ΔORF1/ORF2 virus caused significantly shorter primary pyrexia and significantly reduced nasal shedding, and an attenuated decrease in PBMC IL-8 as well as increased Tbet responses compared to WT-infected ponies. In conclusion, our findings are (i) that infection of ponies with EHV-1 leads to modulation of immune responses, which are correlated with disease pathogenesis, and (ii) that the ORF1/2 genes are of importance for disease outcome and modulation of cytokine responses.

Antimicrobial drug use and antimicrobial resistance in enteric bacteria among cattle from Alberta feedlots.

The purpose of this study was to determine whether antimicrobial resistance (AMR) in foodborne pathogens (Escherichia coli O157, Salmonella, and Campylobacter) and non-type-specific E. coli obtained from fecal samples of feedlot cattle was associated with antimicrobial drug (AMD) use. A secondary objective was to determine if AMR in non-type-specific E. coli could be used as a predictor of AMR in foodborne pathogens. Fecal samples were collected from pen floors in 21 Alberta feedlots during March through December 2004, and resistance prevalence was estimated by season (Spring, Fall) and cattle type (fewest days-on-feed and closest to slaughter). AMD exposures were obtained by calculating therapeutic animal daily doses for each drug before sampling from feedlot records. Generalized linear mixed models were used to investigate the relationship between each AMR and AMD use. Non-type-specific E. coli was commonly recovered from fecal samples (88.62%), and the highest prevalence of resistance was found toward tetracycline (53%), streptomycin (28%), and sulfadiazine (48%). Campylobacter jejuni was recovered from 55.3% of the fecal samples, and resistance was generally less for the drugs that were evaluated (doxycycline 38.1%, ciprofloxacin 2.6%, nalidixic acid 1.64%, erythromycin 1.2%). E. coli O157 and Salmonella were recovered much less frequently (7% and 1% prevalence, respectively). The prevalence of recovery for the bacteria studied varied between seasons and cattle types, as did patterns of AMR. Among non-type-specific E. coli, resistance to tetracycline, streptomycin, and sulfadiazine was found to be positively associated with in-feed exposure as well as injectable tetracycline, but these differences were relatively small and of questionable practical relevance. Among C. jejuni isolates, cattle type was significantly associated with doxycycline resistance. Results suggested that resistance in non-type-specific E. coli to chloramphenicol, trimethoprim/sulfamethoxazole, and tetracycline might be used as predictors of resistance to these drugs in E. coli O157 recovered from the same fecal samples.

Assessment of the tissue diffusion of anesthetic agent following administration of a low palmar nerve block in horses

OBJECTIVE To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses. DESIGN Randomized clinical trial. ANIMALS 12 adult horses. PROCEDURES In 9 horses, mepivacaine hydrochloride-iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region. RESULTS Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region. CONCLUSIONS AND CLINICAL RELEVANCE In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.

Prevalence of Dysphoria after Fentanyl in Dogs Undergoing Stifle Surgery

OBJECTIVE To describe the prevalence of dysphoria after intraoperative administration of fentanyl by infusion and identify other risk factors influencing this in dogs undergoing stifle surgery. STUDY DESIGN Prospective, randomized clinical study. ANIMALS Dogs (n = 92) that had tibial plateau leveling osteotomy (TPLO) or tibial tuberosity advancement (TTA). METHODS Dogs were anesthetized using a standardized anesthetic protocol, and randomly assigned to receive a loading dose followed by 1 of 3 infusions of fentanyl perioperatively: 2 μg/kg/h, 10 μg/kg/h, or 20 μg/kg/h. Dog characteristics and all additional medications were recorded and included as part of the statistical analysis. Dog behavior was scored before anesthesia and during recovery using a scale of 1-4 (Appendices A and B). If no improvement in behavior was seen in 3-5 minutes postextubation, dogs with a score of 3 or 4 during recovery were administered fentanyl (2 μg/kg intravenously [IV]) in the event that the behaviors associated with the higher scores were related to pain. If they did not respond favorably to the administration of additional fentanyl and wound palpation did not elicit a response, but the untoward behaviors continued, dogs were administered either a tranquilizer, sedative, or opioid antagonist, and were considered dysphoric. RESULTS Of 92 dogs, 22 (23.9%) were considered dysphoric using aforementioned criteria. CONCLUSIONS About one-fourth of dogs enrolled in this study were dysphoric based on study criteria.

Evaluation of infectivity of a canine lineage H3N8 influenza A virus in ponies and in primary equine respiratory epithelial cells

OBJECTIVE To evaluate whether an equine-derived canine H3N8 influenza A virus was capable of infecting and transmitting disease to ponies. ANIMALS 20 influenza virus-seronegative 12- to 24-month-old ponies. PROCEDURES 5 ponies were inoculated via aerosol exposure with 10(7) TCID(50) of A/Canine/Wyoming/86033/07 virus (Ca/WY)/pony. A second group of 5 ponies (positive control group) was inoculated via aerosol exposure with a contemporary A/Eq/Colorado/10/07 virus (Eq/CO), and 4 sham-inoculated ponies served as a negative control group. To evaluate the potential for virus transmission, ponies (3/inoculation group) were introduced 2 days after aerosol exposure and housed with Ca/WY- and Eq/CO-inoculated ponies to serve as sentinel animals. Clinical signs, nasal virus shedding, and serologic responses to inoculation were monitored in all ponies for up to 21 days after viral inoculation. Growth and infection characteristics of viruses were examined by use of Madin-Darby canine kidney cells and primary equine and canine respiratory epithelial cells. RESULTS Ponies inoculated with Ca/WY had mild changes in clinical appearance, compared with results for Eq/CO-inoculated ponies. Additionally, Ca/WY inoculation induced significantly lower numbers for copies of the matrix gene in nasal secretions and lower systemic antibody responses in ponies than did Eq/CO inoculation. The Ca/WY isolate was not transmitted to sentinel ponies. CONCLUSIONS AND CLINICAL RELEVANCE Inoculation of ponies with the canine H3N8 isolate resulted in mild clinical disease, minimal nasal virus shedding, and weak systemic antibody responses, compared with responses after inoculation with the equine H3N8 influenza isolate. These results suggested that Ca/WY has not maintained infectivity for ponies.

Current treatment of ascending colon volvulus in horses: a survey of ACVS Diplomates.

OBJECTIVE To report the results of a survey of opinions on current treatments and estimated outcomes of ascending colon volvulus in horses. STUDY DESIGN Web-based survey. SAMPLE POPULATION American College of Veterinary Surgeons (ACVS) Diplomates (n = 151) who perform gastrointestinal surgery in horses. METHODS ACVS Diplomates with credentials in the large animal specialty obtained by examination in 2010 or earlier (n = 410) were solicited by e-mail to complete a web-based survey designed to determine ascending colon volvulus treatment preferences and outcomes. RESULTS Responses were obtained from 162 ACVS Diplomates, of which 151 currently performed gastrointestinal surgery in horses. Horses surgically treated with ascending colon volvulus accounted for ≤ 20 cases/year and primary treatment was most often anatomic reduction with or without pelvic flexure enterotomy. Median estimated survival rate was 70% and surgical treatments were not associated with estimated survival (P = .27). Diplomates identified early surgical correction as the single most important factor impacting survival of horses surgically treated for ascending colon volvulus. CONCLUSIONS Reported survival rates for horses with ascending colon volvulus were good. Respondents indicated this might be due in part to early surgical treatment. Survey investigations can provide preliminary data for future prospective studies and facilitate a consensus among Diplomates in treatment of surgical disease.

Comparison of peritoneal fluid values after laparoscopic cryptorchidectomy using a vessel-sealing device (Ligasure™) versus a ligating loop and removal of the descended testis.

OBJECTIVE To determine the effect of unilateral laparoscopic cryptorchidectomy and removal of the descended testis on peritoneal fluid values, and to compare effect between 2 methods for cryptorchid testis vessel hemostasis. STUDY DESIGN Randomized clinical study. ANIMALS Stallions (n = 10) with unilateral abdominal cryptorchid testis. METHODS During standing laparoscopic cryptorchidectomy, blood vessels within the mesorchium of the cryptorchid testis were either sealed and transected with the LigaSure Atlas™ or 2 ligating loops were placed proximal to the testis and the tissue transected with laparoscopic scissors. The testis was removed through the body wall. After laparoscopic cryptorchidectomy, stallions were anesthetized and the descended testis was removed using a closed technique leaving the scrotal incision open. Abdominocenteses were performed before surgery, and 24, and 72 hours after surgery. RESULTS Values for peritoneal total nucleated cell count (TNCC), total protein concentration (TP), and red blood cell count (RBCC) were all elevated at 24 and 72 hours when compared with baseline. Median TNCC for LigaSure™ (59,780 cells/μL) was nearly twice that of the ligating loop (32,880 cells/μL) at 24 hours postoperatively. There was no statistically significant difference in TNCC, TP, or RBCC between groups. CONCLUSIONS TNCC, TP, and RBCC increase appreciably from baseline 24 hours after laparoscopic cryptorchidectomy and closed castration but are markedly reduced by 72 hours.