Evaluation of administration of West Nile virus vaccine to pregnant broodmares

OBJECTIVE: To determine whether administration of killed West Nile virus vaccine was associated with pregnancy loss among broodmares. DESIGN: Retrospective cohort study. ANIMALS: 595 mares. PROCEDURE: Records of pregnant mares with known vaccination history from 4 farms were reviewed. Information obtained from 595 mares included mare's identification; farm; age; breed; reproductive status; last breeding date; date last known pregnant; vaccination date; age of conceptus at vaccination; vaccination during the early embryonic, early fetal, and late fetal periods; and whether an early embryonic death (EED), early fetal loss (EFL), or late fetal loss (LFL) occurred. The relationships between the dichotomous outcomes of loss (eg, EED, EFL, LFL) and independent categoric variables (eg, vaccination during the early embryonic, early fetal, or late fetal periods) were examined. RESULTS: Vaccination of pregnant mares during any period of gestation was not associated with increased incidence of pregnancy loss. CONCLUSIONS AND CLINICAL RELEVANCE: Many mares are already pregnant at the onset of mosquito season, when mares are more likely to be vaccinated than at other times. Our findings provide evidence that vaccine administration will not compromise pregnancy in horses.     

Effect of dietary corn oil supplementation on equine gastric fluid acid, sodium, and prostaglandin E2 content before and during pentagastrin infusion

The effect of corn oil (approximately 60% [wt/vol] linoleic acid) dietary supplementation on various components of equine gastric secretion was studied by use of a repeated-measures experimental design. Four healthy adult ponies were surgically fitted with gastric cannulas. The ponies were then fed a free-choice hay diet for 5 weeks, which was followed by 5 weeks of the same diet supplemented with 45 mL of corn oil daily. Gastric contents were analyzed under basal and pentagastrin-stimulated conditions once weekly during the latter 2 weeks on each diet. Gastric contents were collected at 30-minute intervals, and volume, hydrogen ion concentration, sodium content, and prostaglandin E2 (PGE2) content were measured. Data were analyzed by a linear fixed-effect modeling procedure. During the diet supplemented with corn oil, the ponies had, under basal and pentagastrin-stimulated conditions, significantly decreased acid output and significantly increased PGE2 and sodium outputs compared to those measured before corn oil supplementation. We conclude that corn oil supplementation may be an effective and inexpensive way to increase the protective properties of equine glandular gastric mucosa. This could be particularly helpful in reducing the chances of ulceration associated with nonsteroidal anti-inflammatory drug (NSAID) administration.     

Foal-related risk factors associated with development of Rhodococcus equi pneumonia on farms with endemic infection

OBJECTIVE: To identify foal-related risk factors associated with development of Rhodococcus equi pneumonia among foals on farms with endemic R. equi infection. DESIGN: Prospective case-control study. ANIMALS: 220 foals at 2 equine breeding farms in Texas during a 2-year period. PROCEDURE: Information collected for each dam included age, time housed on the farm prior to parturition, whether there were any peripartum illnesses, parity, and health of previous foals. Information collected for each foal included breed, sex, gestational age, month and year of birth, location of birth, type of flooring and bedding in stall, postpartum management and preventive health care, passive immunity status, supplementation of immunoglobulins, exposure to other farms or foals affected with R. equi pneumonia, stall and pasture exposure, commingling with other mare-foal pairs, age at weaning, and whether the foal developed R. equi pneumonia. RESULTS: 32 of the 220 (15%) foals developed R. equi pneumonia, of which 4 (13%) died. Foals at 1 of the 2 farms and foals born during the second year of the study were more likely to develop R. equi pneumonia. Foal-related factors that were examined were not significantly associated with risk of R. equi pneumonia in multivariate analyses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that there are farm- and year-related effects on the risk that foals will develop R. equi pneumonia. Other foal-related factors significantly associated with R. equi pneumonia were not identified.     

Evaluation of acetaminophen absorption in horses with experimentally induced delayed gastric emptying

OBJECTIVE: To evaluate the correlation between the half-time of liquid-phase gastric emptying (T50) determined by use of nuclear scintigraphy, using technetiumTc 99m pentetate, and absorption variables of orally administered acetaminophen in horses with experimentally delayed gastric emptying. ANIMALS: 6 mature horses. PROCEDURE: Delayed gastric emptying was induced by IV injection of atropine sulfate. Twenty minutes later, acetaminophen and technetium Tc 99m pentetate were administered simultaneously via nasogastric tube. Serial lateral images of the stomach region were obtained, using a gamma camera. Power exponential curves were used for estimation of T50 and modified R2 values for estimation of goodness-of-fit of the data. Serial serum samples were obtained, and acetaminophen concentration was determined, using fluorescence polarization immunoassay. Maximum serum concentration (Cmax), time to reach maximum serum concentration (Tmax), area under the curve for 480 minutes, and the appearance rate constant were determined, using a parameter estimation program. Correlations were calculated, using a Spearman rank correlation coefficient. RESULTS: A significant correlation was detected between T50 determined by use of scintigraphy and Tmax determined by use of acetaminophen absorption. Correlation between T50 and other absorption variables of acetaminophen was not significant. CONCLUSIONS AND CLINICAL RELEVANCE: The acetaminophen absorption method was a valid technique in this model of delayed gastric emptying in horses. The method may be a valuable tool for use in research as well as in clinical evaluation of gastric emptying in horses.     

Medical Management of Right Dorsal Colitis in 5 Horses: A Retrospective Study (1987–1993)

Right dorsal colitis in horses has been associated with administration of phenylbutazone. Although reports of right dorsal colitis in this species have described surgical treatment associated with a poor prognosis, we have had success treating this condition medically. This report describes 5 horses with right dorsal colitis confirmed during celiotomy that were initially managed medically. All horses had a history of intermittent abdominal pain; weight loss was noted in only 1 horse. The doses (2.0 to 4.6 mg/kg PO bid) and duration (5 to 30 days) of administration of phenylbutazone were not unusually high relative to those recommended (4.4 mg/kg PO bid). Hypoproteinemia and hypoalbuminemia were observed in all horses at the time of admission; packed cell volume was low in 4 horses, and hypocalcemia was also observed in 4 horses. Three of 5 horses (60%) appeared to respond to dietary management and discontinuation of administration of nonsteroidal anti-inflammatory drugs. Dietary management consisted of feeding pelleted feed, and restricting or eliminating roughage for a period of at least 3 months. Two horses developed strictures of the right dorsal colon. One horse that developed a colonic stricture, possibly because its owners did not comply with recommendations for management, was subsequently treated surgically. The remaining horse that developed a stricture of the right dorsal colon was euthanized. These data indicate that some horses with right dorsal colitis can be successfully managed with medical treatment.     

Urinary Indices of Horses After Intravenous Administration of Crystalloid Solutions

Saline or glucose solution was infused for approximately 4 hours into six healthy mares in two separate experiments to determine the effect of infusion of crystalloid solutions on fractional excretion (FE) of sodium (Na), chloride (Cl), potassium (K), and phosphorus (P), ratio of urinary creatinine to serum creatinine (U_Cr/S_Cr), and ratio of urinary osmolality to serum osmolality (U_osm/S_osm). After intravenous infusion of either saline or glucose solution, FE_Na, FE_Cl and FE_P were significantly increased, whereas U_Cr/S_Cr and U_osm/S_osm were significantly decreased. In addition, FE_K was significantly increased after infusion of glucose solution. It was concluded that urinary indices were altered by intravenous infusion of crystalloid solutions in healthy mares and that fluid therapy may interfere with the use of these indices for diagnostic purposes. (Journal of Veterinary Internal Medicine 1993; 7:241–246. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Efficiency of two commercial ELISA kits compared with the BAM culture method for detecting Listeria in naturally contaminated foods.

The efficiency of 2 commercial enzyme-linked immunosorbent assay (ELISA) kits (Listeria-Tek and Tecra) for detecting Listeria in naturally contaminated foods was evaluated and compared with that of the culture method described in the Bacteriological Analytical Manual (BAM). Both ELISAs use modified University of Vermont (UVM-1) medium as a primary enrichment; the BAM method uses Listeria enrichment broth. Secondary enrichments for Listeria-Tek and Tecra, respectively, were Fraser broth and UVM-2, which contains additional acriflavin-HCl. When ELISA test results differed, secondary enrichments were tested against the other ELISA; Fraser broth was used to determine recovery rates because of its superiority over UVM-2. Of the 178 food samples examined, the presence of Listeria was detected and culturally confirmed in 38, 37, and 40 samples by the BAM, Listeria-Tek, and Tecra methods, respectively. Differences in results of the ELISAs compared with those of the BAM method were not statistically significant; however, differences between results of the 2 ELISA methods were significant. It was concluded that as rapid screening methods, the Listeria-Tek and the Tecra kits qualify as alternative methods to the BAM cultural method.     

Effect of hyperimmune plasma on the severity of pneumonia caused by Rhodococcus equi in experimentally infected foals

This study evaluated the prophylactic effectiveness of hyperimmune plasma (HIP) as an aid in the prevention of pneumonia caused by experimental infection with Rhodococcus equi. Thirty neonatal foals were administered R. equi HIP or saline at 2 days of age and were infected with virulent R. equi at 7 days. All foals developed signs or symptoms of respiratory disease. Radiographic scores on day 28 and neutrophil concentrations on day 49 were significantly greater in control foals, and time to respiratory effort score of 2 or higher was significantly shorter for control foals. Three foals, all in the principal group, died or were euthanized before the end of the study, but there was no significant difference in mortality between groups. VapA titers were significantly greater in principal foals. Administration of R. equi HIP decreased the severity of radiographic lesions and prolonged time to increased respiratory effort due to R. equi-induced pneumonia.