Effects of enalapril maleate on survival of dogs with naturally acquired heart failure. The Long-Term Investigation of Veterinary Enalapril (LIVE) Study Group.

OBJECTIVE: To test the long-term effect of enalapril maleate treatment on progression of clinical signs of heart disease in dogs with moderate or severe naturally acquired heart failure associated with chronic degenerative mitral valvular disease (mitral regurgitation [MR]) or dilated cardiomyopathy (DCM). DESIGN: Prospective multicenter study. ANIMALS: 110 dogs enrolled at 15 locations in the United States. PROCEDURE: All dogs enrolled in this study were maintained on their randomly allocated treatment regimen until death, treatment failure (deterioration of condition requiring additional medication), or termination of the study. All dogs entered in the study received standard heart failure treatment (furosemide with or without digoxin). Statistical analysis (log-rank test) was performed to compare the distribution of number of days in the study between dogs that received placebo tablets and dogs that received enalapril tablets. RESULTS: When dogs with MR and DCM were grouped together, mean number of days until treatment failure was significantly different between those receiving enalapril and those given placebo tablets (157.5 and 77.0 days, respectively). For dogs with MR, mean number of days until treatment failure was significantly different between those receiving enalapril and placebo tablets (159.5 and 86.6 days, respectively). Mean number of days until treatment failure among dogs with DCM receiving enalapril and placebo tablets was 142.8 and 56.5, respectively. CLINICAL IMPLICATIONS: Use of enalapril in combination with standard treatment (diuretics with or without digoxin) appears to be beneficial over an extended period, compared with standard treatment alone.

Evaluation of the persistence of the effect of ivermectin and abamectin against gastrointestinal and pulmonary nematodes in cattle.

The persistence of the effect of ivermectin and abamectin against gastrointestinal nematodes and lungworm in cattle was evaluated in two trials, each involving 28 animals. Groups of seven cattle either remained untreated, or were treated topically with ivermectin at 500 micrograms/kg bodyweight or subcutaneously with either ivermectin or abamectin at 200 micrograms/kg bodyweight. Starting on the day of treatment the cattle were given daily trickle infections with various infective nematode larvae for two weeks (Haemonchus species, Trichostrongylus axei and Cooperia species), three weeks (Ostertagia ostertagi and Oesophagostomum radiatum) and four weeks (Dictyocaulus viviparus). The cattle were killed 49 to 51 days after treatment and their worm burdens measured. An efficacy of > 99 per cent was recorded in all the groups demonstrating that the products controlled Haemonchus species, T axei, C oncophora, C punctata and C surnabada for at least two weeks, O ostertagi and O radiatum for at least three weeks and D viviparus for at least four weeks.

Effects of enalapril on exercise tolerance and longevity in dogs with heart failure produced by iatrogenic mitral regurgitation.

This study was conducted to evaluate the effects of enalapril on exercise capacity and longevity in dogs with left-sided heart failure produced by iatrogenic mitral regurgitation. After surgical creation of mitral regurgitation, 18 dogs were allocated into replicates according to exercise capacities. One dog in each replicate received placebo, and the other received 0.5 mg/kg of enalapril sid for 9 days and bid thereafter. Exercise tolerance was studied after 10, 19, 52 to 53, and 80 to 81 days, respectively. Finally, the percentage of dogs in each group that survived 357 days was compared. The duration of exercise for dogs in the placebo and enalapril groups did not differ at baseline (P > .1) or after 19 days (P > .1). Dogs that received enalapril had significantly reduced (P < .001) exercise tolerance at day 10, and significantly increased (P = .002) exercise tolerance at days 52 to 53 and 80 to 81 when compared with controls. At 357 days, 22% of dogs receiving placebo were alive, compared with 67% of dogs receiving enalapril; however, these differences were not statistically significant (P = .124). This study shows that enalapril increases exercise tolerance in dogs with left-sided heart failure induced by iatrogenic mitral regurgitation.

Efficacy of an in-feed ivermectin formulation against gastrointestinal helminths, lungworms, and sarcoptic mites in swine.

The efficacy of ivermectin as an in-feed formulation was evaluated against naturally acquired gastrointestinal helminths, lungworms, and sarcoptic mites (experiment 1; n = 24) and against induced infection with intestinal nematodes (experiment 2; n = 24) in pigs. Treatments consisted of ivermectin administered in feed at concentrations calculated to provide 100 or 200 micrograms/kg of body weight/d for 7 days or of nonmedicated feed (controls) for 7 days. At concentration of 100 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 97.7% for Ascaris suum, 97.8% for Metastrongylus spp, greater than 99% for Oesophagostomum spp, 100% for Macracanthorhynchus hirudinaceus, and 89.7% for Ascarops strongylina. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 96.9% for Oesophagostomum spp. At concentration of 200 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 100% for A suum, Hyostrongylus rubidus, Metastrongylus spp, and Ascarops strongylina; greater than 99% for Oesophagostomum spp; and 85.9% for Macracanthorhynchus hirudinaceus. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 95% for Oesophagostomum spp. At concentrations of 100 and 200 micrograms of ivermectin/kg/d, efficacy against Sarcoptes scabiei var suis was evidenced by elimination of the mite by posttreatment day 14.

Effect of efrotomycin on gain and feed efficiency for pigs from weaning until market weight.

Six studies involving 700 pigs were conducted in five separate swine research facilities to evaluate weight gain and efficiency of feed utilization in pigs fed the antibiotic efrotomycin. Pigs averaging 8.4 kg at the beginning of the studies were fed fortified corn-soybean meal diets that contained efrotomycin at 0, 2, 4, 8 or 16 ppm for an average of 120 d to market weight, about 92.1 kg. Pigs fed efrotomycin gained 5.9 to 8.9% faster (P less than .01) and were 1.7 to 4.0% more efficient (P less than .01) than those fed control diets. The improvement in growth rate was linear from 2 through 16 ppm, while feed efficiency (gain/feed) plateaued at 4 ppm efrotomycin. Treatment X study interactions were not significant for average daily gain or feed efficiency, showing that the response to efrotomycin was similar in each study. These studies indicate that efrotomycin is effective in improving gain and efficiency of feed utilization in swine from weaning until market weight.

Precision of assessing anthelmintic efficacy.

In counting internal helminthic parasites (the "worm burden") of domestic animals, physical restrictions often lead to sampling by small aliquots of unequal size among affected organs, among animals treated alike, and among groups of animals treated differently. We assess the impact of that type of sampling on the precision of the analyzed variable (log of estimated worm burden), derive the variance of the standard nonlinear estimator of efficacy of anthelmintic treatment, and examine the problem of number of animals required for adequate sensitivity of experiments. The standard error of sample geometric mean worm burden, for a particular anthelmintic treatment, and the standard error of estimated efficacy of a treatment, relative to control, are given for the case of log-normal burdens. Small aliquots affect precision critically only if mean burden is small, i.e., when sampling by small aliquots is unnecessary, because the physical effort required is not great. The minimal number of animals per treatment, required for at least 80% power to detect efficacy of .7 or higher, is about 4 to 6 for species of parasites constituting major burdens (where the coefficient of variation of worm burden often is near .7). However, the minimal number of animals may be as high as 15 to 20 per treatment for cases with lowly-abundant species of parasites (where the coefficient of variation may be as high as 2 or 3). An example is given to illustrate procedures.