Canadian journal of comparative medicine : Revue canadienne de medecine comparee最新文献

Trichinoscopic examination, pepsin-hydrogen chloride digestion and the ELISA assay were used in an epidemiological survey for the presence of Trichinella spiralis in slaughterhouse pigs over a period of 12 months. The first two methods failed to detect any cases of trichinellosis in sows aged between two to three years. The ELISA assay, however, detected a 2.5% prevalence amongst the 2046 blood specimens tested. Foci of T. spiralis are localized in certain regions only. The discrepancy between the results obtained is likely to be due to the low infection density, undetectable by conventional methods. It is postulated that pigs which are not confined indoors came in contact with the sylvatic strain of Trichinella which is known for low muscle invasiveness.

Ewes (N = 7) and their lambs (N = 12) were vaccinated with a commercial modified live infectious bovine rhinotracheitis-parainfluenza type 3 virus vaccine. Both the vaccinated ewes and lambs and a group of unvaccinated ewes (N = 8) and their lambs (N = 13) were subsequently challenged with virulent parainfluenza type 3 virus. Although absolute immunity to infection and clinical response was not conferred, the clinical response was less severe in vaccinated lambs. Vaccinated animals also shed parainfluenza type 3 virus in nasal secretions for a shorter time than nonvaccinated animals. Some vaccinated lambs developed a persistent infectious bovine rhinotracheitis virus infection that was recrudesced by treatment with dexamethasone. It was concluded that vaccination was of benefit in reducing the severity of infection with parainfluenza type 3 virus. However, the inclusion of infectious bovine rhinotracheitis virus in a vaccine for sheep respiratory tract disease is highly questionable as it might increase the risk factor associated with vaccination. The consequences of the persistence of infectious bovine rhinotracheitis virus are now known.

A comparison of titers was made between an egg assay and a direct fluorescent antibody assay of three chlamydial strains propagated in Vero cells with and without cortisone plus cytochalasin B. The titer of NJ-1 strain was similar in the egg titration and the fluorescent antibody assay in the untreated sample and a little lower for the sample treated with cytochalasin B and cortisone. The SCT and CDC strains had approximately the same titers in the egg titration and the fluorescent antibody assay for samples with and without the antimetabolites.

A mail survey of feedlot owners was conducted to evaluate the efficacy of prophylactic antimicrobials, given in the water, or in the ration at preventing illness and/or death. One hundred and twenty-seven farmers from southwestern Ontario collaborated in the study. The percentage of calves requiring individual antimicrobial treatment, for any reason within 28 days of arrival was 22.6% (median 17.8%) and 0.6% (median 0.2%) died in that period. The use of medicated starter rations was not associated with either treatment or mortality rates until the effects of a number of other variables were controlled, analytically. Thereafter, the use of medicated feed was associated with a decrease in mortality rate, but was unrelated to morbidity rate. Overall, the use of medicated water was not associated with treatment or mortality rates. The use of sulphonamides was associated with decreased morbidity, but increased mortality rates. After controlling, analytically using multiple regression, the effects of other variables, the use of medicated water was associated with a significant increase in mortality rates. The other major factors which influenced mortality rates were the number of calves per group, the number of subgroups of calves in each group and whether the group contained cattle from different sources; all were related to increased mortality rates. During a two year period, more feedlot owners appeared to be using medicated rations as opposed to medicated water, as a means of providing antimicrobials to their newly arrived calves.

A survey of the efficiency of production of Ontario beef cow-calf herds was conducted using a stratified systematic random sample of Ontario producers. In general, about 87% of females exposed to breeding produced a live calf and 6% of these died before reaching four weeks of age. The herd to herd variation in these rates was quite large, the coefficient of variation being about 17%. The stillbirth rate was 1.7% and the abortion rate 1.2%. In general, herds in northern Ontario and herds whose owners kept breeding and calving records, had reduced livebirth rates, the latter probably reflecting accuracy of data. Herds with a restricted (less than three months) breeding season had increased livebirth rates. Herds using injectable vitamins ADE, and prophylactic antibiotics, had increased neonatal losses. Herds with a restricted calving season (less than or equal to 3 months) and/or feeding free choice salt to cows had decreased neonatal losses. Herdsize and calf mortality rate were directly related, but this did not appear to be due to increased density of cows at calving time. In herds, where calving occurred during the spring, using scour vaccines in calves was associated with increased calf mortality.

Analysis of 45 sera was performed employing five techniques which are currently in use in three laboratories to measure anti-Pasteurella haemolytica antibodies. The enzyme linked immunosorbent assay, passive hemagglutination, complement fixation and direct and indirect bacterial agglutination assays were employed and a relationship between tests in the measurement of anti-P. haemolytica antibodies was demonstrated. Regression analysis together with prediction and confidence intervals were tabulated also. The conclusion drawn from statistical analysis was that all five tests are similar in their ability to detect immune responses (antibody and antigen(s) interactions) to Pasteurella haemolytica.

The incidence of cystic ovaries following 1830 calvings of 1061 dairy cows maintained in total confinement was evaluated. The overall incidence was 14% of lactations and 22% of cows during a three year period. Fewer primiparous than multiparous cows became cystic, 5.7% vs 18%, respectively. There was an unexplained higher incidence (18%) among calvings in 1979 than in 1980 (12%) and 1981 (13%). There were no effects due to season of calving or genetic line of cow. During the last year of the study milk production by cystic cows was significantly greater than that by non-cystic cows.

The effects of gonadotrophin releasing hormone (GnRH) on the reproductive performance of dairy cows with retained placenta were studied. Three hundred and seventy-eight cows diagnosed as having retained placenta received intramuscular injections of either 2 mL sterile water or 200 micrograms of GnRH in 2 mL sterile water between day 8 and day 14 postpartum. Rectal palpation was performed at the time of treatment and ten to 20 days after treatment in order to determine the rate of uterine involution. Thereafter, monthly rectal examinations were carried out until insemination. Pregnancy diagnosis was made by rectal palpation at 40 days or more after breeding. Using the entire experimental population, there were no significant differences between GnRH-treated and control cows for the rate of uterine involution, the occurrence of reproductive problems, the interval from parturition to first observed estrus, the interval from parturition to first insemination, the interval from parturition to conception, the number of services per conception, the total number of services per cow regardless of conception and the incidence of culling for infertility. When the data for herds in which breeding began earlier in the postpartum period (herds having a mean less than or equal to 80 days from parturition to first service for retained placenta cows) were considered, the GnRH treatment resulted in a significantly shorter (p less than or equal to 0.01) calving to conception interval as compared to control cows. Also, there was a significant reduction (p less than or equal to 0.05) in the total number of services per cow regardless of conception and a significant reduction in the interval from parturition to first service.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficacy of ivermectin against later fourth-stage Strongylus vulgaris larvae was studied in pony foals at 14 and 35 days after treatment. These foals had been reared parasite-free, inoculated with 500 infective larvae and 56 days later given either ivermectin at 200 micrograms/kg or a placebo intramuscularly. At necropsy, foals were examined for lesions and larvae grossly and histologically. Ivermectin was found to be highly effective (98.6%) against later fourth-stage larvae in five foals which were examined at 35 days after treatment, but not in five others examined at 14 days (72.5%). In some foals larvae were found in the tunica media of the ileocolic arteries. The conformation of these larvae appeared normal, but there were degenerative changes which suggested that they were dying or dead. Questions as to how the larvae attained that site and the consequences of their presence there were raised.

Two dogs were diagnosed as malignant hyperthermia susceptible based on increased susceptibility (P less than 0.001) of biopsied muscle to caffeine-induced contracture. Erythrocytes from malignant hyperthermia and normal dogs were then examined for an antioxidant system deficiency. Values for serum muscle enzymes, reticulocytes and corpuscular hemoglobin were mildly elevated. Osmotic fragility was increased: hemolysis occurred at a NaCl concentration 10 mM higher than for normal dogs (P less than 0.001). A 35% glucose-6-phosphate dehydrogenase deficiency (P less than 0.001) with a 40% compensatory increase (P less than 0.01) in 6-phosphogluconate dehydrogenase activity was found. The membrane Ca2+-activated ATPase activity was abnormal: 100% increased with a 40% decreased Arrhenius activation energy (P less than 0.005) and increased thermostability. A 40% increased intracellular accumulation of total Ca2+ occurred in response to in vitro energy depletion in erythrocytes from one malignant hyperthermia dog (P less than 0.01). The multifactorial pattern of inheritance and the broad spectrum of malignant hyperthermia susceptibility are proposed to result from an antioxidant system deficit unmasking or aggravating an intrinsic muscle membrane anomaly. An individual from a family with a history of malignant hyperthermia or unexplained anesthetic death should be considered malignant hyperthermia susceptible if erythrocyte osmotic fragility is abnormal and there is a mild, unexplained elevation in serum creatine kinase.