Equine helminth infections: control by selective chemotherapy

A programme of selective anthelmintic therapy was used in a herd of 31 horses. Faecal egg counts were done during the months of September, November, January, March, May and the following September. Horses with greater than or equal to 100 eggs per gram (epg) were treated with ivermectin, and those with less than 100 epg were not treated. The criteria for adequate internal parasite control in the herd was a median herd faecal egg count of less than or equal to 100 epg. Effectiveness of selective therapy was assessed by faecal egg count after nine months of treatment and was determined to be adequate when a median herd egg count of 0 epg was obtained. However, on returning from pasture the following September, median herd egg count had risen to 325 epg. A statistically significant correlation was seen in the paired September faecal egg counts of the horses in that initial September faecal egg count was predictive for the following September. Initial September faecal egg count was related to the number of anthelmintic treatments required during the period of selective therapy, whereas age of horse was not. We propose that faecal egg counts be incorporated into strategic anthelmintic programmes as an economical tool for identifying and targeting herd members predisposed to shedding elevated numbers of helminth eggs.     

Vetch toxicosis in cattle grazing Vicia villosa ssp dasycarpa and V benghalensis

SUMMARY The epidemiological, clinical and pathological features of a disease syndrome in adult cattle grazing woolly-pod vetch (Vicia villosa ssp dasycarpa) or popany vetch (V benghalensis) are reported. Outbreaks of toxlcosis occurred between midwinter and midsummer in 3 dairy and 6 beef herds on the north coast of New South Wales, between 1982 and 1992. Friesian, Angus, Murray Grey, Guernsey and Hereford breeds were affected. Mean morbidity and case fatality rates in affected herds were 7% (65 of 889) and 69%, respectively. Signs of pruritic dermatitis, illthrift and death were associated with an eosinophilic granulomatous inflammation of many organs, particularly involving the renal cortex, dermis, myocardium, adrenal glands, lymph nodes and hepatic portal triads.     

Seroprevalence of equine herpesvirus 1 in Thoroughbred foals before and after weaning

Objective To investigate the seroprevalence of equine herpesvirus 1 in foals around weaning and after weaning on two large Thoroughbred farms using a type-specific enzyme-linked immunosorbent assay to determine exposure to infection.
Design A longitudinal population study in groups of Thoroughbred weanling foals.
Study population Two hundred weanling Thoroughbred foals from a population of about 380 foals were enrolled on two adjacent stud farms in the Hunter Valley of New South Wales. Foals on both farms were weaned from February to May 1995 into randomly selected groups of 10 to 15 foals. Farms were selected because of their willingness to cooperate in the survey and because their detailed records of foals and their movements. They were representative of well-managed large Thoroughbred stud farms in New South Wales. Both studs had upper respiratory tract disease among weanling foals around weaning each year although the sero-prevalence of viral respiratory disease on either farm was not known before the study.
Procedure Serum was collected from foals within each group at fortnightly intervals from 9th February until 1st June 1995, and at a single follow-up period in August 1995. Each sample was tested in triplicate using an antibody-detection ELISA which is type-specific for EHV-1 and EHV-4 antibodies.
Results and conclusions There was serological evidence of EHV-1 infection both before and after weaning. The prevalence of EHV-1 antibody in the sample population increased during the study and individual cases of EHV-1 infection were identified. The increase was caused both by the seroconversion of foals within the groups and by the recruitment into the study of foals with pre-existing EHV-1 antibody. Evidence of EHV-1 infection in Thoroughbred foals after weaning has not been reported previously in Australia and this has implications for vaccination regimens.     

Elliptical selection experiment for the estimation of genetic parameters of the growth rate and feed conversion ratio in rabbits

Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C and R) in order to optimize the experimental design for estimating the genetic parameters of the growth rate (GR) and feed conversion ratio (FCR). Twelve males and 19 females from line C, and 13 males and 23 females from line R, were selected from an ellipse defined by a quadratic index based on these traits. Data from 160 rabbits of each of the parental generations of lines C and R and their offspring (275 and 266 animals, respectively) were used for the analysis. A Bayesian framework was adopted for inference. Marginal posterior distributions of the genetic parameters were obtained by Gibbs sampling. An animal model including batch, parity order, litter size, and common environmental litter effects was assumed. Posterior means (posterior standard deviations) for heritabilities of GR and FCR were estimated to be 0.31 (0.10) and 0.31 (0.10), respectively, in line C and 0.21 (0.08) and 0.25 (0.12) in line R. Posterior means of the proportion of the variance due to common litter environmental effects were 0.14 (0.06) and 0.21 (0.06) for GR and FCR, respectively, in line C and 0.17 (0.06) and 0.22 (0.06) in line R. Posterior means of genetic correlation between both traits were -0.49 (0.25) in line C and -0.47 (0.32) in line R, indicating that selection for GR was expected to result in a similar correlated response in FCR in both lines.     

Neuromuscular blocking properties of atracurium during sevoflurane or propofol anaesthesia in dogs

OBJECTIVE: To quantify the neuromuscular blockade (NMB) produced by atracurium in either sevoflurane or propofol-anaesthetized dogs. ANIMALS: Twelve healthy, female adult mixed-breed dogs weighing 13 +/- 3 kg (range 10-22 kg). MATERIALS AND METHODS: Three doses of atracurium (0.1, 0.2 and 0.3 mg kg(-1)) were tested at 1-week intervals. Anaesthesia was induced with inhaled sevoflurane or intravenous propofol and maintained with end-tidal sevoflurane concentrations of 1.95% (1.25 x MAC) or propofol 0.6 mg kg(-1) minute(-1) respectively. Acceleromyography and train-of-four stimulation of the fibular nerve were used for the assessment of NMB. The percentage depression of the first twitch (T1) and the fourth to the first twitch ratio (T4/T1), the maximum degree of neuromuscular block achieved and surgical muscle relaxation were recorded. Before and during neuro muscular blockade (at 10 minute intervals) body temperature, ECG, arterial blood pressure, inspired and expired CO2 concentrations and SpO2 were recorded. RESULTS: Atracurium produced a dose-dependent duration of NMB in both propofol and sevoflurane-anaesthetized dogs. Duration of block was longer in dogs anaesthetized with sevoflurane. All studied doses of atracurium caused twitch depression > or =95% with little or no cardiovascular changes. CONCLUSIONS: Sevoflurane produces a clinically relevant potentiation of atracurium-induced NMB in dogs compared with propofol. CLINICAL RELEVANCE: Significant differences in the potentiation of NMB drugs are encountered with commonly used anaesthetics in the dog.     

Perioperative desmopressin prolongs survival in surgically treated bitches with mammary gland tumours: a pilot study

Desmopressin (1-deamino-8-d-arginine vasopressin, also known as DDAVP) is a safe haemostatic compound capable of inhibiting lymph node and lung metastasis in a mouse model of mammary tumour manipulation and surgical excision. The aim of this study was to test the efficacy and safety of perioperative DDAVP (1microg/kg) in surgically treated bitches with mammary gland tumours (MGT). Twenty-one, otherwise healthy, intact bitches, with malignant MGT stage III or IV were randomly allocated to DDAVP (n=11) or placebo (n=10) groups. En bloc mastectomy of the affected gland/s was performed. DDAVP had a significant beneficial effect on disease-free period (P<0.01) and overall survival time (P<0.05). No side effects were seen in any of the cases. Whatever the mechanism of action, it seems that DDAVP may have a novel use in cancer surgery to minimise spread or survival of residual malignant cells. Additional, large scale controlled trials are required to fully evaluate this adjuvant pharmacological protocol.