A cross-sectional study to show Eperythrozoon ovis infection is prevalent in Western Australian sheep farms

A serological survey and risk factor study was conducted to estimate the prevalence of Eperythrozoon ovis infection in Western Australian weaner sheep, the prevalence of farms with infected sheep, and to identify factors affecting initiation and maintenance of infection on the farm. The study was conducted on 91 farms, purposively chosen from 41 randomly selected regional shires stratified by sheep number and rainfall zones. Twenty sheep were selected systematically from a mixed-sex flock on each farm and tested for serum antibody to E ovis using an enzyme-linked immunosorbent assay. Information on putative risk factors was collected using an interview questionnaire. Antibody to E ovis was detected in 4.5% of sheep on 47% of the farms sampled. The prevalence of E ovis infection in sheep was estimated at the 95% confidence level to be between 3.6 and 5.5%, and the prevalence of farms with infected sheep was estimated to be between 37.5 and 56.5%. Most farms with serological evidence of infection occurred in the Great Southern agricultural region (79.5%), south-east of Perth through to Albany (latitude 32 to 34 degrees S, longitude 116 to 120 degrees E), and in the Northern region (12.8%) surrounding Geraldton (latitude 29 degrees S, longitude 114 degrees E). There were significantly more farms (P less than 0.05) with evidence of infection in the Great Southern region compared to the Central region between Geraldton and Perth, and on farms in the region south compared to north of latitude 32 degrees S. None of the putative risk factors examined in the questionnaire were associated with serological evidence of infection on the farm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidemiology of salmonellosis in the live sheep export industry

SUMMARY Salmonellosis in sheep was studied on 7 commercial voyages from Australia to the Middle East and in one animal house study. Faecal excretion of salmonellas was not a good indicator of pathological changes in the gastrointestinal tract. The ratio of the proportion of sheep excreting salmonellas to the proportion with histological lesions of salmonellosis ranged from 1:1 to 23:1. Increasing excretion rates in our studies indicated that most sheep would be exposed to infection, although deaths from salmonellosis were not spatially or temporally clustered as would be expected if challenge alone was a sufficient cause. We considered that inappetence predisposed to death from salmonellosis, and that sheep with inappetence were likely to be randomly distributed aboard ship. In the animal house study, histological lesions of salmonellosis were exclusively in inappetent sheep although almost all sheep excreted salmonellas in faeces. Lesions of salmonellosis were found only in sheep that were seriously ill or had died, which suggested that, under the conditions of lot-feeding and sea transport, most sheep with enteric lesions are likely to die. Lesions were not found in feeding controls. Adrenal gland weights, an indicator of stress duration and severity, were used to examine the temporal sequence of events in the development of salmonellosis. Weights were greater in sheep that died of inanition than in controls, suggesting that inappetent sheep were already stressed for that reason. The presence of enteric lesions of salmonellosis was associated with further increases in adrenal gland weights. In a small proportion of cases, septicaemic salmonellosis developed rapidly and without adrenal gland hypertrophy suggesting that the sheep succumbed before the adrenal glands had time to enlarge. We concluded that sheep were predisposed to salmonellosis by inappetence and that stress was involved in lesion development. We considered that the development of enteric lesions of salmonellosis, in the live export system, inevitably led to death.     

Identification of lymphocytes in the epidermis of the rainbow trout, Salmo gairdneri Richardson

Abstract The presence of lymphocytes in the epidermis of the rainbow trout, Salmo gairdneri Richardson, was confirmed by light and electron microscopical observation and by the use of an indirect immunocytochemical technique utilizing peroxidase-labelled antibody. These results are compared with those of other workers and the source and function of these cells in the epidermis of teleosts is discussed.     

An epidemiological study of sheep deaths before and during export by sea from Western Australia

A study was conducted to record the deaths that occurred during export, and to examine the temporal pattern of pellet feeding in the feedlot and ascertain the variation in mortality between groups of sheep from different farms. Between November 1985 and April 1987, 5 cohorts of sheep were selected on arrival at a feedlot before live export by sea from Western Australia to the Middle East. Each cohort consisted of 4,118 to 9,612 Merino wethers from 15 to 35 farms (lines). There were few deaths during trucking to the feedlot (rate 0.9, range 0.0 to 3.0 per 10,000 sheep) and during lot-feeding (rate 6.2, range 1.2 to 12.2 per 10,000 sheep). Most of the deaths occurred aboard ship (rate 210.7, range 152.7 to 271.5 per 10,000 sheep). The proportion of sheep that ate pelleted feed increased with increasing length of time in the feedlot. By the end of lot-feeding the percentage of sheep that had not eaten pellets was 23.3, 4.4, 1.2, 2.1 and 0.2 in a representative sample of each of the 5 cohorts. It was considered that offering hay throughout lot-feeding was undesirable for the purpose of maximising the number of sheep that ate pellets before loading on the ship. Half of the deaths aboard ship occurred in 25% of 133 lines of sheep in the 5 cohorts. In each cohort the median per cent death rate (and range) per line was 1.3 (0.3 to 11.9), 1.1 (0.0 to 5.7), 1.8 (0.0 to 6.8), 2.3 (0.0 to 14.3) and 0.9 (0.1 to 5.4).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ovine congenital progressive muscular dystrophy: clinical syndrome and distribution of lesions

The distribution and severity of lesions in the skeletal muscles of 37 Merino sheep with congenital progressive muscular dystrophy (CPMD) are described. An explanation for the clinical signs is offered on the basis of functional defects in regional muscle groups. Lesions in the extensors of the hip, stifle and hock joints and flexors of the digits are primarily responsible for the progressive abnormality of hind limb gait that is characteristic of the clinical syndrome. Lesions in extensors of the elbow and flexors of the shoulder, carpus and digits affected fore limb function in advanced cases. The tendency for some affected sheep to develop ruminal tympany is probably caused by lesions in the diaphragmatic crus. Clinically affected sheep had higher resting and post-exercise concentrations of serum creatine phosphokinase and lactic dehydrogenase than unaffected control sheep. The rise in serum creatine phosphokinase after exercise was greater in affected sheep than in controls. Myotonia was not demonstrated in electromyographic studies in one sheep.     

Differences in cerato-ulmin production between the EAN, NAN and non-aggressive subgroups of Ophiostoma ulmi

A test of comparative in vitro cerato-ulmin wilt toxin production in the aggressive and non-aggressive subgroups of the Dutch elm disease pathogen Ophiostoma ulmi was carried out by turbidity and ELISA methods. Ten non-aggressive, ten EAN aggressive and ten NAN aggressive isolates were tested from a range of geographical sources. In liquid shake cultures the non-aggressive isolates produced the greatest and the NAN aggressives the least mean biomass. Despite considerable variation in cerato-ulmin production by individual isolates in three separate experiments, both the turbidity and ELISA methods showed a clear separation of the non-aggressive and aggressive subgroups. Non-aggressive isolates produced little or no cerato-ulmin (ELISA range of means 0–56.0 ng/ml) and EAN and NAN aggressive isolates moderate to high levels (EAN 1.6–89.0 × 10⁴ ng/ml and NAN 0.2–300 × 10⁴ ng/ml). In the aggressive isolates no correlation was detected between cerato-ulmin production and either biomass or pathogenicity to clonal Commelin elm. The role of cerato-ulmin in the pathogenicity of O. ulmi is discussed.     

An investigation of the parameters of anticoagulant treatment efficiency1

The traditional technique of applying anticoagulant rodenticides, as shaped by long experience in the use of low-toxicity, first-generation anticoagulants such as warfarin, aims to maximize treatment efficiency by maximizing the rate of bait consumption by the target rodents. This is done, somewhat laboriously, by laying surplus amounts of bait initially, and maintaining this surplus throughout the treatment by repeatedly replenishing the bait placements. The suggestion that the high toxicity of the second-generation anticoagulants should enable a more efficient baiting system to be designed is examined experimentally in this field study of the control of Rattus norvegicus on British farms. Bait toxicity, infestation size and the incidence of complete takes of bait were found to be independent and highly significant determinants of treatment duration whilst, in comparison, the size and density of bait points and the frequency with which the bait was replenished were found to be relatively unimportant. However, bait size and, more especially, replenishment frequency had detectable secondary effects, apparently through partial relationships with the incidence of complete takes and infestation size. The results indicate, in relation to the control of commensal infestations of R. norvegicus on British farms, that the use of high-toxicity bait formulations and frequent replenishment schedules increase the speed of control, whilst the number and size of bait placements are relatively unimportant; they also suggest that reductions in the frequency of bait replenishment made in order to save labour could be compensated for by increasing the toxicity of the bait and taking other steps to reduce the incidence of complete takes of bait. The results are discussed in relation to the concept of ‘pulsed baiting'.