Seasonality of sarcoptic mange in pigs in South Australia

Retrospective analysis of records, from July 1987 to June 1991, of 1140 inspections of slaughtered pigs from 154 swine herds in the Pig Health Monitoring Scheme of South Australia was conducted to evaluate patterns of variation in the prevalence and severity of skin lesions typical of sarcoptic mange. An increase in the severity of sarcoptic mange in winter and spring was observed. There was a substantial reduction in the severity of mange over the period of monitoring. These observations support the role of monitoring at slaughter in the management of endemic disease. They provide some basis for refining control programs for mange to improve cost-effectiveness.     

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)     

Detection of Clostridium perfringens epsilon toxin by ELISA

An enzyme-linked immunosorbent assay (ELISA) has been developed as an alternative to neutralisation tests in mice to detect Clostridium perfringens type D epsilon toxin in the intestinal contents of animals which have died from suspected enterotoxaemia. The test was sensitive and quantitative and gave excellent agreement with the mouse protection test.     

Insights into enzyme function from studies on mutants of dihydrofolate reductase

Kinetic analysis and protein mutagenesis allow the importance of individual amino acids in ligand binding and catalysis to be assessed. A kinetic analysis has shown that the reaction catalyzed by dihydrofolate reductase is optimized with respect to product flux, which in turn is predetermined by the active-site hydrophobic surface. Protein mutagenesis has revealed that specific hydrophobic residues contribute 2 to 5 kilocalories per mole to ligand binding and catalysis. The extent to which perturbations within this active-site ensemble may affect catalysis is discussed in terms of the constraints imposed by the energy surface for the reaction.     

Laboratory study of Mycobacterium bovis infection in badgers and calves

Two experiments with badgers infected with Mycobacterium bovis are described. In the first, badgers were infected by intravenous inoculation of a bovine isolate of M bovis. The course of the disease in these and its spread to healthy badgers and calves was monitored by clinical, immunological and bacteriological means. In the second experiment a group of naturally infected badgers were observed for a period of up to four years. They were found to excrete M bovis in their faeces for periods of between 165 and 1305 days before they died of tuberculosis or were killed. M bovis was also shed in the urine. The badgers in both experiments were examined regularly and blood samples were taken for complement fixation tests. Faeces, urine, pus and sputum were also collected for cultural and biological tests and the badgers were skin tested using Weybridge bovine and avian tuberculin. The skin tests were uniformly negative while the complement fixation test were positive in some infected badgers but gave very variable results. Only the isolation of M bovis gave a definite diagnosis of tuberculosis in the living badger but a number of badgers which were found to have tuberculosis at post mortem were not detected while alive by this method. Environmental samples from the yards, including badger faeces, soil, hay, scrapings from feeding bowls and water were regularly examined for the presence of M bovis but apart from faeces only one water sample was positive, indicating that the organism did not persist for long in the environment. In both experiments calves developed sensitivity to bovine tuberculin after six months' exposure to infected badgers. The experiments further demonstrate the potential of a badger population to become endemically infected with M bovis and to act as a source of infection for cattle.     

Oral fluid therapy in neonatal ruminants and swine

Definitive recommendations regarding the best method to treat the diarrheic calf cannot be made at this time. The exact recommendation will probably depend on the situation. At the present time, I do not believe it is detrimental to withdraw milk from the diet for periods up to 24 to 36 hours, as long as the calf is in good condition and is returned to a full ration (maintenance plus) of milk within 3 to 5 days from the start of milk withdrawal. Milk withdrawal is most likely to be beneficial in those situations in which the calf is depressed and has lost its sucking reflex. Oral electrolyte solutions should be fed at the rate of 4-6 L/day if diarrhea is profuse or if the calf is depressed. As the calf feels better and the severity of diarrhea decreases, the amount of oral electrolyte solution can be reduced. It is sensible to continue feeding oral electrolyte solution, perhaps at the rate of 2 L/day, as long as the calf scours. Products containing 40-80 mEq/L of alkalizing agent give the best results. The higher concentrations may be more effective in older calves. Products containing bicarbonate or metabolizable base can be used when the calf is held off milk, whereas only solutions that contain a metabolizable base should be used if the calf is fed milk that day. Milk withdrawal may only be beneficial in calves that are losing their interest in sucking. Early reintroduction to milk and avoidance of milk deprivation in bright calves will help maintain condition and may boost immune function and mucosal repair. Calves that are held off milk for more than 2 days and calves that are deprived of milk while in poor condition should be fed a high-energy electrolyte solution. Beef calves tend to be treated while they are still on the dam, and if they are separated from the cow, it is usually only for a short period. This maintains the cow's lactation and maternal instincts. Cow's milk is better digested than many milk replacers and is available at a steady rate because calves suck frequently. Calves maintained on cow's milk should be fed an oral electrolyte solution containing a metabolizable base. Gastric fill from the electrolyte solution will tend to reduce milk consumption. It is important to prevent the calf from gorging on milk, which sometimes happens when a calf that is depressed and not sucking regains its appetite and has access to a very full udder. Cows that have been separated from their calf or that have distended udders should be milked out.     

Risk factors for mortality from diarrhea in beef calves in Alberta.

A case-study involving 56 randomly selected beef herds in Alberta was conducted to assess the association of a number of suspected risk factors upon the odds of a high mortality from diarrhea among calves less than 30 days of age. Using stepwise logistic regression it was found that an increased percentage of heifers calving in the herd, poor drainage in the nursing area, providing limited shelter in the nursing area, a large calving area, and wintering cows and heifers on the same ground were conditionally associated with an increase in the odds of high mortality from neonatal diarrhea.