Biomedical subjects
Publications and source records attributed to I R Morgan.
A family of tetrahydroxy diesters has been synthesised and observed to gel a range of fluorinated solvents and their mixtures; the phase behaviour and gel microstructure are reported for a homologous family of these diesters in blends of 1H,1H-heptafluorobutanol (HFB) and 2H,3H-perfluoropentane (HPFP).
The microbiological quality of carcases, meat and environmental surfaces was evaluated in commercial boning rooms processing beef and lamb. There was considerable variation in the level of microbial contamination on both carcases and meat, with counts ranging from less than 20 to 10(8)/cm2 on carcases and to 2 x 10(7)/cm2 on meat. The level of microbial contamination on meat was influenced by the level of carcase contamination at boning and by the boning process itself. Carcase contamination was the major determinant of microbiological quality, as more than 70% of carcase had microbial counts greater than 10(3)/cm2. Cutting boards were a major source for microbial dissemination during boning, particularly when carcase counts were less than 10(3)/cm2. If carcases were heavily contaminated, the contamination of processing surfaces was irrelevant in determining microbial loads on meat. Where carcase contamination was at low to moderate levels, the contribution of the boning process to the contamination on meat assumed increased significance. Under these conditions, improved sanitation of cutting surfaces in the boning room resulted in a significant reduction in microbial contamination on the surface of meat. These results can form the basis for ensuring that improvements made in carcase management before boning, to improve microbiological quality, will be preserved through attention to cutting board hygiene during boning.
A spreadsheet program was written to perform decision tree analysis for control of paratuberculosis (Johne's disease), when testing all adults in a herd and culling all animals with positive test results. The program incorporated diagnostic test sensitivity, specificity, and test cost with the cost or value of each of the 4 possible outcomes; true-positive, true-negative, false-positive, and false-negative test results. The program was designed to repeat the analysis for the independent variable pretest paratuberculosis prevalence (0 to 100%). Model output was graphed as profit or loss in dollars vs pretest prevalence. The threshold was defined as the pretest prevalence at which benefit-cost equaled zero. Reed-Frost disease modeling techniques were used to predict the number of Mycobacterium paratuberculosis-infected replacement heifers resulting from infected cows during a control program. Sensitivity analysis was performed on variables of the decision tree model; test sensitivity, specificity, test cost, and factors affecting the cost of paratuberculosis to a commercial dairy. A test and cull program was profitable when paratuberculosis caused greater than or equal to 6% decrease in milk production if the pretest prevalence was greater than 6%, test sensitivity was 50%, test specificity was 98%, and the testing cost was $4/cow. Test specificities greater than 98% did not markedly affect the threshold for tests with a 50% sensitivity and costing $4/cow. Test sensitivity had minimal effect on the threshold. Using a diagnostic test with a 50% sensitivity and a 98% specificity as an example, test cost was shown to affect the threshold prevalence at which the test and cull program became profitable.(ABSTRACT TRUNCATED AT 250 WORDS)
A commercially available absorbed ELISA for the diagnosis of Johne's disease (JD) (paratuberculosis) in cattle, the Johne's Absorbed EIA, was compared with the conventional complement-fixation test (CFT) used in Australia. Stored plasma from 3 Victorian dairy herds with a history of JD, sera from specimens submitted from animals showing clinical signs of JD and sera from the US National Repository for Paratuberculosis Specimens were used to determine the sensitivity of each test. The EIA detected 48.8% of 43 Australian animals with subclinical JD, while the CFT detected only 12 (21.4%) of 56 subclinically affected cattle. Of 150 subclinically infected US cattle, the EIA detected 47.3% and the CFT detected 52.0%. The EIA detected 59.7% of animals which at the time of sampling were shedding Mycobacterium paratuberculosis in their faeces, but showed no clinical signs of JD, while the CFT detected 57.3%. The EIA correctly identified 88.2% of 136 histologically confirmed clinical cases, and the CFT detected 83.4%. The specificity of each test was determined by testing sera collected at slaughter from animals residing in a known JD-free area of Australia, and from samples from the US National Repository of Paratuberculosis Specimens collected from certified-free herds in Wisconsin. The EIA was found to have a specificity of 99.8% when 998 Australian animals were used as the test population, and 99.0% when 196 US animals were used. The specificity of the CFT using Australian samples was 96.9% and 95.2% using American samples.
In May 1985 an outbreak of avian influenza, a disease exotic to the Australian poultry industry, occurred on a farm in central Victoria. The outbreak was contained on that farm by immediate depopulation and disinfection measures. A description of the epidemiology of the outbreak was made during and after the event by interviewing involved personnel and by an extensive sampling and surveillance program both on the affected farm and across Victoria. Although the origin of the infection was not established, it is considered most likely that wild birds introduced the virus. The infection status of wild bird populations in the area has not been ascertained but sampling surveys of the poultry industry indicated that there were no other infected flocks in the state. The infection may have entered the affected flock as long as 2 weeks prior to the clinical outbreak although the exact timing could not be ascertained. The spread of disease on the farm appeared to be largely due to humans acting as mechanical vectors.
Samples were collected at two abattoirs from four sites on pig carcasses as they were being placed in a chiller. Bacteriological examination showed that no single sampling site could be used to assess the microbiological status of pig carcass surfaces. Sampling from multiple sites on a carcass may be required to assess the degree of contamination by different bacteria. It is suggested that the hygiene of slaughtering and dressing of pig carcasses at an abattoir cannot be assessed on a single visit and that a number of visits are necessary to establish a hygiene pattern.
A longitudinal study of the effect of time spent in lairage on salmonellas in the caecum and on the skin surface of 450 slaughter pigs from a single producer was conducted. Pigs were tested in 6 groups at 2 abattoirs, with one-third of a group being slaughtered after 18 h, one-third after 42 h and one-third after 66 h spent in lairage. The salmonella isolation rate from caeca and carcass surfaces increased significantly with increasing time spent in lairage. Salmonellas were isolated from the caeca of 18.5% of pigs held less than 24 h in lairage, 24.1% of pigs held a further 24 h and 47.7% of pigs held for 66 h in lairage before slaughter. The salmonella isolation rates from carcasses were 9.3%, 12.8% and 27.3% for the same groups. Thirteen salmonella serotypes were isolated from the caecal contents and carcasses over the 6 weeks of the trial. One abattoir had a higher salmonella isolation rate from pigs than the other and this was probably related to lairage management. It appeared that lairage is an important factor in the manipulation of the salmonella contamination of pig carcasses.
Fifty cattle thought not to be infected with Brucella abortus but giving persistent positive serological reactions, were investigated. It was concluded that only one of these was infected since exhaustive bacteriological examination produced only one isolate of B. abortus (strain 19) and none of the herds of origin was subsequently shown to be infected with brucellosis. Antibody was detected in stifle joint fluid of 15 cattle, which may have been stimulated by the presence of Strain 19 antigen that persisted in collagenous tissue long after the viable organisms had been eliminated.
A swabbing technique was compared with an excision and maceration technique for bacteriological sampling of pig carcass skin surfaces. Total viable counts at 37 degrees C obtained by swabbing were 46% of those obtained by maceration. At 21 degrees C, swabbing gave total viable counts which were 54% of the counts obtained from excision samples. Escherichia coli counts showed wide variation with both sampling methods. Neither method was more efficient than the other in recovering E. coli, although excision sampling gave generally higher counts. Both methods were equally effective at recovering salmonellae from carcass surfaces. There was no significant difference between the methods in recovering particular Salmonella serotypes.
Serum antibodies to strains of avian paramyxovirus and flavivirus were detected in little blue penguins sampled at Port Campbell and Phillip Island, Victoria, Australia. No antibody to Newcastle disease virus (NDV) was detected in 267 sera collected, although one penguin captured for experimental studies had a hemagglutination-inhibition antibody titer of 2(4) to this virus. Experimental studies showed that the avian paramyxovirus designated APMV-IM and strain V4 of NDV were non-pathogenic for penguins, although the penguins could have been previously infected with these or similar virus strains. A flavivirus designated Saumarez reef virus, and an unnamed virus isolated from ticks on Macquarie Island, Southern Ocean were pathogenic causing disease and mortality in penguins inoculated with the viruses.
Serums from 1002 penguins of 4 species on Macquarie Island, a sub-antarctic island in the Southern Ocean, were examined for antibody to Newcastle disease virus (NDV), influenza A virus, avian paramyxovirus, alphavirus and flavivirus. No evidence of haemagglutination-inhibition antibody to influenza A virus or alphavirus was detected. Serums from 6% of royal penguins sampled gave positive reactions to NDV while the other 3 species were negative. Antibody to a flavivirus and an avian paramyxovirus, other than NDV, was detected in 3 of the 4 penguin species. Cloacal swabs from 831 penguins of 4 species were examined for the presence of viruses. Six isolated of paramyxovirus, other than NDV, were obtained from swabs taken from royal and king penguins at 2 widely separated sites on the island.
Two cases of leptospirosis due to infection with a member of the Hebdomadis serogroup are described in farm workers on a Victorian dairy farm. The source of infection appeared to be the milking herd which had elevated serum antibody titres against a member of the Hebdomadis serogroup. Agglutinin-absorption testing of one patient's serum indicated that the infecting serovar was hardjo. A survey of 1,144 cattle entering abattoirs throughout the State indicated that 44.3% of these animals showed serological evidence of past or present infection with leptospira of the Hebdomadis serogroup and the potential risk for people with occupational contact with cattle is emphasised. The importance of considering leptospirosis in the differential diagnosis of all patients with influenza-like symptoms or pyrexia of unknown origin and having occupational contact with animals, especially cattle, is discussed.
The epizootiology of ephemeral fever in Australia from its first recognition until 1968 was reviewed. Since 1968, ephemeral fever often in a silent form has been shown to be enzootic in northern Australia, by the use of sentinel cattle. The major epizootics which occured in 1970-1971, 1972-1974 and 1974-1975 are described. These epizootics were characterised by an apparently rapid movement of disease in a general north-south direction in summer months. Ephemeral fever antibody was detected in 11% of 1009 domesticated and feral water buffaloes.
Ten viruses isolated from swabs and vesicular fluid collected from the teats of dairy cattle on 4 properties in Northern Victoria were identified as bovine herpes mammillitis (BHM) viruses by their physico-chemical and morphological properties and serological relationship to each other and a Scottish Strain of BHM virus. The viruses, isolated in bovine kidney and testicular cell cultures, produced cytopathic effects characterised by very large syncytia and eosinophilic intranuclear inculsion bodies. The intradermal inoculation of BHM virus into two cattle produced necrosis and ulceration of the skin of the teats about the area of inoculation and the development of serum neutralising antibody. After healing of the ulcers on day 37 after inoculation, the cattle were intravenously inoculated with corticosteroid for 6 days but BHM virus was not re-isolated from the teat skin or vaginal or nasal swabs.
The occurrences of bovine herpes mammillitis in the Cohuna and Numurkah districts of northcentral Victoria is described. The disease was characterised by painful swollen teats, necrosis of variable areas of the teat skin, formation of blue-black scabs which sloughed leaving ulcers which were slow to heal. The outbreaks occurred during tspring months of October to mid-December when as many as 90% of milking cows in herds became infected. Epidemiologically the infection behaved as though it was transmitted by insects but proof of insect transmission was not attempted.
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