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Biomedical subjects

R M Cannon

Publications and source records attributed to R M Cannon.

14 recordsLinked to original sources
PubMed2005

Determining the sensitivity of abattoir surveillance for ovine Johne's disease.

OBJECTIVE: The objective of this study was to determine the sensitivity of abattoir surveillance of intestinal tract lesions for detecting ovine Johne's disease (OJD) under normal meatwork conditions. DESIGN: The design of this study was a diagnostic test validation. The three OJD inspectors were the diagnostic test and follow-up histopathological examination was used for test validation. PROCEDURE: Approximately 1200 sheep were procured from known high prevalence OJD infected farms. The sheep viscera were tagged (numbered) and then examined as they were processed on the abattoir line by three experienced meat inspectors. Their observations were independently recorded on a cassette tape. Specified sections of viscera were prepared and subjected to histopathological examination and these results were compared with the inspector diagnoses. RESULTS: The sensitivity of abattoir inspection for OJD varied between inspectors from 53 percent to 87 percent. The specificity varied from 97 to 100 percent. It appeared that the level of sensitivity for detecting disease was higher in lines of sheep where the disease was more prevalent. It also appeared that formal training was an important aspect in ensuring a high level CONCLUSION: Abattoir surveillance is a very economical and rapid method of assessing the OJD status of sheep. On the basis of these results it is reasonable to suggest that abattoir surveillance has a sensitivity of approximately 70 percent. This technique is useful as an ancillary to other testing regimes for negative assurance programs where a sheep identification system is used.

Abattoirs↗
PubMed2002

Demonstrating disease freedom-combining confidence levels.

Part of the requirements for demonstrating disease freedom usually will be that sufficient testing be done to give a specified confidence of detecting the disease if it were present at a specified level. Often, this requirement is translated into a fixed testing regime that must be followed (an inflexible approach that might not be the most economic or practical solution).A more flexible approach is to specify the capabilities of the various tests that can be used to detect the disease, and let the party hoping to demonstrate disease freedom decide upon the testing regime. The question then arises as to how to combine information that can come from a variety of sources over a period of time to give an overall level of confidence. Two methods are given. The first, an exact method based on multiplying probabilities, would be more appropriate for a survey of an area in which no disease is thought to be present. The second method (more appropriate for a herd-assurance program within an infected area) is a point-based system that takes into account the different sensitivities of the methods used to detect disease and the change in prevalence over time. It allocates points for each test done proportional to the sensitivity of the test and the prevalence at the time of testing.

Animal Diseases↗
PubMed2001

Sense and sensitivity--designing surveys based on an imperfect test.

Designing a survey to detect the presence of a disease is complicated if the test used to detect the disease has non-perfect sensitivity and specificity. This paper gives two new approximations that simplify such a task. The first gives the cumulative probability distribution of the number of apparently diseased animals detected in the survey and the second gives the probability that no diseased animals are detected if the test used has 100% specificity. Both approximations can be used to determine confidence limits for the true prevalence. The main purpose of the approximations is to determine the number of animals that need to be tested to be confident that a herd is free of disease, and then to determine the number of herds that need to be tested to demonstrate area freedom. One approach to such an area survey has been to classify each herd as diseased or not based on the number of reactors found in the herd, and then to use the number of herds classified as diseased to determine the area's status. The paper points out that basing the decision simply on the magnitude of the maximum observed within-herd reactor proportion results in a more accurate survey for the same number of animals and herds tested.

Animal Diseases↗
PubMed1998

Viral haemorrhagic disease of rabbits and human health.

Viral haemorrhagic disease of rabbits (VHD), a potential biological control for wild rabbits in Australia and New Zealand, escaped from quarantined field trials on Wardang Island and spread to the mainland of Australia in October 1995. This study looked for any evidence of infection or illness in people occupationally exposed to the virus. Two hundred and sixty-nine people were interviewed and 259 blood samples were collected. Exposures to VHD-infected rabbits ranged from nil to very high. No VHD antibodies were detected in any of the 259 sera when tested by VHD competitive enzyme immunoassay, which had been validated with 1013 VHDV-specific antibody negative sera. A questionnaire designed to elicit symptoms of disease in a range of organ systems found no significant differences between illness in those exposed and those not exposed to VHD, nor could an association be found between exposure and subsequent episodes of illness. The findings are consistent with the view that exposure to VHD is not associated with infection or disease in humans.

Animals↗
PubMed1997

A review of Q fever in Australia 1991-1994.

Q fever continues to be an important disease in Australia. Despite the development of an effective vaccine that has been commercially available since 1989, the number of cases notified has continued to increase. This study reviewed national notifications of Q fever between 1991 and 1994, together with demographic, socioeconomic and occupational information, to investigate temporal and spatial disease patterns. Based on notification data, Q fever can be considered primarily a disease of adult males that occurs in eastern Australia: southern Queensland and northern New South Wales have the highest levels of activity. A significant association between Q fever activity of areas and the presence of livestock was found. A strong association with the meat industry was also confirmed. Q fever is conservatively estimated to cost Australia around A$1 million and more than 1700 weeks of work time annually. There is a need to increase awareness of this disease and its prevention. An extension program in rural communities and provision of vaccine to all abattoir workers would appear to be sensible public health approaches.

Adolescent↗
PubMed1997

A national serological survey to verify Australia's freedom from porcine reproductive and respiratory syndrome.

OBJECTIVE: To provide serological data to support Australia's claim of freedom from porcine reproductive and respiratory syndrome. DESIGN: A national serological survey was designed to provide 99% confidence of detecting at least one infected pig herd in Australia, assuming that at least 5% of herds would have been exposed to porcine reproductive and respiratory syndrome virus and that at least 25% of the 'finisher' pigs in these herds would have antibodies to the virus. PROCEDURE: A two-stage testing regime was used. All samples were tested with a commercially available enzyme-linked immunosorbent assay. If assay reactions were found, all samples from the herd were to be tested using the indirect immunofluorescence antibody assay. RESULTS: Of the 875 samples from 163 herds from all States in Australia, there was some evidence of reactivity in only four samples from four herds on the enzyme-linked immunosorbent assay. Further testing using the indirect immunofluorescence antibody assay according to the study protocol demonstrated that the reactions were not due to the presence of specific porcine reproductive and respiratory syndrome virus antibodies in the sera. CONCLUSION: The results of this study support the view that Australian pigs are free of porcine reproductive and respiratory syndrome virus.

Animals↗
PubMed1993

Treatment of tibial defects and nonunions using ipsilateral vascularized fibular transposition.

Eight patients had nine ipsilateral vascularized fibular transpositions (IVFTs) in the period 1978-1987. The procedure, which involves no microvascular anastomosis, was done for difficult problems of the tibia including two long-standing posttraumatic nonunions, three allograft nonunions after tumor surgery, and four segmental tibial defects also after tumor surgery. The average duration of problems before surgery was 3.5 years, and the patients averaged 3.1 procedures before IVFT. The patients were followed for an average of 52.4 months. The average time to union was 4.2 months, and in all patients the grafts healed within six months. Late fracture of the graft developed in two patients after fixation removal; one required an additional procedure, and both eventually healed. Ipsilateral vascularized fibular grafting is a useful alternative to conventional, nonvascularized grafts for difficult tibial nonunions and segmental defects. It offers the advantages of a vascularized graft (early healing and hypertrophy), yet avoids the time-consuming microvascular anastomosis and distant donor site morbidity of free fibular grafts.

Adult↗
PubMed1989

Increased peritoneal fluid lactic acid values and progressive bowel strangulation in dogs.

In the present study, we determined values for peritoneal fluid and blood ammonia, amylase, and lactic acid content in 11 dogs after experimental bowel strangulation. In the nine survivors of this group, we demonstrated a near linear increase in peritoneal fluid lactic acid over a 24-hour period, during which the plasma lactic acid remained relatively constant. A significant increase in peritoneal fluid ammonia was also demonstrated, but this did not occur until more than 16 hours after strangulation. In a second group of two dogs in which simple obstruction was produced, no significant increase in peritoneal fluid lactic acid or ammonia occurred. We did not find significant changes in peritoneal fluid amylase in this study. These data suggest that the determination of peritoneal fluid lactic acid content, especially when compared with concomitant plasma lactic acid, may be useful in the accurate preoperative diagnosis of bowel strangulation.

Ammonia↗
PubMed1978

A health program for commercial dairy herds. 2. Data processing.

The development of a computerised data handling and analysis system to aid the operation of a health and management program for commercial dairy herds is described. The aims for the system are outlined, and the development of the system over a period of 8 years to meet these aims is described. The documentation used in the current system is described in relation to the various procedures involved in the operation of the dairy herd health program. Two features which make this system unique are its use for the selection of problem and high risk cows for examination and treatment, and the provision of analyses of recent performance in a number of facets of health and production, which aid in the identification of emerging problems. It is considered that future improvements in the system will be in the areas of milk production recording and calf rearing and disease recording.

Animals↗
PubMed1978

A health program for commercial dairy herds. 3. Changes in reproductive performance.

A health program service was implemented on 9 farms, for periods ranging up to 7 years. Reproductive performance was substantially improved, when performance indicators were compared with values for the herds prior to commencement of the service. On average, the mean calving to conception intervals for the herds were reduced by 24 days over their periods of participation in the program, from an initial value of 119 days. The intercalving interval was reduced by an average of 27 days. This improvement was associated with a reduction in the mean dry period length of 20 days, from an initial value of 117 days. There was a tendency for the lactation lengths to be reduced to an undesirable extent due to slow adaptation by management to the improvement in reproductive performance, but the problem was corrected late in the study. The improvement in performance was attributed to improved oestrus detection, correction of temporary nutritional deficiencies, and prompt treatment of genital tract disorders in individual animals. Results for a range of performance indicators related to reproductive function are reported in detail.

Abortion, Veterinary↗
PubMed1978

A health program for commercial dairy herds. 4. Changes in mastitis prevalence.

A study of mastitis prevalence in 10 herds which participated in a herd health program is reported for varying periods, up to a maximum of 10 years. The program was based on teat dipping with idophor or sodium hypochlorite teat dip, regular maintenance of the milking machine, and selective dry period treatment of quarters which were classified as infected on the basis of California Mastitis Test score and bacteriological examination of milk samples taken before drying off. The procedures reduced mastitis prevalence (measured in cows being dried off), incidence of clinical mastitis, and disposal of cows due to mastitis. Results obtained were similar to those found in short-term studies of control programs based on teat dipping and dry period therapy. The only significant difficulty which arose in maintaining the control program over 10 years was loss of enthusiasm by farmers for teat dipping. This was usually induced by teat irritation problems apparently caused by teat dipping. The use of a monitoring procedure for mastitis prevalence was important in persuading farmers to return to the use of teat dip.

Animals↗
PubMed1978

A health program for commercial dairy herds. 5. The occurrence of specific disease entities.

Disease incidence data was collected from 9 dairy herds which participated in a herd health program. A total of 11,534 cow years was analysed. In common with other Australian data, the important clinical diseases were mastitis and infertility. There was an average level of 43.4 disease incidents per year per 100 animals at risk. An average of 18.6% of the herd left each year. This comprised 1.5% through death and 17.1% through sale. Disease accounted for the disposal of 9.8% of animals, and management reasons for 8.8%. These findings are similar to those of other studies in Australia and in other countries, but the results in this study were based on a longer period and on closer surveillance.

Animals↗
PubMed1978

A health program for commercial dairy herds. 1. Objectives and methods.

A health program for dairy herds is defined as a planned and coordinated approach to achieving and maintaining optimal health and productive efficiency of livestock. A program is described, which has been developed over a period of eight years to fulfill this definition in providing veterinary services to commercial dairy herds. It is demonstrated that clinical veterinary services to participating herds did not satisfactorily achieve the stated aim and therefore an alternative approach was developed. This approach is centred around the concept of performance targets, and each herd is monitored closely by means of a computer-based health and productivity monitoring system in order to detect deviation from target performance. When such deviations occur, the monitoring system is used to diagnose the nature of the problem. The detailed targets adopted in this study are described and the examinations which are undertaken on cattle are outlined. These examinations are aimed at correcting problems, or at confirming satisfactory performance. Further details of the findings of the study are outlined in following papers.

Animals↗