Ovine Johne's Disease (ovine + johne_disease)

Distribution by Scientific Domains

Selected Abstracts


Bernadette Hood
Objective: This paper explores the psychosocial outcomes for individuals and communities in rural Victoria who experienced the outbreak of Ovine Johne's Disease (OJD). Design: The study uses a qualitative methodology to analyse the minutes of evidence provided by the inquiry into the control of OJD to identify the psychosocial events, experiences and outcomes associated with the control of this outbreak. The inquiry was undertaken by the Environment and Natural Resources Committee of the Victorian State Government. Setting: Public hearings were undertaken by the committee across several rural Victorian communities and the state capital, Melbourne. Subjects: The transcripts detail 136 submissions from 98 individuals and 23 organisations. Outcome measures: The analysis aimed to provide insight into the impact of the disease on individuals and communities and also to explore the factors individuals perceived as associated with these outcomes. Results: While the paper identifies that aspects of stock loss associated with the outbreak caused substantial emotional and economic distress, for farmers the most significant finding was the impact of the government control program on individuals, families and rural communities. The control program was perceived as having very limited scientific credibility and its implementation was described as heartless, inflexible and authoritarian. Involvement with the program resulted in farmers reporting emotions, such as, trauma, shame, guilt and stigma. Families became discordant and the sense of community within rural townships fragmented. Psychological outcomes of grief, depression and anxiety emerged as prevalent themes within families and communities. Conclusions: These data highlight the need for significant attention to the management of rural disasters, such as, the OJD program. [source]

Financial modelling of the potential cost of ovine Johne's disease and the benefit of vaccinating sheep flocks in southern New South Wales

RD Bush
Objective To develop an enterprise gross margin (GM) model that predicts the on-farm financial impact of ovine Johne's disease (OJD) for various sheep enterprises in Australia. In addition, to estimate the benefits and costs of control through the use of the GudairÔ vaccination, including a breakeven point. Design and population Data for the model was gained from an observational study conducted over a 3-year period from 2002 to 2004 using sheep from 12 OJD-infected flocks from southern New South Wales. Flocks ranged between 3500 and 20,000 sheep, with owner estimates of 5% or greater OJD mortality at the start of the study. Procedure A GM model was developed to predict the on-farm financial impact of OJD for various sheep enterprises in Australia, comparing non-infected, infected (status quo) and infected (vaccination) disease scenarios. Results Vaccination breakeven points are achieved within 2 to 3 years for breeding enterprises if OJD mortalities are high, rising towards 7 years for a Merino ewe enterprise if OJD mortalities are low. Conclusion The GM model demonstrates the returns to investment of vaccination for Australian sheep producers with OJD-infected flocks. [source]

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 of sensitivity. 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. [source]

Longitudinal study of the spread of ovine Johne's disease in a sheep flock in southeastern New South Wales

Objective The aim of this study was to apply whole flock testing over time to determine the prevalence, distribution and spread of infection in a recently infected flock, with a view to planning intervention strategies for disease control. Procedure Serology, pooled faecal culture (PFC) and histology were used to determine the distribution and persistence of infection in a sheep flock in south east New South Wales between 1997 and 2002. Partial flock testing was done up to June 2000, after which annual whole flock testing, using PFC was performed. Results Faecal shedding of M a paratuberculosis was not detected in home-bred sheep until 7 years after the introduction of infected sheep in 1993. For at least 7 years there was clustering of infection and shedding within two age groups only. The infected groups appeared to have been exposed to infection (mycobacterial contamination) at an early age (< 12 months) and commenced shedding at 5 years of age or older. Groups that were exposed to contamination as adults did not shed detectable amounts of M a paratuberculosis during the study period. Conclusion Clustering of detectable infection in age groups of sheep that were exposed as lambs was a feature on this farm, providing indirect evidence of finite duration of survival of M a paratuberculosis on pasture and the influence of age on the susceptibility of sheep to develop detectable M a paratuberculosis infection. Spread of infection occurred very slowly and was probably related to the long incubation period (exposure to shedding interval) of 5 years observed on this farm. The findings suggest that partial flock culling, selective grazing management and vaccination could lead to a reduction in mycobacterial contamination on farm to a level at which patent infection no longer occurs. Better understanding of disease spread within flocks over time through flock profiling using PFC will help in devising surveillance strategies (including testing protocols for market assurance testing) to detect infected flocks where there has been clustering and slow spread of infection. [source]

Temporal patterns and quantification of excretion of Mycobacterium avium subsp paratuberculosis in sheep with Johne's disease

Objectives To determine the frequency of excretion of Mycobacterium avium subsp paratuberculosis in Merino sheep with Johne's disease and to quantify excretion in a group of Merino sheep. Design A pen and laboratory experiment Procedure Seven sheep selected from an affected flock on the basis of acid-fast bacilli in the sheep's faeces were housed and total daily faecal output was collected, weighed and subjected to culture for M avium subsp paratuberculosis. An end-point titration method was used to enumerate viable M avium subsp paratuberculosis in a 15 day pooled sample from five sheep that had acid-fast bacilli in their faeces while housed. Results Four sheep with subclinical multibacillary Johne's disease excreted M avium subsp paratuberculosis each day for 11 days of cultural observation. A further three sheep were intermittent excreters but lacked other evidence of infection with M avium subsp paratuberculosis. The average number of viable bacteria excreted was 1.09 × 108 per gram of faeces while total daily excretion was 8.36 × 1010 viable M avium subsp paratuberculosis per sheep. Examination of faecal smears stained with Ziehl Neelsen was an unreliable means of assessing daily excretion in individual animals except in those with severe lesions. Conclusion Excretion of M avium subsp paratuberculosis in Merino sheep with multibacillary Johne's disease occurred daily, proving that environmental contamination can be continuous on farms with endemic ovine Johne's disease. Faecal culture is a useful method for detecting infection as it does not appear to be affected by the timing of collection of a sample from sheep with multibacillary disease however, to maximise the sensitivity of disease surveillance using faecal culture, sampling rates should be adjusted to take account of the proportions of multibacillary and paucibacillary cases. [source]