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The Prevalence of Johne’s disease in New Zealand Ruminants - NEW |
Providing an accurate estimate of the prevalence of Johne’s disease (JD) in New Zealand is a critical component in understanding the steps needed to control and manage the disease. In 2011 findings from the JDRC funded prevalence study, undertaken at Massey University, were published in VetScript (reproduced with permission). The results describe, for the first time, the extent of JD and MAP infection in New Zealand livestock farms. The analysis showed that about two-thirds of sheep flocks and deer herds were infected, with clear regional variations in prevalence. More cattle and deer herds are infected in the South Island, and sheep flocks in the North. Further analysis of the data is ongoing to quantify economic consequences of the disease.
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Diagnosing Johne’s disease - NEW |
The study of the immune response of dairy cattle to MAP infection has highlighted limitations of common diagnostic tests for the early stage diagnosis of Johne’s disease in cattle. The most commonly used tests measure antibody response in blood (serology) or detect bacteria shed in faeces (culture). In young cattle antibody and faecal shedding have been shown to be unreliable indicators of disease. In practical terms this means there is little value in testing for Johne’s disease in young cattle. It is considered most effective to monitor and test older stock when looking for Johne's disease in dairy herds.
This information is consistent with what we know about the diagnosis of Johne's disease in all species. While there are a number of tests that can be used to detect infection and disease, it is very important to use the right test at the right time to have the best chance of arriving at a correct diagnosis. The value of a test varies with species, the age of an animal and the stage of the disease. Testing is not always recommended and should always be done in consultation with your veterinarian.
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Controlling the Transmission of MAP - NEW |
One strategy for reducing the impact of MAP on farm is to minimise or stop the transmission of MAP between animals on farm. Three major factors have been identified as goals for this purpose; controlling on farm transmission, controlling entry of MAP into a herd/flock and maximizing herd health. JDRC is working with industry groups to develop schedules of specific actions that can be taken by farmers to achieve these goals in differing farming situations. While many of these techniques and actions are based on information from international studies, the advice to New Zealand farmers must take account of New Zealand’s pastoral farming environment. 
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How age affects susceptibility to Johne’s disease |
In a study jointly funded by JDRC, DEEResearch and the Ministry of Science and Innovation (formerly the Foundation for Research Science and Technology), research has established that deer show an age-related resistance to Johne’s disease. Three age classes of red deer (weaners, yearlings and adults) given oral doses of bacteria were monitored for 50 weeks before slaughter. While almost all of the animals became infected with the bacteria, the younger animals were far more likely to progress to subclinical and clinical disease than the adults. This demonstrated that older animals are more resistant to the disease than younger animals. Results from this trial were published last month in the international journal Veterinary Microbiology ( Volume 143, issues 2-4). Farmers should therefore take practical steps to minimise the exposure of young deer to MAP to help control the spread of Johne’s disease on farm. |
Genetic Link to Johne's disease resistance |
Preliminary results from Colin Mackintosh's JDRC funded longitudinal study indicate that resistance or susceptibility to Johne's disease is highly heritable. the results were presented at the NZVA Deer Branch Cervetec 2010 conference and published in Issue 43 of the Deer Industry News (Pages 22 and 23, Aug-Sep 2010) |
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