Abstract / Description of output
Bovine tuberculosis (bTB) is an infectious disease of cattle caused by Mycobacterium bovis. Zoonotic transmission of M. bovis, from cattle to people, can potentially lead to debilitating disease and is the main driver for disease control in cattle. People contract M. bovis, by living in close contact with cattle or by drinking raw milk. Thus primarily public health is usually protected through pasteurisation of milk and identifying infected cattle for removal in test and slaughter programs. In high income countries bTB is either eradicated or controlled to a low level through test and slaughter programs, with are reliant upon accurate diagnosis of infected cattle.
Diagnosis of infection in live cattle is difficult because clinical signs, such as pneumonia and weight loss, do not always develop, are not very specific and commonly animals can appear healthy. Progression of disease leads to characteristic abscesses developing in organs of infected cattle, such as the lungs and lymph nodes, however they can only be identified post mortem. Subsequently bTB diagnosis is dependent upon detecting immune responses to M. bovis in live cattle. The predominant response is the cell-mediated immune response and can be detected using the single comparative intradermal skin test (SCITT) or the interferon-gamma (IFN-) assay. The IFN-assay is potentially useful for epidemiological studies, as it only requires a single blood sample and cattle can be tested on mass. However neither test is 100% accurate, with accuracy varying between cattle populations, and false negative results are common especially in early or late stage infections. It is not completely known why false negative IFN-assay test results occur and false negative results can ultimately lead to underestimation of bTB prevalence. Liver fluke parasites may dampen down IFN-immune responses to M. bovis resulting in bTB false negative test results in co-infected cattle, although this has been minimally investigated in natural infection settings.
Diagnosis of infection in live cattle is difficult because clinical signs, such as pneumonia and weight loss, do not always develop, are not very specific and commonly animals can appear healthy. Progression of disease leads to characteristic abscesses developing in organs of infected cattle, such as the lungs and lymph nodes, however they can only be identified post mortem. Subsequently bTB diagnosis is dependent upon detecting immune responses to M. bovis in live cattle. The predominant response is the cell-mediated immune response and can be detected using the single comparative intradermal skin test (SCITT) or the interferon-gamma (IFN-) assay. The IFN-assay is potentially useful for epidemiological studies, as it only requires a single blood sample and cattle can be tested on mass. However neither test is 100% accurate, with accuracy varying between cattle populations, and false negative results are common especially in early or late stage infections. It is not completely known why false negative IFN-assay test results occur and false negative results can ultimately lead to underestimation of bTB prevalence. Liver fluke parasites may dampen down IFN-immune responses to M. bovis resulting in bTB false negative test results in co-infected cattle, although this has been minimally investigated in natural infection settings.
| Original language | English |
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| Qualification | Ph.D. |
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| Publication status | Published - 2017 |