SOUTH African scientists have identified a set of proteins that may help them develop a better diagnostic test for bovine tuberculosis (TB) in African buffalo.
It is a potentially significant advance as current tests miss some infected animals and incorrectly identify others as diseased.
Early detection of bovine TB in the African buffalo is important because it is one of the wildlife reservoirs of the disease in SA.
The disease rarely proves fatal to the buffalo, but it passes it on to cattle and other mammals.
As farmers with infected animals have to quarantine their herds at significant economic cost, better detection and control of the disease has important implications for agriculture.
Bovine TB is caused by the Mycobacterium bovis (M bovis) bacterium, which is closely related to Mycobacterium tuberculosis, the micro-organism that causes TB in humans. It is found in the saliva of infected animals, and is spread through airborne particles from the respiratory tract or through contaminated feed and watering sites. While it prefers animals, M bovis can spread to humans.
The only government-approved test available in SA for African buffalo is a tuberculin skin test, in which the animal gets an injection of TB proteins under the skin and is checked for a reaction 72 hours later. However, this test is not 100% accurate and results yield false negatives and false positives.
It also requires handling the animal twice, unlike blood tests which require a single handling.
More hi-tech interferon-gamma release assays, which test an animal’s blood for the amount of interferon-gamma it produces in response to purified protein derivatives from bovine TB are also available, but even these tests were not as sensitive as farmers would like, says Michele Miller, who holds the research chair in animal TB at the University of Stellenbosch.
"If you have a valuable herd, you really want to minimise the false positives and pick up all the true infections," she says.
Now scientists from the Medical Research Council’s Centre for Tuberculosis Research have shown testing African buffaloes’ blood for a protein, interferon-induced protein 10 (IP-10), after exposure to M bovis may be a more accurate gauge of infection than testing for interferon-gamma alone.
In a study published in the August edition of Clinical and Vaccine Immunology, they describe how they tested 84 African buffalo from the Hluhluwe-iMfolozi Game Reserve, and looked for elevated levels of interferon-gamma and IP-10. Screening for interferon-gamma identified 31 of the 44 infected animals, while screening for IP-10 identified 38.
"We are now refining the tests, looking for more bio-markers that will hopefully give us even higher sensitivity. We are aiming for 100% detection," says Prof Miller, one of the study’s co-authors.
An estimated 50-million animals are infected with M bovis worldwide at an estimated cost of $3bn, she said.
A better diagnostic test for bovine tuberculosis in African buffalo may be on the cards. Picture: ISTOCK
SOUTH African scientists have identified a set of proteins that may help them develop a better diagnostic test for bovine tuberculosis (TB) in African buffalo.
It is a potentially significant advance as current tests miss some infected animals and incorrectly identify others as diseased.
Early detection of bovine TB in the African buffalo is important because it is one of the wildlife reservoirs of the disease in SA.
The disease rarely proves fatal to the buffalo, but it passes it on to cattle and other mammals.
As farmers with infected animals have to quarantine their herds at significant economic cost, better detection and control of the disease has important implications for agriculture.
Bovine TB is caused by the Mycobacterium bovis (M bovis) bacterium, which is closely related to Mycobacterium tuberculosis, the micro-organism that causes TB in humans. It is found in the saliva of infected animals, and is spread through airborne particles from the respiratory tract or through contaminated feed and watering sites. While it prefers animals, M bovis can spread to humans.
The only government-approved test available in SA for African buffalo is a tuberculin skin test, in which the animal gets an injection of TB proteins under the skin and is checked for a reaction 72 hours later. However, this test is not 100% accurate and results yield false negatives and false positives.
It also requires handling the animal twice, unlike blood tests which require a single handling.
More hi-tech interferon-gamma release assays, which test an animal’s blood for the amount of interferon-gamma it produces in response to purified protein derivatives from bovine TB are also available, but even these tests were not as sensitive as farmers would like, says Michele Miller, who holds the research chair in animal TB at the University of Stellenbosch.
"If you have a valuable herd, you really want to minimise the false positives and pick up all the true infections," she says.
Now scientists from the Medical Research Council’s Centre for Tuberculosis Research have shown testing African buffaloes’ blood for a protein, interferon-induced protein 10 (IP-10), after exposure to M bovis may be a more accurate gauge of infection than testing for interferon-gamma alone.
In a study published in the August edition of Clinical and Vaccine Immunology, they describe how they tested 84 African buffalo from the Hluhluwe-iMfolozi Game Reserve, and looked for elevated levels of interferon-gamma and IP-10. Screening for interferon-gamma identified 31 of the 44 infected animals, while screening for IP-10 identified 38.
"We are now refining the tests, looking for more bio-markers that will hopefully give us even higher sensitivity. We are aiming for 100% detection," says Prof Miller, one of the study’s co-authors.
An estimated 50-million animals are infected with M bovis worldwide at an estimated cost of $3bn, she said.
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