Tackling tuberculosis (Countryfile)

cowtbBroadcaster: BBC1
Year: 2016
Genre: Magazine

URLs: (full episode) https://learningonscreen.ac.uk/ondemand/index.php/prog/0D9D7D7F
Clip 1 (6:43): https://learningonscreen.ac.uk/ondemand/index.php/clip/23517
Clip2 (6:16): https://learningonscreen.ac.uk/ondemand/index.php/clip/23518

The BBC’s rural affairs programme Countryfile (first broadcast on 9th October 2016) looked at ongoing issues with TB infection cattle populations. The topic was covered in two sections. The first focuses on the current tests for TB infection. The second looks more closely at the science being used to develop new tests and better vaccines against TB.

The current test for TB in cattle involves pinching a section of the skin with calipers (see here for more on the caliper skin test). There are concerns about the accuracy of this test, which dates back to the 1920s, which may contribute to the fact that one on five cattle herds declared “TB free” actually retain infection. Although DEFRA believe badgers may be a source for TB, they acknowledge that once infection is within a herd then cattle to cattle transmission is a greater issue. Be aware that the first section includes footage of a cow that fails the caliper test and although no footage of culling is shown, the dialogue makes clear that this will be her fate.

This outcome is also mentioned in the introduction to the second section, alongside the statistic that more than 50,000 cattle in the UK were culled due to TB in the previous 12 months. One problem stems from the fact that the caliper test is only 80-90% effective and cannot detect TB in the early stages, hence the interest in more advance scientific interventions.

Tom Heap interviews Dr Cath Rees (University of Nottingham) about a new blood test she and colleagues have developed (see this link for a press release). The new detection method looks directly for the bacteria rather than relying on the immune response they generate. This test will be cheaper, quicker and clearer than the current test. Dr Rees doesn’t envisage her test as additional to the current on site system rather than as a replacement. It would, for example, be invoked when a cow tested positive. The more definitive screen would then be undertaken on the rest of that herd to examine the extent of the issue. This would make the process quicker; at present the only way to know if other cattle in the herd are infected but currently symptom-less is to return several months later when they have had opportunity to develop an immune response of their own.

An alternative application of science would involve development of a new vaccine. An existing vaccine, similar to the BCG vaccine used for humans, is not appropriate since the symptoms of ‘vaccinated’ and ‘infected’ cows are indistiguishable. A potential alternative comes through work in which Dr Jean Van den Elsen (University of Bath) has fused a protein from Staphylococcus aureus to a protein from TB. In experiments using mouse models, this appears to have two advantages. Firstly, the TB protein remains exposed to the immune system for longer, allowing antibodies to be raised. Secondly, the combined protein triggers an immune profile that differs from that seen with the bacterial infection itself (and the BCG vaccine) so that immunised and infected cows can be distinguished (or at least should be distinguishable if the work is replicated in cattle!) For more details on this story follow this link.

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