TB transmission - why we bother.

Every so often the comment comes up 'why bother'?

Why bother to test and slaughter cattle? - milk is pasteurised, meat inspected at slaughter and cooked, so why not just ignore tuberculosis? But although Defra are making a fine job of doing exactly that, it is of course a statutory requirement of EU and OIE trading, that tuberculosis be cleared from cattle and farmed deer herds, to protect human beings. And although badgers carry bTB in spades, (they must do or why is Defra spending a huge amount of taxpayer's cash telling cattle farmers how to avoid their animal's contact with them?) they do not "suffer" from this disease - so some would argue, let them live with it.

But to concentrate on sentinel tested and slaughtered cattle, the numbers, trading implications or otherwise - or even the maintenance reservoir of tuberculosis in badgers, is missing the point. We have mentioned spillover into camelids and other species several times (and will continue to do so) because that IS the point.
Exposure to tuberculosis, from whatever source is to be avoided.

The young vet in this Veterinary Record report was examining a dead cria (young alpaca) and was wearing protective gloves during the postmortem, although she did not wear gloves to euthanase the animal.

Six weeks after the postmortem examination, she noticed a tingling sensation in the tip of her right thumb, but no lesion was visible at that time. After a further three weeks, a painful, circular, pale lesion approximately 4 mm in diameter developed at the site. Despite initial antibiotic treatment with cefalexin and amoxicillin/clavulanic acid, the thumb lesion enlarged and assumed a verrucose appearance (Fig 3), with associated swelling
and pain in the elbow, lymphadenopathy of the trochlear and axillary nodes, and pyrexia. She was referred to North Devon District Hospital, where mycobacterial infection was suspected.

The lesion was tested, and samples sent for mycobacterial culture. M. bovis was identified with the strain being spoligotype SBO140, VLA 9, VNTR 6-5-5-4*-3-3.1.

.." 21 days after sampling, the skin lesion, which had regrown, was surgically debrided, and a six-month programme of anti-TB therapy was prescribed, comprising isoniazid, rifampicin and ethambutol. The symptoms resolved completely after this programme of therapy had started, and there has been no recurrence of mycobacterial disease at the time of writing, four years later.

The alpaca cria on which she performed a postmortem, was considered to be a possible source of infection.

We have showed you photos of the ravages of the disease on badgers, in the posting below. So for those who may not be up to speed with what tuberculosis does when it takes hold, here are some more photos - this time of some alpacas. The animals whose tuberculous lesions we show were euthanased either as a 'dangerous contact' to an animal showing clinical signs, or with the second photos, an X ray and blood test positive. Both had passed skin tests, the second animal 3 rounds over several months. Neither had clinical symptoms.

His body condition was good, giving no indication of what was lurking underneath his curly, white coat... but his lungs (first picture) at 20 percent, were barely functioning. He weighed over 100kg when euthanased.

The second alpaca also showed no symptoms but post mortem showed black spots on his trachea (pic. right) indicating open lesions right up to his throat. TB bacteria from these was available to other alpacas, his owner and any other mammal every time he exhaled, or spat, or coughed....


In the final picture, the lymph nodes on that second animal had been doing their job, hugely enlarged and sifting infection from his body. They are choc full of m.bovis 'cheese' - or in veterinary terms, "caseous abscessation".

This animal weighed 92 kg at the time of his death, but he had multiple tuberculous lesions throughout his body, including:

Abdominal cavity: Multifocal 2-20mm diameter creamy-white well encapsulated gritty focal lesions were present throughout the liver.

Alimentary system: Multifocal creamy-white well encapsulated gritty focal lesions, up to 10mm in diameter, were present at the junction of C2 and C3 stomachs and extended on to the proximal wall of C3 stomach and the distal wall of C2 stomach.

Respiratory system: Multifocal red/purple raised ovoid approximately 10 x 3mm plaques were present on the mucosa of the trachea, containing occasional gritty focal lesions. Multifocal 1-2mm diameter generally red-purple gritty focal lesions were present throughout the lung lobes. Two approximately 20mm diameter creamy white gritty focal lesions in the caudal left and right lung lobes also were seen.

Lymphoreticular system: Occasional up to 5mm diameter creamy-white well encapsulated gritty focal lesions were present within the spleen. The mediastinal, gastric, hepatic and bronchial lymph nodes were massively enlarged, often up to chicken egg size and effaced by caseous abscessation. The cervical lymph nodes were partially effaced by abscessation.

Urinary system: One approximately 1mm diameter creamy-white focal lesion was present in the right kidney cortex.

We are grateful for permission from the owner of these animals to publish the photos, and we offer thanks to the organisers of the recent " Alpaca TB Awareness " meetings, for raising the profile of this disease amongst their members, and for allowing these photos a wider audience.

The alpaca wearing blue, is the animal in the second and third postmortem pics - in happier times.


And he, his dead companions and the young vet described in the Vet. Record article above, as contracting tuberculosis while performing her job, is why we bother.