Sunday, August 09, 2009

Update - New tests for TB in Alpacas

In case anyone is under any illusion about just what 'tuberculosis' does to a lung when it takes hold, this is a photo of pulmonary cavitation in an alpaca called Willow. He had passed a skin test in late January 2009, and another in early May.

His companion developed a cough and was subsequently euthanased. This was just six weeks after a clear skin test and his very responsible owner agreed to have Willow put down as a dangerous contact at the same time. The postmortem showed pulmonary cavitation and lesions in his throat. But at no time did Willow show any of the physical symptoms normally associated with TB: no weight loss, unthriftyness or cough.

As an update on the testing saga of Dianne Summers' Cornish alpaca herd which we covered here, the news is mixed. Having volunteered and gained permission to use the Chembio Rapid Stat-Pak blood test on her herd, the results were 4positives. Miss. Summers then agreed to pay for X rays to confirm any lung damage ahead of proposed slaughter. The whole herd was Xrayed and when the films were read at the Cambridge Veterinary School, two animals gave 'cause for concern'.

These were not two of the four animals which were positive on bloods. These two animals were isolated, and will be Xrayed again this week. The four alpaca which were positive on bloods are also isolated separately and the herd will be Xrayed at regular intervals to confirm blood results.

Miss Summers points out that if she had relied on the skin test results, her herd would be clear, despite having animals with the tuberculous lungs pictured above.
If she had relied on the blood test, another four alpaca would be for the chop, but having Xrayed the herd she comments that:
" ... if I relied on the results of the blood test alone - 2 of my herd who have shown on X ray as a 'concern', [but] who didn't show positive on Blood test would have fallen below the radar and wouldn't have been isolated and therefore possibly infect my other animals. My 4 positive blood test alpacas have been isolated because the blood test may detect very early signs of TB before it shows up on X Ray.."

Miss Summers's alpacas are not out the woods yet, and the herd will continue to be monitored and Xrayed regularly. Any sign of lesions, will mean the animals are culled. The unreliable results on camelids of the intradermal skin test, described in a 2007 paper as 'so poor as to be meaningless' leave owners who want to protect their herds from tuberculosis little choice but to pioneer different diagnostic tests which in tandem, may give a degree of antemortem confirmation of disease.

Dianne finishes her story thus:
"I will continue to Xray my entire herd every 3 months and will cull any that show TB lesions. I am taking advice from industry experts and have done everything they have recommended.
This is important research but it is going to take a long time before we know how accurate any of this is but its a start. At least I am trying and this may just help currently infected herds and newly infected herds."

We wish her well.

On further Xrays, the two alpacas which gave cause for concern on Xrays, appear clear. Cambridge recommend a repeat screening in a few months. (Xrays will pick lesions less than 1/2 centimetre across, thus at a very early stage). Their results on these two state "So, in summary, the new films do NOT show areas of concern anymore."
And how that leaves the four alpacas, positive to the unvalidated Rapid Stat-pak blood test, (all of which were clear on skin), is anybody's guess.


Raelene from Mariah Hill Alpacas & Exports said...

ratulations to Dianne Summer for being proactive and doing the right thing, by her herd, but also the alpaca industry.
It is hard to have to loose any alpaca, but Dianne shows the right inititive.

Matthew said...

We are sure that Miss Summers will be delighted to have your support. Thanks for the comment Raelene.
Unfortunately, alpacas appear to be very susceptible to bTB and highly infectious to each other (and anything else?) when they do get it. Defra are very slow at catching up with this. So any pressure from BAS, or individual breeders is welcome.

Dianne Summers said...

Hi Raelene

Thank you so much for your comment - kind words are always appreciated. This is a very serious issue and we need to address it - accept it and face up to the fact that camelids are highly susceptible to the disease and can pass it on so easily. We need to protect not only the alpaca industry but our fellow livestock industry - let alone the public. I am trying to get the message out there.
Thanks again - Di

Leo said...

Do you have any photo's of how tb looks on a x-ray. We have a digital machine and like to test it ourselves. I guess little tuberkels are shown as a white spot? Are there many in the positive animals? Or just a few.
Is it possible to put a picture on the internet. Can I contact the vetpractice who made the photo's?

Matthew said...

We have forwarded your request on to alpaca owners who have had Xrays carried out, Leo.
Local vet did the procedure, but diagnosis was made by a leading veterinary college who received his data.

Dianne said...

Hi Leo

Yes I do have digital files of one of my recent alpacas who I had X Rayed and it showed obvious lesions on his lungs - but I don't have a copy of it - Gina Bromage does have a copy which I can get her to email you if you wish but please bear in mind she is away on holiday and won't be back until 7th Feb. I also have the PM film which I can send you if you wish.
Lots of X rays are being shown at the Tb meetings which are currently going around the country details of which are posted on the blog somewhere.
Some lesions show up and look like loads of very large rice grains - others show up like circles the size of 50p pieces so they do vary. hope that helps.

Anonymous said...
This comment has been removed by a blog administrator.
Anonymous said...

"The unreliable results on camelids of the intradermal skin test, described in a 2007 paper as 'so poor as to be meaningless' leave owners who want to protect their herds from tuberculosis little choice..."

which 2007 paper is this? do you have a copy/link to it?


Matthew said...

Anon 6.10
Have forwarded your request on to the contributer who posted this.
Hope to get a reply later.

Previous post deleted. B**!!%£y spam. Again. how do these muppets get in?

Matthew said...

Anon 6.10
The quote to which we referred can be viewed in this post.

Originally published in Veterinary Record, (Twomey and others, 2007) referring to an outbreak in llamas which occurred in Devon, the quote to which you refer was contained in a letter, published as a follow up to the original article.
No link.