Golden Guernseys

The label attached to micobacterium bovis is proving very wide of the mark. We have had comments of the site, reminding us that 'bovis' means cattle and thus the disease must be primarily a disease confined to cattle. This is 'unfortunate' (in politocospeke) and totally misses the point; which is that bTB is a zoonosis affecting many species. And, as we said before, the single most sensible thing baby-Ben Bradshaw did during his tenure astride Defra's fence, was to make it notifiable in all mammalian species. This means Defra picks up the tab for postmortems and VLA log results.

As well as many tens of domestic moggies, a handful of pet dogs, free range pigs, camelids and a few sheep, the latest spillover has appeared in goats. Specifically - this time - in a breed of very rare Golden Guernsey goats, which had the misfortune to co-habit the pastures of West Wales where sentinel tested cattle in the area are showing big problems, and RTA badgers also badly infected. More on the story from BBC Wales

"The disease was discovered in some rare golden Guernsey goats which were being sold by a Carmarthenshire breeder. Nick Clayton of The Goat Veterinary Society said the outbreak had come as a "complete shock" to the industry and "it was only the second of its type in more than 50 years".
Twenty-two goats have been culled and 20 had lesions typically associated with the effects of TB. Bovine TB was diagnosed in a small number of goats in England 12 months ago, but it is not clear at present if that is linked to the latest scare.

However, a "significant portion" of the rare golden Guernsey breed was now at risk, Mr. Clayton said.

Mr Clayton added. "Six herds dotted around England and Wales have been tested now and a few cases have been found". Tracing of contacts is ongoing we understand, and this weeks' Vet. Record carries a summary of the problem thus far.

"Reports of caprine TB have been very rare in the UK since the introduction of a mandatory TB testing and slaughter scheme for cattle herds in the 1950s. However, the extent of the current outbreak illustrates that goats are susceptible to M bovis infection and TB should be considered as a differential diagnosis in goats with respiratory signs and weight loss, particularly if kept in regions of high bovine TB incidence.

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As a result of Bradshaw's notification instruction, one goat from the Welsh farm was submitted for postmortem in June 2008. Results revealed two large lesions, and multiple smaller lesions in the lungs. Culture from the lesions identified M bovis spoligo type SB0140 (VLA type 9). (VLA mapping shows 20 percent of outbreaks in Dyfed are found to share this spoligotype, and it is found in 44 percent of outbreaks in Devon / Cornwall.)

The remaining goats in the herd were tested using the intradermal comparative tuberculin test. Thirteen of 20 animals tested were disclosed as reactors using the standard bovine interpretation. Postmortem examination of these goats at the VLA showed gross lesions similar to the first case in all but one of the reactors. Four other nonreactor goats, slaughtered as dangerous contacts, did not show any gross tuberculous lesions at postmortem examination. Three goats with negative test reactions, all belonging to a separate management group, remain on the holding.

The goats on the holding showed anorexia, particularly refusing concentrate food, a sometimes precipitous fall in milk production, a chronic intermittent cough and sometimes loss of weight. Pulmonary lesions were the most obvious pathological sign on postmortem examination. Lesions in the bronchial, mediastinal, and mesenteric lymph nodes were more caseous, sometimes with 'gritty' calcification. Lesions have also been seen in the retropharyngeal lymph nodes, liver, spleen and udder.

The most likely source of infection for the herd appears to be the movement in May 2007 of three golden Guernsey goats from another herd in west Wales that was dispersed last April. Tracings from these two herds are being investigated by Animal Health and include goats moved to other holdings in England and Wales. At the time of writing, tracings involve 20 destination herds in 13 different counties of England and Wales. To date this has revealed a further eight herds with skin test reactor golden Guernsey goats presenting with tuberculous lesions at slaughter. Mycobacterial cultures on tissues from these goats are in progress.

The report concludes:

This outbreak has shown that goats can be very susceptible to M bovis infection and that the within-herd prevalence of infection can be high. It also highlights the importance of considering the risk of the introduction of M bovis infection when moving animals between herds and the potential consequences of failing to do so.
The positive predictive value of tuberculin skin tests performed so far on the at-risk goats has been very high.

The authors remind veterinary practioners that they should be consider TB when investigating goats with chronic respiratory disease and weight loss, and goats that die or are euthanased should undergo postmortem examination. [That warning applies to any 'mammal' - ed] However, skin testing goats is not mandatory, and any veterinary surgeon undertaking skin testing of goats must seek prior permission from the DVM and notify Animal Health of the results.

And as it appears to work well on goats, the skin test should be considered as part of a regular testing regime, we think. We understand that Wales is considering this route. If however the wildlife maintenance reservoir of disease is not tackled simultaneously, then goat keepers will find themselves in the same position as cattle farmers. A heap of dead animals - and no nearer to clearing the problem.