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tomkellyvet@gmail.com
tomkellyvet@gmail.com
ph: 001 760 291 70 66
ph: 001 760 291 70 66
Sent: Wednesday, March 31, 2010 11:40 AM
Subject: Re: Response to http://www.irishveterinaryjournal.com/Links/PDFs/Peer/Peer_December_06.pdf
Dear Editor,
As a practitioner who had spent a quarter of a century tuberculin-testing cattle in west Donegal, including herds located in what formed the Removal, Reference and Buffer Areas of the FaP (or Four-areas Project), I studied with great interest the paper, A case study of bovine tuberculosis in an area of County Donegal, Ireland, which appeared in Volume 59 (12) : December, 2006 Irish Veterinary Journal.
I believe that the the outbreaks of btb in that cluster of 19 herds bore temporal and spatial characteristics typical of badger-related incidents. Further, they exhibited patterns of infection suggestive of tuberculosis in cattle which have been exposed to infected badgers and/or their infected excreta/discharges. This is in contrast to the much lower-grade outbreaks one now associates with bought-in and with bovine-to-bovine infections. If btb reappears on any Irish farm nowadays, given the findings of that same FaP, I suggest that the first residue to suspect is the badger residue. I therefore cannot understand - much less agree with - the reasoning of the authors in their preamble:
"The increased number of BTB breakdowns during the fifth year most likely occurred because of the recrudescence of infection, herd-to-herd transmission and, to a lesser extent, purchase of infected cattle. Infected badgers remain as a possible but less likely source of infection, especially as an explanation for the cluster of infected herds."
The following passage of the Discussion baffles me.
"In addition to herd-to-herd spread, the possible role of infected badgers cannot be disregarded. All the ER76 forms indicated that land fragments grazed by cattle (in herds with multiple ‘standard reactors’ during the fifth year) had evidence of badger activities. Four herds had active setts on their land and, in all the remaining farms, badger latrines or badger passes were identified and confirmed by a veterinary inspector. However, only four badgers were caught (from eight setts) and only one (25%) badger was diagnosed as M. bovis positive at histology examination. This level of infection does not differ from the 26.1% prevalence in badgers in the other three reference areas of the FAP. Thus, even though the role (infected) badgers can play in BTB in cattle (O’Connor and O’Malley, 1989; Dolan, 1993; Martin et al., 1997; Olea-Popelka et al., 2005; Griffin et al., 2005) is recognised, the authors do not think the outbreaks during the fifth year should be attributed primarily to badgers."
A reported haul of just four badgers from eight active setts, and particularly in November, a month so favourable to snaring, begs the question, "What happened to their fellows?"
"We have no evidence of excess TB in badgers, nor of a high density of badgers in this area. In such circumstances, transmission of BTB from a single, infected and highly-active, badger to a number of herds does not seem biologically-plausible."
The absence of evidence in such circumstances is certainly NOT evidence of absence, and, contrary to the reasoning of the authors, does nothing to exonerate the missing badgers.
Finally, the absence of any reference in this paper to the strain-typing of M. bovis isolates from any/all reactor cattle in Co. Donegal, and certainly from those grazed or housed in the areas of study, as well as of any badger-derived isolates, is a conspicuous omission.
Yours very sincerely,
Tom Kelly, MVB, MRCVS.
Thomas P. Kelly
Escondido, California
USA
mobile: (760) 291-7066
(dialing from Ireland... 001 + 7602917066)