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Wildlife Reservoirs, is the badger a costly distraction, a scapegoat ...?

 Added by  Thomas (Guest)
 22 Jul 2010, 6:43 PM

Prof John Bourne, who conducted the infamous ten year, government-funded study which showed that badger killing is a waste of time and money, recalled what he was told by a senior politician:
"Fine, John, we accept your science, but we have to offer farmers a carrot. And the only carrot we can possibly give them is culling badgers."
This strand on the forum deals mainly with the wildlife reservoirs involved in the bovine TB saga. In the UK this is, as we are probably all aware by now, believed to be mainly the badger. No other mammal has been studied in the UK as intensely as the badger so actually we don't really know just how other animals are implicated. In other countries different species are implicated. There are some anomalies too, including the example below.
Has anyone an explanation for the following!
According to last issue of Gwlad, Australia is now bTB free after 27 years of trying. We are told it has no wildlife reservoir. New Zealand is still aiming for eradication. It has a wildlife reservoir - possums - which are considered a pest species as not indigenous so are being culled - and vaccinated!
HOWEVER - possums ARE native to Australia and bTB was rife in country for years so - why are the Australian possums not a reservoir?

Dr Dan Forman (conservation and ecology) has said that the behaviour of possums in New Zealand (alien spp) is very different to those in Australia (native spp). The epidemiology of diseases is context and locally specific. What happens in the UK is likely to be very different to that which occurs in New Zealand / Australia, between Australia and New Zealand, New Zealand and S America etc – this is because the environments, ecology, animal spp, their densities, behaviour, landscape management and land use all differ significantly. Quite why no possum has succumbed to bTB infection (even as a non-aggressive form of TB) is not currently clear. Possums are an easy option to cull in New Zealand as they aren’t native and the national pride is to restore the ecology of New Zealand back to pre-non-native species introduction status. In Australia this would be a very different issue and one not tested in courts over there yet!
Also, Ruth, in her email dated 21 July 2010 says, 'I don't know why the Australian brush tailed possums were not a reservoir in Australia but they weren't. The climate, the distribution of possums etc are very different in Australia to NZ. The problem with the introduced animals to New Zealand is the extraordinary way in which they have thrived- grown larger, bred more and of course have no natural predators or diseases. It may be there are more possums in NZ than Australia, and their density is also greater etc. The climate is milder and reliably wetter, again features that may favour the survival of M bovis in the environment. They are not sparing vaccinated possums but are seeking to kill all possums in NZ. The trouble is there are 20 million of them!'
We were sent this link to a more detailed report on this very subject. http://www.wildlifehealth.org.au/AWHN_Admin/ManageWebsite%5CFactSheets%5CUploadedFiles/119/Possums%20and%20TB%20in%20Australia%201%20Apr%202010%20%20(1.1).pdf
On 22 July, Ruth, after reading the report in the link above, commented, by email, 'they seem rather certain the organism survived for 2 or 3 weeks in dens but only 2 days on pasture. I expect that is from swabbing and culture. Prof Elizabeth Wellington from Warwick University did a sophisticated PCR analysis specific not only for M bovis but also for metabolic competence and presumed viability that suggests that in Ireland in favourable conditions on pasture, damp and shaded, the organism may be viable fo 6 months.
Poor NZ. I saw they are looking at sterilising vaccines for possums and that may be the way to get the population down so they can poison the remaining few. The possum is described as a folivore and if it hasn't eaten the native NZ fauna it destroys the flora, so depriving the NZ fauna and destroying the biodiversity of the ecosystem. Also I read that possums established in the wild in NZ in the mid 19th century so it is interesting that they have been implicated as M bovis reservoirs only recently, perhaps M bovis infection in cattle became widespread shortly before the possum became a reservoir through infection from cattle. I don't know if NZ has variety in the spoligotypes and genotypes of M bovis as we do (badgers largely coinciding with the same in cattle in the same area). Interestingly our efforts at M bovis elimination from cattle has narrowed the genetic variation in current M bovis strains- old humans who reactivate do so with strains not currently present in cattle.'


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