Wildlife Reservoirs, is the badger a costly distraction, a scapegoat ...?
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?
25 Aug 2010, 5:21 PM
Even Professor John Bourne, who co-ordinated the RBCT killing 'experiment', stated to the BBC . 'I think it is true to say the badger has been made a scapegoat,'
'... we conclude that badger culling cannot meaningfully contribute to the future control of cattle TB in Britain.' (ISG Final Report, 2007 The science that says a cull will not work (Prof Krebs) was actually set up for the Conservative government by Angela Browning MP in November 1996.
23 Aug 2010, 7:36 PM
The following post is of interest from www.warmwell.com/2010fink.html 'I am still of the opinion that feeding stations with high dosage of triple antibiotics for say 6 months coordinated, could be worth a try. It would not be that expensive, but would need very good attention to detail. It would at least reduced the bacterial load in those wild animals that are a reservoir for infection and often excluded from the badger setts'. Email received January 7 2010 from Dr Colin Fink, There is a problem with badgers highlighted to me by Professor Liz Wellington at Warwick, whose team have done the surveillance work. Evidently there will be a few badgers who are the high excreters of Mycobacterium bovis. They are ill and often excluded from the setts. The question which is difficult to answer is how many unaffected badgers are carrying the bacterium? They may remain healthy and not excrete particularly. We could decide to eliminate whole sett populations. If we do we would have to destroy and disinfect the setts as they will be re-colonised by other individuals and the Mycobacteria will still be there to infect the new population. It may be possible to both undertake sett elimination if the evidence of infection is available, and also treat geographically around the sett with triple antibiotic loaded bait (repeatedly). So those locally will at least have any infection reduced and carriage eliminated. It may also be possible to bait with contraceptive hormones so populations also naturally decline. I do not think that any single policy is a panacea and we need to consider combined approaches, to reduce the carriage and excretion of organisms, minimise population pertubation, which creates stress and increases mycobacterial disease ( rather than carriage), by using selective sett culling and also consider in conjunction, both contraception and antibiotic baiting. Any combined approach will need very careful policing and implementation. Surely that is a better investment than constantly killing herds of cattle and all that which goes into raising these animals? We have no other alternative as vaccines are not available because the organism is not amenable, and we are losing herds of cattle, alpacas etc and increasing the organism load in the wild population at an alarming rate. (Dr Colin Fink is Clinical Virologist & Hon. Senior Lecturer in Biological Sciences University of Warwick, and Company Medical Director, Micropathology Ltd Research and Diagnosis).
Comments received from Ruth by email 24/7/10 I was not previously aware that latent TB could be treated to prevent its reactivation at any time in future life, (unless reinfection takes place later (reinfection is documanted in humans and when opportunitiy for reinfection is high it commonly occurs)). Latent TB can be treated by 9 months of ISONIAZID alone (and a shorter course for chemoprophylaxis after exposure), unless the infecting organism was already resisitant at the time of initial infection. I believe this is what some camelid owners are doing for exposed camelids. Both camelids and goats as species seem to be particularly susceptible to M bovis with progressive infection from which they die.
The infection rate in a confined space such as a social group or sett of badgers will be between 25 and 50% if comparable to humans, but genetics and species may make it higher or lower. The diagnosis of latent M bovis infection in badgers is not accurate in microbiological terms as yet and would be likely to be underestimated by any tests currently used on them.
If Isoniazid alone is put out for badgers then the actively infected badgers that eat it (one cannot exclude actively infected badgers from eating the bait) are likely to develop resistance and the M bovis shed will be resistant to isoniazid within weeks or months and infect other badgers with resistant M bovis, so that strategy won't work.
In humans active infection is treated with multiple antibiotics taken every day, isoniazid, rifampicin, pyrazinamide and ethambutol for example- 2 months on this combo, then depending on the culture, typing and sensitivity report, reducing to 3 for a further 4 months, but in the case of M bovis dropping pyrazinamide as M bovis is intrinsically resistant so that in M bovis 3 drug treatment is given for 9 months in total. If the treatment is taken reliably then the person is cured of that M tuberculosis or M bovis infection. For example elephants have been cured of M tuberculosis infection (they are only rarely infected with M bovis). (It is likely to be unaffordable for farmers to treat cattle)
As you have probably heard multiple drug resistant and even extremely drug resistant M tuberculosis is now circulating in humans because they have not taken the full course of treatment. These organisms can infect hitherto uninfected individuals and may be untreatable and lead to death or indefinite confinement if excretion cannot be stopped by surgical removal of infected lung.
For this reason I have argued against Colin Fink's idea of putting out triple antibiotic therapy bait for badgers hitherto.
However if there is essentially a reservoir of M bovis in badgers and cattle (and deer, camelids, cats etc) that humans almost never get maybe such an approach together with vaccination of badgers and birth control of badgers / population reduction would not be such a bad idea afterall. Vaccination of cattle and testing and culling of infected cattle would have to continue to get rid of M bovis infection. The cycles of infection would be broken, stopping reinfection of either badgers or cattle from the other species.
The reasoning would be 1 The closely observed sett would thus have triple drug treatment of the active and latent infected badgers if this was continued for at least 9 months hopefully eliminating infection from that sett. 2 All the setts in possible contact with each other would have to be treated simultaneously. 3 If multiple drug resistant M bovis developed (part of the monitoring) then that group of badgers would have to be culled as it could spread to other badger setts. If such resistant M bovis infected a human which would be very unlikely that human is anyway very unlikely to pass it on to another human (though this has been recorded on rare occasion). An epidemic of resistant M bovis in humans would not happen as it is essentially a preventable zoonosis (by pasteurisation of milk). 4 Having small numbers of closley observed and monitored setts would necessitate reduction in the badger population, at least of infected setts (ie latrine PCR positive for M bovis) 5 However vaccination with the live attenuated vaccine BCG would not be successful if treatment was being given simultaneously (vaccine is killed by treatment), so perhaps vaccination could follow the treatment in infected areas. 6 Birth control would be a way of reducing the population without the suffering of culling, the consternation of animal rights people, and be ulikely to perturb the badger society.
A question that I couldn't answer is whether it is possible to get the badgers to eat sufficient of the bait daily for 9 months so that the triple drug therapy had an opportunity to work. In a way the badgers of the treated setts would have to be trained. Would some eat so much they would poison themselves?
A method such as this could only be used in a developed country and would have to have the full co-operation of people.
I have corresponded with badger trust people in Wales and they are implaccably against population control of badgers by birth control methods.
I also suspect that DEFRA and the HPA would never countenance the treatment of badgers with triple drug therapy. The EU rules would be a problem I am sure.
In conclusion I do think Colin's idea is more interesting and possible than I thought as a first reaction. People have no difficulty getting badgers to come to their gardens and eat peanuts for example.
The problem is that to do anything other than killing is obstructed and slowed for lots of different reasons, rules, bureaucracy and scientific difficulties, so that nothing can be given a try. Why should the Irish be at the stage of trialling oral vaccine for badgers and yet we be 5 years away from it?
28 Jul 2010, 7:14 PM
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!
22 Jul 2010, 6:49 PM
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.'