CAL: wildlife and zoonoses Flashcards
Which wild animal species are most frequently implicated in emerging diseases?
Bats have often been found to be the wildlife reservoir of new diseases, especially viruses. In particular, fruit-eating bats in parts of Africa and Asia.
Which countries were affected by Ebola?
Countries affected by the 2014-15 Ebola outbreak can be split into three categories:
1. Countries with widespread human-to-human transmission: Guinea, Liberia, Sierra Leone.
2. Countries with localised human-to-human transmission: Congo, Mali, Nigeria, Spain, USA.
3. Countries with travel-associated cases (but no evidence of further transmission): Senegal.
You could add the UK because there was one case here in a healthcare worker but this is not strictly a UK case of infection because this person was imported deliberately for treatment.
Which species can act as maintenance hosts for bovine TB in the UK?
In this disease, both a wildlife species (badgers) and livestock species (cattle) can maintain the bacterial infection independent of the other host species.
What methods are available for managing TB in badgers in the UK? Write brief notes on the pros and cons of each method and indicate which are licensed.
- vaccination
- culling
- test and cull, or test and vaccinate
- treatment
- do nothing
Pros of badger TB vaccination
Badgers can be cage-trapped and given a BCG vaccination by intramuscular injection. BadgerBCG is licensed under a Limited Marketing Authorisation for the active immunisation of badgers to reduce TB lesions caused by M. bovis. The recommended dose and route of administration of BadgerBCG is 2 to 8 × 106 colony-forming units (cfu) of BCG (the manufacturer’s specified range) intramuscularly, which is a 1 ml reconstituted vial per animal. Intramuscular administration has the practical advantage of being relatively easy to perform on trapped wild badgers, without the need for sedation or anaesthesia.
Field trials indicate approximately 75% reduction in incidence of positive blood serological tests in vaccinated badgers. Furthermore, vaccinating one third of the adults resulted in a 79% reduction in risk of infection in unvaccinated cubs, a form of herd immunity.
Farmers and landowners can apply for a licence to trap and vaccinate badgers.
Cons of badger TB vaccination
Badgers that are already infected may not receive a benefit of vaccination.
Trapping badgers is difficult and expensive, so an oral badger vaccine which can be left with bait is in development but is still some years away.
There is currently no data on how much badger vaccination might reduce cattle TB in cattle.
Vaccination of badgers in the edge area (between regions of the country with high and low TB prevalence in cattle) is planned as a contribution to reducing risk of infection spreading.
Pros - badger culling
Strong farmer support in some areas
Evidence in other countries suggests that culling of wildlife may be beneficial in terms of reducing disease risk (but evidence comparable to the UK situation is sparse)
Free-shooting without trapping (the method used since 2013) is the easiest method, but there is potential for wounded badgers to flee causing animal welfare concerns and making the carcase a source of infection.
Cons - badger culling
Vast majority of public opinion is against culling.
Trapping followed by shooting (the method used in Randomised Badger Culling Trial) is relatively expensive and difficult to carry out.
Free-shooting without trapping (the method used since 2013) is the easiest method, but there is potential for wounded badgers to flee causing animal welfare concerns and making the carcase a source of infection.
Culling does not kill all the badgers in an area and those remaining may roam more widely afterwards which can actually increase the spread of TB (this is known as the perturbation effect).
Gassing and snaring were used in culls during the 1970s but have been deemed inhumane and are not being considered now.
Farmers can club together in certain (but not all) regions to apply for a culling licence.
Outline badgers - Test and cull, or test and vaccinate
This is being trialled in Northern Ireland. The idea is nice, in that you catch badgers and test them for TB. Those that test negative are vaccinated and released whereas those that test positive are culled. However, current tests for TB in live animals (including badgers, cattle and humans) are not terribly sensitive and so this method is expected to result in many infected animals being released or vaccinated. Thus the control of TB may be limited.
Further information on test and cull, or test and vaccinate strategies can be found on this website and some of this method’s potential limitations are described in this newspaper report.
Outline the do nothing policy for badger
Strange as it may seem, there is a case to be made for doing nothing (after careful consideration of the options rather than just doing nothing and hoping it will go away). Perhaps resources could be better targeted on other diseases where they are more likely to have a bigger benefit to health and welfare. However, there is limited support for this argument.
What was the remit of the Independent Expert Panel for the badger cull?
- the effectiveness of badger culling (what proportion of badgers can practically be killed using controlled shooting) AND
- the humaneness of badger culling (how long it takes badgers to die and what is the potential for suffering.
How was the severity of incidents of animal suffering with the badger cull measured?
Number of animals that experience suffering.
Duration of that suffering.
Intensity of the suffering.
How effective was the badger cull?
The Panel said that it “can be 95% certain that controlled shooting removed less than 24.8% of the pre-cull badger population in Somerset, and less than 37.1% of the pre-cull population in Gloucestershire” (section 4.3.2 of the Report).
It went on to say it “can be 95% certain that a combination of controlled shooting and cage trapping removed less than 48.1% of the pre-cull population of badgers in Somerset and less than 39.1% of the pre-cull population in Gloucestershire” (section 4.3.4 of the Report).
The target of the culls was to achieve a 70% reduction in badger numbers.
Thus the culls fell a long way short and can be considered ineffective in their current form.
How humane was the badger cull?
The Panel said that it “can be 95% confident that the number of badgers estimated as taking more than 5 min to die exceeded 5%” (section 5.3 of the Report). Further details of the range of times is given in the Report. You might like to consider whether you consider this acceptable (it is a balance between the potential for suffering to the badgers and the potential for gains in terms of disease control). There is no easy answer.
How safe was the badger cull for the public?
It was concluded the cull was safe to the public.
