Timescales associated with vaccinating badgers against bovine TB

Costs | Vaccination | EU funding | Badger culling | TB testing | New Zealand | Cats & dogs
A leading expert is saying that badgers may require annual vaccination over some 4 - 5 generations and that this may need to be enforced over a 20-year timescale.

A report released by DEFRA (Ref 1) states that

"If only 50% of badgers can be trapped and injected with a vaccine which is only 50% effective, and only 50% of farms are involved the disease control benefit becomes rapidly diminished in any given year - 50% of 50% of 50% = 12.5% of the potential available benefit. While there will be a benefit, as any level of vaccination will produce a benefit, it will take substantially longer to appear in terms of reduced cattle breakdowns and vaccination will have to continue for a much longer time in order to accrue the benefit."

DEFRA will be rolling out the vaccination to areas where the percentage of infected badgers is likely to be high as inferred in the statement released by DEFRA (Ref 2) and for which an extract is shown below.

"The vaccine will be used in six areas of up to 100kmē where there is a high incidence of bovine tuberculosis (bTB) in cattle. Vaccination will start in 2010 and continue for at least five years."

Realising a benefit from vaccinating badgers where the proportion of diseased badgers is high will take longer than vaccinating in an area where the proportion is low. Reference 1 states the following.

"As the vaccine only benefits uninfected badgers the proportion of the population which is uninfected will influence how quickly benefits are seen. Benefits may take longer to appear in high prevalence areas as it will take longer for the proportion of uninfected badgers to rise."

DEFRA (Ref 1) further states the following.
  • As discussed above, vaccination will need to be continued for a number of years in order to maximise the benefits.
  • The replacement rate for badgers is estimated to be around 30% per year so each year there will be new cubs needing vaccination.
  • The estimated lifespan of a badger is 3-5 years. An infected badger will not benefit from the vaccine so non-infected badgers need to be protected from infection until infected animals naturally die off.
  • Some badgers may also be missed in any given cycle of vaccination. Further vaccination cycles provide an additional opportunity to vaccinate these. The duration of immunity is also currently unknown so repeated vaccination may be required to maintain immunity.
  • The duration of the vaccination programme required to be effective is currently being modelled. The current best estimate is that vaccination will be required on an annual basis for a minimum of five years. Subsequent less frequent vaccination may be required to maintain immunity in the badger population. The longer vaccination is maintained the greater the disease control benefits.
The above gives an estimate of minimum timescale. The British Cattle Veterinary Association has referred to a timescale of 12 years. See Reference 3. Paul Livingstone who is the Technical Manager of the Animal Health Board in New Zealand has referred to a timescale of 20 years. See Reference 4.

References
  1. Options for the use of badger vaccines for the control of bovine TB
  2. Benn announces deployment of injectable badger TB vaccine
  3. Bovine TB vaccination will not be effective in badgers for next 12 years says BCVA
  4. Ways in which New Zealand has reduced bovine TB
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Last Modified 14 Jul 2009 13:05
Costs | Vaccination | EU funding | Badger culling | TB testing | New Zealand | Cats & dogs