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Development of an oral BCG vaccine for badgers - research component - SE3246

Description
There was an estimated 225% increase in the number of bovine tuberculosis (TB) incidents in Great Britain between the years 1996 and 2006. This adversely affects animal health and welfare, and is a cause of considerable economic loss to farmers and Government. Although transmission of Mycobacterium bovis between cattle is an important factor in spread of the disease, the Eurasian badger (Meles meles) represents an additional wildlife source of recurrent M. bovis infection to cattle in both the UK and Ireland. Following the recent Ministerial statement that badgers would not be culled as part of control measures for bovine TB (http://www.defra.gov.uk/corporate/ministers/statements/hb080707.htm), the vaccination of badgers against TB has come to the fore as a possible means to reduce and control bovine TB alongside other control measures.

It has long been recognised that delivery of vaccine in oral bait holds the best prospect for vaccinating badgers over a wide geographical area and has proved highly successful for mass vaccination of other wildlife species against rabies. In the short to medium term, the human TB vaccine, M. bovis Bacille Calmette-Guérin (BCG), represents the best available option for vaccinating badgers against TB. BCG vaccine has the advantage of a long history of safety and protection in a variety of animal species including badgers, but generally doesn’t work unless the vaccine is live. This is a challenge in the case of oral delivery as live BCG by itself is killed by stomach acid. Therefore, the success of an oral BCG vaccine for badgers will depend in large part on the ability to maintain live vaccine for prolonged periods in bait and subsequently when consumed by badgers.

The other critical component of the oral vaccine for badgers is the bait itself. The success of any badger vaccination strategy will be dependent on both the number of badgers consuming the bait and the effectiveness of the oral vaccine once consumed. At its most simplistic, the intention is to use the most attractive and palatable bait possible. However, numerous other considerations must be taken into account including, the properties of the bait (such as cost, shelf-life, compatibility with the vaccine formulation, ease of manufacture, handleability), factors affecting attractiveness of bait to badgers (such as age of badger, geographical location, weather, season, access to alternative foodstuffs), and method of bait deployment (including quantity, duration, location, frequency).

The overall aim of this project is to complete the research and development on the vaccine formulation and bait already started by the Veterinary Laboratories Agency and Central Science Laboratory for oral delivery of live BCG vaccine to badgers. The two components (vaccine formulation and bait) must be compatible with each other such that: (1) the vaccine stays alive for an appropriate time in the bait; and (2) the bait containing the vaccine is highly palatable to badgers.

Experimental work on the vaccine formulation will focus on determining how long BCG vaccine remains alive in different formulations in and out of bait, generating data on the oral vaccine suitable for licensing purposes, such as production methods and quality control measures, and indentifying the best way to place the vaccine into bait.

Experimental work on the bait will use captive badgers to identify palatable baits and then evaluate the most promising of these in populations of wild badgers in order to assess palatability, identify the optimal strategy for bait deployment, quantify the uptake rate of the bait in different badger populations around the country, and estimate the risk of cattle exposure to bait. No vaccine will be present in the bait for these studies. On the basis of this work, recommendations can then be made to Defra on the optimal baiting strategy for badgers.

Before any oral vaccine for TB in badgers can be licensed, further work will be required to evaluate the effectiveness of the oral vaccine in badgers, as well as conducting regulatory studies to determine if the oral vaccine is safe; first to captive badgers, then to wild badgers. These studies are subject to successful completion of the objectives of this project, which are:

01 Determine most suitable formulation for incorporating live BCG vaccine into bait.
02 Determine most suitable bait for oral vaccine delivery to badgers.
03 Determine optimal strategy for deployment of bait to wild badgers.
Time-Scale and Cost
From: 2009

To: 2015

Cost: £6,777,329
Contractor / Funded Organisations
Veterinary Laboratories Agency
Keywords
Animal Diseases              
Animal Health              
Badgers              
Plants and Animals              
Tuberculosis              
Vaccines              
Fields of Study
Animal Health