Detection of live M. bovis BCG in tissues and IFN-γ responses in European badgers (Meles meles) vaccinated by oropharyngeal instillation or directly in the ileum.

BACKGROUND: Oral vaccination with Mycobacterium bovis Bacille of Calmette and Guerin (BCG) has provided protection against M. bovis to badgers both experimentally and in the field. There is also evidence suggesting that the persistence of live BCG within the host is important for maintaining protection against TB. Here we investigated the capacity of badger inductive mucosal sites to absorb and maintain live BCG. The targeted mucosae were the oropharyngeal cavity (tonsils and sublingual area) and the small intestine (ileum). RESULTS: We showed that significant quantities of live BCG persisted within badger in tissues of vaccinated badgers for at least 8 weeks following oral vaccination with only very mild pathological features and induced the circulation of IFNγ-producing mononuclear cells. The uptake of live BCG by tonsils and drainage to retro-pharyngeal lymph nodes was repeatable in the animal group vaccinated by oropharyngeal instillation whereas those vaccinated directly in the ileum displayed a lower frequency of BCG detection in the enteric wall or draining mesenteric lymph nodes. No faecal excretion of live BCG was observed, including when BCG was delivered directly in the ileum. CONCLUSIONS: The apparent local loss of BCG viability suggests an unfavorable gastro-enteric environment for BCG in badgers, which should be taken in consideration when developing an oral vaccine for use in this species.

The Effect of Oral Vaccination with Mycobacterium bovis BCG on the Development of Tuberculosis in Captive European Badgers (Meles meles).

The European badger (Meles meles) is a reservoir host of Mycobacterium bovis and responsible for a proportion of the tuberculosis (TB) cases seen in cattle in the United Kingdom and Republic of Ireland. An injectable preparation of the bacillus Calmette-Guérin (BCG) vaccine is licensed for use in badgers in the UK and its use forms part of the bovine TB eradication plans of England and Wales. However, there are practical limitations to the widespread application of an injectable vaccine for badgers and a research priority is the development of an oral vaccine deliverable to badgers in bait. Previous studies reported the successful vaccination of badgers with oral preparations of 108 colony forming units (CFU) of both Pasteur and Danish strains of BCG contained within a lipid matrix composed of triglycerides of fatty acids. Protection against TB in these studies was expressed as a reduction in the number and apparent progression of visible lesions, and reductions in the bacterial load and dissemination of infection. To reduce the cost of an oral vaccine and reduce the potential for environmental contamination with BCG, it is necessary to define the minimal efficacious dose of oral BCG for badgers. The objectives of the two studies reported here were to compare the efficacy of BCG Danish strain in a lipid matrix with unformulated BCG given orally, and to evaluate the efficacy of BCG Danish in a lipid matrix at a 10-fold lower dose than previously evaluated in badgers. In the first study, both BCG unformulated and in a lipid matrix reduced the number and apparent progression of visible lesions and the dissemination of infection from the lung. In the second study, vaccination with BCG in the lipid matrix at a 10-fold lower dose produced a similar outcome, but with greater intra-group variability than seen with the higher dose in the first study. Further research is needed before we are able to recommend a final dose of BCG for oral vaccination of badgers against TB or to know whether oral vaccination of wild badgers with BCG will significantly reduce transmission of the disease.

Improving the persistence of a formulation of the avian repellent cinnamamide, for the protection of autumn-sown oilseed rape.

In a previous pilot field trial on autumn-sown oilseed rape (Brassica napus L), a suspension concentrate formulation of the avian repellent cinnamamide, using Acronal 4D (50 g litre(-1)) as the sticker, was shown to reduce damage by woodpigeons (Columba palumbus L). However, the persistence of cinnamamide on rape leaves was poor. This paper describes the development of a weather-resistant formulation by the inclusion of a more effective sticker. In vitro studies were used to investigate wash-off of cinnamamide, which was identified as being the major mechanism of loss in the field. Rainfastness of cinnamamide was assessed by washing deposits on glass slides and rape leaves using a 'rain-washing machine'. A number of stickers were evaluated and the effect of sticker concentration, ageing of deposits, freezing and intermittent washing on rain-fastness was investigated. None of the candidate stickers showed increased rainfastness compared to Acronal 4D. However, two of the stickers, Crovol T40 G and Emoleo L1, when combined with Acronal 4D in small amounts, did reduce wash-off compared with Acronal 4D alone. Freezing led to an increase in wash-off of cinnamamide, but inclusion of Emoleo L1 with Acronal 4D reduced this effect. Increasing the concentration of the sticker was also shown to improve the rainfastness; doubling the concentration of Acronal from 50 to 100 g litre(-1) halved the wash-off of cinnamamide.