The efficacy of badger vaccination programmes can only be accurately assessed if there is strong supporting data on the local population, a recent study on TB spread in Kilkenny has suggested.

A presentation to the TB Forum on the study – entitled ‘An investigation into an increase in bTB levels in cattle herds in northwest Kilkenny and adjacent parts of counties Laois and Tipperary during the period 2016–23’ – said determining the level of vaccination coverage within a badger population was crucial.

It was also recommended in the presentation that the true infection levels for TB in vaccinated and non-vaccinated badgers in the vaccination zones must be established.

In addition, the researchers proposed that methods for estimating the size, density and demographics of the local badger population will be needed.

Some mechanism for tracking and projecting changes in the badger population over time would also provide greater clarity around the efficacy of vaccination programmes.

The Kilkenny study was centred in the northwest of the country, in the area around the towns of Urlingford and Johnstown, where there has been a massive increase in TB breakdowns over the last nine years.

The herd incidence rate for TB in the area rose from 5.1% in 2016 to 13.1% in 2023, with the total number of TB cases increasing six-fold from 272 to 1,595 over the same period.

The presentation noted that while just 77 of 1,518 herds in the area had at least one TB case in 2016, this figure increased to 179 out of 1,368 herds by 2023.

While badgers were suspected by local farmers to have contributed significantly to the spread of TB, a badger vaccination programme was in place in the area since 2013.

It was pointed out in the presentation that significant resources were devoted to the vaccination programme and that vaccinations were carried out at 87% of known setts in 2020.

Despite the vaccination efforts, the study found that high levels of TB were identified at post-mortem in badgers culled in the area.

However, the authors claimed that the sample on which this information is based was “heavily biased”.

In 2020 the emphasis regarding badgers switched from vaccination to culling. Just 16 badgers were culled in 2020, but this figure increased steadily in the three subsequent years and reached 237 by 2023.

In relation to deer, the authors said there was a “very limited” examination of the red, fallow and sika deer present in the study area but there was evidence that some were infected with TB.