BCG Vaccination Of Badgers Could Be ‘Highly Effective’ In Reducing TB Incidence – Report

A three-year field study in Co. Kilkenny looked at the efficacy of the Bacille Calmette-Guérin (BCG) vaccination in badgers, and found that it could be a highly effective means of reducing the incidence of tuberculosis (TB) in badger populations.

The recently published TB-focused study was funded by the Department of Agriculture, Food and the Marine (DAFM), and involved the School of Veterinary Medicine at University College Dublin (UCD).

The study, Protective immunity against tuberculosis in a free-living badger population vaccinated orally with Mycobacterium bovis Bacille Calmette-Guérin, involved 934 badgers and covered an area approximately 755km2 characterised by low level and rich pasture.

The area was divided into three zones (A,B and C) with different levels of vaccine/placebo coverage.

It was “extensively surveyed” for badger setts and when discovered the sett locations were recorded and assigned a unique identification.

All setts were visited twice in each year – September to February and March to July.

According to the study, a considerable body of scientific evidence shows that badgers are an important reservoir of Mycobacterium bovis, and are associated with the transmission of infection to cattle.

Reservoir
Where the an infectious pathogen naturally lives/reproduces.

Culling and vaccination are key to reducing infection rates within badger populations or to minimise the potential transmission of infection from infected badgers to cattle, according to the study.

It continued:

“The development of a vaccination strategy targeted at badgers is often advocated as an alternative option, where the key objective is to reduce the transmission rate of infection within a badger population by reducing the level of susceptibility to infection.”

Kilkenny TB Study

In the Kilkenny study, badgers were treated orally with:

  • Placebo (100% in zone A);
  • BCG (100% in zone C);
  • Randomly assigned 50%: 50% treatment with BCG or placebo (in zone B).

At the end of the study 275 badgers were removed from the trial area and underwent a detailed post-mortem examination followed by histology and culture for M. bovis.

Among these badgers, 83 (30.2%) were captured for the first time across the three zones, representing a non-treated proportion of the population (meaning they had not been previously vaccinated).

Analysis of the data – based on the infection status of treated animals – showed a prevalence of:

  • 52% infection in zone A (placebo);
  • 39% in zone B (placebo);
  • 44% in zone B (BCG vaccinated);
  • 24% in zone C (BCG vaccinated).

Among the 83 non-treated badgers removed at the end of the study, the infection prevalence of animals in zone A and zone B was similar to the treated animals in these zones.

However, in Zone C, no evidence of infection was found in any of the untreated badgers.

“This is consistent with an indirect protective effect in the non-vaccinated badgers leading to a high level of population immunity,” the report stated.

“The results suggest that BCG vaccination of badgers could be a highly effective means of reducing the incidence of tuberculosis in badger populations.”

(Source – Agriland – Bernie Commins – 01/09/2021)

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