New research from a recent Trinity College Dublin study has found that badgers living with helminth parasite infections (worms) are more likely to have TB.
To test whether this theory was right, zoologists from Trinity assessed the levels of helminth worms present in badgers culled for non-TB-related reasons and also checked them for TB.
Their results, published on Tuesday in the International Journal for Parasitology – Parasites and Wildlife, show that badgers infected with TB were more likely to be infected with worms.
Professor Nicola Marples, from Trinity’s School of Natural Sciences, said other aspects of animal health have largely been neglected in previous studies, but it is well known that if animals, or humans, have parasites, such as helminth worms, they are more likely to catch illnesses such as TB.
"That’s because the immune system can’t do everything at once.
"If it’s busy fighting helminth worms, it has fewer resources available to protect against bacterial infections, like TB, which require a different immune pathway.
"And it’s true the other way round too; if an animal has a bacterial infection, it is more susceptible to parasites," she said.
Domestic cattle are routinely treated for helminths, but badgers are not, she explained.
"We hypothesised that if badgers were living with a lot of worms and we know that some do, they might be more likely to catch TB and pass it on to the local cattle," she said.
Male badgers were more likely to be infected with TB
Zoologist David J Kelly from Trinity said that from their assessment, 71% of the badgers had gut worms and 16% also had a TB infection.
"Crucially, when assessing the link between the two, we found that badgers infected with TB were indeed more likely to be infected with worms.
"We also found that male badgers were more likely to be infected with TB than female badgers. This probably relates to differences in the territorial behaviour of males and females," he said.
Professor Marples said that this discovery has implications for TB management strategies and expands the understanding of the plight of badgers in the Irish environment.
"As we cannot treat wild badgers for helminth worms, it is important to consider that this will make them more susceptible to carrying TB, she said.