Laboratory studies have shown that helminths can skew the immune response to increase the susceptibility of the host to co-infecting bacteria or viruses. Therefore, it has been suggested that targeting helminths could be an effective strategy for combating microbial co-infections. In this study, Ezenwa and Jolles assessed how anthelmintic treatment affects the spread of bovine tuberculosis (BTB) in wild populations of African buffalo (Syncerus caffer). The authors found that animals treated with an anthelmintic had an increased ability to secrete interferon-γ compared with untreated controls. Treatment with the anthelmintic had no effect on BTB acquisition rates in buffalo, but led to a ninefold decrease in mortality following the acquisition of BTB. However, anthelmintic treatment had a negative effect at the population level as it increased the spread of BTB among buffalo. These findings suggest that anthelmintics can have a positive effect at the individual level, but may ultimately have a detrimental effect at the population level by enhancing pathogen spread.