Gut helminths are the worms that live in the gut. While it should be no surprise that they infect many animals, they actually infect approximately 1 billion humans as well, mostly from traditional societies. Their role and criticality to the microbiome has been an ongoing topic of research, and as we have written about before, there is research to show helminths can be both beneficial and harmful to humans. A study published last week in Science shines a new light on this subject, showing helminths may be bad for individuals, but good for communities.
The study focused on wild Africa buffalo from Kruger National Park in South Africa. Helminths naturally affect almost all of the wild buffalo, so the scientists gave some of them anti-helminth medication. The scientists then measured how these buffalo survived bovine tuberculosis, a bacterial infection. As it turns out, all buffalo, treated and untreated, were at equal risk for becoming infected with the tuberculosis. However, the treated buffalo with no helminths had a 9 times higher survival rate from the disease. The scientists believe that the immune system of these buffalo can exert all its resources to combat the bacteria, rather than having to deal with both the helminths and the tuberculosis at the same time. Interestingly though, because all buffalo were at equal risk for infection, those buffalo that survived due to lack of helminths became efficient carriers of the disease. Therefore the tuberculosis could spread to many more buffalo in the community, and a lack of helminths could usher in a buffalo tuberculosis outbreak.
I think the most important aspect of the paper as it relates to humans is that individual survival rates were much better in buffalo treated with anti-helminth drugs, so humans considering helminth therapy should keep this in mind. The immune system has limited resources, and in buffalo it seems that helminth – bacterial co-infections increase morbidity. Once again, though, research shows helminths to be a sort of double edged sword. While individual buffalo may be better off without the worms, the overall population prospers with the worms.