Parasitic worms are set to become a whole lot more common because of climate change, study says

There dwells a terrifying creature that disguises itself amidst faeces and filth, cunningly and patiently waiting for the right opportunity to squirm its way to your innards. Once there — and it is a lot more successful than you might think — this grotesque beast uses its many-fanged face to latch onto the walls of your intestines, stealing your hard-earned nutrition for a third of your life and growing to 80 feet in length, all the while dispersing eggs inside you.

While this might sound like some beast from some Goosebumps novel, you actually just read about the usual life cycle of the many species of real-life parasitic worms that very much exist in our world. While animals are more likely to catch an infection from these critters, they are set to become a more common sight among humans as well, all thanks to climate change.

Climate change is often associated with rising temperatures, but it has also led to an overall increase in global humidity, since warmer air is generally able to hold more moisture. And a new study has suggested that both of these factors are set to play a significant role in the spread of parasitic worms in many parts of the world. In particular, the research focused on soil-transmitted helminths, a common group of parasitic worms infecting roughly 25% of the global population, as per the World Health Organisation (WHO).

While killing the problem with more fire may seem like the obvious solution, researchers decided to employ a more civilised approach and ascertain the scale of the issue first. The team used mathematical models to map the effects of temperature and humidity on the free-living stages (meaning the eggs and larvae) of nine helminth species that commonly infect livestock and wildlife. These species were categorised based on whether they lived in the stomach or intestines, and models were developed to assess future infection risks under various climate change scenarios across Europe.

The study revealed that different worm species respond differently to climate variables. Intestinal worms exhibited a strong correlation with temperature — the highest infection risk was found at 10°C — while humidity had a negligible effect. Conversely, while temperature played some part, humidity played a major role in the hazard from stomach worms, finding that they thrived at humidities of 80% or higher.

Researchers also observed seasonal variations in infection risk, with 1-2 peaks in spring and summer for intestinal worms, and one peak for stomach worms. These patterns are expected to change in the future, with a potential increase in the intensity and number of seasonal peaks.

Finally, the study predicts a northward shift in the geographical distribution of the worm nuisance. Northern Europe, historically having a low infection risk, is projected to experience a rise in infection hotspots due to milder climatic conditions. Scandinavian countries, facing the greatest risk from these squirmy beasts, could witness their risk double by the end of the century! Many mid- to high-latitude regions could see more co-infections since many helminth species have been predicted to thrive together in the future.

These worms significantly impact the livestock industry, causing substantial economic losses. Traditionally, climate change and infectious diseases have been studied in the context of vector-borne diseases like those transmitted by mosquitoes and ticks. This study highlights the importance of considering other neglected tropical diseases, like those caused by helminths, and the broader range of climate variables beyond just temperature.

The findings of this research have been published in Ecology Letters.