Climate change can lead to warmer environments, facilitating higher pathogen growth and increasing disease burden. Climate change can also reduce the nutritional value of food resources, causing malnutrition, which can lead to impaired immunity and disease vulnerability. However, despite these associations, no experiments have tested how dietary manipulations and temperature variations interact to drive the effects of pathogenic infections. In this work, we conducted laboratory experiments with the model insect Drosophila melanogaster to test these effects. Virgin flies raised on low-carbohydrate diets throughout development and early adulthood exhibited improved post-infection survival rates and more resilience to pathogen burden compared to those reared on regular or high-carbohydrate diets. However, such a survival advantage of the low-carbohydrate diet was lost in their mated counterparts. Notably, temperature stress decreased survival rates in flies only when they were reared on a regular diet. This effect was not observed in flies reared on high- or low-carbohydrate diets, indicating that the impact of temperature on infection responses might depend on diet. Besides, flies reared on a low-carbohydrate diet showed greater reproductive output at standard temperatures than those on other diets, indicating an apparent lack of fitness costs associated with improved post-infection response. Also, high-carbohydrate diets conferred greater resistance to starvation, suggesting differences in resource allocation among somatic maintenance tasks that could increase vulnerability to pathogens. Overall, these findings imply a complex interaction between diet, temperature, and fitness traits that influences variation in infection responses. As many organisms around the world face environmental warming and poor diets, examining these patterns and processes can provide a deeper understanding of variations in health and disease responses amid a changing climate.
Shit et al. (Thu,) studied this question.