Temperature variability increases Trypanosoma cruzi load but not the extrinsic incubation period in Triatoma infestans

Background Trypanosoma cruzi , the etiologic agent of Chagas disease, is transmitted via the dejections of triatomine insects such as Triatoma infestans . The extrinsic incubation period (EIP), parasite load, and infectivity of the vector are sensitive to environmental temperatures. Global warming is expected to increase both mean temperatures and their variability, potentially altering vector competence. Methods We experimentally infected T. infestans with the T. cruzi Dm28c strain and exposed them to four temperature regimes: two constant (18 °C and 27 °C) and two variables (18 ± 5 °C and 27 ± 5 °C). Over 42 days, we collected dejection samples for parasite quantification via qPCR and recorded the time of the first positive detection to estimate the EIP. Dejection samples were collected every two days throughout the study to quantify the parasite load using qPCR, enabling us to assess infection dynamics over time. Results Higher temperatures significantly shortened the EIP and increased the overall parasite load. However, temperature variability alone did not significantly alter the EIP. In contrast, variability increased the peak parasite load in the cold treatments without affecting the probability of positive dejections. The parasite load exhibited a bell-shaped curve over time, peaking earlier and higher under warmer conditions. A larger volume of ingested blood also reduced the EIP, especially under cold treatments. Conclusions Temperature increases accelerate T. cruzi development in T. infestans , potentially enhancing vector competence under climate change scenarios. Although variability in temperature did not affect EIP, it did influence parasite load, suggesting that both mean temperature and variability must be considered to understand the impact of climate change on Chagas disease transmission.