The role of temperature in the start of seasonal infectious disease epidemics

Abstract

Many infectious diseases display strong seasonal dynamics. When both hosts and parasites are influenced by seasonal variables, it is unclear if the start of an epidemic is limited by host or parasite factors or both. The Daphnia–Pasteuria host–parasite system exhibits seasonal epidemics. We aimed to ascertain how temperature contributes to the timing of P. ramosa epidemics in early spring. To this aim, we experimentally disentangled this effect from the effects of temperature on host development and phenology and from that of host traits on parasite time to visible infection. We hypothesized that the parasite is additionally directly limited by low temperatures beyond its need for available hosts. We found that parasite time to visible infection decreased with increasing temperature at a faster rate than host time to hatching and maturity did, consistent with this hypothesis. We also found that hosts hatched from sexual resting stages are less likely to become infected than those produced clonally, and that hosts resistant to many known parasite strains are slower to show signs of visible infection compared to those susceptible to many. Together, these results imply that climate change could lead to earlier seasonal epidemics for this host–parasite system, which may also impact longer‐term population dynamics.

Temporal changes in streamflow regime and host-related factors affect parasitism of freshwater prawn in Southeast Brazil

“…Temporal changes in the hydrological regime act as a strong drive to sustain and alter the structure of benthic invertebrate communities (Poff and Zimmerman, 2010;Northington and Webster, 2017;Poff et al 2018;Herbst et al 2019;Palmer and Ruhi, 2019), as well as the infectious disease and parasite dynamics in freshwater ecosystems (Altizer et al 2006;Groner et al 2018;Schmid-Hempel, 2021;Tadiri and Ebert, 2023). Variability in temperature and rainfall are important aspects in understanding host-parasite interactions (Marcogliese, 2016;Shearer and Ezenwa, 2020), and can alter host susceptibility and exposure to parasites, and as a consequence, it can increase or decrease parasite loads (Groner et al 2018;Vestbo et al 2019;Shearer and Ezenwa, 2020).…”

“…Furthermore, most studies have concentrated on the effects of increasing temperature rather than altered hydrology (Marcos-López et al 2010;Lõhmus and Björklund, 2015;Marcogliese, 2016;Lymbery et al 2020). Therefore, it is fundamental in aquatic parasitology to disentangle the contribution of these sources of variation, particularly in streamflow changes and habitat area, to better understand how these hydrological changes correlate with host-related factors to affect parasite loads over space and time (Poulin, 2007;Kamiya et al 2014b;Cattadori et al 2019;Poulin, 2021;Tadiri and Ebert, 2023).…”