Cold snaps lead to a 5-fold increase or a 3-fold decrease in disease proliferation depending on the baseline temperature

Abstract

Background: Climate change is driving increased extreme weather events that can impact ecology by moderating host-pathogen interactions. To date, few studies have explored how cold snaps affect disease prevalence and proliferation. Using the Daphnia magna-Ordospora colligata host-parasite system, a popular model system for environmentally transmitted diseases, the amplitude and duration of cold snaps were manipulated at four baseline temperatures, 10 days post-exposure, with O. colligata fitness recorded at the individual level.

Results: Cold snaps induced a fivefold increase or a threefold decrease in parasite burden relative to baseline temperature, with complex nuances and varied outcomes resulting from different treatment combinations. Both amplitude and duration can interact with the baseline temperature highlighting the complexity and baseline dependence of cold snaps. Furthermore, parasite fitness, i.e., infection prevalence and burden, were simultaneously altered in opposite directions in the same cold snap treatment.

Conclusions: We found that cold snaps can yield complicated outcomes that are unique from other types of temperature variation (for example, heatwaves). These results underpin the challenges and complexity in understanding and predicting how climate and extreme weather may alter disease under global change.

Keywords: Daphnia magna; Ordospora colligata; Climate change; Cold snap; Cold spell; Disease; Host; Parasite; Pathogen; Temperature variation.

Fig. 1

Experimental setup. TIMELINE; illustrates the timeline for the experiment starting at day − 10 and terminating at day 27, exposure occurred on day 0, and every cold snap began on day 10. PREPARATION; preparation started 3 weeks prior to exposure when 10–12 mothers were added to a 400 mL microcosm, 72 h before the experiment began offspring were collected and females were kept. INFECTION; a dose of ~ 60,000 Ordospora colligata spores was given to each exposed individual, while unexposed controls were given a placebo dose made of crushed up uninfected individuals. BATH SETUP; each temperature had three baths, and each bath held four trays with 27 microcosms in each, each bath contained 20 cold snap treated individuals (five replicates per cold snap treatment), eight constant temperature treatments, and four uninfected controls. To simulate a cold snap, microcosms were moved between baths and then returned to the baseline bath when the cold snap finished. TREATMENTS; 16 treatments were included in the experiment (four baseline temperatures · two amplitudes · two durations). Additionally, at the cold snap specific temperatures (8 °C and 11 °C), each bath was organized the same as the baseline temperatures; however, no cold snap treatments were included. MAINTAINENCE; maintenance and measurements were carried out between days − 4 and day 27. Figure created on Biorender.com

Fig. 2

The effect of cold snaps treatments on proportion infected at 10 days post-exposure, in Daphnia magna infected with Ordospora colligata. Error bars represent the standard error, and each dashed line is the quadratic fit of the elastic net regression (see Additional file 1: Table S1 for statistical results)

Fig. 3

The effect of cold snaps treatments on burden (average number of spore clusters) 10 days post-exposure, in Daphnia magna infected with Ordospora colligata. Each spore cluster contains 32–62 individual Ordospora. Error bars represent the standard error, and each dashed line is the cubic fit of the elastic net regression (see Additional file 1: Table S5 for statistical results). Absence of the data point at 8 °C, for the constant temperature, is due to the absence of infection at this temperature. The asterisk and bracket (*[) indicates significant contrasts between means of the cold snap treatments when compared to the constant treatment

Fig. 4

Burden (average number of spore clusters) by baseline temperature, amplitude, and duration, for Daphnia magna infected with Ordospora colligata. Error bars represent the standard error; light gray area represents the standard error for the constant treatments. An asterisk (*) near the gray dashed line indicates that all cold snap treatments are different from the constant temperature treatment and an asterisk next to a solid black bracket (]*) indicates a difference between two single treatments