Data from: Disentangling the role of parasite infectivity and environmental density in infection development and parasite proliferation
Abstract
Understanding the environmental drivers of host-parasite interactions is a major concern for human health and conservation, particularly in the context of emerging infectious diseases. The likelihood of contracting an infection can be related to both the rate of contact between host and parasite, as well as innate features of hosts (susceptibility/resistance) and parasites (infectivity, virulence, within-host proliferation rate). This study uses a host-parasite system with a matching allele model for host susceptibility and parasite infectivity to disentangle contact rate from parasite infectivity while accounting for the effects of host susceptibility. Using three exposure doses from several parasite isolates to hosts with known susceptibility, we find significant differences in parasite infectivity (in terms of number of successful infections) and proliferation rate inside the host among parasite isolates, after controlling for exposure rate and host genotype. Exposure dose did not impact the number of infections but had a modest effect on infection intensity, while host known susceptibility accounted for nearly half of the variance in infectivity and a third of the variance in proliferation. No significant relationship between infection success and parasite proliferation rate was detected, indicating an independent variability among isolates for both variables.
Dataset DOI: 10.5061/dryad.7wm37pw5z
Description of the data and file structure
Nine clones of Daphnia magna were exposed to three calculated doses of six isolates of their parasite, Pasteuria ramosa, in a full factorial design, replicated at the individual level ten times for a total of 1620 individuals in isolated jars. Individuals were then monitored three times per week for 28 days, and at the end of the experiment, all individuals showing any signs of infection (no eggs, reddish colour, large size) were frozen in Eppendorf tubes with 1 mL of water. Tubes were then defrosted, their contents crushed with a pestle, and shaken at 4500 rpm for 2 hours to separate parasite spores, and a sample was placed in a hemocytomer. This was used to 1: confirm the presence of parasite spores to determine that the individual had been infected, and 2: count the spore density to determine the total number of parasite spores produced over the course of infection.
Files and variables
File: DVE.csv
Description: This file describes the data presented in DVE.csv. This experiment used a range of Daphnia magna clones exposed to a range of Pastueria ramosa isolates at three different initial doses of P. ramosa spores to disentangle parasite infectivity, growth rate and density from host susceptibility. Daphnia were kept in individual jars and monitored for 28 days, after which any with potential signs of infection were preserved in 1mL of water. Preserved individuals were then crushed, shaken at 4500 rpm for 2 hours to separate Pastueria spores, and the density of spores in that 1mL was counted twice using a hemocytometer. This data describes the identifying information of each individual and their parasite dose and spore treatment, as well as whether or not they became infected over 28 days (parasite infectivity) and their estimated final spore load counts (parasite proliferation).
Variables
- ID: Jar ID in which individual Daphnia was kept
- Clone: clonal line of Daphnia used
- parasite: P. ramosa isolate used
- dose: number of P. ramosa spores introduced to the jar
- preserved: y= yes (individual showed signs of infection within 28 days); n: individual showed no signs of infection and was not preserved for spore counts
- total: number of Daphnia (in two jars, it was determined after the fact that two individuals were accidentally placed inside instead of 1)
- finalspore1: 1st hemocytometer count; not applicable (NA) if final spores were not counted because individual showed no signs of infection
- finalspore2: 2nd hemocytometer count; NA if final spores were not counted because individual showed no signs of infection
- finalsporeavg: average of the two hemocytometer counts, used to estimate spore density; NA if final spores were not counted because individual showed no signs of infection
- adjfinalspore: final spore desnity per individual (for the jars that contained two individuals the total spore density was divided by 2); NA if final spores were not counted because individual showed no signs of infection
Code/software
All analyses were conducted in R. No original code/packages were written to analyse the data