Data from: Host nutrition alters the variance in parasite transmission potential

The environmental conditions experienced by hosts are known to affect
their mean parasite transmission potential. How different conditions may
affect the variance of transmission potential has received less attention
but is an important question for disease management, especially if
specific ecological contexts are more likely to foster a few extremely
infectious hosts. Using the obligate-killing bacterium Pasteuria ramosa
and its crustacean host Daphnia magna, we analysed how host nutrition
affected the variance of individual parasite loads, and therefore
transmission potential. Under low food, individual parasite loads showed
similar mean and variance, following a Poisson distribution. In contrast,
among well-nourished hosts, parasite loads were right-skewed and over
dispersed, following a negative binomial distribution. Abundant food may
therefore yield individuals causing potentially more transmission than the
population average. Measuring both the mean and variance of individual
parasite loads in controlled experimental infections may offer a useful
way of revealing risk factors for potential highly infectious hosts.