Persistence and spread of gastro-intestinal infections: the case of enterotoxigenic Escherichia coli in piglets.

Several gastro-intestinal infections in animal husbandry not only greatly reduce the well-being of animals, but also have the potential to cause large economical damage. Understanding of the dynamics of such diseases is thus of great importance. In this paper, we focus on within-host dynamics and present a model describing the dynamics of pathogens in the intestine of a single host. Our motivation to study the problem stems from the case of enterotoxigenic Escherichia coli in newly weaned piglets, but the models we present offer an acceptable description of within-host dynamics of several other gastro-intestinal infections. We begin by studying the case where infection is a one-time event and derive an explicit expression for the distribution of pathogens inside the intestine at an arbitrary time after the infection took place. Since farm animals often come into contact with faeces, we furthermore investigate the reinfection case, in which a fraction of the shed pathogens is reintroduced into the intestine. We find the condition that guarantees persistence of colonization in the reinfection case and determine when the microbial distribution in the intestine obeys the so called asynchronous exponential growth. We outline possibilities for infection control and point out some challenges for further research on the subject.