Model or meal? Farm animal populations as models for infectious diseases of humans

Abstract

In recent decades, theory addressing the processes that underlie the dynamics of infectious diseases has progressed considerably. Unfortunately, the availability of empirical data to evaluate these theories has not grown at the same pace. Although laboratory animals have been widely used as models at the organism level, they have been less appropriate for addressing issues at the population level. However, farm animal populations can provide empirical models to study infectious diseases at the population level.

Figure 1. Designs of transmission experiments.

a | One-to-one experiments. One infectious animal (I) is housed with one susceptible animal (S). A transmission chain can be obtained by using the infected animals to infect the next generation of susceptible animals. b | Group experiments. A number of infectious and susceptible animals are housed together. c | Extended transmission experiments. Artificially inoculated animals are mixed with susceptible animals. Artificially inoculated animals are removed, and the newly infectious animals (yellow and green), infected by contact with the inoculated animals, are used to start the transmission experiment by mixing them with new susceptible animals (blue). This design is useful when the artificial inoculation creates highly infectious animals; however, the initial infection process is less controlled. Aspects that need to be considered in the design of the experiment are the infection route, inoculation dose, mathematical model and statistics used to infer transmission parameters.