The Universiteitsfonds Wageningen (UFW) has selected the thesis of Dries Hulst, entitled “Genetic epidemiological analysis of endemic diseases", as the best master thesis in the domain of life sciences at WUR. In his thesis Dries shows that genetic selection against endemic infectious diseases is much more promising than currently believed.
Infectious diseases are a major threat for animal welfare, for the efficiency of our food production, and, in the case of zoonoses, also for human health. Artificial selection for greater resistance against infectious diseases in livestock populations is therefore important, but perceived as problematic due to low heritability values.
Positive feedback effects
In his thesis research, Dries shows that this perception is based on a misconception, resulting from improper statistical methods used in the field of quantitative genetics. Disease transmission models show that positive feedback effects are a key factor determining the prevalence of an infectious diseases, and may result in the phenomenon known as herd immunity. Common statistical methods in livestock genetic improvement, however, ignore such feedback, and therefore considerably underestimate the potential response to selection in the prevalence of endemic infectious diseases.
Moreover, results of the research demonstrate that genetic selection may lead to the extinction of infectious diseases, which is believed to be impossible in classical breeding theory. This thesis demonstrates the value of the integration of scientific disciplines, quantitative genetics and epidemiology in this case, by young scientists who are not hampered by the history of the field.
The jury highlights the societal relevance of the findings of the research, and the independence shown by Dries. The research was a collaboration of Animal Breeding and Genomics and Quantitative Veterinary Epidemiology, and Dries was supervised by Piter Bijma (ABG) and Mart de Jong (QVE).
Dries continues his research in this field as a PhD-student at QVE and ABG. The primary aim of his project is a further integration of the theoretical foundation of these two disciplines, which is essential for a sustainable food production by healthy livestock.