‘From an epidemiological perspective, populations matter more than individuals’

Mart de Jong (67) studied Forestry at Wageningen University & Research. He enriched his subject package with a hefty number of mathematical subjects. ‘In those days, you had a lot of freedom in choosing subjects that matched your interests,’ he says. After his graduation, he transferred to Leiden where he did PhD research in the Department of Theoretical Biology. This research gave him the opportunity to combine his passion for mathematics with the epidemiological aspects of biology. Even before completing his PhD, he was asked to apply for the position of epidemiologist at the Central Veterinary Institute (CDI, now Wageningen Bioveterinary Research) in Lelystad. He joined there on June 1, 1989.

Uncharted territory

‘Epidemiology was a new discipline for the institute in Lelystad at the time. I was given the task of setting up this type of research,’ De Jong recalls. Illustrative of the unfamiliarity of the field of epidemiology, according to De Jong, was the question asked when he took office: ‘Do you really need a computer all day?’

Gradually, the field proved its added value for veterinary research. Careful, incremental expansion of the department followed. ‘Once analysts were also recruited, the opportunity arose to set up transmission studies,’ says De Jong.

Programming

Especially in the early years, he created the computational computer programs needed for the epidemiological analyses himself. ‘At that time, we did not have extensive computer packages suitable for the type of analysis we were doing,’ he says. One of the achievements of the epidemiological work De Jong did with his epidemiology department was modelling the eradication - through vaccination - of Aujeszky's disease, a viral disease in pig farming. ‘Based partly on our models, the vaccination program was implemented. That set-up led to the Netherlands being granted the Aujeszky-free status,’ De Jong said. The approach was based on getting the reproductive number (the ‘R’) below 1. ‘Something everyone has come to understand since Covid-19,’ the professor says with a smile.

Population versus individual

Important difference in the Aujeszky eradication compared to today's disease control programs, according to De Jong, is the fact that in this case the pig population was the focus, not the individual animal or pig farm. ‘In many contemporary transmission trials, the focus is more on the individual than the population.’

That difference in approach continues to raise concerns in the field, says the professor. ‘Especially since the corona pandemic. After all, every life counts, but viewed from the population perspective, a different approach may be better.’ De Jong compares it to paying Tax: individually, everyone tries to keep the amount to be paid as low as possible, for the population, and thus ultimately for the individual, it is important that sufficient money is available to provide for collective interests. ‘This also holds for animal disease control: the individual is important, but we should not lose sight of the population,’ he warns.

Partly for this reason, the professor argues that epidemiological research should also involve other disciplines, for example sociologists, economists and communication experts. ‘Especially in sensitive topics like health and disease and the making of potentially hard societal choices, these experts can contribute to a good foundation for the choices to be made,’ De Jong believes.

Professor

Ten years after joining CDI as an epidemiologist, De Jong was approached for the position of professor by both Utrecht University and Wageningen University. Combining three positions proved no mean feat. De Jong opted for the combination CDI + WU and five years later (2004) made a full transition to the chair of Quantitative Veterinary Epidemiology (QVE, now IDE) at Wageningen University. ‘In the early years, QVE was a small chair. We provided one graduate course. Only ten years later a second one was added, which became a success partly thanks to Quirine ten Bosch's efforts.’

Broadly applicable

Epidemiology is a subject that De Jong says is broadly applicable and, partly because of this, attracts not only animal science students, but also veterinary and biology students. Especially students who, like De Jong, have an excessive interest in mathematics and numerical solutions find their way to QVE. In the professor's view, because of the great importance of the field, there should be many more than the current number. ‘We now attract about 10 to 15 students a year with our courses,’ he says. One of the causes of reduced interest, according to De Jong, is the disappearance of overall numeracy in society. ‘You see that reflected in students. Math skills are declining,’ he observes.

Students

That mathematical knowledge gap is certainly not there among students who choose to take the QVE courses or do a master's thesis or PhD research with the department, but De Jong would like to see that more students realize its importance. During his years as a professor, he thoroughly enjoyed the conversations with students and PhD students. ‘Such conversations provide depth. Master and PhD students come up with unexpected questions, can surprise you and make you think. That also helps you to challenge yourself and explore new solution directions,’ according to the professor. Recently, while clearing out a cupboard, he collected all the dissertations of PhD students he supervised. There were 42 of them. ‘I kept all the booklets,’ he laughs. At least three more will be added in the coming period, he expects, the last one in 2027.

Growth

The professor is convinced that under the new name ‘Infectious Disease Epidemiology’, the QVE department can and will continue to profile itself within and outside the context of WUR. ‘Models and model calculations remain of great importance, especially in mapping disease progression in a population, both for animals and humans.’ Statistic underpinning has also helped to ensure that research on disease transmission or drug application can be done with an increasingly small number of animals. ‘Small numbers, provided the research design is well chosen, provide a lot of useful information. With this, we as a field of expertise have contributed to the goal of greatly reducing the use of animals in research.’

De Jong is optimistic about the future of his field. ‘Epidemiology is an important tool that has great significance for developments in society, both for humans and animals. Modelling and thus predicting expected trends lays an important basis for policy decisions and choices we make as a society. This makes epidemiology indispensable for the future.’