Today I heard a talk by Brett Finlay from the University of British Columbia at the Max Planck Institute for Infection Biology (MPIIB) which, as it turned out, had something called the ‘hamburger disease’ (which I had never heard of before) as one of its main themes. To describe the wider context let me recall that while the occurrence of E. coli in the human gut is usually not harmful and may even be beneficial due to its competition with bacteria whose effects are less pleasant, there are some special pathogenic strains of E. coli. Two of these are called EPEC (enteropathogenic E. coli) and EHEC (enterohaemorrhagic E. coli). The first of these causes diarrhoea in young children, mainly in developing countries. The second causes the hamburger disease to be discussed further below. It also involves diarrhoea but may have very serious complications. In particular this bacterium produces the Shiga toxin known from the bacterium of the genus Shigella which causes dysentery. These two strains were two of the main protagonists in the talk along with a bacterium Citrobacter rodentium naturally occurring in mice with analogous properties. The last organism provides a useful animal model for studying EPEC and EHEC.
The EHEC bacterium affects cattle. The cattle do not get seriously ill but they spread the bacterium. During slaughtering it can happen that the meat gets infected with the bacteria. As an example hamburgers can be affected leading to outbreaks of disease among humans. This kind of incident explains the name ‘hamburger disease’. Since the cause is known it is possible to test meat for infection. If an infection in found in one place in a large delivery all the meat will be rejected for human consumption due to the health risk. This can be a very costly affair. Hence producers of meat and hamburgers have a strong financial motivation to solve this problem.
Finlay had the idea of vaccinating the cattle. At first sight this does not seem reasonable – after all the cattle do not mind the disease. It does, however, prevent the spread of the bacteria and thus can solve the problem. Using the insights gained from basic research it was possible to produce a cost-effective vaccine rather rapidly. There were some problems of a more political nature to be solved. Who pays for the vaccine? Should it be approved by authorities for human or animal health? It seems that these have been solved satisfactorily. The vaccine now has official approval in Canada and is expected to get approval in the US soon.
In the course of his description of the development of the vaccine the speaker said something like ‘At this point the mathematicians come in’. He said it in such a way that he obviously expected his audience to know exactly what he meant. I did not and unfortunately I did not have an opportunity to ask him. Did he mean some kind of statistics, or some kind of model for the population dynamics of the bacterium, or something quite different? I do not know.
Hydrobates 
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