Problem 1
By treating house martins (Delichon urbica) with antimalarial drugs, Marzal et al. (2005) were able to show that the malarial blood parasites in Spain reduced production of young birds by about \(40 \%\) In Denmark house martins do not carry this malarial parasite. Would you expect the population density of these birds to be higher in Denmark? Why or why not?
Problem 4
One resolution to emerging human health problems with diseases is to use evolutionary thinking to manage virulence. The suggestion is that with appropriate public health measures and treatment protocols, we could reduce disease and cause the parasites to become less virulent. In this way we could engineer the AIDS virus, for example, to become like the common cold. How might we drive evolution to manage virulence in human diseases? Ebert and Bull (2003) discuss this approach to virulence management.
Problem 5
Simple models of host-parasite systems do not have any spatial component. What advantages might be gained by constructing a spatial model of disease? Rabies is an example of a disease with interesting spatial spread patterns (see Figure 13 ). Foxes defend discrete, nonoverlapping territories. How might territorial behavior affect the spatial dynamics of rabies spread in foxes?
Problem 6
Why do not all pathogens evolve to become highly virulent and durable so that they survive a long time in the external environment? Is it possible to design a perfect pathogen?
Problem 7
Barlow (1995) showed that the vaccination rate required to eliminate a disease will always be greater than the culling rate required for elimination, given the standard SIR host-parasite model. If this is correct, why might we still prefer vaccination as a strategy for disease control in wild animals?
Problem 10
Anthrax, a bacterial disease caused by Bacillus anthracis, is lethal to most mammalian herbivores. Within a few months during \(1983-1984\) an anthrax epizootic wiped out \(90 \%\) of the impala population in Lake Manyara National Park in Tanzania. How is it possible for an epizootic of this type to suddenly appear in a population and then disappear for decades? Discuss the biological mechanisms that might permit this type of phenomenon. Prins and Weyerhaeuser (1987) discuss this particular impala epizootic.
