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Ecology : The Experimental Analysis of Distribution and Abundance

Charles J. Krebs

Chapter 13

Species Interactions IV: Disease and Parasitism - all with Video Answers

Educators

Chapter Questions

02:23

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?

Courtney Burson
Courtney Burson
Numerade Educator
10:23

Problem 2

Calculate the population changes from Equations (1) to (3) in a hypothetical host-parasite system. The parameters for the interaction are: $\beta=0.025$ (transmission rate) and $\gamma=0.01$ (recovery rate). Start the population with 500 susceptibles and 5 infecteds, and investigate how the dynamics would change if $\beta$ increased to 0.040 or 0.060.

Yaw Asomani
Yaw Asomani
Numerade Educator
03:04

Problem 3

About 20 million waterfowl die each year in North America from avian cholera, which is caused by the bacterium Pasteurella multocida (Blanchong et al. 2006)$.$ Over 100 species have been known to be infected. Epizootics are typically explosive and involve hundreds and sometimes thousands of birds. There is high variation from year to year in the incidence of this disease. Plan a research program to determine the effects of avian cholera on a species of duck. What are the key questions you need to answer to be able to control this disease?

Nimi Das
Nimi Das
Numerade Educator
08:19

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.

Sana Riaz
Sana Riaz
Numerade Educator
02:37

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?

Dennis Howard
Dennis Howard
Numerade Educator
01:54

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?

Sulav Pokhrel
Sulav Pokhrel
Numerade Educator
00:44

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?

Sam Limsuwannarot
Sam Limsuwannarot
Numerade Educator
03:54

Problem 8

One of the controversies in disease ecology is whether the parasitic nematode Trichostrongylus temuis has a strong effect on red grouse populations in Scotland and northern England. Review this controversy and evaluate the experiments that have been done to resolve the different points of view. Hudson et al. $(1998),$ Moss and Watson $(2001),$ and Redpath et al. (2006) discuss the differing points of view.

John Barone
John Barone
Numerade Educator
00:44

Problem 9

Anderson and May (1980) suggested that fluctuations in forest insect populations could be explained as host-parasite interactions, because simple disease models could generate population cycles or outbreaks of the host insect species. Review the subsequent history of this suggestion from the papers in Berryman (2002) and the discussions in Turchin (2003).

Zachary Papazian
Zachary Papazian
Numerade Educator
03:32

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.

Sana Riaz
Sana Riaz
Numerade Educator