Chapter 27
Two Age-Class Parasites
Men who reject the responsibility of thought and reason can only
exist as parasites on the thinking of others.
(Ayn Rand, The Virtue of Selfishness)
27.1 Two Age-Class Parasite Model
This model shows how a disease spreads in an insect population, such as asexually
reproducing aphids, consisting of two life stages—nymphs and adults. The model
has two parts, one for the healthy population and one for the diseased population.
Diseased nymphs can infect healthy nymphs and become diseased adults. Diseased
adults cannot infect healthy adults or nymphs but can produce infected nymphs.
Note how these features are expressed in the model by the appropriate flows and
links.
Unlike in the previous section of this chapter, the infection coefficient is based
on an exponential model.
INFECTION COEF ¼ 1 À EXP À:3 Ã NYMPHS Ã NYMPHS D
ð
Þ
ð 27:1Þ
NYMPHS and NYMPHS D refer to the population sizes of healthy and infected
nymph populations, respectively. The INFECTION RATE is calculated as the
product of the INFECTION COEF, the number of healthy nymphs, divided by
the model maturation rate for survivors, MNSF/TN
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_27,
© Springer International Publishing Switzerland 2014
223
Two Age-Class Parasites
Men who reject the responsibility of thought and reason can only
exist as parasites on the thinking of others.
(Ayn Rand, The Virtue of Selfishness)
27.1 Two Age-Class Parasite Model
This model shows how a disease spreads in an insect population, such as asexually
reproducing aphids, consisting of two life stages—nymphs and adults. The model
has two parts, one for the healthy population and one for the diseased population.
Diseased nymphs can infect healthy nymphs and become diseased adults. Diseased
adults cannot infect healthy adults or nymphs but can produce infected nymphs.
Note how these features are expressed in the model by the appropriate flows and
links.
Unlike in the previous section of this chapter, the infection coefficient is based
on an exponential model.
INFECTION COEF ¼ 1 À EXP À:3 Ã NYMPHS Ã NYMPHS D
ð
Þ
ð 27:1Þ
NYMPHS and NYMPHS D refer to the population sizes of healthy and infected
nymph populations, respectively. The INFECTION RATE is calculated as the
product of the INFECTION COEF, the number of healthy nymphs, divided by
the model maturation rate for survivors, MNSF/TN
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_27,
© Springer International Publishing Switzerland 2014
223