Climate Dependent Malaria Disease Transmission Model and its Analysis
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Date
2018-01-05
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Addis Ababa University
Abstract
The impact of climate change on human health, particularly through the potential increase
in vector- and water-borne diseases, has received increasing attention in recent
years. Environmental variables are known to a_ect signi_cantly the population dynamics
and abundance of insects major catalysts of vector-borne diseases, but the exact
extent and consequences of this sensitivity are not yet well-established. Malaria infection
continues to be a major problem in many parts of the world including Africa. We
focus here on mathematical model that describes the impact of climate variation on
the malaria dynamics. To study this relation, a non-autonomous deterministic model
is designed by incorporating the e_ect of both temperature and rainfall to the dispersion
and mortality rate of adult mosquitoes and this is used to assess the impact of
the variability in temperature and rainfall on the transmission dynamics of malaria in
a population. In the model, the periodic variation of seasonal variables as well as the
non-periodic variation due to the long term climate variation has been incorporated and
analysed. In both cases, it has been shown that the disease-free solution of the model
is globally asymptotically stable when the basic reproduction ratio is less than unity
in the periodic system and when the threshold function is less than unity in the nonperiodic
system. The disease is uniformly persistent when the basic reproduction ratio
is greater than unity in the periodic system and when the threshold function is greater
than unity with some additional conditions in the non-periodic system. The model has
been validated using epidemiological data collected from western region of Ethiopia, by
considering the trends for monthly number of microscopically con_rmed cases of malaria
during the years 2000-2012 and the climate variation in the region. Then time dependent
optimal control theory in the non periodic environment is applied to investigate
optimal strategies for controlling the spread of malaria disease using insecticide treated
bed nets, spray of mosquito insecticide and treatment as the system time dependent
control variables. The possible impact of using combinations of two controls or one at
a time on the spread of the disease is also examined.
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Keywords
Asymptotic Stability, Periodic and Non-Periodic Climate Dependent Growth Rates, Validation Using Epidemiological Data, Time Dependent Optimal Control