Theoretical modelling of temperature and rainfall inuence on Schistosoma species population dynamics
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Date
2018
Authors
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Publisher
University of Zululand
Abstract
Schistosomiasis, otherwise known as snail fever or bilharzia, is caused by parasitic
at-
worms called schistosomes. In human, these schistosomes infected the intestines or the
urinary tract where they develop to form other acute and chronic diseases which include
fever, malaise, severe abdominal pain, skin rashes, liver disease, lung disease, intestinal
disease and urinary tract disease depending on the schistosomes. The reoccurrence of
Schistosoma infections over the years may result into cancer of the bladder, obstruction
in urinary tract, portal or pulmonary hypertension and even death. This study was de-
veloped to investigate the in
uence of temperature and rainfall on population dynamics
of Schistosoma species over South Africa. Also, to investigate time-dependent control
strategies, so as to ascertain the best cost-e ectiveness optimal control strategy for schis-
tosomiasis eradication/control.
In this study, a deterministic schistosomiasis climate-based model was developed using
di erential equations. The numerical simulations of the system were done using MAT-
LAB and Ferret software in order to examine the e ect of climate variability on the
transmission dynamics of schistosomiasis. Furthermore, a deterministic model for the
transmission of schistosomiasis disease and optimal control analysis of the model was also
derived and analyzed. The model is found to exhibit multiple equilibria, the necessary
conditions for the optimal control of the disease was derived and analyzed. In addition,
the cost-e ectiveness of the controls was investigated in order to determine the most e ec-
tive strategy to control the disease with minimum costs. Finally, the numerical solutions
were presented.
vi
Numerical simulations showed that the impact of climate change on population dynamics
of schistosomiasis infection is greatly pronounced on the production, survivability and
fecundity rate of both freshwater snails and schistosomes. It was also showed by the nu-
merical simulations that all the strategies employed for schistosomiasis control have great
e ects both on the population of infected human and infected snail with control strate-
gies B, D, F, G, I and J showed great decrease e ects on the number of infected human
population. In the cost-e ectiveness of the control strategies, the results suggest that in
the presence of limited resources, policy makers may adopt the strategy I (combination
of the prevention, treatment and snail control) over J which includes additional cost of
controlling loss of immunity. Finally, the model further suggested future opportunity for
modi cation and re nement for the prediction of the e ects of climate variability on the
transmission dynamics of Schistosoma.
Description
Dissertation submitted to the Department of Biochemistry and Microbiology in partial fulfilment of the requirement for the degree of Masters (MSc)in Biochemistry. Faculty of Science and Agriculture at the University of Zululand, 2018.
Keywords
Schistosoma species, temperature, Schistosoma infections