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■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

active immune response usually leading to lifelong protection. However, this is not same

for some diseases such as Malaria, which requires continuous exposures to sustain it’s pro-

tective efficacy that is not lifelong [34]. The duration for which an individual is protected

can vary markedly depending on the pathogen and antigens involved. Thus, individuals get

reinfected to certain diseases either because the pathogen mutated and our immune system

no longer recognizes it, which is believed to be the case with malaria.

Plasmodium parasites have developed mechanisms to down-regulate protective im-

mune responses against ongoing and subsequent infections [20], [195]. The parasites un-

dergo an essential expansion phase in the liver prior to the erythrocytic infections. Again,

Plasmodium parasites have high level of antigenic diversity which is believed to be main-

tained by both gene conversion and recombination events that give rise to multitudes of

variants in humans. This mechanism helps them to overcome recognition of existing anti-

gens and makes it difficult to achieve lifelong immunity to malaria [34]. Moreso, NAI to

malaria in humans comprises two stages: liver-stage and blood-stage immunity. Thus, anti-

genic functions are split between liver- and blood-stage parasites [197].

These mechanisms and more, discussed in the later part of this review, form the major

reasons why efforts made to provide a foolproof commercial malaria vaccine have proven

to be elusive [20],[21], [23], [22],[33]. Moreover, many anti-malaria drugs are becoming

inefficient as a result of evolving drug resistance mechanisms by some malaria parasites

[5], [25]. Universal coverage with insecticide-treated nets (ITNs) and indoor residual in-

secticidal sprays are currently the front-line preventive measures undertaken in malaria

endemic areas [3], [4], [13]. This is because the principal malaria vectors primarily feed

indoors at night when people are asleep. However, NAI (Table 5.1) to the parasite can help

to limit the health burden posed by malaria in older previously-exposed individuals [34],

[37]. Although the mechanisms behind this have not been fully explored, there exist some

general consensus view.

This work aims at reviewing the state of research on NAI so as to have a comprehensive

understanding of its underlying mechanisms and how modelling has contributed to the

consensus view of NAI. By so doing, more efficient ways of studying the consequences

of immunity in a given population can be suggested. Also, it will inform the research on

malaria vaccine, since one of the difficulties of producing a malaria vaccine lie on the

insufficient knowledge of the mechanisms behind NAI to malaria [23], [24], [101]. This is

detailed in the following research questions/objectives:

• RQ1: What are the current perceptions about NAI to malaria; what is true, mislead-

ing, or yet unclear?

• RQ2: How can the modeling approaches currently used to study the impact of NAI

in a population and their possible deficiencies be constructively assessed?

• RQ3: What are the opportunities for further improvement of models of immunity to

malaria infection?

In the rest of the chapter, we will explain how understanding and modelling approaches

have evolved together. Moreso, we will discuss how separate, parallel developments with