Malaria is a life-threatening disease caused by Plasmodium parasites transmitted via mosquito bites. P. falciparum is the deadliest species. In 2010, malaria killed approximately 600,000 people, mostly young children and pregnant women in Africa. While control efforts have reduced malaria significantly outside of Africa, it remains a major public health challenge, exacerbated by emerging drug resistance and the overlap of malaria with poverty. Accurate diagnosis via microscopy of blood smears remains essential for effective treatment and control of this widespread and complex disease.

1. 1.Malaria
Malaria is a common life-threatening disease in many tropical and sub-tropical areas.
It is currently endemic in over 100 countries [1]. In 2010 its an estimated 600,000
people were killed by malaria most of whom are children under 5 yrs of age and
pregnant women [2]. Malaria is a vector borne infection caused by unicellular
parasite of the genus plasmodium. Plasmodium are obligate intracellular parasites
that are able to infect and replicate within the erythrocytes after a clinically silent
replicative phase in the liver. Plasmodium is transmitted by female Anopheles
mosquitoes, which bite mainly between sunset and sunrise.
2. Parasites
Four species of malaria parasites infect people – Plasmodium falciparum, P. vivax, P.
Malariae and P. ovale of which P. falciparum and P. vivax are the most common.
Falciparum malaria can be fatal. Severe falciparum malaria has been found to have a
case-fatality rate of around 10% in reasonably well-equipped hospitals [3] .
3. Epidemiology
According to the WHO malaria control handbook of 2005 the current distribution of
malaria in the world. WHO [1] reported the four human malaria species not evenly
distributed across the malaria-affected areas of the world and their relative
importance varies between and within different regions. The risk of contracting
malaria is therefore highly variable from country to country and even between areas
in a country. P. falciparum was found to be the commonest species throughout the
tropics and subtropics, and predominates in sub-Saharan Africa. P. vivax has the
widest geographical range, present in many temperate zones but also in the
subtropics, and coexists with P. falciparum in the Horn of Africa and in tropical parts
of the Americas and Asia. P. ovale occurs in Africa and sporadically in south-east
Asia and the western Pacific. P. malariae has a similar geographical distribution to P.
falciparum but is far less common and its incidence is patchy. Knowing which
species are present in any particular area and the relative importance of each species
is very important because this will affect the choice of treatment.
Bob car [4], Australian minister for foreign affairs in his briefing to the world health
organisation ( WHO) on Roll back Malaria WHO campaign described Malaria as a
resilient foe. With 3.3 billion people at risk of infection globally, the disease is still a
major burden on health systems in poor countries. Outside of Africa, malaria inflicts
the heaviest toll in the Asia-Pacific.
The World Health Organization (WHO) has reported around 34 million cases of
malaria in regions outside of Africa in 2010 causing 46 000 deaths. India is shown to
by far be the most affected, but also of high rates are Indonesia, Pakistan, Myanmar,
Solomon Islands, and Papua New Guinea. The worldwide public health risk of
malaria is further compounded by the recent emergence of artemisinin resistance in
Cambodia, Thailand, Myanmar, and Viet Nam coupled with the long term
chloroquine resistance. Failure to contain drug-resistant malaria could trigger its
spread throughout the world. This would lead to a surge in cases and deaths, and
undermine global progress in malaria control. This is because every place in the
world has a certain potential for malaria transmission that is intrinsic to it at a given
point in time, ranging from zero to some level above zero [5]; a characteristic often

2. referred to as ’receptivity’, indicating the extent to which conditions are favourable
for malaria transmission in a specific location. The potential for malaria transmission
is a function of many varied factors, including (but not limited to):
The mosquito vector species, their abundance and behaviour
The Plasmodium species
Temperature and rainfall
Geography and topography of the land
Amount and type of agriculture or land-cover in that area
Strength of the health system
Quality of housing in which people live
How people spend their time in the places and times when vectors are feeding.
Together, these characteristics lead to a specific malaria baseline: the level of malaria
burden that would exist in a given place if no interventions are implemented to
control it [4]
Epidemiologically the African continent carries the major burden of malaria along
with other 50 countries [4]. According the the WHO there are 20 countries with
ongoing malaria transmission in the South-East Asia and Western Pacific regions, 21
countries in the Region of the Americas, and 10 in the Eastern Mediterranean and
European regions. Outside of Africa, a total of 2.5 billion people are at risk of the
disease.
Countries in Asia and the Pacific (i.e. the WHO South-East Asia and Western Pacific
regions) carry the biggest disease burden, with an estimated 88% of cases and 91%
of malaria-related deaths . India, Indonesia, Pakistan, Myanmar, and Papua New
Guinea have the highest malaria incidents [5]
According to a WHO policy maker briefing; over the last decade, the global malaria
landscape has changed dramatically, and malaria has presently has a worldwide
recognition as a priority public health issue. The increased availability of
international funding—primarily through the Global Fund to Fight AIDS,
Tuberculosis and Malaria has enabled ministries of health to vastly expand their
malaria control operations. Also delivery mechanisms have been established for mass
distribution of conventional insecticide-treated nets (ITNs) and long-lasting
insecticidal nets (LLINs); indoor residual spraying (IRS) programmes have been
consolidated; diagnostic testing, treatment, and surveillance have been scaled up.
However the WHO also noted that Despite the successes of malaria control outside of
Africa, the disease continues to be a major burden not only on individuals and
families, but also on national health systems, requiring constant vigilance and tailored
control strategies for different geographical areas within countries. It continues to be
a barrier to economic development, tourism, and foreign investment. The fight
against malaria is further complicated by growing parasite resistance to antimalarial
drugs and emerging mosquito resistance to insecticides. If these threats are not
contained, they could undermine global malaria control efforts and reverse the
impressive gains made in the last decade. It is in view of this that the WHO rolled out
in 2012 a campaign of malaria elimination. The objective of which is to reduce the
incidence of and mortality from malaria as rapidly and economically as possible.
Achieving a 50% reduction in the malaria burden by 2010 compared to the levels in

3. 2000, and at least a 75% reduction in malaria incidence and deaths by 2015. These
goals are relevant for high-burden countries implementing malaria control
programmes. Elimination of malaria is defined as the complete interruption of the
chain of local malaria transmission. Elimination programmes require more technical
malaria expertise than standard malaria control programmes, especially in malaria
epidemiology and entomology. [6]
However this ambitious target is considered a developmental challenge. This is
because the distribution of malaria overlaps with the global map of poverty; within
endemic countries, poor and vulnerable communities are impacted more severely
than others. Controlling and eliminating malaria is therefore very much a
development challenge—one that is inextricably linked with poverty reduction and
infrastructure development as well as health system strengthening [7].
Access to formal health care and preventive measures may be more difficult due to
language barriers or traditional beliefs. It is also often more difficult, and
therefore more costly, to offer services to such populations due to infrastructural
challenges, security concerns, or political considerations.
Furthermore mobile populations such as migrant workers, refugees, and internally
displaced people are also disproportionately affected by malaria. These populations
have limited access to preventive interventions and health facilities, and often do not
receive proper and timely treatment for their malaria infection. This is mostly
evidenced in displaced populations in Asia. Whilst in Africa, it is becoming
increasingly concentrated in marginalized population groups, including poor and rural
communities; ethnic, religious, and political minorities; and communities living in
hard-to-reach areas and border regions [7].
Population movement due to demographic, economic, political pressures, and natural
disasters or conflict may also push vulnerable communities to leave malaria-free
areas and move into endemic zones. Asia is the region of the world's most affected
sudden-onset natural disasters, and the likelihood of such events growing in number
in the future is very high.
Given the treatment costs and the financial losses resulting from work absenteeism,
malaria imposes a substantial burden on individuals and affected families. The
disease causes disruption to schooling and reduces the days worked not only of the
sufferers but of those who care for them.
The fight against malaria is also rendered difficult by weak pharmaceutical
regulation, the wide availability of oral artemisinin-based monotherapies (and other
antimalarials that do not meet international quality standards), and a lack of adequate
access to quality-assured ACTs. All of these factors are important drivers of drug
resistances.
Given their resource constraints and weak health systems, most endemic countries
lack adequate funding to deliver prevention tools or access to treatment to all
populations at risk. Thus, impoverished populations are denied access to essential
interventions that can prevent or cure malaria. While the number of conventional
ITNs and LLINs delivered outside of Africa rose seven-fold from 2003 to 2010, only
125 million of the 640 million people at high risk of the disease were protected
through vector control interventions in 2010

4. 4. Malaria Infection
P. falciparum is the higly infectious and most deadly malaria parasite in humans. It
was discovered by Charles Alphonse Laveran ; a french Army surgeon , deployed by
Constantine ( Algeria) in 1880, he originally named the parasite Oscillaria malariae.
Below is the classification of the parasite:
Classification of human protozoa of the genus Plasmodium
Domain : Eukaryota
Kingdom : Chromalveolata Superphylum Alveolata
Phylum : Apicomplexa
Class : Aconoidasida
Order : Haemosporida
Sub-order : Haemosporidiidea
Family : Plasmodiidae
Genus : Plasmodia
Sub-genus : Plasmodium; Laverania
Species : P.falciparum, P.malariae, P.ovale, P.vivax , P.knowlesi
 P.knowlesi is a primary parasite of monkey that can infect humans
FIGURE 1
As indicated in the above diagram;
Malaria is usually transmitted by the bite of an infected female anopheles mosquito
during blood meal, although blood- borne transmission such as blood or blood
product transfusion,transplantation, needle -sharing among intravenous drug addicts,

5. accidental nosocomial transmission or congenital transmission may occur [8]
The female Anopheles mosquito takes blood meal to carry out egg production and
such blood meal are the link between the human and the mosquito hosts in the life
cycle of the parasite. The successful development of the malaria parasite in the
mosquito is what is referred to as the gametocyte stage to the sporozoite stage. Which
depends on several factors most notably ambient temperature and humidity. Unlike
the human host the mosquito host has not been found to suffer noticeably from the
presence of the malaria parasite.
There are about 3,500 species of mosquito grouped into 41 genera; of this, human
malaria is transmitted only by the female of the genus Anopheles and of
approximately 430 Anopheles species only 30 – 40 transmit malaria.
Where transmission is mosquito -borne, as is usually the case, the sporozoite; the
infective plasmodial stage is normally injected along with the saliva of the mosquito
into the subcutaneous capillaries .Which disappears from the blood within
approximately 45 minutes of injection and enters the liver parenchimal cells (
hepatocytes). Inside the hepatocytes , each sporozoite rapidly begins a phase of
asexual reproduction resulting in the formation of a schizont, which contains
thousands of merozoites ; the clinically silent replicative phase of the parasite. After
about 7 to 10 days the schizonts matures and raptures releasing the merozoites into
the host bloodstream – onsetting the diagnostic stage. Within the red blood cells the
merozoites matures either into uni nucleate gametocyte- the sexual stage -infection
for the Anopheles mosquito or over 48 to 72 hours into the erythrocytic stage
schizont with 10 to 30 merozoites. The erythrocytic schizongony is characterised by
the appearance of young rings in the infected red blood cells. There is no enlargement
of the infected erythrocytes during the development and maturation of the schizonts.
Rapture of the schizonts from the infected red blood cells releases the merozoites
which infect other Red blood cells. The uni nucleate gametocyte are sequestered
away from circulation and only the matured crescent – shaped are released into the
pheripheral blood to be ingested by female Anopheles mosquito during blood meal
establishing the infection cycle - the gametocytes develop in the mosquito gut to
gametes, which undergo fertilization and develops in 2 to 3 weeks to sporozoites (
figure 2- the malaria cycle)
5. Symptoms

6. FIGURE 2
Above is a diagrammatic presentation of malaria symptoms, these are common
accepted norms in diagnosing malaria infection and usually a concomitant of more
than one symptom for diagnosis is to be made; This is because the clinical
manifestation ranges from the mild to the severe which are several and anatomical.
The parasite and the host related factors contribute to the severe form. Al et al [9]
found fever only as a sensitive indicator of clinical malaria in children under 5 years
but not in older children and adults in the highlands of kenya. While other researchers
like Bousema et al [10] found that most of the P. falciparum malaria infections
detected in community surveys are characterised by low density parasitaemia and the
absence of clinical symptoms. Therefore they argue that molecular diagnostic tools be
used for adequate insight into the epidemiology and infection dynamics of malaria if
elimination is to be achieved.
6. Malaria Diagnosis

7. To distinguish malaria from other causes of fever the WHO recommends parasite
based diagnosis as very essential for all ages before administration of antimalarial
treatment .This is because accurate diagnosis improves disease management and
reduces risk of parasite resistance.
6.1 Microscopy
This is the gold standard for the laboratory confirmation of malaria infection. Gustav
Giemsa introduced the methylene blue and eosin staining method which is now the
mainstay diagnostic tool in malaria diagnosis. This is because it is inexpensive, able
to differentiate malaria species and quantify the malaria parasite indicating parasitic
load for correct treatment. ( appendix 1)
Table 1. Morphological features of the different stages of Plasmodia by species in
stained thin blood films
P. malariaeP. ovaleP. vivaxP. falciparum
Ring form,small and
regular in shape,
with no
pseudopodes.
Older forms may be
large, with vacuole
Occasionally,
equatorial band
form present
Polymorphous
in shape from
ring forms often
showing a
central clear
vacuole
surrounded by
regular
cytoplasm
(younger forms)
to large
ameboid masses
(mature forms).
Their
dimensions are
slightly inferior
toP. vivax.
Polymorphous
in shape from
large ring
forms younger
forms) to
ameboid mass
occupying the
entire red
blood cell
(mature
forms).
Always present in
peripheral blood.
Ring-shaped, small
to medium size in
dimension (Æ = 2-4
mm) depending on
maturation. Young
form may lay in
marginal position.
Polyparasitism and
double chromatin
dots possible.
Trophozoit
es
Compact, rosetta-
like forms with 8-10
merozoites
surrounding a
central
pigmented area
Normally
present in
peripheral
blood. Large
(Æ = 10-12
mm),
round bodies
containing 4 to
12 merozoites
and dark
pigmentation
Normally
present in
peripheral
blood. Large
(Æ = 12-16
mm),
round bodies
containing 12
to
24 merozoites
and loose
golden brown
Solely present in
more severe
infections.
Small and compact,
containing 15 to 30
merozoites and a
dense dark brown
pigmented residual
body.
Schizonts

8. residual
pigmentation
Compact large
single dense purple
nucleus (female
form) or
loose violet nucleus
(male form).
Scattered coarse
pigment granules
are present
Round regular
bodies with a
single
voluminous
nucleus (dense
and red purple
in
female
gametocytes,
loose and pink
in male forms).
Their
dimensions are
usually
inferior than
in P. vivax
Round regular
bodies with a
single
voluminous
nucleus (dense
and red purple
in
female
gametocytes,
loose
and pink in
male forms).
Present in the second
phase of the
erythrocytic cycle.
Crescent-shaped
with coarse rice-like
granules and
pigment. The female
is blue in
colour and granules
are in
central position,
while the
male form is violet
and
granules are
scattered over
the parasite
Gametocyt
es
usually very low
(average 6.000, max
20.000)
usually
moderate
(average 9.000,
max 30.000)
intermediate
level
(average
20.0000, max
50.000)
may be very high
(average 20-
500.000, max
2.000.000)
Parasitic
density
6.8 Molecular Diagnosis
Parasite nucleic acids are detected using polymerase chain reaction (PCR). This
technique is more accurate than microscopy. However, it is expensive, and requires a
specialized laboratory (even though technical advances will likely result in field-
operated PCR machines).
6.9. Serology
Serology detects antibodies against malaria parasites, using either indirect immuno
fluorescence (IFA) or enzyme-linked immunosorbent assay (ELISA). Serology does
not detect current infection but rather measures past experience.
6.10 Indirect Fluorescent Antibody Test
Malaria antibody detection is performed using the indirect fluorescent antibody (IFA)
test. The IFA procedure can be used to determine if a patient has been infected with

9. Plasmodium spp. Because of the time required for development of antibody and also
the persistence of antibodies, serologic testing is not practical for routine diagnosis of
acute malaria. However, antibody detection may be useful for:
 Screening blood donors involved in cases of transfusion-induced malaria
when the donor's parasitemia may be below the detectable level of blood film
examination
 Testing a patient with a febrile illness who is suspected of having malaria
and from whom repeated blood smears are negative
 Testing a patient who has been recently treated for malaria but in whom
the diagnosis is questioned.
Species-specific testing is available for the four human species: P. falciparum, P.
vivax, P. malariae,and P. ovale. Blood stage Plasmodium species schizonts (meronts)
are used as antigen. The patient's serum is exposed to the organisms; homologous
antibody, if present, attaches to the antigen, forming an antigen-antibody (Ag-Ab)
complex. Fluorescein-labeled anti-human antibody is then added, which attaches to
the patient's malaria-specific antibodies. When examined with a fluorescence
microscope, a positive reaction is when the parasites fluoresce an apple green color.
Enzyme immunoassay have also been employed as a tool to screen blood donors, but
have limited sensitivity due to use of only Plasmodium falciparum antigen instead of
antigens of all four human species.
7.0 Mechanism of antimalaria drug action
Both diagrams below show the site of action of antimalaria drugs in use
FIGURE 3

10. FIGURE 4
The primary means of treating malaria infection is chemotherapy. The success of
which depends on the ability to exploit differences between the parasite and host. The
major problem confronting parasitic chemotherapy is the ability of the pathogens to
mutate and become drug resistant; most common with malaria parasites.
Effective drugs exhibit or should exhibit selective toxicity for the pathogen as

11. compared to the host. The following are factors that underpin drug selective toxicity:
 Unique target ( cellular or biological processes that drugs specifically interfere
with) in parasite( pathogen)
 Ability to discriminate between host and parasite targets
 Target is more important to parasite than host
 Greater drug accumulation by parasite
 Drug activation by parasite
Due to the complex biological cycle of malaria plasmodia the ideal drug should have
the following properties [11]
firstly the ability to act rapidly primarily against schizontz; the blood erythrocytic
asexual forms which are responsible for the clinical manifestation of the disease .
Which they refer to as parasitological cure .
Second is what they refer to as the radical cure; the ability of the drug to act against
liver hypazoites.
Also the ideal drug they argued must have high resistance barrier.
Figures 6 and 7 above showed diagrammatically the sites of drug action currently in
use in the chemoprophylaxis of malaria. Which principally are The Blood stage and
the Liver stage prophylaxis. Due to the differentially sensitivity of the malaria
parasite to drugs in each form of its cycle ; drug that acts on the liver stage will not
necessarily act on the erythrocyic stage and vice versa. Furthermore the propylaxis
does not prevent the infection but acts on killing the parasite either in the erythrocytes
or the hypatocytes thereby preventing the clinical disease. Therefore based on the
parasites lifecyle there are 2 types of malaria chemoprophylaxis based on the sites of
action ( figure 3 and 4):
The blood stage prophylaxis. The blood stage prophylaxis refers to drugs that act only
on parasites within the red blood cells , these drugs are good in complete prevention
only in P. falciparum.
The liver stage prophylaxis refers to drugs that acts on the parasites in the
hypatocytes, they kill the parasite early on the onset of infection.
Below is a list of common antimalaria drugs
8. Antimalaria drugs

 Chincona alkaloids-- Quinine
 4 Aminoquionoline—chloroquine, hydroxchloroquine
 8 Aminoquionolies-- Primaquine
 Diguanides-- Proguanil

 Diaminopyridines---Pyrimethamine
 Quinoline -----Meflaquine, Methanol
 Phenathrene – Halofantrine
 artemisinin derivatives --Artesunate, Artemether, Arteether
 Miscellaneous ---Sulfonamides, Ataraquone,Teracycline


12. The attachment has a diagram depicts pictorially the prophylaxis of these drugs with
their site action.
Quinine
The selective prophylaxis of the quinines was first suggested by Franscesco Torti in
Italy (`1912) and this drug was very much in use until the 20th
century as a single
drug in the treatment of malaria until recently .Pamaquine and chloroquine were
discovered in Germany in 1924 and 1934 respectively, proguanil in England ( 1944),
pyrimethamine in England ( 1952) , primaquine in USA ( 1956), sulphonamides and
mefloquine in USA ( 1960- 1966,1971-1975) and halofantrine ( 1989). With
decreased sensitivity of P falciparum to chloroquine since the 1960's the practice of
monotherapy treatment of malaria has shifted to combination based treatment with
recent artemisinin( ACT) treatment which shows greater action on both the sexual
and blood asexual forms of the parasite. However this form of treatment is now also
found to show less sensitivity with resultant resistance of P falciparum . Which has
now emerged in South East Asia and is said to be close to the India border [12] .
Chloroquine resistance also began around South east Asia . The main explanation for
the development of the resistance of the parasite to both Artemisinin combination
therapy and chloroquine on-setting from south East Asia is that the area has lower
levels of natural immunity. According to Woodrow [12], this resistance could be
buoyed up by the other drug in combination with artemisinin but inevitably it will
fail.
Once more with this recent development there are very few drugs on the table , so its
once again to the drawing table and which where the use of other great possibilities
like nanotechnology comes in.
9. Advancements in malaria treatment and drug resistance
Advancements in malaria treatment has always been motivated by the parasite's
resistance to drug in use.
According to Castelli et al [11] WHO defined malaria drug resistance as “ the ability
of a parasite strain to survive and /or multiply despite the proper administration and
absorption of an antimalaria drug in the dose normally recommended”
P falciparum has shown high propensity to developing drug resistance. Drug
resistance involves mutations in the drug target hindering binding or inhibiting the
target. Accumulation of mutations in the same or different targets will have additive
or synergistic effect. Mutations can confer drug resistance quickly, also the
expression of higher levels of the target either through increased transcription ,
translation and gene amplification that it will require high levels of the drug to
achieve high levels of inhibition. Furthermore , resistance can result in decreased
drug accumulation and or metabolisation of the drug to non toxic products that less
drug reach the target.
The probability of resistance occurring is said to be a function of the replicating
parasites and the the drug concentration the parasites are exposed to. [11]
10. Avoiding drug resistance

13. Avoiding drug resistance in malaria elimination has over the years given rise to
development of effective drugs which only to sadly become less sensitive and less
potent with more drug resistance put up by the parasites. Avoiding the parasite
resistances includes ; insecticide -impregnated bednets: Mosquito nets for use are
treated at intervals of usually six months for effective pathogenicity and several
surveys have shown this method of control effective [13] .Insecticide spraying; using
insecticides like deltamethrin,lambadacyhalothrin amongs others have been found to
be highly effective in the control of the anopheles vector [13]. Also the use of
antimalaria drugs both in monotherapy and combination therapy[14]. Despite all of
these measures in 2010 there were an estimated 220 million clinical cases and 0.66 to
1.24 million deaths cause by malaria [14,15]
A number of approaches are now on the table on eliminating malaria; from the use of
advanced evolutionary modelling such as selective sweep ; which is the sudden
removal of DNA sequence variation at the genomic location of an advantageous gene
under strong positive selection [16] or by identifying numerous genes that underwent
recent adaptive evolution, most recent examples of selective sweep are mutations in
genes pfcrt, dhfr,and dhps causing resistance to chloroquine , pyrimethamine and
sulfadoxine [17]
Factors that determine the relative speed of drug resistance evolution can be obtained
by the use of selective sweep most especially in endemic areas with different
demography and epidemiological characteristics [17]
As far back as the first half of the 20th
century the use of vaccines has been
promulgated as the best for eradicating malaria . Early attempts were modelled after
the Pastuer approach of inactivating the pathogen ,however formalin-inactivated
malaria sporozoites failed to initiate immunity because little was known then about
the hypatocytic mechanism of invasion and pathogenesis of the parasite [18.]
However in a major advance in 1967 malaria sporozoites extracted from the salivary
glands of infected mosquitoes and irradiated, induced immunity in mice without an
adjuvant [19]. Similar findings were obtained from human volunteers exposed to
irradiated mosquitoes infected with human malaria parasites ; because the sporozoites
and mosquitoes were irradiated the mice and human volunteers did not become
infected but their immune system elucidated an immune response that could protect
them from subsequent infection [20, 21]
Though very promising this vaccine approach laid dormant largely due to 1.
Difficulty of harvesting adequate parasite , 2. difficulty in cloning Plasmoduim
antigens [22,23]. However in subverting this difficulty the 'sub-unit' approach of
vaccine research was ushered in. The underpinning aim of this approach is that
individual parasite proteins and safe adjuvants would be effective as it was with
other vaccines produced for other infectious diseases.
An approach that paid off presently is a subunit malaria vaccine called RTS.S; that is
based on the coat proteins of the sporozoites of P falciparum ability to kill the
parasite before it reaches the live cells . Which is now in level 111 clinical trails in
some African countries [24,25]. This is said to be the lead subunit malaria vaccine
currently in development.

14. However the set back with this vaccine along with all other subunit vaccines is the
insufficient immunogenicity they suffer from due to the high polymorphism of the
individual malaria protein on which they are based, thus enabling the parasite to
evade the induced immunity [18]
Other researchers have proposal that drug resistance may make the parasite
vulnerable to other drugs, Researchers from the university of St George's London
discovered that the mutation that gives the parasite resistance to artemisinins makes
it more sensitive to another substance ; cyclopiazonic acid ( CPA) . Though CPA is
thought to be too toxic, but findings suggests its derivatives can be used in the
treatment of malaria [26]
While other researchers have experimentally proved that antimalarial drugs that have
lost their potency could be given new lease of life when administered differently;
Researchers at the Australian national university and Germany's university of
Heidelberg have found out that the protein that causes resistance in the parasite
against chloroquine has an Achilles heel . According to member of this team, Dr
Martin “ we have studied diverse versions of this protein and in all cases found that
its limited in its capacity to remove the drug completely from the parasite”
Furthermore they reported ; “ we found that the protein gains the ability to move
chloroquine out of the parasite through one or two evolutionary pathways , but that
this process is rigid, one wrong turn and the protein is rendered useless, therefore this
“ indicates that the protein is under conflicting pressures ,which is a weakness that
could be exploited in future antimalaria strategies” she concluded [27].
Could one of this “ future strategies” be actually be a now strategy in the way of
Nanomedicine?
11. The need of drug aiming and controlled release
Ideally a drug when administered example by oral route should reach diseased part of
the body stealthily without affecting the tissues en route and at the diseased part it
should release its ingredient at the correct moment and in right dosage set to heal that
part. As well as have the properties for any remnant particles to be expelled from the
body after the healing process of the diseased part , so that the body's normal
functioning is not impaired [28]
A thorough understanding of the biological environment is therefore very important
in designing and developing nanoparticles formulations. Other key factors include the
knowledge of ; 1. target cell population, 2. target cell surface receptors, 3. changes in
cell receptors that occur with progression of disease, 4. Mechanism and site of drug
action, drug retention , multiple drug administration, molecular mechanisms and
pathology of the diseased part in question.[28]
12 Nanomedicine
How interesting that a century later Paul Enriich's dream of a 'magic bullet ' that will
destroy invading microorganisms is now a major aspect of clinical medicine as
nanotechnology / nanomedicine.
Nanomaterial offer manifold advantages as drug transport and delivery vehicles.
Normally drugs could not reach certain remote parts of the body due to large size ,
the particle has to be in nanoscale dimension to penetrate and cross the cell boundary.
Also nanomaterials are consumed more easily by cells than larger micromolecules

15. raising the level of drug effectiveness. Using nanaomedicine ,the drug is usually
integrated inside the nanoparticle matrix or attached to the particle surface, due to
their very high surface to volume rate their dissolution rate is increased according to
Neyes whitney equation relating the dissolution rate of solids to its properties and the
dissolution medium [28] . Furthermore , a nanoparticle should have a hydrophilic
surface to escape microphage capture [28].
A nanoparticle function is to evade the immune system, effectively reach target, and
deliver therapeutics,- all of which is determined by properties such as the size, ligand
density , surface change and drug content [29] . Furthermore nanomedicinne is also
able to confer advantages which are; efficient and convenient drug delivery systems
that protects drug or vaccine from intracellular degradation, improve selectivity as
relates to retention to the target, reduction of the frequency of administration,and
duration of the treatment so as to improve the pharmacokinetic profile of the drug(
improved absorption, bioavalability, elimination half-life) and reduction in drug
toxicity [30]. Usually 'nanocarriers' are <1000nm sizes: of this size most
nanoparticles are suitable than microparticles for intravenous delivery because the
tiny capillaries have a size of -6 micron in diameter, a range which most
microparticles or their conglomerates are impeded , for system delivery the sizes
should be in the range of 10-100nm.[28]. Therefore size has been shown to play a
major role in nanomedicine efficacy and can be controlled during synthesis.[31]
Nanomaterials are of many flavours they include lipid-based vehicles
(liposomes,solid lipid nanoparticles and micelles) [32-34],Polymer carriers , such as
hydrogels, polysomes, denrimers and nanofibers [35-37], metallic nanoparticles such
as silver, gold and titanium,[38- 41], inorganic particles such as silica, carbon
structures (nanohoms, nanodiamonds)[42-45] and graphene
Nanomedicine has already impacted other diseases, e.g. cancer, exemplified by the
reformulation of doxorubicin to provide a potent, and extended half-life therapy with
reduced side effects. The vision is to see nanomedicine do the same for malaria
chemotherapy, radically improving treatment outcomes using currently available
drugs, saving lives, and advancing the global goal of eradicating malaria.
However the implementation of this holy grail continues to have challenges in 1.
identifying the right molecular or cellular targets for a particular disease due to the
intracellular and strewn location of the parasite 2. having a drug that is effective
against it and 3. finding a strategy for the efficient delivery of sufficient amount in
active state exclusive for the selected target. Therefore designing and developing the
right nanoparticle for a target is very important. In the context of malaria the most
important characteristics/ properties of a nanocarrier is the ability to remain in the
blood stream for a long time so as to improve the interaction with the infected red
blood cells and parasite membranes [46]. Others include, ability to protect unstable
drugs , cell- adhesion properties and ability to be surface -modified by conjugation of
specific ligands [47,48]
13. Drug targeting approaches
There are 2 drug targeting approaches used in nanomedicines as tabulated below:

16. Passive and active targeting are the 2 main intravenous routes in use in delivery of
antimalaria drugs to infected red blood cells ( fRBC's) and hepatocytes using
nanocarries
Table 3
Passive targeting Active targeting
Utilises the special deviated conditions
prevailing in the diseased part of the body
Depends on th specie that is oerv
expressed during disease
Less selective Highly active
Restricted in use Very versatile
More likely to produce side effects Less likely to induce side effects
[28]
13.1 Passive Targeting
Passive targeting is also known as physical targeting and the direct drug injecion and
characterisation are examples of passive targeting. It is where the drug carrier
complex avoid removal from body through body mechanisms including ,metabolism,
opsonisation, excretion, and phagocytosis such that it remains circulating in the blood
stream permitting its transmission to the target receptors by properties like ph,
molecular size, temperature or shape.
Passive targeting is less employed in malaria because the nature of the host's
infected RBC's and mononuclear phagocytic system. RBC's are phagocytically and
endocytically inactive making them hard to target
Table 4 Passive drug targeting scheme
1.Understanding the physiological conditions of diseased area
2. Preparation of the delivery carrier having a definite molecular weight ( > 30kDa) ,
molecular size ( 100-200nm), possessing hydrophilicity and neutral charge.
Adjusting the delivery system to be sensitive to ph ,temperature or an enzyme. The
coating of the carrier is designed so that during circulation in blood its stable .
3.But on entering the target site the temperature is usually high the coating melts and
discharges the drug which accumulates at target site and begins its action. such a
carrier is said to be thermosensitive
4.Modifying the surface of nanocarriers with hydrophilic polymers such as poly(
ethyleneglycol, PEG) delays phagocytosis effecting prolonged drug half-life in the
blood thus allowing the modulation of biodistribution and pharmacokinetic profile
of the drug
[49-51]
Passive targeting can be used in malaria treatment by targeting the mononuclear
phagocyte system( MP) , however due to increased contact with RBC's long
circulating nanocarriers are more suitable to intravenous delivery..
This is because there will be resultant less toxic effect to tissues due to the reduced

17. volume of distribution of the antimalaria drug.[52,53]
13.2 Active targeting
Active targeting is the coupling of moieties like antibodies , antibody fragments and
peptides to drug and nanocarriers, to act as homing devices for strapping to receptor
structures expressed at the target site[28]. With the resultant accumulation of the drug
in the target cell or tissue [51]
This approach is found to be successful in instances where the receptors for the
surface bound ligands expression is differentially higher in the diseased cells
compared to the healthy cells and also where the ligands are expressed uniquely(.
Active targeting in malaria therapy mainly targets the erythrocytes in the RBC's and
the hepatocytes in the liver [54]
Disadvantages of active targeting
The cell recognition of the nanocarrier is very important which is as a result of the
number of ligands per carrier and the suitable PEG chain length at the surface of the
nanocarrier [51]. Also due to the nature of the ligand the ligand at the surface of the
nanocarrier may induce undesirable immunologic response [54]
Table 5.Commonly used Ligands in drug delivery
Name of the Ligand Definition Characteristics
Sugar Any class of sweet , soluble
,crystalline carbohydrates,
white when pure
The specificity of carbohydrate -
protein interactions is much larger
than that of many other ligand -
binding systems , through its great
ability to undergo site-specific
modification. This use of
carbohydrates to target protein
receptors at site of localisation is
termed “glycotargeting”. Which
exploits the highly specific
interactions of endogenous lectins
with carbohydrates
Folic acid Water -soluble vitamin,
yellowish-orange, belonging
to the B-complex group of
vitamins
Employed as a targeting moiety in
some drugs through covalent
conjugation to drugs
Peptide Natural or synthetic , short
polymer chain compound
containing 2 or more amino
acids linked by the carboxyl
group of one amino acid to
the amino group of another
Peptide-conjugated ligands
example the D4 peptide -
conjugated liposomes bind to and
enter the cells by endocytosis
Antibody An immunoglobulin, a
specialised immune protein
generally found in the blood
Example the anti-CEA (
carcinoembryonic antigen) half -
antibody conjugated lipid -polymer

18. that detects and destroys
invaders ; such as bacteria,
paasites , produced as a
result of the introduction of
antigens in the body
hybrid which showed enhanced
cancer killing effect compared to
nontargeted nanoparticle
[28]
14.Drug Targets in the body
 Receptor Cell membranes; Receptors on cell membrane that allows specific
interactions of drug carriers with cells, facilitating their uptake via receptor -
mediated endocytosis [55].
 Lipid components of cell membrane : The alteration of of the lipid composition
membrane fluidity by the interaction of synthetic phospholipid analogs with
cellular membranes effecting signal transduction mechanisms inducing
apoptosis.
 Antigen or Proteins on Cell surfaces
15. Existing nanosytems
The available nanosystems are liposomes ,polymeric micells ,polymer -drug
conjugates,and endrimers, some of the newer nanosytems include; nanocontainers,
nanocages, nanofibres, nanogels, nanoshells and nanorods.
Table 6. Common carriers of nanomedicines
Name of the carrier Definition Explanation and advantages
Liposomes Spherical vesicle with a
phospholipid bilayer, with
multifunctional properties
Its used to convey vaccines,
drugs, enzymes, or other
substance to organs. They
are used to encapsulate
drugs and biological active
compounds .In vaccines
they serve as
immunological adjuvants.
Best nanocarriers for either
passive or active targeting.
Suitable nanocarriers for
malaria prophylaxis and
treatment.
Polymer misceles Nanosized particle (
~10~100nm) composed of
block or graft copolymers,
with co-shell structure. The
core contains the drugs,
while the shell interacts
with the solvent making the
Especially used for poor
water-soluble
pharmaceutical active
ingredients. Increases the
stability of drugs and
lessens undesirable side
effects because contact of

19. nanocarrier stable in the
liquid
the drug with enzymes in
biological fluids is
minimised. This high
stability makes them
promising drug delivery
system for antimalarials
Dendrimer It originates from the Greek
;dendron ( tree). A
macromolecule with highly
branded 3D structure
consisting of of 3 main
components core, branches
and end groups. It provides
high degree of surface
functionality and versatility
Small enough to enter cells
carrying the drugs , with
other advantages ;
thermodynamic, stability,
high solubility in water ,
morphology and functional
groups on the surface , with
uniform size distribution.
Nanosuspension Nanosuspension are sub-
micron colloidal dispersions
of pure poorly water-soluble
drug without any matrix
material suspended in
dispersion..
A nanosuspension not only
solves the problems of poor
solubility and
bioavailability, but also
alters the pharmacokinetics
of drug and thus improves
drug safety and efficacy.
Nanocapsules Nanocapsules are made up
of one or more active
materials (core) and a
protective matrix (shell) in
which the therapeutic
substance may be confined
The advantage of
nanocapsule as carriers for
lipophilic drugs is the lower
polymer content and low
inherent toxicity. Other
advantages include;
solubilization of poorly
water- soluble drugs,
protection against drug
toxicity,prolongation of
injected drugs in blood
circulation, protection
against drug inactivation in
the gastrointestinal tract and
increased permeation of
drugs through mucosal
surface
[28, 56]
16. Advances in nanomedicines for malaria treatment
The use of nanomedicine in malaria treatment has come along way, large number of
successful work has been carried out with the different antimalaria drugs in the
market. More research also have been exploited with antimalaria drugs that have

20. developed resistances with the aim of making them once again active especially those
widely used around the world in-spite of the developed resistance example
chloroquine. A few of which are cited in this article.
Liposomes have been used in varied forms in malaria nanomedicines either with
phospholipids, as immunoliposomes and as nanogels( gel state liposomes).
Plasmodium normally modifies the host RBC plasma membrane through out its
intra-erythrocytic phase,this has made lipid based nanocarrier as the most promising
carrier for targeting the infected RBC's [57] . Liposomal nanovessels( aqueous core
surrounded by one or several phospholipid bilayers pioneered by Bangham [54]
)containing amino acid sequence of P. berghei have been used to target the hepatocyte
stage of Plasmoduim [58]. However despite these appreciable results liposomal –
based delivery has a limited use in disease rescue programme due to its non-
selectivity to parasitised RBC. In this context Urban and co- researchers developed
immunoliposomal nanovector for the targeted delivery of antimalaria drug
chloroquine exclusively to P. falciparum infected Red blood cells ( pRBCs), they
found this to show improved efficacy when delivered inside immunolipososmes
targetted with the pRBC-specific monoclonal antibody BM1234. Further work by
these researchers indicated that immunoliposome encapsulation of chloroquine and
fosmidomycin( another antimalaria drug) improved the efficacies of these drugs by
tenfold.[59]. Also Tayade and Nagarsenker formulated microemulsions of artemether
which has 1.5 times better antimalarial activity than the marketed one (Larither),
mainly due to the quick release of drug from their formulations. In the same vein
antibody bearing liposomes were found to have better antimalarial activity at lesser
dose and specific binding to infected erythrocytes both invivo and invitro [60]
Other antimalaria drugs like Primaquine, used as drug of choice for P. vivax,( as
hypnozoitocidal drug) and P falciparum ( gametocytocidal) and known to cause
heamolysis and methaemoglobinemia in persons with with G6PD deficiency was
found to show enhanced therapeutic activity and loss toxicity [61]. When it was
formulated as primaquine -glycoprotein conjugates trapped within liposomes and
synthesised to selectively deliver the drug to hepatocytes. Also lipid nanoemulsion of
Primaquine was found to hold great promise for delivery of the drug to the liver with
potential to treat latent stage malaria with minimal toxicity [ 62, 63]
17. Nanomedicine and avoidance of drug resistance
Drug resistance lowers its efficacy through the P-glycoprotein efflux pump . This
efflux is responsible for the removal of toxic substances outside the cell. The ability
of this system to recognise substances is based on physiochemical properties like
hydrophobicity,aromaticity and ionizable character. One suggested approach of
circumventing this efflux is to confer on the drug inside the endosome evading
recognition by the pump and it does this by its confinement inside the endosome.
Ligand -assisted targeting is favourable against drug resistance because the drug
internalization occurs through the receptor -mediated endocytosis, though the
possibility of the drug being released out of the lysosome and out of the cell still exist
[ 28]