Malaria disease since the vectors require specific habitats


Malaria is a
vector-borne disease caused by protozoan parasites belonging to the genus
Plasmodium and transmitted by the bite of infected female Anopheles species mosquitoes;
about 60 species of the genus Anopheles can transmit malaria (Walker K,
2002, Cox FE.2010). Until recently, five species of Plasmodium, namely: P.
vivax, P. falciparum, P. ovale (two sub species: P. ovale curtisi and P.
ovale wallikeri), P. malariae and P. knowlesi are known to cause
human disease (Cox-Singh J, 2010; Yusof R;,et al., 2014). The conditions of the
parasite, vector and the human host are characterized by different factors,
which are highlighted here.

 

It is caused by
Plasmodium parasites, is a blood-borne disease which is transmitted through the
bite of an infected female Anopheles mosquito. It is a major public health
issue which affects the global population at large (Kumi-Boateng et al.,
2015; Ahmed, 2014). Malaria is typically found in warmer regions of the world, i.e.,
the tropical and subtropical countries. Vectors (female Anopheles mosquitoes)
require specific habitats with surface water for production, humidity
for adult mosquito survival and the development rate of both vector and
parasite are dependent on temperature (Ahmed, 2014; Ashenafi, 2013).

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 Malaria is essentially an environmental
disease since the vectors require specific habitats with surface water for
reproduction, humidity for adult mosquito survival and the development rates . The
increase in malaria prevalence is determined by several factors: mosquito
resistance to insecticides, parasite resistance to drugs, changes in land-use
patterns, and reductions in funding and manpower dedicated to control
activities. Most of the determinants are heterogeneously distributed, changing
over both space and time. Factors such as topography, temperature, rainfall,
land use, population movements, and degree of deforestation have a profound
influence on the temporal and spatial distribution of malaria vectors and
malaria. (FMoH, 2009).

 Globally, about half of the
world populations (3.3 billion) are at risk of malaria infection (World
Health Organization WHO 2011).Adult female
mosquitoes of the genus Anopheles are vectors for the Plasmodium parasites and
are thus responsible for malaria transmission.

 

There are 490 species in the genus Anopheles, and 70 of these are
vectors of malaria. In sub-Saharan Africa, there are 140 Anopheles species of
which approximately 20 are known to transmit malaria parasites to human beings.
Of these, Anopheles gambiae s.s, Anopheles arabiensis Patton, and Anopheles
funestus Giles are the most widely distributed and important malaria vector
species in tropical Africa (Gillies and Coetzee 1987, Foley et al. 2010).

 

 According to Kaya et al. (2002), malaria
remains one of the greatest killers of human beings, particularly in the
developing countries. The World Health Organization (WHO,2012), estimated over
one million malaria cases each year, where more than 80% of the cases are in
Sub-Saharan Africa countries.

Malaria
is one of the main health problems in Ethiopia in which its cases are one of
the highest and it is increasing in an alarming rate. Ethiopians live at
altitudes ranging from ?100 to >4220 m, the topography made a fertile ground
for the reproduction of the epidemic. More than 50 million (68%) of the
population live in areas below 2000 m above sea level are at risk of malaria.
With consequent variation in minimum and maximum temperatures. In general, the
main reasons given for the increment are ecological and climatic changes. The
peak of Malaria incidence follows the main rainfall season in July, August,
September, October and November each year. (Negassi F., 2008).

Currently
Remote Sensing techniques provide valuable information on such environmental
conditions. Several studies have used Remote Sensing imagery and Geographical
Information System (GIS) techniques to map the distribution of vector species
at different spatial scales such as the entire world, continent, national,
regional, even at small village level. According to Tran et al (2008),
in endemic areas, mainly in tropical and subtropical regions, these vector maps
are designed to improve vector control, which is currently one of the essential
methods in limiting the burden of important vector-borne diseases such as
malaria or dengue fever. In disease free areas, analyzing the link between the
environment and potential vector distribution may help evaluate the risk of
emergence of the disease, and lead to better mitigation and control measure of
the invasive vector species. In particular, the evolution of geographic
information systems (GIS), the global positioning system (GPS), and remote
sensing (RS) technologies has enabled the collection and analysis of field data
in ways that were not possible before the advent of the computer(Milla et al.,
2005).

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