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).
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.
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).
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.,
has several applications to the study of mosquito biology and ecology (Eskinder
etal., 2010), suggesting that GIS is the best or available method to answer
questions regarding mosquito ecologyas well studies of risk as a function of
distance from known breeding sites and others are one common application of
GIS. GIS in combination with remote-sensing (RS) technology, has also been
employed to predict areas of high productivity of mosquitoes and potential
malaria epidemics based on the detection of proxy ecological variables (Hay et
al., 2000). Therefore, the aim of this study will be to assess the spatio
temporal variation of malaria in the study area
1.2. Statement of the of the
Globally, about half of the world populations (3.3 billion) are at
risk of malaria infection (World Health Organization WHO
2011). It has widely known impacts on the
economic, social, and political sphere of the society As a result wide range of
measures were taken by national and international organizations to reduce the
impact of the epidemic but most of the efforts were invested on managing the
results than prevention. Therefore, the cost of preventive plan and medical
treatment becomes affect the GDP and as well as the individual economy due to
estimated numbers of billion peoples are at risk of this infections and 3000 to
5000 million suffering a short period with the disease each year perhaps 90
percent of these occur in tropic of Africa (WHO, 2012) Malaria kills between
1.1 and 2.7 Million people per year. Of these deaths, approximately one million
are children in the tropic of Africa between the ages of 18 months and 5 years
Malaria risk becomes higher
developing countries (Donnelly, 2005). According to Stratton, (2008) mentioned
the multiplicity of malaria causing factors in semi urban areas as the main
cause of its prevalence as they are difficult to control at the same time.
Due to its tropical location and availability
of many rivers and lakes, Ethiopia is suitable for breeding of plasmodium (Womie,
2008). As aresult it is a major public health problem in Ethiopia (FMoH, 2009).
Accordingly its occurrence in most parts of the country is unstable mainly due
to the country’s topographical and climatic features