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The importance of Earth observations
in the assessment of malaria,
respiratory and ocular diseases in South Asia
A. P. Mitra, National Physical Laboratory, India
S
outh Asia is a unique region. It has only three per cent of
the total world land area, yet in 2002, more than 22 per
cent of the world population lived there.
1
This region
consists of developing countries like Bangladesh, Bhutan,
India, Maldives, Nepal, Pakistan and Sri Lanka, which are
predominantly inhabited by resource-starved populations
trying to achieve economic well-being for their respective
countries. This region is also one of the most densely popu-
lated, ranging from about 250 people per square kilometre in
Nepal to about 800 persons per square kilometre in
Bangladesh.
Human health is of significant importance for South Asia, as it
affects the overall productivity and thus impacts the development
process of the region. The total per-capita expenditure on health
care in 2001 ranged from USD58 for Bangladesh to USD122 for Sri
Lanka, which is less than one-fifth of the global average of USD629,
indicating a poor affordability of health care systems in the region.
2
Earth observation systems have great potential in assisting measures
to address human health concerns in the region, as can be seen
from their importance in the context of malaria, respiratory and
ocular diseases.
Malaria
Malaria is endemic in all parts of the South Asian region, except in
areas of higher elevation and some coastal areas. Developing coun-
tries, where the health system is yet not geared up to meet the needs
of all sections of society, especially the tribal population living in
forest areas and poor people living in urban slums, are prone to be
adversely affected by malaria outbreaks. Within the vulnerable
communities, those most affected are children, senior citizens, the
chronically ill, the disabled, people living off the land, people living
on islands, and pockets of overcrowded and poorly-serviced settle-
ments in urban and rural areas which are a potential breeding
ground for disease hosts such as mosquitoes, rats, mice and flies.
Communities surrounded by these poverty belts also become more
vulnerable to disease outbreaks.
The three main climate factors (i.e. climate determinants) that
affect malaria generation and its transmission are temperature,
precipitation and relative humidity. Climate predicts, to a large
degree, the natural distribution of malaria. Therefore, the network
of meteorological stations available in the South Asian region can
contribute very significantly by providing quality data for under-
standing the links between climate determinants and
malaria occurrence. The modelling of future climate
scenarios and their impacts on malaria occurrences will
also help in the allocation of appropriate resources to
priority areas for the effective control of malaria inci-
dences in the region. In South Asia, the systemic
meteorological data collection process is overseen
mainly by government agencies, through their respec-
tive networks of meteorological stations.
In India, a study has been carried out to assess the
climate parameters governing malaria transmission and
the likely extent of malarial activity in the future due
to climate change, using empirical relations.
3
This
study revealed the dominant role of temperature and
relative humidity in malaria transmission, leading to
the development of a new set of transmission windows
(named as class I, II and III) that govern the transmis-
sion of P. vivax and P. falciparum in India. Using the
transmission window criteria thus developed, malaria
has been found to be endemic in the central and
eastern Indian regions of the country, covering states
like Madhya Pradesh, Jharkhand, Chhattisgarh, Orissa,
West Bengal and Assam in the current climate.
Applying the same criteria under the climate change
conditions for the period 2050s as derived from
HadRM2 using the 1S92a scenario, it has been
projected that malaria is likely to persist in Orissa,
West Bengal and southern parts of Assam, bordering
north of West Bengal. However, it may shift from the
central Indian region to the southwestern coastal
states of Maharashtra, Karnataka and Kerala. Also the
northern states, including Himachal Pradesh may
become malaria-prone in the future climate change
regime. The duration of the transmission windows is
also likely to widen in northern and western states and
shorten in the southern states in India. This study is
not conclusive by itself as the influence of other
factors like socio-economic, environmental and vector
related parameters could not be included in this study.
Therefore, there is a need to undertake comprehen-
sive studies on malaria in South Asia using region
specific data and models to help in designing the most
effective policy and technological interventions in
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EALTH