Disease surveillance and control of vector to protect climate
The Daily Star
climate change is caused by the accumulation of "green-house" gases in
the lower atmosphere. The concentration of these gases is increasing
mainly due to conversion of fossil fuel and deforestation. For example,
individuals are responsible for about 40 percent of emissions in the
UK, with energy use in homes, driving and air travel the biggest
The temperature of the earth is escalating
dangerously. As a result, the ice-caps and glaciers in the polar
regions are melting, submerging low-lying coastal lands, including that
of Bangladesh. The viruses and microbes that were inactive and buried
under freezing ice, are now starting to wake up as optimum temperature
for their activities is coming back. They are invading human and animal
bodies. Human settlers are occupying and destroying forests, disturbing
the flora and fauna including the vectors, viruses and microbes.
Reciprocally, the viruses are also finding new hosts in humans and
animals, causing illness.
Occurrence of drought in erstwhile
rainy areas is causing water crisis. Man and crops are facing disaster
for this. The Human Development Report 2007/2008 of UNDP shows that
climate change is not just a future scenario. Increased exposure to
droughts, floods and storms is already destroying opportunity and
Climate-related increases in sea surface
temperature and sea level can lead to higher incidence of water-borne
infectious and toxin-related illnesses. Climate stress on agriculture
causes malnutrition. Increased flux of ultraviolet radiation will cause
alterations in the human immune system, thus increasing vulnerability
Climate change may increase the risk of some
infectious diseases, particularly those that appear in warm areas and
are spread by mosquitoes and other insects, like malaria, dengue fever,
yellow fever and encephalitis. Disease transmission is directly
affected by climate change by removing the vector's habitat, increasing
reproductive and biting rates, and shortening the disease incubation
Vector-borne diseases are very sensitive to
temperature, humidity and rainfall. Climate change may alter the
distribution of important vectors species, and that may increase the
outbreak of diseases into new areas.
Disease surveillance facilities in Bangladesh The
Institute of Epidemiology, Disease Control & Research (IEDCR) is an
important public health institute of Bangladesh. The main activities of
IEDCR include disease surveillance as well as entomological
surveillance, and disease outbreak investigation.
climate change, the pattern of distribution and duration of existing
disease may be changed. On the other hand, new types of illnesses might
emerge. An effective surveillance system is needed to monitor all these
At present, nine types of disease surveillance systems
are in operation. IEDCR conducts 7 of them: Priority Communicable
Disease Surveillance, Outbreak Related Emergency Surveillance,
Institutional Disease Surveillance, Sentinel Surveillance, Nipah
Surveillance, Acute Meningo-Encephalitis Surveillance and
Hospital-based Influenza Surveillance.
Two other types are
conducted by other institutions. Expanded Program for Immunisation
(EPI) conducts surveillance for EPI diseases, Medical Information
System (MIS) conducts routine disease surveillance for disease profile.
Besides these formal surveillance activities, the Directorate
General of Health Services (DGHS) and Director (Disease Control)
receive reports of illness having public health importance from all
over the country. Data are also received from existing programs, e.g.,
Malaria Eradication Program, Kala-azar Control Program, Tuberculosis
Control Program, HIV/AIDS Surveillance Program, Filariasis Control
Recently, IEDCR has taken an initiative to build
a coordinated mechanism for all the surveillance activities and data
collection, and analysis and reporting of illnesses of public health
Impact of climatic change on vector-borne disease Malaria:
Over the last 10 to 15 years, the prevalence and geographic
distribution of malaria worldwide has increased slowly but steadily.
Its recent worldwide increase is due mainly to mosquito resistance to
insecticide, breakdown of control efforts, migration of vectors and
However, its spread is also related to
environment. Agriculture extension and road building have created
better habitats for vector mosquitoes. With gradual increase in global
temperature since the last ice age (8-9.5° C) transmission of malaria
has migrated from Africa to Southern Europe.
Specific experiment has been conducted on the effect of temperature on
the ability of Aedes aegypti to transmit DEN-2 virus. The pattern of
temperature and vector efficiency parallels the climatic pattern of
Dengue Haemorrhagic Fever (DHF) outbreak in Bangkok, Thailand where the
case rate rise in hot season (80°-30° C) and decrease during the cool
season (25°-28° C).
Vector-borne disease control strategies in changed climatic condition Both
disease and vector surveillance, and treatment and control of vectors
should be part of a comprehensive public health policy that promotes
co-operation among researchers, medical clinicians and government staff
at local, regional and international level.
policy makers should consider modern technology as a means for
collecting information about vector-borne diseases, developing
effective control strategies and setting appropriate priorities. Four
types of surveillance should be conducted to track vector-borne
-Recording human cases
-Determining the distribution and infectivity of vectors
-Monitoring a broad range of non-human vertebrates reservoir species
the weather patterns to help predict vector distribution. Monitoring
climatic parameters provide sufficient information to forecast the
population of key vector
Basic research both in the field and
laboratory should be taken to examine the disease agent's ability to
adapt to changing climatic condition to allow prediction of which
pathogen might migrate and their potential destination. Information
about the parameters limiting vectors are equally important.
measures can be targeted at several different aspects of the life cycle
of vector. Vaccination for animals and humans are aimed at preventing
the proliferation of pathogens and pesticides, and breeding place
management will reduce or eliminate the vectors. Immigration policies
and custom inspections may limit pathogen and vector entrance. Drug
treatment may limit future transmission of diseases.
Looking forward Satellite-based
remote sensing of ecologic conditions, geographic information system
(GIS) analytic techniques, inexpensive computational power, and
molecular techniques to track the geographic distribution and transport
of specific pathogens are some of the rapid advances in science which
are used in developed countries for disease epidemiology and
surveillance. They enable the public health scientists to analyse the
evolution and distribution of microbes, and their relationship to
different environments. It may contribute to quantify the disease
impacts of climatic and environmental changes.
disease control mostly relies on surveillance, followed by a rapid
response. Climate forecasts and environmental observations could be
used to identify high-risk locations for disease outbreaks. Operational
early warning systems are not yet possible for our limited knowledge of
climate-disease relation and limited climate forecasting capabilities.
But establishing this goal will help to develop analytic,
observational, and computational capacities.
should be co-ordinated with meteorologic, ecologic, and epidemiologic
surveillance systems. Together, this information could be used to
identify risky locations and could be a wake-up call as surveillance
data confirm earlier projections. Early warning systems of disease
should also include vulnerability and risk analysis, response plans,
and effective risk communication.
The lack of high-quality
epidemiologic data for most diseases is a serious obstacle to improve
our understanding of climate and disease linkages. These data are
necessary to establish a baseline against which one can detect unusual
changes, and develop and validate models. A concerted effort should be
made to collect long-term, area specific disease surveillance data,
along with the appropriate set of meteorologic and ecologic
Centralised, electronic databases should be
developed to facilitate rapid, standardised reporting and sharing of
epidemiologic data among researchers. If an effective, modern and
co-ordinated surveillance system could be built, then it will be
possible to rapidly identify any outbreak of existing or emerging
disease, known or unknown disease in any locality. Then it will be
possible to take appropriate measures for prevention and control of
those illnesses of public health importance.
Prof. Mahmudur Rahman, PhD is Director, Institute of Epidemiology Disease Control and Research (IEDCR). Dr. M. Mushtuq Husain PhD is Senior Scientific Officer, Dept of Medical Social Science, IEDCR. Nuzhat Naseen Bano is Scientific Officer, Dept of Medical Entomology, IEDCR.