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Contributions in the First 21st Century Decade to Environmental
Health Vector Borne Disease Research
Alice L. Anderson
Assistant Professor, Department of Health Education and Promotion, Environmental Health Program, East Carolina
University, Greenville, NC, USA.
Abstract: A selective review of recent concepts, events and major recent research methodologies, and educational approaches in the
field of vector-borne disease are drawn together in this article. Since vector borne disease is a major contributor to world disease burdens, and also comprises list of neglected diseases, recent research in the field elucidates the uncertain and far-reaching consequences of
these diseases to human health and well-being. Some of the specific findings included in this review are the following: Chickungunya
virus disease range is changing as a result of global climate change; Tick-borne disease vaccinations are being pursued with the help of
PCR techniques; the wide availability of remote sensing and ecology are providing habitat surveillance tools to improve predictability
of risk areas; environmental health education approaches are incorporating community and cultural aspects to improve success and
reduce risk.
Keywords: vector borne disease, Chickungunya, PCR, remote sensing, health education
Infectious Diseases: Research and Treatment 2010:2 17–24
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© the author(s), publisher and licensee Libertas Academica Ltd.
This is an open access article. Unrestricted non-commercial use is permitted provided the original work is properly cited.
Infectious Diseases: Research and Treatment 2010:2
17
Anderson
Developing countries in the world today contend
with environmentally related diseases and conditions
that are considered by the developed world to be in
categories such as “reemerging diseases”, “neglected
diseases” and “emerging diseases”. In the World
Health Organization’s 2006 publication “Preventing
Disease through Healthy Environments: Towards an
estimate of the environmental burden of disease”,
Pruss-Ostun and Corvalan present information on
global disease risk and burden. They estimate that
24% of the global disease burden and 23% of deaths
can be attributed to environmental factors. Often
this is the result of unregulated industrialization
by-products such as hazardous waste, hospital waste,
air pollutants, and waste water. The list of diseases
with the largest absolute environmental source
includes: diarrhea, lower respiratory infections, injuries, and malaria. The environmental causes of these
diseases places one quarter of the world’s population
at high risk. Additionally, in many places, even
where industrialization has not developed, infectious
disease, especially vector borne disease, is on the top
of disease burden lists because of mosquito borne
malaria.
In a recent article, authors Beyrer, et al1 discussed
a list of emerging and reemerging diseases, calling
them “neglected” diseases, and emphasized their
close association with civil conflicts. A concept both
sets of authors introduced was the “right to health”.
In the vision statement of the Bill and Melinda
Gates foundation “all people deserve a chance to live
a healthy and productive life”. Environmental Health
professionals, especially those in developed countries, have important responsibilities to apply existing
experience, knowledge and research to old and new
environmental health problems, with a global goal of
bringing health education to our world neighbors. To
address these and other problems in our present rapidly changing civilization, we need to first ask “What
are the diseases, concepts, and methods in environmental health that are receiving research attention?”
A second question would be: “Is this research addressing the crucial environmental factors contributing
to disease?” And finally, a question that cannot be
fully answered in a short review: “Are environmental health and health education professionals using
that research to addressing the needs of people in the
greatest need?
18
The remainder of this article is a review of some
concepts, events and major recent research methodologies, and educational approaches in the field of
vector-borne disease related these questions. Vector
borne disease is a major contributor to world disease
burdens, and also comprises the list of neglected diseases in Beyrer et al.1 The political and economic perturbations of humans to the environment and society
often result in uncertain and far-reaching consequences to human health and well-being, many times
resulting in increased disease vectors. The specific
topics included in this review are:
• the link of vector borne disease burdens with
global climate change, a result of industrialization
in part,
• the disease vectors mosquitoes, ticks and triatome
bugs,
• the research methodology of genetic mapping and
molecular analysis, remote sensing and ecology,
• Successful environmental health education
approaches.
An important new global event affecting environmental health research is the nearly unassailable
legitimacy of global climate change, which has an
important effect on vector borne disease. In Harrus
and Baneth’s2 review of the drivers for emergence and
reemergence of vector borne diseases, atmospheric
and climate changes are primary. In addition, Harrus
and Baneth include habitat changes, alterations in
water storage and irrigation habits, immunosuppression by HIV, pollution, insecticide and drug resistance,
war and civil unrest, increase in international trade,
tourism and travel, and government management
failure. This review recommends that physicians,
veterinarians, and biosecurity officers in addition to
health care workers play an important part in prevention of vector borne diseases. Topics for research
at the Southeastern Center for Emerging Biologic
Threats Conference in the US3 included vector borne
disease and epidemiological surveillance techniques,
including modeling and mapping.
One item in this list of global disease dispersion
drivers that may be changing is global traffic. Tatem,
Hay and Rogers4 as well as Harrus and Baneth2 saw an
increased potential for vector borne disease dispersal
in travel, tourism and trade. An example used was the
range change in the mosquito Aedes albopictus from
Infectious Diseases: Research and Treatment 2010:2
21st century vector borne disease research
Asia to the US through ship and air traffic. Comments
by scientists on the program “60 Minutes” in 2009,5
displayed a convincing argument that Ae. Albopictus
could have arrived by aircraft as well as in truck tires.
Slower distribution increases in other vectors, such
as Anopheles gambiae from Africa were explained
partly by the low volume of sea and air traffic from
endemic areas to Europe and the US.
Since the aftermath of the NY twin towers bombing in 2004, when air travel and tourism dropped
dramatically, political and economic events in the
world have had continuing effects on many parts of
our global life. It is possible that there may be less
travel and tourism since the 2008 oil price climate
change, and the 2009 recession than these authors
imagined and thus less influence on the global dispersal of disease and vectors as well.
Concepts, Events and Current
Methodologies
Global climate change
The effects of global climate change by itself continue
to provide evidence of change in disease dispersal.
Chretien, Anyamba and Bedno6 provide evidence of
the spread of Chickungunya virus, a mosquito borne
disease, from Kenya to the Indian Ocean Islands and
India in 2005–2006 (Fig. 1). Drought conditions preceded the outbreaks as recorded by satellite data.
Along with drought conditions were the infrequent
replenishment of water stores (through pumping or
transport of water) by the populations affected. As
populations soared and water supplies shrank, unexpected consequences arose, including the spread of
this reemerging disease, since the vector responded
positively to the fluctuating water conditions. Knowledge and surveillance by environmental health professionals of the vector would have been useful in
preventing a mosquito vector build up and in tracking
the spread of the disease.
A method that is available worldwide to increase
such knowledge is satellite-generated data. Anyamba,
Chretien and Small,7 used satellite data to describe
climate anomalies such as the “unscheduled”
El Nino advisory in 2006. El Nino/Southern Oscillation (ENSO) was then related to changes in infectious
diseases such as those found in Indonesia, Malaysia
Chikungunya and dengue - Indian Ocean update. Status as of 17 March 2006
India - Nasik District/Malegaon town
>2000 chikungunya suspected cases
India - Orissa State
4904 suspected cases
India - Andra Pradesh State
5671 chikungunya suspected cases
Country with occurence of
dengue and/or chikungunya
Maldives
602 dengue suspected cases
Affected areas
Affected city
Country
Seychelles
6099 chikungunya suspected cases
Data Source: WHO/EPR
Map Production: Public Health Mapping and GIS
Communicable Diseases (CDS),
World Health Oraganization.
Mayotte
2833 chikungunya suspected cases
Madagascar - Tomasina
dengue outbreak and sporadic
cases of chikungunya
Mauritius
8818 chikungunya suspected cases
Réunion
8818 chikungunya suspected cases
The boundries and names shown and the
designations used on this map do not imply
the expression of any opinion what so ever
on the part of the World Health Oraganization
concerning the legal status of any country,
temitory, city of area or of its authorities, or
concerning the delimitation of its frontiers
or boundaries. Dotted lines on maps represent
approximate border lines for which there may
not yet be full agreement.
World Health
Organization
© WHO 2006. All rights reserved
Figure 1. Chickungunya and Dengue in the Indian Ocean Islands and India.28
Infectious Diseases: Research and Treatment 2010:2
19
Anderson
and the Philippines from drought conditions. In
other parts of the world, above normal rainfall was
expected to occur. The authors list the following parts
of the world at risk for disease outbreaks: Indonesia,
Malaysia, Thailand, and most of the southeast Asia
Islands for increased dengue fever transmission;
Coastal Peru, Ecuador, Venezuela, and Columbia for
increased risk of malaria; Bangladesh and coastal India
for elevated risk of cholera; East Africa for increased
risk of Rift Valley fever and malaria, southwest USA
for increased risk for hantavirus and plague; southern
California for increased West Nile virus transmission,
and northeast Brazil for increased dengue fever and
respiratory illness.
Other authors, e.g. Hunter8 include waterborne
diseases with vector borne diseases in predictions of
increased incidence following climate change, though
the “actual impacts of climate change on public health
are still far from clear”. Vector borne and water borne
disease outbreaks often lag behind direct climatic or
geologic events, causing more widespread harm than
the direct climatic event itself. Experts and insurance
agencies are not yet sure how to relate distal causes
and proximate effects of climate change and natural
disasters that may follow.
Ecological shifts, particularly those towards decreased
species diversity may have an increased effect on
vector borne disease. Ostfeld and Keesing9 proposed a hypothesis of “dilution effect” due to diversity in intermediate hosts as a mediating factor in
the transmission of Lyme disease in the Eastern US.
The vector borne disease model typically includes
RESERVOIR-VECTOR-HOST (Fig. 2). These relationships can be dampened or improved depending
Vector
Pathogen
Host
Figure 2. The classic relationship of the vector-borne disease triangle
where a break in any of the lines can interrupt transmission.
20
on the specialization of the vector and the transmission
competence of the hosts. Because lowered diversity
often follows disastrous climatic or political events,
these protective ecological relationships may also be
disrupted and open yet another pathway for increased
vector borne disease transmission. In 2006, Keesing,
Holt and Ostfeld10 listed a set of research priorities in
the ecological area: 1) describing patterns of change
in disease risk with changing diversity 2) identifying
the mechanisms responsible for observed changes in
risk; 3) clarifying additional mechanisms in a wider
range of epidemiological models; and 4) experimentally manipulating disease systems to assess the impact
of proposed mechanisms.
Mosquito borne diseases
In the area of mosquito borne diseases (other than
malaria, which continues to defy researchers and
foundations, government organizations, and private
corporations), West Nile virus, especially in the
US, Dengue Fever in the rest of the Americas, and
Chickungunya, an emerging or re-emerging disease
are receiving research attention. Chickungunya is an
important example of an emerging disease because
it is in the beginning stages of emergence. The word
“chickungunya” which is used for both the virus
and the disease, means “to walk bent over” in some
African languages. This meaning refers to the sym­
ptom of severe joint pain which characterizes this
dengue-like infection. Aedes albopictus is the presumed vector in a recent outbreak of this disease
in Reunion Pialoux, Gauzere, Jaurebuiberry, and
Strobel.11 Chickungunya has reemerged on the
Indian subcontinent and in the Indian Ocean region,
for unclear reasons. Possible explanations are similar to those for West Nile Virus (WNV): increased
tourism, virus introduction into a naive population,
and viral mutation.
Further investigation by Charrel, Lamballerie, and
Raoult12 found that the outbreak in the Indian Ocean
region and in the Indian Subcontinent, which resulted
in 2.3 million cases at the time of the article, was
caused by a new variant of the virus genome. This
change may also be responsible for the virus adapting
to a new mosquito vector. Prior to its adaptation to
Aedes albopictus, the vector had been Aedes aegypti.
Both of these mosquitoes are anthropophilic, and
extremely widespread. Aedes albopictus is the famed
Infectious Diseases: Research and Treatment 2010:2
21st century vector borne disease research
“Asian tiger mosquito” which was transported in tires
to Texas in the 1990’s. Since both mosquitoes are
found in the US, and since Ae. Albopictus is the most
common urban mosquito in many areas, the threat of
imported Chickungunya disease through human travelers is an extremely important area of needed surveillance and research.
Research methodologies: molecular
and genetic research
Another extremely important area of research is the
methodology of molecular identification, and genetic
mapping. In order to find new vaccines, repellents,
and pesticides, PCR/Serology methodology is used.
Nuttall, Trimnel, Kazimirova and Labuda13 discuss
the need for anti-tick vaccines. Their research in prevention of tick borne disease found a group of antigens that combines the properties of exposed and
concealed antigens which offers the prospect of broad
spectrum vaccines.
A tick responsible for the transmission of Lyme disease, an emerged disease in the US Northeast, Ixodes
scapularis is the subject of a genome project.14,15
These authors affirm that genomics approaches
are being applied increasingly to blood-feeding
arthropod vectors. The National Institute of Allergy
and Infectious Diseases (NIAID) has also made
a firm commitment to genomic sequencing of
bioterrorism agents, emerging and reemerging
pathogens, and to arthropod vectors of human disease, giving this methodology an important place
in the future of vector borne disease research.
Another genomic sequencing project reported by
Pittendrigh, Clark and Johnston16 has a new target
genome, Pediculus humanus humanus (Phthiraptera: Pediculidae), the body louse. This pest transmits the bacterial agents of louse-borne relapsing
fever, trench fever, and epidemic typhus. In times
of civil disturbance or war, these diseases take a toll
on migrant populations and troops. Hill, Kafatos,
Stansfield and Collins17 state that “radical changes
in vector-biology research are required if scientists are to exploit genomic data and implement
changes in public health”. Surveillance patterns
using morphologically-based taxonomic data are
often riddled with misidentification, and molecularly-based taxonomic data impossibly slow and
difficult to acquire. Scientists working together on
Infectious Diseases: Research and Treatment 2010:2
these two approaches to biological diversity and
distribution would improve predictive accuracy.
Tick and louse vector genomics is aimed at tracing patterns of evolution and distribution of vectors,
but researchers are also using genetics in other
ways. An example is to trace the evolution of a
virus, St. Louis encephalitis, a mosquito borne disease. The genome of St. Louis encephalitis has just
recently been completed at the Sackler Institute for
Comparative Genomics at the American Museum of
Natural History (AMNH).18 Molecular methodology
can advance genetic manipulation of vectors and diseases for control. For example, the vector of yellow
fever, Aedes aegypti, was reported to be transformed
with the Hermes element from the housefly in an
article by Jasinskiene, Coates and Benedict, et al.19
This line of investigation shows promise in reducing the capacity of Ae. aegypti to carry and transmit
the yellow fever virus. Perhaps the virus itself could
be altered. Another report from Aultman, Beaty and
Walker20 is an overview of genetically manipulated
vectors of human disease. Because of the current
lack of new pesticide development, the increasing
resistance of vectors to currently used pesticides,
and because of government regulatory processes,
these authors recommend molecular and genomic
research as vitally needed alternatives. Genomics
can provide information and maps to assist in favorable genetic manipulation of vectors and of the diseases they carry.
Research methodologies: satellite
imagery and modeling
A major area of recent research in vector borne disease is the use of satellite imagery data to study the
distribution and ecology of disease vectors and their
habitat. In 2005, 61 countries agreed to implement
the global Earth Observation System of Systems
(GEOSS). The purpose was to provide geo-referenced
data and analysis software that could be used worldwide. The US contribution was the Integrated Earth
Observation System (IEOS). Seventeen federal agencies comprised the working group to develop the plan
for IEOS. Within this plan is an Integrated Ocean/
Coastal Observing System (IOOS) to collect measurements of the air, water and land from the ground,
air or from space. Of the societal goals listed, climate
change monitoring and reduction of public health
21
Anderson
risks are high on the list. Other components are safety
and homeland security.
Making use of this abundant world data, Kalluri, Gilruth, Rogers, and Szczur21 reviewed the use
of remote sensing techniques in the surveillance
of arthropod vector borne infectious disease. The
review reports a fertile environment for research
found in the use of simple image classification techniques associating land characteristics with vector
habitats and in the more complex image processing algorithms for analyzing multi-temporal meteorological observations with vector biology and
ecology. Examples of vectors used in these studies
were mosquitoes, ticks, black flies, tsetse flies and
sand flies, which the authors claim as responsible for
the majority of vector-borne diseases in the world.
In one of the recent articles using remote sensing22
researchers have applied remotely sensed vegetation indices (ASTER) to an analysis of West Nile
vectors in the northeastern US. Multivariate analysis of the environmental variables vs. the mosquito
distribution data explained 86% of the variance
in mosquito/environmental data. The use of these
complex analytical algorithms with remotely sensed
data can help in pinpointing landscape features for
maximum control effectiveness. These techniques
involve considerable expense and expertise not
available to many worldwide researchers, but show
promise because of the worldwide availability of
remotely sensed data.
Jouda, Perret and Gern23 used a regional scale analysis of Lyme borreliosis (Lyme disease) on the Swiss
Plateau and in an Alpine valley. They state that Lyme
borreliosis is the most important vector-borne disease in the Northern hemisphere. Direct fluorescent
antibody assay was used in this study to determine
infection in collected ticks, and comparisons made to
determine correlations between nymphal infection,
location and density, and adult infection, location and
density. Infection rates were higher for adults at high
densities. All locations but one produced infected
ticks. No satellite imagery was used in this case, but
could have been added for a richer description of
environmental variables.
Mathematical analysis of remotely sensed data
also takes the form of modeling as Eisen and Eisen24
illustrate in their article “Spatial modeling of human
risk of exposure to vector-borne pathogens based
22
on epidemiological versus arthropod vector data”.
Their recommendations for risk modeling include the
use of both epidemiological and vector data on a sub
county level, using simulation or analytical models.
The aim of the model is to predict critical vector
abundance thresholds needed to maintain enzootic
pathogen maintenance. This is a persistent question
vector control managers are asked, but a difficult
one to find for a particular site. The recommendation
specifies sub county levels of input data, implying
that models are not widely geographically applicable.
Cost is again a factor for worldwide use of this technique, but it also shows promise.
Education and community involvement
In order to provide immediate improvement to
high disease risk burdens, education and community involvement in vector and disease management
techniques are needed. Chaves, Cohen, Pascual, and
Wilson25 investigated the changes in American cutaneous leishmaniasis concurrent with changes in forest cover. Their conclusion was that “social factors ....
play a critical role that may ultimately determine disease risk.”
In a further development of community involvement, Van den Berg, von Hildebrand, Ragunathan,
and Das26 investigated the technique of empowering farmers in integrated vector management. The
approach was to integrate education on improving
rice yields with managing vector borne diseases.
This was an important step in total integration
using the “farmer field school” method to provide
farmers with an ecologically realistic demonstration of all the aspects of their interaction with the
environment.
Providing farmers first-hand experience with vector
control actions also improved general sanitation and
personal protection against pesticides. In a study done
in Trinidad and Tobago, authors Rawlins, Chen, Rawlins, Chadee and Legall27 found that knowledge of
prevention and protection techniques against Dengue
Fever risk did not coincide with practice, and found a
need for the demonstration of its efficacy, and a need
for community involvement in the educational process. This confirmed the efficacy of “active learning”
and community involvement. A more detailed model
of the vector borne disease triangle includes these educational and community involvement details (Fig. 3).
Infectious Diseases: Research and Treatment 2010:2
21st century vector borne disease research
Vector/
Competence
Environment
Pathogen/
Genetic viability
Host/Prevention
Education
Figure 3. Vector triangle including environmental health aspects.
Note: Vector triangle including 21st century research priorities.
Conclusions
The diseases, concepts, and methods in current environmental health vector borne disease research that
are receiving research attention can be summarized
by the examples of continued surveillance projects
aided by GIS mapping and software modeling analysis, and by a movement to collaborate in these projects with molecular genomic analysis. Research is
addressing the crucial environmental factors contributing to disease through efforts to understand effects
of global warming on disease and vector distribution.
And finally, a question that cannot be fully answered
in a short review: “Are environmental health and
health education professionals using that research to
addressing the needs of people in the greatest need”
is beginning to be answered with health educational
translational projects such as the Van den Berg et al26
research.
An extremely hopeful sign for global disease management is the convergence of methods regardless of
the vector borne disease, environmental conditions,
or geographic location that has emerged in recent
research. Vector borne disease research consortia and
Infectious Diseases: Research and Treatment 2010:2
global organizations have evolved to coordinate and
disseminate important geographic and environmental information to researchers. Geneticists, molecular
biologists, and mathematical modelers have combined
methodology with epidemiologists, medical therapists and educators. A real effort has been made to
involve communities in the management of their own
food production and disease control. Vector borne
disease in environmental health has thus provided a
broad focus for collaboration on human public health
problems that have direct research threads through
all of the methodologies and diseases illustrated in
this article. Convergent collaborative research has
begun to emerge, where complex methodologies
can provide answers to health education researchers
who can empower communities with active learning
techniques to manage their own local vector borne
disease risk. Problems of application to local situations of great need are still very common, however,
has Translational research now a priority in many US
funding agencies (NSF for example) and in private
foundations to aid in the transmission of research
information.
23
Anderson
Disclosure
The author reports no conflicts of interest.
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