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Vector-borne Disease Surveillance in Southeast Asia – Challenges and Opportunities in Vector Collection and

Pathogen Detection

MAJ Brian Evans, Ph.D.; Jim McAvin; Alongkot Ponlawat, PhD; Ratree Takhampunya, PhD; LTC Jason Richardson, PhD


Agenda Agenda

• Mission

• Intelligence requirements

• PM detachment capabilities

• Detection capabilities (JBAIDS)

• Value of pathogen assays

• Where is the gap?

• Conclusion


MissionMission

To accurately asses the risk of vector-borne disease in an AO and to recommend/ implement measures that reduce the disease threat among soldiers.


Intelligence Requirements Intelligence Requirements

• Human case data

• Vector data (presence/absence)

• Pathogen data (presence/absence)

• Environmental data


PM Detachment CapabilitiesPM Detachment Capabilities

• Pre-deployment intelligence

• Gather case data (non-specific/specific)

• Limited vector surveillance

• Limited or no pathogen detection capability.


Detection Capability Detection Capability

JBAIDS Assay GRI Rank* Activities Underway Comments

Dengue virus 5 Deployed Vector Surveillan

ce AFPMB Approved

Chikungunya virus 6 Wet Assay Optimization Funded: Pending FY10 Award

Aedes aegypti mosquitoes not rankedDeployed Vector Surveillan

ce AFPMB Submission Planned

Leishmania spp 50Deployed Vector Surveillan

ce AFPMB Approved

Leishmania visceral genotype 20

Deployed Vector Surveillance AFPMB Approved

Leishmania human pathogenic spp Various Wet Assay Optimization Funded: Pending FY10 Award

Plasmodium spp, P. f and P. v 1 Wet Assay Optimization Funded: Pending FY10 Award

Flavivirus spp Various Wet Assay Optimization Funded: Pending FY10 Award

Japanese enchephalitis virus 24 Wet Assay Optimization Funded: Pending FY10 Award


Value of Pathogen Assays Value of Pathogen Assays

Information Availability Cases Vector Pathogen Risk accuracy Control efficacy

Pathogen assay (value added) Example

X X X Accurate Effective Limited Dengue - Thailand

X X Accurate Efffective NA

X Accurate Partial NA Malaria - Thailand

X Inaccurate Ineffective NA

** X X Partially Partial Significant Dengue – Thailand

X NA NA NA

X X NA NA NA

Relative impact of information availability on risk accuracy, control efficacy, and on the added value of a pathogen detection assay

Assumptions: Case data is specific in number and location.

Vector surveillance, pathogen detection tools, and control tools are effective.


Case data

is valuable!


Where is the gap? Where is the gap? Adult mosquito/sand fly collection devices minimally effective;

taxonomic keys - 1 or 2 Ae. aegypti /house (15 mins/house); countless man-hours and

houses needed for sufficient sample sizes (1 in 1000 infected); this is an area where there is transmission of dengue year-round.


Where is the gap? Where is the gap?

Bed net trap - NAMRU-2

BG Sentinel (BG Lure)


Where is the gap? Where is the gap?

Rodent-baited traps as a tool for collecting chigger mites, vectors of scrub typhus.

&

Figure 13: Field caught rodent on snap trap

Figure 4: Rodent with chiggers


Other Challenges? Other Challenges? • Low densities; seasonality?

• How does pathogen/vector data translate into risk?

– What does it mean to have 6 in 1000 infected; should I be concerned?

• Even when we know the vector locations and where the pathogen is most prevalent in the vector, do we understand the biology?

• Not one-size fits all solutions; same species from different locations may have evolved independently; different vector ecology


Conclusion Conclusion

Bottom-line: Pathogen detection has greatest added value for risk determination and control efficacy in instances where there is limited or no case data. If disease is seasonal, a valuable forecasting tool.

Challenge: Relevancy of pathogen detection data is highly-dependent on the vector surveillance tool.

Pathogen surveillance should be a critical part of the PM mission; need more effective surveillance tools to complement this mission; need trained soldiers who can interpret information/data.

Where time/resources/money are limited, should be very selective about when and where to use pathogen detection assays.

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