Vector and dengue control program core activities include:

• Proactive vector control - Vector control measures implemented prior to knowledge of vector or disease surveillance results.
  


• Vector surveillance - Surveillance for presence or abundance of Aedes aegypti or for resistance to insecticides used to control the immature or adult life stages.
  


• Pathogen surveillance - Surveillance for presence of dengue virus or rate of infection with dengue virus in vector or human populations.
  


• Disease surveillance - Surveillance for presence or incidence of fevers of unknown origin, clinically diagnosed dengue cases, or dengue cases confirmed by diagnostic laboratory tests.
  


• Reactive emergency vector control - Vector control measures implemented in direct response to vector or disease surveillance results.

Proactive vector control measures:

Benefit:

Focuses on prevention rather than control of dengue outbreaks.

Drawback:

May be difficult to sustain over time, especially when the approach is successful and dengue cases first decline and then stabilize at low levels and dengue no longer is viewed as an important public health concern by local decision makers.

Vector surveillance:

Benefits:

• Information on vector abundance can help to determine the level of risk for a dengue outbreak before it occurs.
• Information on insecticide resistance ensures use of appropriate insecticides.

Drawbacks:

• The association between vector abundance and risk of a dengue outbreak is strongly influenced by herd immunity to dengue virus in the human population. This makes it difficult to determine critical vector abundance thresholds to trigger control activities.
• The impact of laboratory determined insecticide resistance (bioassays, biochemical assays, genetic assays) on operational outcomes is poorly understood. This makes it difficult to determine critical thresholds to trigger changes in insecticide use patterns.

Pathogen surveillance:

Benefits:

• Demonstrates that dengue virus is circulating.
• Information on herd immunity in the human population can help to determine the level of risk for a dengue outbreak before it occurs.
• Can provide early warning of introduction of a dengue virus serotype likely to result in a dengue outbreak based on knowledge of local serotype-specific herd immunity.

Drawbacks:

• Surveillance for dengue virus in either vector or human populations is time-consuming and costly.
• Currently available inexpensive tests are not adequate to determine serotype-specific dengue virus exposure.

Disease surveillance:

Benefits:

• Fevers of unknown origin can provide early warning of an impending dengue outbreak.
• Clinically diagnosed dengue cases can provide information of increased levels of suspected dengue activity.
• Dengue cases confirmed by diagnostic laboratory test demonstrate that dengue transmission is occurring.

Drawbacks:

• Fevers of unknown origin or clinically diagnosed dengue cases may result from diseases other than dengue.
• Laboratory confirmation of dengue cases often is too slow for effective emergency vector control response.

Reactive emergency vector control:

Benefits:

• Inescapable fallback when all other approaches have failed.
• Can be effective in stopping an outbreak or at least changing its temporal pattern towards cases occurring over a longer time period which can save lives because health care facilities are less likley to be overwhelmed and unable to provide appropriate supportive care for patients with severe disease manifestations.

Drawback:

• Unless vector control response is triggered by clinically diagnosed dengue cases or turn-around time for laboratory confirmation is rapid, reactive control measures may fall into the trap of always being one step behind the spatial dynamic of the dengue outbreak.

Possible methodologies for use in different core activities in vector and dengue control. Methodologies in common operational use in dengue endemic countries are shown in bold.

Click on the table below to view an enlarged version



^aCan be implemented by either vector control programs or community members
^b Implemented by individual home-owners

What is the best resource allocation scheme for vector and dengue control programs?



We need a better understanding of presently used versus desired resource allocations in vector/dengue control programs!