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Dengue proposal. Considerations for design of the phase II follow up. Background. DPSEEA was used to introduce the notion of urban ecosystem health. The framework was applied to chronic aspect of urban conditions in Cayo Hueso. Participatory approaches were used to define key indicators.

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dengue proposal

Dengue proposal

Considerations for design of the phase II follow up

background
Background
  • DPSEEA was used to introduce the notion of urban ecosystem health.
  • The framework was applied to chronic aspect of urban conditions in Cayo Hueso.
  • Participatory approaches were used to define key indicators.
  • The findings:
    • Measurable improvements in subjective indicators.
    • Inconclusive change in more objective indicators.
follow on research for dengue
Follow on research for dengue
  • Reapply the phase I methods again.
  • Elaborate on DPSEEA introducing:
    • the importance of context,
    • ecosystem processes and their interactions
    • Broader ecosystem health/integrity perspective.
  • Refine the indicators:
    • learning why there is a gap between the subjective and objective outcomes.
  • Create a new decision-making and evaluation framework emphasizing learning objectives and adaptive management:
    • Dengue is an episodic risk in Cuba. Monitoring and intervention for such problems are not the same as those of a chronic issue such as housing.
lessons from phase i
Lessons from Phase I
  • Relative importance of exogenous factors.
  • Challenges in attributing effects to intervention without a “control” population.
why does an overall framework matter
Why does an overallframework matter?
  • Monitoring is like our eyes
  • Decision-making is like our brain
  • We cannot look everywhere
  • We cannot think of everything
  • We need to think about costs and benefits of every monitoring and intervention action.
  • We need to find the efficient and effective set of observations (monitoring) that allow appropriate actions (campaigns).
issues in control of epidemics
Issues in control of epidemics
  • Monitoring is less than perfect
    • e.g. infected are asymptomatic but have viremia
    • Symptoms of potential infection may go mal-reported (know 5 day bed-rest could lead to over reporting (if compensated) and under reported (if time substitution is unavailable to the patient).
  • Intervention efficacy is less than perfect:
    • depends on social acceptance,
    • depends on suitability to ecosystem (e.g. “closed” buildings),
    • depends on being timely, which is itself reliant on frequency of monitoring and speed of interpretation.
  • Direct and intended benefits of monitoring depend on the efficacy of interventions that could be triggered by it.
  • Imperfect monitoring and interventions erodes social acceptance and trust.
three dimensions to evaluation
Three dimensions to evaluation

The challenge of sustainability in the absence of a signal

  • Effects:
    • direct and intended
    • indirect and ancillary
  • Benefits and costs:
    • cases of dengue and DHF
    • other health effects
    • improved living conditions, …
  • Measures:
    • Objective, subjective
    • Information flow and feedback to decision making

The opportunity for sustainability through indirect benefits

an ideal policy
An Ideal Policy
  • Has community support.
  • Has positive impacts.
  • Is monitored and enforced effectively.
  • Has self-righting properties.
  • Has free-drivers.
  • Meets more than one objective.
take the case of dengue in cuba we need to identify the policy goal approach constraints
Take the case of dengue in Cuba:We need to identify the policy goal, approach & constraints
  • Goal
    • prevent dengue
  • Actions:
    • Reduce breeding sites for A. aegypti
    • Eradicate mosquito population
    • Isolate potential infected people from healthy
  • Means:
    • Monitoring, interpretation and dissemination of information,
    • Decision-making processes
  • Constraints:
    • The time of field workers
    • The time of households
    • The cost of fumigation (money and incidental health impacts)
    • The implications of forced bed-rest for feverish people
    • Loss of public interest for participation
the overall framework
The overall framework

Ecology

The scientific input

Society

Goals and values

The ecologically possible

The socially preferred

Whatoutcome to encourage and when

How

Intervention

Monitoring

Governance

design alternatives
Design alternatives

when to act?

what to do?

Find best system

monitor what?

monitor how?

Mosquito habitat

Mosquito density

Disease locally

Disease regionally

Weakly active network until trigger

Adaptive hotspot monitoring

  • [1 » a]
  • [2 » a+b]
  • [3 » a+b+c]
  • [2+3 » a+b+b]
  • [4 » 1 » a+b]

Destroy habitat

Destroy mosquito

Change behaviour

how should the monitoring intervention evolve at different levels of force of infection
How should the monitoring/intervention evolve at different levels of force of infection?

The iterative cycles of monitoring and intervention. E.g.:

  • The first 90% can be controlled through identification and elimination of the 1st levels risk factors.
    • The next 90% through identification of 2nd level risk factors and interventions
      • The next 90% through identification of 3rd level risk factors and interventions.
        • The next 90% …

The rule for when to stop is determined by the whole human-vector-virus ecology. For a disease that is hard to transmit, we can stop at the level of the first risk factors. For a disease that is easily transmitted we need to go to understanding and controlling smaller and smaller risk factors.

transmission of dengue virus by aedes aegypti

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

Extrinsic incubation period(~9 days)

Intrinsic incubation period (~7 days)

Illness

Illness

A.aegypti inecosystem

Transmission of Dengue Virusby Aedes aegypti

Viremia

Viremia

0

5

8

12

16

20

24

28

Days

Infectedhuman inecosystem

Human #1

Human #2

transmission of dengue virus by aedes aegypti1

Illness

A.aegypti inecosystem

Fumigation kills mosquitoes

Transmission of Dengue Virusby Aedes aegypti

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

Viremia

Viremia

Viremia

0

5

8

12

16

20

24

28

Days

Illness

Infectedhuman inecosystem

Human #1

Human #2

transmission of dengue virus by aedes aegypti2

Illness

A.aegypti inecosystem

Transmission of Dengue Virusby Aedes aegypti

Breeding site elimination

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

Viremia

Viremia

Viremia

0

5

8

12

16

20

24

28

Days

Illness

Infectedhuman inecosystem

Human #1

Human #2

transmission of dengue virus by aedes aegypti3

Illness

A.aegypti inecosystem

Transmission of Dengue Virusby Aedes aegypti

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

Forced bedrest isolates viremia from vector

Viremia

Viremia

Viremia

0

5

8

12

16

20

24

28

Days

Illness

Infectedhuman inecosystem

Human #1

Human #2

research ideas from ubc partners
Research Ideas from UBC partners
  • Retrospective: A full evaluation (costs and benefits, intended and unintended) of the monitoring-intervention program.
    • What can be learned about dengue ecology because of the extra-ordinary setting?
    • A retrospective of health and environmental impacts of the control campaign in 2002.
  • Prospective: How should the monitoring/intervention evolve at different risks of epidemic? (refinement of methodology given Cuba’s special situation)
  • What are the pre-requisites for introducing self reinforcing and self-adjusting elements to the process?
c b of interventions monitoring blood samples
Costs

High cost

May be too late for prevention epidemic

Loss of privacy

Benefits

Screening for other diseases & behavioural change

C&B of Interventions:monitoring blood samples
  • Weakness
  • Could change behaviour in seeking medical help
  • Strength
  • Least ambiguous test of dengue
  • Prerequisite to level of concern about DHF
c b of interventions destruction of habitat
Costs

Continuous effort

High labour input

Benefits

Cleaner environment

C&B of Interventions:destruction of habitat
  • Weakness
  • Some households will not be able to comply.
  • As the vector is not eradicated but pressed for habitat it will change its behaviour
  • Strength
  • Could contribute to community spirit if organized as a social event.
c b of interventions quarantine
Costs

Loss of work

Familiar discord

More babies?

Benefits

More babies?

Good to have a rest

C&B of Interventions:quarantine
  • Weakness
  • Hosts have viremia long before they show symptoms.
  • Non-compliance
  • Could change behaviour in seeking medical help
  • Strength
  • It may provide spatially specific information for concentration of effort.
c b of interventions fumigation spraying
Costs

Needs coordination of episodic effort & opportunity cost of labour and material input

Contamination of environment

Loss of ecosystem integrity

Human health effects

Benefits

Destruction of mosquitoes

C&B of Interventions:fumigation & spraying
  • Weakness
  • Closed houses.
  • Impatient home owners.
  • Poor public relations.
  • Does not kill larvae
  • Strength
  • Fast deployment
  • Politically visible
  • Triggers behavioural change
c b of interventions reliable domestic water supply
Costs

High investment costs

Only part of the solution

Benefits

Eliminates major habitats at home

Reduced water-borne epidemics

Better hygiene

Saves time

Reduces injury

C&B of Interventions:reliable domestic water supply
  • Weakness
  • A long lead time
  • Strength
  • Strong public support
  • Will be easier to maintain
what aspects of the ecosystem health approach are more readily adopted why
What aspects of the ecosystem-health approach are more readily adopted, why?
  • Does the approach have value if partially adopted?
    • Spatial and functional organization challenges?
    • What critical aspects are missing and why?
  • Does possibility of formal risk assessment, cost and benefit estimation, … approaches impact adoption patterns?
    • They did not resonate to the notion of cost.
    • How is “value” of information get translated into something of similar implication here?
  • What would be the features of a self-righting approach?
need to identify goal approach constraints
Need to identify goal, approach & constraints
  • Goal
    • prevent dengue
  • Actions:
    • Reduce breeding sites for A. aegypti
    • Eradicate mosquito population
    • Isolate potential infected people from healthy
  • Means:
    • Monitoring, interpretation and dissemination of information,
    • Decision-making processes
  • Constraints:
    • The time of field workers
    • The time of households
    • The cost of fumigation (money and incidental health impacts)
    • The implications of forced bed-rest for feverish people
    • Loss of public interest for participation
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