MALARIA ELIMINATION IN ZANZIBAR - Soper Strategies

The first objective of the responses triggered at level 1 is to avoid
onward transmission. The second objective is to determine and/
or confirm whether transmission is still ongoing. The mass
screening proposed aims at identifying secondary cases, which
will determine if moving to level 3 is warranted.
When no secondary cases can be identified it is still recommended
to remain cautious (especially when the index case was likely
locally acquired). The active case detection should therefore be
repeated twice with an interval of 4 weeks (more or less the time
of the parasite cycle). When two consecutive mass screenings
cannot identify any secondary cases, the outbreak can be declared
over and the area can return to vigilance level 0. In a scenario
where effective coverage of preventive vector control measures
is kept at around 75%, our simulations indicate that secondary
cases will almost never occur and the risk of epidemics is low.
However, when prevention is called back, epidemics become a
real risk, and the thresholds for moving towards level 3 should
therefore be far more conservative. We propose three secondary
cases; far less than what is used in the simulator (outbreak defined
as 50 cases in 2 weeks).
At level 3, the ZMCP (in collaboration with all its partners) should
initiate a massive response that aims at interrupting transmission.
We suggest considering mass treatment of fever cases if the
organization of a mass campaign is likely to be delayed. House to
house visits by a small team that does not need to have training
to do an RDT, might be easier to rapidly start and in the case
of a locally-acquired infection, the time gained could be crucial.
Mass screening, regardless of the presence of fever, follows the
same more cautious rationale and has the added advantage that
some asymptomatic cases, when treated, are cleared of parasites.
Requirements of Implementation
District staff, with assistance from the ZMCP, will be responsible
for initiating confirmation procedures within 24 hours of
receiving a report. The response activities will be labor intensive
and have the potential to overwhelm the DHMT. If necessary,
district staff from non-health sectors should be made available
to assist with personnel needs. The government may also want
to establish dedicated surveillance teams in key districts as
suggested above (minimum three teams per high risk district) to
ensure sufficient capacity for and execution of this activity. The
surveillance teams could be taken from existing district health
staff. We recommend that the 2 districts that are considered
to have a higher transmission potential employ five full time
investigation teams while for medium risk districts four teams
would be sufficient most of the time. When a more elaborate
response is required in low risk districts, additional temporary
staff will need to be hired. Numbers will depend on the size of
the area to be screened.
Ideally, each district would also have a car and an emergency
fuel stock on stand-by for investigation and the initial phases of
the rapid response. In addition, spraying equipment (including
protective gear) and a small stock of insecticides could be made
available at the district level. A small stock of RDTs for initial
stages of mass screenings can be kept at the district level with
larger stocks available at the central level where storage conditions
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are likely to be more adapted (ideally < 350). The ZMCP will
also need to ensure that the necessary forms (and stationary) are
available at the health facility level (case notification forms) and
the district level (outbreak investigation forms). The ZMCP is
also responsible for the management of ACT stocks, and they
should ensure that areas where a case has been notified has
sufficient emergency stocks at their disposal. Over time, these
outbreaks will become increasingly rare with each outbreak
resulting in fewer secondary cases. This will make forecasting the
necessary emergency stand-by stocks challenging. In the worstcase
scenario, Zanzibar could be faced with a massive epidemic
in a non-immune population which would require large amounts
of ACTs. However, keeping large stocks only for this purpose
would not be cost-efficient. Zanzibar will therefore need to set
up a system with manufacturers or neighboring malaria endemic
countries that would give them quick access to large amounts of
ACTs in an emergency.
Entomological Surveillance
A robust entomological surveillance system is a crucial component
of any malaria elimination program. Entomological surveillance
is, in essence, the monitoring of the vector population to assess
the effect of vector control interventions in these populations and
to ensure that control methodologies are effective, targeted and
proactive. As such, entomological surveillance plays a key role in:
�� Monitoring the effectiveness of vector control interventions
�� Identifying active transmission foci
�� Monitoring potential transmission foci
�� Helping to establish the receptivity of an area to malaria
transmission
At a basic level, routine vector collection and processing will
define vector populations in terms of species, biting and resting
behavior, immature and adult stage density, and infection rates.
However, additional investigation can be used to define the levels
of resistance to insecticides. Levels of resistance are especially
important when evaluating the effectiveness of vector control
interventions such as IRS and LLINs. Insecticide resistance
genes can develop rapidly when mosquitoes are exposed to
similar chemical families (e.g., pyrethroids). These factors are
important to monitor, especially when evaluating how the vector
population reacts when intensive vector control measures, such
as IRS, are scaled back.
These population effects are extremely important when assessing
the potential receptivity of an area to re-infection from outside.
WHO states that the degree of receptivity of an area is, amongst
others, defined by its malaria history (WHO, 2007), specifically:
�� Original degree of endemicity: This can be obtained from
case records and any entomological data from the specific
area (see technical feasibility chapter).
�� Vectorial capacity before the implementation of intensive
control measures
This will define the nature of the vector population and give
a baseline for comparison after control measures are scaled