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