Malaria control strategies in the Kilombero Valley, Tanzania

Malaria is major public health problem in Tanzania and increasing trends have been observed
in the last two decades. A significant consequence of repeated malaria infections in high
transmission areas is anaemia in very young children. The control of malaria in Tanzania
includes both preventive and curative strategies. On the preventive side insecticide treated
bed nets (ITNs) are a promising tool. ITNs have been shown to be effective in reducing
malaria morbidity and mortality in controlled trials. Large-scale implementation of the
technology is currently being initiated in many African countries. We report the impact of a
large social marketing programme of ITNs on malaria morbidity through a series of studies, in
a population of about 55,000 people in Tanzania. The ITNs social marketing programme resulted in a rapid increase in any net ownership (from
58 to 83%) and an increase in ITNs ownership (from 10 to 61%) in children under two years
of age within 2 years of implementation. As a result the overall mean haemoglobin levels
increased (from 8.0 to 8.9 g/dl) in the study children during the successive surveys. The
prevalence of anaemia in the study population decreased from 49% to 26%. Comparison
between children with ITNs and those without nets showed that ITNs had a protective efficacy
of 63% (95% CI: 38 to 77) on the prevalence of parasitaemia, and 63% (95% CI: 27 to 82) on
anaemia (haemoglobin £ 8 g/dl). These results endorse the wide scale implementation of
ITNs in Tanzania. ITNs can only reduce the risk of malaria dis ease but cannot eliminate it. Hence, appropriate
effective treatment is required. Chloroquine is a cheap and safe antimalarial and it was until
recently the first line drug of choice in the National Malaria Treatment Policy. Resistance to
chloroquine has been reported with increasing frequency in Tanzania and has been linked to
the increasing admissions with severe disease in hospitals. A comparative randomised,
open clinical trial of chloroquine against Co-artemâ (fixed combination of Artemether +
Benflumetol) an alternative new antimalarial, showed seven-day parasitological cure rates of
94% for Co-artemâ and only 35% for chloroquine. Generally, Co-artemâ showed a superior
clearance rate, successfully cleared higher parasite densities and suppressed new infections over a longer period of time. Furthermore, Co-artemâ suppressed more effectively
gametocytes in these children, indicating a potential benefit for reducing malaria transmission.
The unacceptably high chloroquine failure rates call for an urgent review of the National
Malaria Treatment Guidelines. The decision to change the first line antimalarial and the choice of a new drug depend on a
number of factors that include the clinical, epidemiological and social-economical factors, as
well as the health infrastructure. Considering all of these dimensions, sulphadoxinepyrimenthamine
(SP) was identified as a good interim replacement for chloroquine. Further
Phase IV evaluation of Co-artemâ and other combination therapy regimens are required
before considering their inclusion in the national treatment policy. Much work is also needed
to identify suitable compounds to be used for home management of malaria, within the
national treatment guidelines. Experience gained with these studies gives a description of the different methodologies and
tools that can be used to evaluate different components of the National Malaria Control
Programme. For example, it was difficult to assess the impact of the ITNs programme using
the case-control approach. Repeated cross-sectional assessments were found to be more
suitable for assessing the impact of ITNs under programme conditions, especially on malariarelated
anaemia in this area of high transmission. Specific indicators for programme
evaluation may need to be identified for specific interventions. These may be different from
the ones used in randomised controlled trials. The use of molecular markers for monitoring
and evaluation of antimalarial intervention programmes illustrate the need to develop and
validate novel tools and approaches for programme evaluation. Better malaria control is expected by combining ITNs and an effective antimalarial, especially
combination therapy. The evaluation, implementation, and monitoring of all these control
activities requires a partnership between researchers, policy makers, health managers, in
close collaboration with other stakeholders in the public and private domain, including the
beneficiaries - the community.