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13. Mass drug administration

13. mass druG administration

There is no evidence of long-term benefits to support mass drug administration (MDA)
in large population groups. There is strong logic that MDA should be selected for drug-
resistant genotypes of parasites. The larger the population of parasites that is targeted with
MDA, the greater the chance that resistance will emerge against the medicines used.
During MDA campaigns, every individual in a defined population or geographical
area is required to take antimalarial treatment on a given day, in a coordinated manner,
including the people who are not sick and not infected with malaria parasites at the time.
Depending on the contraindications of the medicines used, pregnant women, young
infants and other population groups are excluded from the campaign. The concept of
MDA is based on the notion that if all people living in a given area could be effectively
treated and rid of malaria parasites on a synchronized day, and the procedure repeated
at intervals once or twice thereafter, the parasite reservoir of malaria in the area could
be effectively reduced and eventually eliminated.
An effectively conducted MDA programme will result in a very significant reduction in
the parasite prevalence. However, once MDA is terminated, malaria endemicity in the
area will eventually return to its original levels (unless the vectorial capacity is reduced
in parallel and maintained at a very low level). The time it takes to return to the original
18
levels of transmission will depend on the prevailing vectorial capacity.
The rebound may be associated with higher morbidity and mortality if the MDA was
maintained long enough for people to lose herd-immunity against malaria. The rebound
may have lower consequences in terms of malaria morbidity and mortality if local
improvements in housing and the socioeconomic situation have meanwhile resulted
in reduced man-vector contact (i.e. people getting fewer mosquito bites), and/or if local
access to reliable health services has improved to such a degree that people get diagnosed
and treated much earlier in the course of a malaria infection (i.e. infections are treated
before progression to severe disease and death, and before gametocytes are generated
for transmission to take place). Mass drug administration is generally carried out over
relatively short periods of time, while improvements in housing and the socioeconomic
situation occur over much longer timeframes.

17
Mass screening and treatment is not the same as and must not be confused with Mass Drug Administration, which is
the administration of a complete treatment course of antimalarial medicines to every individual in a geographically
defined area on a specific day.
18 Vectorial capacity: number of new infections the population of a given vector would distribute per case per day at
a given place and time, assuming conditions of non-immunity. Factors affecting vectorial capacity include: (i) the
density of female anophelines relative to humans; (ii) their longevity, frequency of feeding and propensity to bite
humans; and (iii) the length of the extrinsic (i.e. in the mosquito) cycle of the parasite.
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