Malaria incidence and efficacy of intermittent preventive treatment in infants (IPTi).
BACKGROUND
Intermittent preventive antimalarial treatment in infants (IPTi) is currently evaluated as a malaria control strategy. Among the factors influencing the extent of protection that is provided by IPTi are the transmission intensity, seasonality, drug resistance patterns, and the schedule of IPTi administrations. The aim of this study was to determine how far the protective efficacy of IPTi depends on spatio-temporal variations of the prevailing incidence of malaria.


METHODS
One thousand seventy infants were enrolled in a registered controlled trial on the efficacy of IPTi with sulphadoxine-pyrimethamine (SP) in the Ashanti Region, Ghana, West Africa (ClinicalTrial.gov: NCT00206739). Stratification for the village of residence and the month of birth of study participants demonstrated that the malaria incidence was dependent on spatial (range of incidence rates in different villages 0.6-2.0 episodes/year) and temporal (range of incidence rates in children of different birth months 0.8-1.2 episodes/year) factors. The range of spatio-temporal variation allowed ecological analyses of the correlation between malaria incidence rates, anti-Plasmodium falciparum lysate IgG antibody levels and protective efficacies provided by IPTi.


RESULTS
Protective efficacy of the first SP administration was positively correlated with malaria incidences in children living in a distinct village or born in a distinct month (R2 0.48, p < 0.04 and R2 0.63, p < 0.003, respectively). Corresponding trends were seen after the second and third study drug administration. Accordingly, IgG levels against parasite lysate increased with malaria incidence. This correlation was stronger in children who received IPTi, indicating an effect modification of the intervention.


CONCLUSIONS
The spatial and temporal variations of malaria incidences in a geographically and meteorologically homogeneous study area exemplify the need for close monitoring of local incidence rates in all types of intervention studies. The increase of the protective efficacy of IPTi with malaria incidences may be relevant for IPTi implementation strategies and, possibly, for other malaria control measures.
Kobbe
Robin
R
Infectious Disease Epidemiology Group, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, D-20359 Hamburg, Germany. kobbe@bni-hamburg.de
Adjei
Samuel
S
Kreuzberg
Christina
C
Kreuels
Benno
B
Thompson
Benedicta
B
Thompson
Peter A
PA
Marks
Florian
F
Busch
Wibke
W
Tosun
Meral
M
Schreiber
Nadine
N
Opoku
Ernest
E
Adjei
Ohene
O
Meyer
Christian G
CG
May
Juergen
J
D000818:Animals; D000962:Antimalarials / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D004338:Drug Combinations; D004351:Drug Resistance; D006801:Humans; D007223:Infant; D016778:Malaria, Falciparum / Q000208:ethnology / Q000517:prevention & control*; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000276:immunology; D011739:Pyrimethamine / Q000494:pharmacology / Q000627:therapeutic use*; D013413:Sulfadoxine / Q000494:pharmacology / Q000627:therapeutic use*; D016896:Treatment Outcome
D000962:Antimalarials; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D011739:Pyrimethamine