Multiplicity of Plasmodium falciparum infection following intermittent preventive treatment in infants

Malar J. 2010 Aug 26;9:244. doi: 10.1186/1475-2875-9-244.


Background: Intermittent preventive treatment in infants with sulphadoxine-pyrimethamine (IPTi-SP) reduces malaria morbidity by 20% to 33%. Potentially, however, this intervention may compromise the acquisition of immunity, including the tolerance towards multiple infections with Plasmodium falciparum.

Methods: Plasmodium falciparum isolates were obtained from children participating in two Ghanaian IPTi-SP trials (Tamale, Afigya Sekyere) at 15 months of age, i.e., six months after they had received the second dose of IPTi-SP or placebo. By typing the polymorphic merozoite surface protein 1 (msp1) and msp2 genes, multiplicity of infection (MOI) was assessed in 389 isolates. A total of additional 133 samples were collected in Tamale at 3, 6, 9, and 12 months of age. Comparisons of MOI between groups were done by non-parametric statistical tests.

Results: The number of distinguishable P. falciparum clones (MOI) ranged between one and six. Mean MOI in Tamale was stable at 2.13 - 2.17 during the first year of life, and increased to 2.57 at age 15 months (P = 0.01). At no age did MOI differ between the IPTi-SP and placebo groups (each, P ≥ 0.5). At 15 months of age, i.e., six months after the second dose, MOI was very similar for children who had received IPTi or placebo (means, 2.25 vs. 2.33; P = 0.55) as was the proportion of polyclonal infections (69.6% vs. 69.7%; P = 0.99). Adjusting for study site, current and prior malaria, parasite density, and season did not change this finding.

Conclusions: IPTi-SP appears to have no impact on the multiplicity of infection during infancy and thereafter. This suggests that tolerance of multiple infections, a component of protective immunity in highly endemic areas, is not affected by this intervention.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Protozoan / genetics
  • Antimalarials / administration & dosage*
  • Chemoprevention / methods*
  • Drug Combinations
  • Female
  • Ghana
  • Humans
  • Infant
  • Malaria / parasitology*
  • Malaria / prevention & control*
  • Male
  • Merozoite Surface Protein 1 / genetics
  • Placebos / administration & dosage
  • Plasmodium falciparum / classification*
  • Plasmodium falciparum / genetics
  • Plasmodium falciparum / isolation & purification*
  • Protozoan Proteins / genetics
  • Pyrimethamine / administration & dosage
  • Sulfadoxine / administration & dosage
  • Treatment Outcome


  • Antigens, Protozoan
  • Antimalarials
  • Drug Combinations
  • Merozoite Surface Protein 1
  • Placebos
  • Protozoan Proteins
  • merozoite surface protein 2, Plasmodium
  • fanasil, pyrimethamine drug combination
  • Sulfadoxine
  • Pyrimethamine