%0 Journal Article
%T Assessment of the relative success of sporozoite inoculations in individuals exposed to moderate seasonal transmission
%A Adama Tall
%A Cheikh Sokhna
%A Ronald Perraut
%A Didier Fontenille
%A Laurence Marrama
%A Alioune B Ly
%A Fatoumata D Sarr
%A A£¿ssatou Toure
%A Jean-Fran£¿ois Trape
%A Andr¨¦ Spiegel
%A Christophe Rogier
%A Pierre Druilhe
%J Malaria Journal
%D 2009
%I BioMed Central
%R 10.1186/1475-2875-8-161
%X One hundred and ten individuals from the village of Ndiop (Senegal), aged between one and 72 years, were cured of malaria by quinine (25 mg/day oral Quinimax£¿ in three equal daily doses, for seven days). Thereafter, thick blood films were examined to detect the reappearance of Plasmodium falciparum every week, for 11 weeks after treatment. Malaria transmission was simultaneously measured weekly by night collection of biting mosquitoes.Malaria transmission was on average 15.3 infective bites per person during the 77 days follow up. The median reappearance time for the whole study population was 46.8 days, whereas individuals would have received an average one infective bite every 5 days. At the end of the follow-up, after 77 days, 103 of the 110 individuals (93.6%; CI 95% [89.0¨C98.2]) had been re-infected with P. falciparum. The median reappearance time ('re-positivation') was longer in subjects with patent parasitaemia at enrolment than in parasitologically-negative individuals (58 days vs. 45.9; p = 0.03) and in adults > 30 years than in younger subjects (58.6 days vs. 42.7; p = 0.0002). In a multivariate Cox PH model controlling for the sickle cell trait, G6PD deficiency and the type of habitat, the presence of parasitaemia at enrolment and age ¡Ý 30 years were independently predictive of a reduced risk of re-infection (PH = 0.5 [95% CI: 0.3¨C0.9] and 0.4; [95% CI: 0.2¨C0.6] respectively).Results indicate the existence of a substantial resistance to sporozoites inoculations, but which was ultimately overcome in almost every individual after 2 1/2 months of natural challenges. Such a study design and the results obtained suggest that, despite a small sample size, this approach can contribute to assess the impact of intervention methods, such as the efficacy vector-control measures or of malaria pre-erythrocytic stages vaccines.Exposure to parasites induces immune responses, which can reduce parasite loads. The acquisition of a state of protection against clinical mala
%U http://www.malariajournal.com/content/8/1/161