A longitudinal study of immune responses to Plasmodium falciparum sexual stage antigens in Tanzanian adults.

Next to children, adults form a substantial part of the infectious reservoir that is responsible for the spread of malaria. In this longitudinal study, we determined sexual stage immune responses to Plasmodium falciparum and infectiousness to mosquitoes in adults from an area with intense malaria transmission. A cohort of 43 Tanzanian adults was followed for 18 months.

Transmission-reducing immunity is inversely related to age in Plasmodium falciparum gametocyte carriers.

Immunity to the sexual stages of Plasmodium falciparum is induced during natural infections and can significantly reduce the transmission of parasites to mosquitoes (transmission reducing activity; TRA) but little is known about how these responses develop with increasing age/exposure to malaria. Routinely TRA is measured in the standard membrane feeding assay (SMFA). Sera were collected from a total of 199 gametocyte carriers (median age 4 years, quartiles 2 and 9 years) near Ifakara, Tanzania; 128 samples were tested in the SMFA and generated TRA data classified as a reduction of > 50% and > 90% of transmission.

Treatment failure of pyrimethamine-sulphadoxine and induction of Plasmodium falciparum gametocytaemia in children in western Kenya.

Sub-Saharan Africa faces increasing levels of resistance of Plasmodium falciparum parasites to the first-line drug pyrimethamine-sulphadoxine (SP). Successful treatment with SP is reported to induce gametocytes and drug resistance may further increase gametocytaemia after treatment. Treatment success, gametocyte prevalence and gametocyte density were determined in 224 asymptomatic children in western Kenya on day 7 after treatment with SP.

Dynamics of P. falciparum gametocytemia in symptomatic patients in an area of intense perennial transmission in Tanzania.

We investigated the dynamics of Plasmodium falciparum gametocytemia in symptomatic patients attending a local dispensary in the Kilombero district, Tanzania. Consenting individuals aged one and above, with varying asexual and sexual parasitemias were treated appropriately and asked to return weekly for 28 days. Gametocyte prevalence was highest on Day 7 of follow-up in all age groups (overall 30.