Serological evidence of high exposure to Plasmodium falciparum gameto-cytes in dry-Season in Kenieroba, Mali.

BACKGROUND

Malaria transmission in the Sahel persists during the dry season despite low microscopic parasite prevalence, maintaining reservoirs that hinder elimination efforts. Understanding serological markers of Plasmodium falciparum gametocyte exposure may help identify hidden transmission reservoirs during low‑transmission periods.

MATERIALS AND

METHODS

We conducted a cross‑sectional survey in Kéniéroba, Mali, at three time points representing key seasonal periods: December 2024 (end of rainy season), May 2025 (dry season), and August 2025 (rainy season). A total of 356 participants were enrolled across three age groups (5-8, 9-17, and ≥18 yrs). Parasitaemia and gametocytaemia were assessed by microscopy. IgG and IgM responses to clinically isolated late-stage gametocytes were quantified by ELISA, and seropositivity thresholds defined using malaria‑naïve controls.

RESULTS

Microscopic P. falciparum infection prevalence remained stable across surveys (~13%), but gametocyte carriage declined from 5.7% in December to ~2% in May and August, whereas gametocyte density was higher in the latter months. IgG/IgM seropositivity exceeded 95% throughout, with IgM peaking in May, consistent with recent antigenic stimulation. Age‑stratified analyses revealed weak but statistically significant associations between antibody levels and gametocyte carriage restricted to children aged 5-8 yrs, while no associations were observed in older children or adults.

CONCLUSIONS

In conclusion, serological analyses indicate widespread and seasonally variable exposure to P. falciparum in Kéniéroba, with consistently high IgG and IgM responses to gametocytes reflecting intense background malaria exposure and cross‑reactive immunity from asexual stages. Seasonal and age‑stratified patterns identify school‑aged children as an important reservoir sustaining transmission. Although overall correlations with gametocyte carriage were weak, age‑specific associations suggest an age‑dependent relationship between antibody responses and carriage.