H3Africa is developing capacity for health-related genomics research in Africa

BackgroundBased on highly successful demonstrations in Israel that attractive toxic sugar bait (ATSB) methods can decimate local populations of mosquitoes, this study determined the effectiveness of ATSB methods for malaria vector control in the semi-arid Bandiagara District of Mali, West Africa.MethodsControl and treatment sites, selected along a road that connects villages, contained man-made ponds that were the primary larval habitats of Anopheles gambiae and Anopheles arabiensis. Guava and honey melons, two local fruits shown to be attractive to An. gambiae s.l., were used to prepare solutions of Attractive Sugar Bait (ASB) and ATSB that additionally contained boric acid as an oral insecticide. Both included a color dye marker to facilitate determination of mosquitoes feeding on the solutions. The trial was conducted over a 38-day period, using CDC light traps to monitor mosquito populations. On day 8, ASB solution in the control site and ATSB solution in the treatment site were sprayed using a hand-pump on patches of vegetation. Samples of female mosquitoes were age-graded to determine the impact of ATSB treatment on vector longevity.ResultsImmediately after spraying ATSB in the treatment site, the relative abundance of female and male An. gambiae s.l. declined about 90% from pre-treatment levels and remained low. In the treatment site, most females remaining after ATSB treatment had not completed a single gonotrophic cycle, and only 6% had completed three or more gonotrophic cycles compared with 37% pre-treatment. In the control site sprayed with ASB (without toxin), the proportion of females completing three or more gonotrophic cycles increased from 28.5% pre-treatment to 47.5% post-treatment. In the control site, detection of dye marker in over half of the females and males provided direct evidence that the mosquitoes were feeding on the sprayed solutions.ConclusionThis study in Mali shows that even a single application of ATSB can substantially decrease malaria vector population densities and longevity. It is likely that ATSB methods can be used as a new powerful tool for the control of malaria vectors, particularly since this approach is highly effective for mosquito control, technologically simple, inexpensive, and environmentally safe.

A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa

Background The World Health Organization (WHO) recently recommended that the time to first malaria episode serve as the primary endpoint in phase III malaria vaccine trials—the first of which will be held in Africa. Although common red blood cell (RBC) polymorphisms such as sickle hemoglobin (Hb) S are known to protect against malaria in Africa, their impact on this endpoint has not been investigated. Methods A longitudinal study of 225 individuals aged 2-25 years was conducted in Mali. The association between common RBC polymorphisms and the time to first malaria episode was evaluated. Results Among children aged 2-10 years, sickle cell trait (HbAS) was associated with a 34-day delay in the median time to first malaria episode (p=0.017). Cox regression analysis showed that age (hazard ratio [HR] 0.87 [95% CI, 0.80-0.94]; p=0.001), HbAS (HR 0.48 [95% CI, 0.26-0.91]; p=0.024), and asymptomatic parasitemia at enrollment (HR 0.35 [95% CI, 0.14-0.85]; p=0.021) were associated with decreased malaria risk. Conclusion Given the delay in the time to first malaria episode associated with HbAS, it would be advisable for clinical trials and observational studies that use this endpoint to include Hb typing in the study design where HbAS is prevalent.

Currently, there are no commercially available human vaccines against leishmaniasis. In rodents, cellular immunity to salivary proteins of sand fly vectors is associated to protection against leishmaniasis, making them worthy targets for further exploration as vaccines. We demonstrate that nonhuman primates (NHP) exposed to Phlebotomus duboscqi uninfected sand fly bites or immunized with salivary protein PdSP15 are protected against cutaneous leishmaniasis initiated by infected bites. Uninfected sand fly-exposed and 7 of 10 PdSP15-immunized rhesus macaques displayed a significant reduction in disease and parasite burden compared to controls. Protection correlated to the early appearance of Leishmania-specific CD4(+)IFN-γ(+) lymphocytes, suggesting that immunity to saliva or PdSP15 augments the host immune response to the parasites while maintaining minimal pathology. Notably, the 30% unprotected PdSP15-immunized NHP developed neither immunity to PdSP15 nor an accelerated Leishmania-specific immunity. Sera and peripheral blood mononuclear cells from individuals naturally exposed to P. duboscqi bites recognized PdSP15, demonstrating its immunogenicity in humans. PdSP15 sequence and structure show no homology to mammalian proteins, further demonstrating its potential as a component of a vaccine for human leishmaniasis.