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Strategies to detect Human African Trypanosomiasis (HAT) cases rely on serological screening of populations exposed to trypanosomes. In Guinea, mass medical screening surveys performed with the Card Agglutination Test for Trypanosomiasis have been progressively replaced by door-to-door approaches using Rapid Diagnostic Tests (RDTs) since 2016. However, RDTs availability represents a major concern and medical teams must often adapt, even in the absence of prior RDT performance evaluation. For the last 5 years, the Guinean HAT National Control Program had to combine three different RDTs according to their availability and price: the SD Bioline HAT (not available anymore), the HAT Sero-K-SeT (most expensive), and recently the Abbott Bioline HAT 2.0 (limited field evaluation). Here, we assess the performance of these RDTs, alone or in different combinations, through the analysis of both prospective and retrospective data. A parallel assessment showed a higher positivity rate of Abbott Bioline HAT 2.0 (6.0%, n = 2,250) as compared to HAT Sero-K-SeT (1.9%), with a combined positive predictive value (PPV) of 20.0%. However, an evaluation of Abbott Bioline HAT 2.0 alone revealed a low PPV of 3.9% (n = 6,930) which was surpassed when using Abbott Bioline HAT 2.0 in first line and HAT Sero-K-SeT as a secondary test before confirmation, with a combined PPV reaching 44.4%. A retrospective evaluation of all 3 RDTs was then conducted on 189 plasma samples from the HAT-NCP biobank, confirming the higher sensitivity (94.0% [85.6-97.7%]) and lower specificity (83.6% [76.0-89.1%]) of Abbott Bioline HAT 2.0 as compared to SD Bioline HAT (Se 64.2% [52.2-74.6%]-Sp 98.4% [94.2-99.5%]) and HAT Sero-K-SeT (Se 88.1% [78.2-93.8%]-Sp 98.4% [94.2-99.5%]). A comparison of Abbott Bioline HAT 2.0 and malaria-RDT positivity rates on 479 subjects living in HAT-free malaria-endemic areas further revealed that a significantly higher proportion of subjects positive in Abbott Bioline HAT 2.0 were also positive in malaria-RDT, suggesting a possible cross-reaction of Abbott Bioline HAT 2.0 with malaria-related biological factors in about 10% of malaria cases. This would explain, at least in part, the limited specificity of Abbott Bioline HAT 2.0. Overall, Abbott Bioline HAT 2.0 seems suitable as first line RDT in combination with a second HAT RDT to prevent confirmatory lab overload and loss of suspects during referral for confirmation. A state-of-the-art prospective comparative study is further required for comparing all current and future HAT RDTs to propose an optimal combination of RDTs for door-to-door active screening., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Camara et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Vector control tools are urgently needed to control malaria transmission in Africa. A native strain of Chromobacterium sp. from Burkina Faso was recently isolated and preliminarily named Chromobacterium anophelis sp. nov. IRSSSOUMB001. In bioassays, this bacterium showed a promising virulence against adult mosquitoes and reduces their blood feeding propensity and fecundity. The current study assessed the entomopathogenic effects of C. anophelis IRSSSOUMB001 on larval stages of mosquitoes, as well as its impacts on infected mosquitoes reproductive capacity and trans-generational effects., Methods: Virulence on larvae and interference with insemination were assayed by co-incubation with C. anophelis IRSSSOUMB001 at a range of 10 4 to 10 8  cfu/ml. Trans-generational effects were determined by measuring body size differences of progeny from infected vs. uninfected parent mosquitoes using wing size as a proxy., Results: Chromobacterium anophelis IRSSSOUMB001 killed larvae of the pyrethroid-resistant Anopheles coluzzii with LT 80 of ~ 1.75 ± 0.14 days at 10 8  cfu/ml in larval breeding trays. Reproductive success was reduced as a measure of insemination rate from 95 ± 1.99% to 21 ± 3.76% for the infected females. There was a difference in wing sizes between control and infected mosquito offsprings from 2.55 ± 0.17 mm to 2.1 ± 0.21 mm in infected females, and from 2.43 ± 0.13 mm to 1.99 ± 0.15 mm in infected males., Conclusions: This study showed that C. anophelis IRSSSOUMB001 was highly virulent against larvae of insecticide-resistant Anopheles coluzzii, and reduced both mosquito reproduction capacity and offspring fitness. Additional laboratory, field, safety and social acceptance studies are needed to draw firm conclusions about the practical utility of this bacterial strain for malaria vector control., (© 2023. The Author(s).)

Background: Domesticated animals play a role in maintaining residual transmission of Plasmodium parasites of humans, by offering alternative blood meal sources for malaria vectors to survive on. However, the blood of animals treated with veterinary formulations of the anti-helminthic drug ivermectin can have an insecticidal effect on adult malaria vector mosquitoes. This study therefore assessed the effects of treating cattle with long-acting injectable formulations of ivermectin on the survival of an important malaria vector species, to determine whether it has potential as a complementary vector control measure., Methods: Eight head of a local breed of cattle were randomly assigned to either one of two treatment arms (2 × 2 cattle injected with one of two long-acting formulations of ivermectin with the BEPO ® technology at the therapeutic dose of 1.2 mg/kg), or one of two control arms (2 × 2 cattle injected with the vehicles of the formulations). The lethality of the formulations was evaluated on 3-5-day-old Anopheles coluzzii mosquitoes through direct skin-feeding assays, from 1 to 210 days after treatment. The efficacy of each formulation was evaluated and compared using Cox proportional hazards survival models, Kaplan-Meier survival estimates, and log-logistic regression on cumulative mortality., Results: Both formulations released mosquitocidal concentrations of ivermectin until 210 days post-treatment (hazard ratio > 1). The treatments significantly reduced mosquito survival, with average median survival time of 4-5 days post-feeding. The lethal concentrations to kill 50% of the Anopheles (LC 50 ) before they became infectious (10 days after an infectious blood meal) were maintained for 210 days post-injection for both formulations., Conclusions: This long-lasting formulation of ivermectin injected in cattle could complement insecticide-treated nets by suppressing field populations of zoophagic mosquitoes that are responsible, at least in part, for residual malaria transmission. The impact of this approach will of course depend on the field epidemiological context. Complementary studies will be necessary to characterize ivermectin withdrawal times and potential environmental toxicity., (© 2023. The Author(s).)

Background: There is a global consensus that new intervention tools are needed for the final steps toward malaria elimination/eradication. In a recent study in Burkina Faso, the Lehmann Funnel Entry Trap (LFET) has shown promising results in the reduction of mosquito densities, even in areas where insecticide resistance is as high as 80%. The LFET requires no chemicals and is self-operated. However, one of the issues with the original LFET is the size of the funnel, which often occupies too much space within users' homes. Here, the performance of three new, smaller-sized LFET prototypes that combine a screening and killing effect on mosquitoes was assessed., Methods: The study was carried out over three months during the rainy season in low and high malaria vector density sites, Soumousso and Vallée du Kou, respectively. The original LFET (or 'Prototype 1'/'P1') was modified to produce three new prototypes, which were referred to as prototype 2 ('the Medium' or 'P2'), prototype 3 (P3) and prototype 4 (P4). Each of the new prototypes was tested on eight days per month over the three-month period to assess their effectiveness in trapping and killing mosquitoes entering houses through the windows compared to the original LFET., Results: Overall, 78,435 mosquitoes (mainly Anopheles gambiae sensu lato) were collected in the two study sites, both in the traps and in the houses. A total of 56,430 (72%) mosquitoes were collected from the traps. In Vallée du Kou, the original LFET caught a greater number of mosquitoes than the medium (prototype 2), whereas no difference was observed between the other new prototypes (3 and 4) and the medium. In Soumousso, both the original and medium LFETs collected significantly greater numbers of mosquitoes compared to prototypes 3 and 4., Conclusion: This study has shown that the new LFET prototypes are effective in trapping mosquitoes in high mosquito density settings. A large-scale study with one of the prototypes will be needed to assess community acceptance of the traps and their ability to control malaria vectors.