P. falciparum phenotypic plasticity is linked to the variant expression of clonal multigene families such as the var genes. We have examined changes in transcription and histone modifications that occur during sporogonic development of P. falciparum in the mosquito host. All var genes are silenced or transcribed at low levels in blood stages (gametocyte/ring) of the parasite in the human host. After infection of mosquitoes, a single var gene is selected for expression in the oocyst, and transcription of this gene increases dramatically in the sporozoite. The same PF3D7_1255200 var gene was activated in 4 different experimental infections. Transcription of this var gene during parasite development in the mosquito correlates with the presence of low levels of H3K9me3 at the binding site for the PF3D7_1466400 AP2 transcription factor. This chromatin state in the sporozoite also correlates with the expression of an antisense long non-coding RNA (lncRNA) that has previously been shown to promote var gene transcription during the intraerythrocytic cycle in vitro. Expression of both the sense protein-coding transcript and the antisense lncRNA increase dramatically in sporozoites. The findings suggest a complex process for the activation of a single particular var gene that involves AP2 transcription factors and lncRNAs.

BackgroundIn Burkina Faso, malaria remains the overall leading cause of morbidity and mortality accounting for 35.12% of consultations, 40.83% of hospitalizations and 37.5% of deaths. Genotyping of malaria parasite populations remains an important tool to determine the types and number of parasite clones in an infection. The present study aimed to evaluate the merozoite surface protein 1 (msp1) and merozoite surface protein 2 (msp2) genetic diversity and allele frequencies in Bobo-Dioulasso, Burkina Faso.MethodDried blood spots (DBS) were collected at baseline from patients with uncomplicated malaria in urban health centers in Bobo-Dioulasso. Parasite DNA was extracted using chelex-100 and species were identified using nested PCR. Plamodium falciparum msp1 and msp2 genes were amplified by nested polymerase chain reaction (PCR) and PCR products were analyzed by electrophoresis on a 2.5% agarose gel. Alleles were categorized according to their molecular weight.ResultsA total of 228 blood samples were analyzed out of which 227 (99.9%) were confirmed as P. falciparum-positive and one sample classified as mixed infection for P. malaria and P. falciparum. In msp1, the K1 allelic family was predominant with 77.4% (162/209) followed respectively by the MAD20 allelic family with 41.3% and R033 allelic family with 36%. In msp2, the 3D7 allelic family was the most frequently detected with 93.1 % compared to FC27 with 41.3%. Twenty-one different alleles were observed in msp1 with 9 alleles for K1, 8 alleles for MAD20 and 4 alleles for R033. In msp2, 25 individual alleles were detected with 10 alleles for FC27 and 15 alleles for 3D7. The mean multiplicity of falciparum infection was 1.95 with respectively 1.8 (1.76–1.83) and 2.1 (2.03–2.16) for msp1 and msp2 (P = 0.01).ConclusionsOur study showed high genetic diversity and allelic frequencies of msp1 and msp2 in Plasmodium falciparum isolates from symptomatic malaria patients in Bobo-Dioulasso.

BackgroundInfection by the human malaria parasite leads to important changes in mosquito phenotypic traits related to vector competence. However, we still lack a clear understanding of the underlying mechanisms and, in particular, of the epigenetic basis for these changes. We have examined genome-wide distribution maps of H3K27ac, H3K9ac, H3K9me3 and H3K4me3 by ChIP-seq and the transcriptome by RNA-seq, of midguts from Anopheles gambiae mosquitoes blood-fed uninfected and infected with natural isolates of the human malaria parasite Plasmodium falciparum in Burkina Faso.ResultsWe report 15,916 regions containing differential histone modification enrichment between infected and uninfected, of which 8339 locate at promoters and/or intersect with genes. The functional annotation of these regions allowed us to identify infection-responsive genes showing differential enrichment in various histone modifications, such as CLIP proteases, antimicrobial peptides-encoding genes, and genes related to melanization responses and the complement system. Further, the motif analysis of regions differentially enriched in various histone modifications predicts binding sites that might be involved in the cis-regulation of these regions, such as Deaf1, Pangolin and Dorsal transcription factors (TFs). Some of these TFs are known to regulate immunity gene expression in Drosophila and are involved in the Notch and JAK/STAT signaling pathways.ConclusionsThe analysis of malaria infection-induced chromatin changes in mosquitoes is important not only to identify regulatory elements and genes underlying mosquito responses to P. falciparum infection, but also for possible applications to the genetic manipulation of mosquitoes and to other mosquito-borne systems.Electronic supplementary materialThe online version of this article (10.1186/s13072-018-0250-9) contains supplementary material, which is available to authorized users.

Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium–Anopheles vectors interactions, is presented. The assay uses small pieces of cotton wool soaked in sugar solution to collect malaria sporozoites from individual mosquitoes during sugar feeding to monitor infection status over time. This technique has been tested across four natural malaria mosquito species of Africa and Asia, infected with Plasmodium falciparum (six field isolates from gametocyte-infected patients in Burkina Faso and the NF54 strain) and across a range of temperatures relevant to malaria transmission in field conditions. Monitoring individual infectious mosquitoes was feasible. The estimated median EIP of P. falciparum at 27 °C was 11 to 14 days depending on mosquito species and parasite isolate. Long-term individual tracking revealed that sporozoites transfer onto cotton wool can occur at least until day 40 post-infection. Short individual EIP were associated with short mosquito lifespan. Correlations between mosquito/parasite traits often reveal trade-offs and constraints and have important implications for understanding the evolution of parasite transmission strategies.

The spread of insecticide resistance in Anopheles mosquitoes and drug resistance in Plasmodium parasites is contributing to a global resurgence of malaria, making the generation of control tools that can overcome these roadblocks an urgent public health priority. We recently showed that the transmission of Plasmodium falciparum parasites can be efficiently blocked when exposing Anopheles gambiae females to antimalarials deposited on a treated surface, with no negative consequences on major components of mosquito fitness. Here, we demonstrate this approach can overcome the hurdles of insecticide resistance in mosquitoes and drug resistant in parasites. We show that the transmission-blocking efficacy of mosquito-targeted antimalarials is maintained when field-derived, insecticide resistant Anopheles are exposed to the potent cytochrome b inhibitor atovaquone, demonstrating that this drug escapes insecticide resistance mechanisms that could potentially interfere with its function. Moreover, this approach prevents transmission of field-derived, artemisinin resistant P. falciparum parasites (Kelch13 C580Y mutant), proving that this strategy could be used to prevent the spread of parasite mutations that induce resistance to front-line antimalarials. Atovaquone is also highly effective at limiting parasite development when ingested by mosquitoes in sugar solutions, including in ongoing infections. These data support the use of mosquito-targeted antimalarials as a promising tool to complement and extend the efficacy of current malaria control interventions.

Background Mass drug administration (MDA) with azithromycin (AZ) is being considered as a strategy to promote child survival in sub-Saharan Africa, but the mechanism by which AZ reduces mortality is unclear. To better understand the nature and extent of protection provided by AZ, we explored the profile of protection by time since administration, using data from a household-randomised, placebo-controlled trial in Burkina Faso and Mali. Methods Between 2014 and 2016, 30,977 children aged 3-59 months received seasonal malaria chemoprevention (SMC) with sulphadoxine-pyrimethamine plus amodiaquine and either AZ or placebo monthly, on four occasions each year. Poisson regression with gamma-distributed random effects, accounting for the household randomisation and within-individual clustering of illness episodes, was used to compare incidence of pre-specified outcomes between SMC+AZ versus SMC+placebo groups in fixed time strata post-treatment. The likelihood ratio test was used to assess evidence for a time-treatment group interaction. Results Relative to SMC+placebo, there was no evidence of protection from SMC+AZ against hospital admissions and deaths. Additional protection from SMC+AZ against malaria was confined to the first two weeks post-administration (protective efficacy (PE): 24.2% [95% CI: 17.8%, 30.1%]). Gastroenteritis and pneumonia were reduced by 29.9% [21.7; 37.3%], and 34.3% [14.9; 49.3%], respectively in the first two weeks post-administration. Protection against non-malaria fevers with a skin condition persisted up to 28 days: PE: 46.3% [35.1; 55.6%]). Conclusions The benefits of AZ-MDA are broad-ranging but short-lived. To maximise impact, timing of AZ-MDA must address the challenge of targeting asynchronous morbidity and mortality peaks from different causes.

objective A trial was conducted in Burkina Faso and Mali to investigate whether addition of azithromycin to the antimalarials used for seasonal malaria chemoprevention reduces mortality and hospital admissions of children. We tested the sensitivity of nasal isolates of Streptococcus pneumoniae obtained during this trial to azithromycin and other antibiotics.methods Azithromycin or placebo was administered monthly, in combination with the antimalarials used for seasonal malaria chemoprevention, for four months, over the annual malaria transmission seasons of 2014, 2015, and 2016. Nasopharyngeal swabs were collected from 2773 Burkinabe and 2709 Malian children on seven occasions: in July and December each year prior to and after drug administration, and at a final survey in early 2018. Pneumococci were isolated from nasopharyngeal swabs and tested for sensitivity to azithromycin and other antibiotics.results A total of 5482 samples were collected. In Burkina Faso, the percentage of pneumococcal isolates resistant to azithromycin among children who had received it increased from 4.9% (95% CI: 2.4%, 9.9%) before the intervention to 25.6% (95% CI: 17.6%, 35.7%) afterward. In Mali, the increase was from 7.6% (95% CI: 3.8%, 14.4%) to 68.5% (95% CI: 55.1%, 79.4%). The percentage of resistant isolates remained elevated (17.7% (95% CI: 11.1%, 27.1%) in Burkina Faso and 19.1% (95% CI: 13.5%, 26.3%) in Mali) among children who had received azithromycin 1 year after stopping the intervention. An increase in resistance to azithromycin was also observed in children who had received a placebo but it was less marked.conclusion Addition of azithromycin to the antimalarial combination used for seasonal malaria chemoprevention was associated with an increase in resistance of pneumococci to azithromycin and erythromycin, which persisted 1 year after the last administration of azithromycin.

BackgroundMedicinal plant research may contribute to develop new pharmacological control tools for vector borne diseases, such as malaria.MethodsThe effects of methanol extracts (ME) obtained from seed kernel of ripe and unripe Azadirachta indica fruits were studied on erythrocytic proliferation of the rodent malaria parasite Plasmodium berghei strain ANKA and on mice pro-inflammatory response, as evaluated by measuring the matrix-metalloproteinase-9 (MMP-9) and tumour necrosis factor (TNF) plasma levels, in two mouse strains (C57BL/6 and BALB/c) which are considered as prototypical of Th1 and Th2 immune response, respectively.ResultsME obtained from seed kernel of unripe Azadirachta indica fruits decreased by about 30% the proportion of erythrocytes infected with the malaria parasite in C57BL/6 mice in the 4 days suppressive test. In this treatment group, MMP-9 and TNF levels were notably higher than those measured in the same mouse strain treated with the anti-malarial drug artesunate, Azadirachta indica kernel extracts from ripe fruits or solvent. In BALB/c mice, treatment with kernel extracts did not influence parasitaemia. MMP-9 and TNF levels measured in this mouse strain were notably lower than those recorded in C57BL/6 mice and did not vary among treatment groups.ConclusionsThe effects of the ME on the parasite-host interactions appeared to be mouse strain-dependent, but also related to the ripening stage of the neem fruits, as only the unripe fruit seed kernel extracts displayed appreciable bioactivity.Electronic supplementary materialThe online version of this article (10.1186/s12936-019-2671-8) contains supplementary material, which is available to authorized users.