Genetic and Environmental Factors Associated with Laboratory Rearing Affect Survival and Assortative Mating but Not Overall Mating Success in Anopheles gambiae Sensu Stricto

Anopheles gambiae sensu stricto, the main vector of malaria in Africa, is characterized by its vast geographical range and complex population structure. Assortative mating amongst the reproductively isolated cryptic forms that co-occur in many areas poses unique challenges for programs aiming to decrease malaria incidence via the release of sterile or genetically-modified mosquitoes. Importantly, whether laboratory-rearing affects the ability of An. gambiae individuals of a given cryptic taxa to successfully mate with individuals of their own form in field conditions is still unknown and yet crucial for mosquito-releases. Here, the independent effects of genetic and environmental factors associated with laboratory rearing on male and female survival, mating success and assortative mating were evaluated in the Mopti form of An. gambiae over 2010 and 2011. In semi-field enclosures experiments and despite strong variation between years, the overall survival and mating success of male and female progeny from a laboratory strain was not found to be significantly lower than those of the progeny of field females from the same population. Adult progeny from field-caught females reared at the larval stage in the laboratory and from laboratory females reared outdoors exhibited a significant decrease in survival but not in mating success. Importantly, laboratory individuals reared as larvae indoors were unable to mate assortatively as adults, whilst field progeny reared either outdoors or in the laboratory, as well as laboratory progeny reared outdoors all mated significantly assortatively. These results highlight the importance of genetic and environment interactions for the development of An. gambiae''s full mating behavioral repertoire and the challenges this creates for mosquito rearing and release-based control strategies.     

Wild Anopheles funestus Mosquito Genotypes Are Permissive for Infection with the Rodent Malaria Parasite,Plasmodium berghei

Background

Malaria parasites undergo complex developmental transitions within the mosquito vector. A commonly used laboratory model for studies of mosquito-malaria interaction is the rodent parasite, P. berghei. Anopheles funestus is a major malaria vector in sub-Saharan Africa but has received less attention than the sympatric species, Anopheles gambiae. The imminent completion of the A. funestus genome sequence will provide currently lacking molecular tools to describe malaria parasite interactions in this mosquito, but previous reports suggested that A. funestus is not permissive for P. berghei development.

Methods

An A. funestus population was generated in the laboratory by capturing female wild mosquitoes in Mali, allowing them to oviposit, and rearing the eggs to adults. These F1 progeny of wild mosquitoes were allowed to feed on mice infected with a fluorescent P. berghei strain. Fluorescence microscopy was used to track parasite development inside the mosquito, salivary gland sporozoites were tested for infectivity to mice, and parasite development in A. funestus was compared to A. gambiae.

Results

P. berghei oocysts were detectable on A. funestus midguts by 7 days post-infection. By 18–20 days post-infection, sporozoites had invaded the median and distal lateral lobes of the salivary glands, and hemocoel sporozoites were observed in the hemolymph. Mosquitoes were capable of infecting mice via bite, demonstrating that A. funestus supports the complete life cycle of P. berghei. In a random sample of wild mosquito genotypes, A. funestus prevalence of infection and the characteristics of parasite development were similar to that observed in A. gambiae-P. berghei infections.

Conclusions

The data presented in this study establish an experimental laboratory model for Plasmodium infection of A. funestus, an important vector of human malaria. Studying A. funestus-Plasmodium interactions is now feasible in a laboratory setting. This information lays the groundwork for exploitation of the awaited genome sequence of A. funestus.     

A Phase 1b Randomized,Controlled, Double-Blinded Dosage-Escalation Trial to Evaluate the Safety,Reactogenicity and Immunogenicity of an Adenovirus Type 35 Based Circumsporozoite Malaria Vaccine in Burkinabe Healthy Adults 18 to 45 Years of Age

Background

Ad35.CS.01 is a pre-erythrocytic malaria candidate vaccine. It is a codon optimized nucleotide sequence representing the P. falciparum circumsporozoite (CS) surface antigen inserted in a replication deficient Adenovirus 35 backbone. A Phase 1a trial has been conducted in the USA in naïve adults and showed that the vaccine was safe. The aim of this study is to assess the safety and immunogenicity of ascending dosages in sub Saharan Africa.

Methods

A double blind, randomized, controlled, dose escalation, phase Ib trial was conducted in a rural area of Balonghin, the Saponé health district (Burkina Faso). Forty-eight healthy adults aged 18-45 years were randomized into 4 cohorts of 12 to receive three vaccine doses (day 0, 28 and 84) of 10⁹, 10¹⁰, 5X10¹⁰, 10¹¹ vp of Ad35.CS.01 or normal saline by intra muscular injection. Subjects were monitored carefully during the 14 days following each vaccination for non serious adverse events. Severe and serious adverse events were collected throughout the participant study duration (12 months from the first vaccination). Humoral and cellular immune responses were measured on study days 0, 28, 56, 84, 112 and 140.

Results

Of the forty-eight subjects enrolled, forty-four (91.7%) received all three scheduled vaccine doses. Local reactions, all of mild severity, occurred in thirteen (27.1%) subjects. Severe (grade 3) laboratory abnormalities occurred in five (10.4%) subjects. One serious adverse event was reported and attributed to infection judged unrelated to vaccine. The vaccine induced both antibody titers and CD8 T cells producing IFNγ and TNFα with specificity to CS while eliciting modest neutralizing antibody responses against Ad35.

Conclusion

Study vaccine Ad35.CS.01 at four different dose levels was well-tolerated and modestly immunogenic in this population. These results suggest that Ad35.CS.01 should be further investigated for preliminary efficacy in human challenge models and as part of heterologous prime-boost vaccination strategies.

Trial Registration

ClinicalTrials.gov NCT01018459 http://clinicaltrials.gov/ct2/show/NCT01018459     

Impact of human activities on the reproduction of Hooded Vultures Necrosyrtes monachus in Burkina Faso

During the last decades, the critically endangered Hooded Vulture Necrosyrtes monachus has strongly declined across its African range. Although direct persecution has been suggested as a major cause of this decline, little is known about the impact of humans on reproductive output in West Africa. We studied the impact of human activities on the reproductive output of Hooded Vultures in the Garango area of Burkina Faso. Twenty and 56 nesting attempts were monitored, respectively, during the breeding season in 2013/14 and 2014/15, to determine reproductive success and identify causes of nest failure. Annual breeding success varied between 0.68 and 0.71 chicks fledged per breeding pair per year and productivity was assessed at 0.57 chicks fledged per territorial pair in 2014/15. The main threats imposed by humans were poaching of eggs, chicks and collection of nest materials, leading to 20% (13 out of 64 breeding attempts) of nest failures over the two years. An additional important reason for nest failure was the pruning and (partial) cutting of nest trees. Despite this high level of human interference, we found that Hooded Vulture nest success increased with proximity to human settlements, probably because breeding vultures benefit from protection by people against persecution and disturbance.     

Risk Factors for Plasmodium falciparum Gametocyte Positivity in a Longitudinal Cohort

Malaria transmission intensity is highly heterogeneous even at a very small scale. Implementing targeted intervention in malaria transmission hotspots offers the potential to reduce the burden of disease both locally and in adjacent areas. Transmission of malaria parasites from man to mosquito requires the production of gametocyte stage parasites. Cluster analysis of a 19-year long cohort study for gametocyte carriage revealed spatially defined gametocyte hotspots that occurred during the time when chloroquine was the drug used for clinical case treatment. In addition to known risk factors for gametocyte carriage, notably young age (<15 years old) and associated with a clinical episode, blood groups B and O increased risk compared to groups A and AB. A hotspot of clinical P. falciparum clinical episodes that overlapped the gametocyte hotspots was also identified. Gametocyte positivity was found to be increased in individuals who had been treated with chloroquine, as opposed to other drug treatment regimens, for a clinical P. falciparum episode up to 30 days previously. It seems likely the hotspots were generated by a vicious circle of ineffective treatment of clinical cases and concomitant gametocyte production in a sub-population characterized by an increased prevalence of all the identified risk factors. While rapid access to treatment with an effective anti-malarial can reduce the duration of gametocyte carriage and onward parasite transmission, localised hotspots represent a challenge to malaria control and eventual eradication.     

Prevalence of the dhfr and dhps Mutations among Pregnant Women in Rural Burkina Faso Five Years after the Introduction of Intermittent Preventive Treatment with Sulfadoxine-Pyrimethamine

Background

The emergence and spread of drug resistance represents one of the biggest challenges for malaria control in endemic regions. Sulfadoxine-pyrimethamine (SP) is currently deployed as intermittent preventive treatment in pregnancy (IPTp) to prevent the adverse effects of malaria on the mother and her offspring. Nevertheless, its efficacy is threatened by SP resistance which can be estimated by the prevalence of dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) mutations. This was measured among pregnant women in the health district of Nanoro, Burkina Faso.

Methods

From June to December 2010, two hundred and fifty six pregnant women in the second and third trimester, attending antenatal care with microscopically confirmed malaria infection were invited to participate, regardless of malaria symptoms. A blood sample was collected on filter paper and analyzed by PCR-RFLP for the alleles 51, 59, 108, 164 in the pfdhfr gene and 437, 540 in the pfdhps gene.

Results

The genes were successfully genotyped in all but one sample (99.6%; 255/256) for dhfr and in 90.2% (231/256) for dhps. The dhfr C59R and S108N mutations were the most common, with a prevalence of 61.2% (156/255) and 55.7% (142/255), respectively; 12.2% (31/255) samples had also the dhfr N51I mutation while the I164L mutation was absent. The dhps A437G mutation was found in 34.2% (79/231) isolates, but none of them carried the codon K540E. The prevalence of the dhfr double mutations NRNI and the triple mutations IRNI was 35.7% (91/255) and 11.4% (29/255), respectively.

Conclusion

Though the mutations in the pfdhfr and pfdhps genes were relatively common, the prevalence of the triple pfdhfr mutation was very low, indicating that SP as IPTp is still efficacious in Burkina Faso.     

Characterization of the fungal flora of dolo,a traditional fermented beverage of Burkina Faso,using MALDI-TOF mass spectrometry

A cross-sectional study was conducted in Bobo-Dioulasso, Burkina Faso, to identify the yeast diversity associated with the manufacture of dolo, a traditional fermented beverage of Burkina Faso. From sixty specimens spread onto chromogenic medium plates, sixty-two strains were isolated then identified using MALDI-TOF analysis. Seven yeast species were identified, Saccharomyces cerevisiae (39%) followed by Pichia manshurica (18%) being the most frequent. Forty-three percent of the samples contained Candida species, notably Candida albicans. In conclusion, the combined use of a chromogenic medium and MALDI-TOF analysis reveals a higher diversity in yeast species present in the dolo than previously thought.     

Diversity,dynamic and ecology of freshwater snails related to environmental factors in urban and suburban streams in Douala–Cameroon (Central Africa)

Urban land use has increased dramatically over the past few decades, resulting in high variability in nutrients loading which is likely to alter the biological component of urban streams. Freshwater snails and environmental variables that might structure their diversity and distribution were studied from September 2012 to September 2013 in three contiguous watersheds in Douala. Twelve stations were monitored monthly, two of these are located in a suburban forest area, and the rest situated in urbanized and industrialized zones. Snails were collected using a long-handled net (30 × 30 cm side, 400-µm mesh). Meanwhile, measurements of the environmental variables were taken. Ten species were recorded which are as follows: Melanoides tuberculata (Thiaridae); Gabbiella africana (Bythiniidae); Physa acuta, Aplexa sp. (Physidae); Lymnaea natalensis, Lymnaea stagnalis, Lymnaea columella (Lymnaeidae); Biomphalaria pfeifferi, Bulinus forskalii (Planorbidae) and one undetermined taxon of Bythiniidae. All these snails were identified at nine of the ten urban stations; no species being found in suburban stations. These urban streams have very poor health status with highly polluted waters. Among the species found P. acuta (76.95 %), L. natalensis (19.46 %) and M. tuberculata (2.79 %) were the most abundant. Multiple stepwise regression analysis, Spearman correlation test and redundancy analysis showed that snail occurrences and abundances were probably influenced by water temperature, conductivity, suspended solids, alkalinity, nitrites, nitrates, ammonium, phosphates, oxydability, biochemical oxygen demand, rainfall, encumbrance rate of the riverbed and water width. Moreover, snail dynamics showed a seasonal pattern with peak population abundances and recruitment of young generations during rainy season. This malacological survey spotlighted the impacts of anthropogenic activities on snail’s diversity and distribution, with the proliferation of the invasive pulmonate P. acuta in Douala urban streams.     

Composition and Intraspecific Chemical Variability of Leaf Essential Oil of Laggera pterodonta from Côte d'Ivoire

The chemical composition of 44 leaf oil samples of Laggera pterodonta (DC.) Sch.Bip. ex Oliv. (Asteraceae) from Côte d'Ivoire was investigated, using combination of chromatographic (GC‐FID) and spectroscopic (GC/MS, ¹³C‐NMR) techniques. Two oil samples chosen according to their chromatographic profiles were submitted to column chromatography and all fractions of CC were analyzed by GC‐FID, GC/MS and ¹³C‐NMR. In total, 83 components accounting for 96.5 to 99.4 % of the whole chemical composition were identified. Significant variations were observed within terpene classes: monoterpene hydrocarbons (0.4–22.7 %), oxygenated monoterpenes (32.9–54.9 %), sesquiterpene hydrocarbons (18.6–38.3 %) and oxygenated sesquiterpenes (3.5–38.4 %). Thus, the 44 compositions were subjected to hierarchical cluster analysis (HCA) and principal component analysis (PCA). Two groups were differentiated according to their composition. All the samples contained 2,5‐dimethoxy‐p‐cymene, α‐humulene and (E)‐β‐caryophyllene among the main components. Other components were present at appreciable contents and allowed differentiation of two groups: sabinene and germacrene D for Group I; 10‐epi‐γ‐eudesmol and eudesm‐7(11)‐en‐4α‐ol for Group II. All the samples collected in Eastern Côte d'Ivoire constituted Group I, while samples collected in the Central area of the country constituted Group II.