Diversity in anopheline larval habitats and adult composition during the dry and wet seasons in Ouagadougou (Burkina Faso)

Background: Several cases of malaria are frequently recorded during the dry period in Ouagadougou town (Burkina Faso). This has led to the design of a series of studies focusing on both parasitological and entomological investigations intended to provide relevant health data on the risk of local malaria transmission according to the way of urbanisation. Methods: A cross-sectional entomological survey was carried out in various districts of Ouagadougou in April and October 2006. Adult malaria vectors were collected using CDC traps and indoor insecticide spraying performed in four houses during four consecutive days/nights. Intensive larval sampling was also done in available water ponds throughout the study sites. Results: In April, the anopheline breeding sites consisted only of semi-permanent or permanent swamps located mainly in the two peripheral districts. Despite the presence of anopheline larvae in these breeding sites, less than five Anopheles gambiae s.l. adults were caught by CDC traps and indoor insecticide spraying. In October, additionally to the permanent breeding sites reported in April, some rainfall swamps were also found positive to anophelines. The number of adults' mosquitoes was higher than that collected in April (2 vs 159 in October). Out of 115 larvae of An. gambiae s.l. analysed by PCR in April, 59.1% (68/115) were identified as Anopheles arabiensis, 39.1% (45/115) as An. gambiae M while the S form represented less than 2%. Overall 120 larvae and 86 females were identified by PCR in October as An. gambiae M form (51%) and An. arabiensis (42.2%). The S form represented only 6.8%. The global sporozoite rate recorded was high (6.8%) and did not differ between the districts except in the central district where no positive mosquito was detected. Conclusion: Although only few adults' mosquitoes were actively caught during the driest month, malaria vectors persisted all year long that increases the risk of urban malaria transmission. The distribution of breeding sites and especially the occurrence of malaria vectors were more abundant in the periphery, which is more like that of a rural settlement. The evolution of malaria prevalence and the factors sustaining the risk of transmission in Ouagadougou as well in many African cities during the dry season are discussed

Evidence for divergent selection between the molecular forms of Anopheles gambiae: role of predation

The molecular forms of Anopheles gambiae are undergoing speciation. They are characterized by a strong assortative mating and they display partial habitat segregation. The M form is mostly found in flooded/irrigated areas whereas the S form dominates in the surrounding areas, but the ecological factors that shape this habitat segregation are not known. Resource competition has been demonstrated between species undergoing divergent selection, but resource competition is not the only factor that can lead to divergence. In a field experiment using transplantation of first instar larvae, we evaluated the role of larval predators in mediating habitat segregation between the forms. We found a significant difference in the ability of the molecular forms to exploit the different larval sites conditioned on the presence of predators. In absence of predation, the molecular forms outcompeted each other in their respective natural habitats however, the developmental success of the M form was significantly higher than that of the S form in both habitats under predator pressure. Our results provide the first empirical evidence for specific adaptive differences between the molecular forms and stress the role of larval predation as one of the mechanisms contributing to their divergence.https://doi.org/10.1186/1471-2148-8-

Personal protection of long lasting insecticide-treated nets in areas of Anopheles gambiae s.s. resistance to pyrethroids

BACKGROUND: The development of mosquito nets pre-treated with insecticide, Long Lasting Impregnated Nets (LLINs) that last the life span of the net, is a solution to the difficulty of the re-impregnation of conventional nets. Even if they showed a good efficacy in control conditions, their efficacy in the field, particularly in areas with resistance of Anopheles gambiae to pyrethroids, is not well documented. This study compares wide (Olyset(®)) and small (Permanet(®)) mesh LLINs in field conditions, using entomological parameters. METHODS: The two LLINs were tested in a rice-growing area of south-western Burkina Faso (West Africa) with year around high density of the main malaria vector An. gambiae s.s. In the study village (VK6), there is a mixed population of two molecular forms of An. gambiae, the S-form which dominates during the rainy season and the M-form which dominates the rest of the year. The two LLINs Olyset(® )and Permanet(® )were distributed in the village and 20 matched houses were selected for comparison with four houses without treated nets. RESULTS: Mosquito entrance rate was ten fold higher in control houses than in houses with LLINs and there was no difference between the two net types. Among mosquitoes found in the houses, 36 % were dead in LLIN houses compared to 0% in control houses. Blood feeding rate was 80 % in control houses compared to 43 % in LLIN houses. The type of net did not significantly impact any of these parameters. No mosquitoes were found inside Permanet(®), whereas dead or dying mosquitoes were collected inside the Olyset(®). More than 60% of mosquitoes found on top or inside the nets had had blood meals from cattle, as shown by ELISA analysis. CONCLUSION: The percentage of blood-fed mosquitoes in a bed net study does not necessarily determine net success. The efficacy of the two types of LLINs was comparable, during a period when the S-form of An. gambiae was carrying the kdr gene. Significantly higher numbers of mosquitoes were collected in control houses compared to intervention houses, indicating that the LLINs provided an additional deterrent effect, which enhanced their expected prevention capacity

Trends in Insecticide Resistance in Natural Populations of Malaria Vectors in Burkina Faso, West Africa: 10 Years’ Surveys

International audienc

Diversity of phytopathogenic polypores and their interaction with host plants in three biotopes in western Burkina Faso

In order to provide data on polypore identification and their taxonomy, survey studies were undertaken in tree biotope of polypore occurrence. The main objective of this study was to provide a scientific database on the diversity of phytopathogenic polypore and interactions with the host plants in their biotope. Transects of 1 km length covering a width of 50 m were selected at each site. Basidiomes were collected along the transects from roots, trunks and/or branches of forest species Sixty-three species of polypore were identified on twenty-three species of host plants belonging to eleven families. The families most prone to polypore infection were Fabaceae, Apocynaceae, Combretaceae, Anacardiaceae and Caesalpiniaceae. These phytopathogenic polypore were annual to perennial. They grow on roots, trunks and branches of trees and shrubs causing crown and root rots, and trunk cankers on the host plants. The genus Phellinus was the most represented in the agrosystems and in the classified forest of Kou. Similarly, the terricolous species represented by the genera Ganoderma, Amauroderma and Laetiporus were found mainly in the classified forest of Niangoloko and gallery forests of Dan.  &nbsp

Magnitude and associated factors of latent tuberculosis infection due to Mycobacterium tuberculosis complex among high-risk groups in urban Bobo-Dioulasso, Burkina Faso

Objectives: To determine the prevalence and risk factors for latent tuberculosis infection (LTBI) among three high-risk groups - household contacts of TB index cases, healthcare workers and slaughterhouse workers - in Bobo-Dioulasso, Burkina Faso. Methods: Participants were recruited to this cross-sectional study from March to July 2020 after giving informed consent. Sociodemographic, clinical and biological data were collected using a structured questionnaire. The QuantiFERON-TB Gold Plus test (QFT-Plus) and the tuberculin skin test (TST) were used for detection of LTBI. Bivariate and multivariate logistic regression analyses were performed to identify risk factors for LTBI. Results: The prevalence of LTBI among 101 participants (age range 15-68 years) was 67.33% [95% confidence interval (CI) 57.27-76.33] and 84.16% (95% CI 75.55-90.66) based on QFT-Plus and TST results, respectively. Compared with healthcare workers and household contacts of TB index cases, the prevalence of LTBI among slaughterhouse workers was significantly higher for both QTF-Plus (96.8%; P /=15 years of exposure (AOR 5.617, 95% CI 1.202-32.198), having an animal at home (AOR 2.735, 95% CI 1.102-6.789) and protozoal infection (AOR 2.591, 95% CI 1.034-6.491) were significantly associated with LTBI on the QFT-Plus assay. Conclusion: The prevalence of LTBI was high in all three groups, particularly slaughterhouse workers. The risk factors identified could form the basis of targeted intervention

Neemazal ® as a possible alternative control tool for malaria and African trypanosomiasis?

Background: Research efforts to identify possible alternative control tools for malaria and African trypanosomiasis are needed. One promising approach relies on the use of traditional plant remedies with insecticidal activities. Methods: In this study, we assessed the effect of blood treated with different doses of NeemAzal ® (NA, neem seed extract) on mosquitoes (Anopheles coluzzii) and tsetse flies (Glossina palpalis gambiensis) (i) avidity to feed on the treated blood, (ii) longevity, and (iii) behavioural responses to human and calf odours in dual-choice tests. We also gauged NeemAzal ® toxicity in mice. Results: In An. coluzzii, the ingestion of NA in bloodmeals offered by membrane feeding resulted in (i) primary antifeedancy; (ii) decreased longevity; and (iii) reduced response to host odours. In G. palpalis gambiensis, NA caused (i) a knock-down effect; (ii) decreased or increased longevity depending on the dose; and (iii) reduced response to host stimuli. In both cases, NA did not affect the anthropophilic rate of activated insects. Overall, the most significant effects were observed with NA treated bloodmeals at a dose of 2000 μg/ml for mosquitoes and 50 μg/ml for tsetse flies. Although no mortality in mice was observed after 14 days of follow-up at oral doses of 3.8, 5.6, 8.4 and 12.7 g/kg, behavioural alterations were noticed at doses above 8 g/kg. Conclusion: This study revealed promising activity of NA on A. coluzzii and G. palpalis gambiensis but additional research is needed to assess field efficacy of neem products to be possibly integrated in vector control programmes