Biting behaviour of Simulium damnosum complex and Onchocerca volvulus infection along the Osun River, Southwest Nigeria

<p>Abstract</p> <p>Background</p> <p>Studies on biting behaviours and infectivity status of insect vectors are pre-requisites in understanding the epidemiology of the vector- borne diseases and planning effective control measures. A longitudinal study was carried out to investigate the transmission index of <it>Simulium damnosum </it>complex species along Osun River, South Western Nigeria. Adult flies were collected on human attractants from 07:00 to 18:00 hours for two consecutive days from February 2008 to June 2009 at three communities: Osun Eleja, Osun Ogbere and Osun Budepo. The infectivity rate was determined by dissection and Polymerase Chain Reaction amplification (PCR) of 0-150 genes of <it>Onchocerca </it>parasite using the pool screening technique.</p> <p>Results</p> <p>The results indicated that the majority of the flies collected at the three sampling points were nulliparous as they accounted for 53.90%, 57.86% and 59.58% of the flies dissected at Osun Budepo, Osun Ogbere and Osun Eleja, respectively. The parous rate was higher during the dry season than the wet season but the difference was not statistically significant (<it>p </it>< 0.05). The biting activity of the parous flies showed two peaks at Osun Budepo and three peaks at Osun Eleja and Osun Ogbere. Of the 1,472 flies dissected and 1,235 flies screened by molecular method, none was infected with <it>Onchocerca </it>parasite at the three sampling points however the annual biting rates at the three communities were higher than 1,000 considered as tolerable value for a person living in an onchocerciasis zone by Word Health Organization.</p> <p>Conclusion</p> <p>The study has provided the baseline data for further study on onchocerciasis transmission dynamics and the need to intercept man- simuliid vector contact at the study area.</p

Oligonucleotide Based Magnetic Bead Capture of Onchocerca volvulus DNA for PCR Pool Screening of Vector Black Flies

The absence of infective larvae of Onchocerca volvulus in the black fly vector of this parasite is a major criterion used to certify that transmission has been eliminated in a focus. This process requires screening large numbers of flies. Currently, this is accomplished by screening pools of flies using a PCR-based assay. The number of flies that may be included in each pool is currently limited by the DNA purification process to 50 flies for Latin American vectors and 100 flies for African vectors. Here, we describe a new method for DNA purification that relies upon a specific oligonucleotide to capture and immobilize the parasite DNA on a magnetic bead. This method permits the reliable detection of a single infective larva of O. volvulus in pools containing up to 200 individual flies. The method described here will dramatically improve the efficiency of pool screening of vector black flies, making the process of elimination certification easier and less expensive to implement

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Variations intra- specifiques chez l'abeille Megachile rotundata F. : comparaisons morphologique, ecoethologique et biochimique de deux souches, une canadienne et une francaise

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Évaluation des déterminants socioculturels influençant l’adoption de la chimioprévention du paludisme saisonnier au Burkina Faso : une étude qualitative

Résumé : La Chimioprévention du Paludisme Saisonnier (CPS) est une stratégie efficace de lutte contre le paludisme chez les enfants de 3 à 59 mois. Depuis 2012, sur la base des données factuelles, la CPS été recommandée par l’Organisation Mondiale de la Santé (OMS), aux pays d’Afrique subsaharienne dont le Burkina Faso où la transmission du paludisme est saisonnière. Dans ces pays d’Afrique subsaharienne, le paludisme constitue un problème majeur de santé publique d’où l’introduction de la CPS au Burkina Faso en 2014 dans les sites pilotes. Mais depuis 2018, les campagnes CPS couvrent tous les 70 districts sanitaires du territoire national. Cependant, en dépit de ces campagnes de distribution de masse, l’adoption de la CPS par les parents au profit de leurs enfants demeure faible sur le terrain à Bobo-Dioulasso. Cette étude vise à analyser les déterminants socioculturels qui influencent l’adoption de la CPS par les parents au profit de leurs enfants. Nous avons privilégié une recherche qualitative où plusieurs techniques comme l’observation directe en temps réel, la recherche documentaire, l’entretien individuel approfondi, le focus group et le récit de vie ont été mobilisées. Les données ont été collectées auprès de la population générale et des acteurs de la santé avant, pendant et après les campagnes CPS dans la commune de Bobo-Dioulasso, sur une période de huit (08) mois allant de mars à octobre 2023. Au total, 87 entretiens individuels, 08 focus groups et 04 récits de vie ont été réalisés. Il ressort des résultats que les principaux déterminants socioculturels entravant l’adoption de la CPS ont trait essentiellement aux représentations sociales du paludisme, aux perceptions populaires autour de la CPS, aux croyances, aux normes sociales et du genre dans la communauté. Mots-clés : Déterminants, socioculturels, adoption, Chimioprévention du Paludisme Saisonnier, Burkina Faso

Design of Onchocerca DNA probes based upon analysis of a repeated sequence family

Repeated DNA sequences have been instrumental in the development of DNA probes for many different parasites. Isolation of such DNA probes has generally been accomplished by differential screening of genomic libraries with total genomic DNA preparations. In the current work, a rational design strategy is presented for the development of oligonucleotide probes based upon repeated sequence families. A repeated sequence family present in the genome of Onchocerca parasites, designated O-150, has been amplified from various samples of genomic DNA using PCR. DNA sequence analysis of the resulting PCR products demonstrated that the sequences may be arranged into clusters within which the individual sequences are identical or nearly identical. Differences among the cluster consensus sequences have been exploited to explain the specificities of previously isolated O-150 based probes and to develop two new oligonucleotide probes. One of these probes hybridizes specifically to Onchocerca volvulus O-150 PCR products, while the second hybridizes specifically to O-150 PCR products from the closely related bovine parasite O. ochengi. These oligonucleotide probes have been used to characterize Onchocerca infective larvae isolated from wild caught infected flies in West Africa. Because repeated sequence families are a common feature of most genomes, including those of parasites, this method should be applicable to the rational design of oligonucleotide probes for other parasitic infections

Proof-of-principle of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: final results of a study in Mali and Senegal.

BACKGROUND: Mass treatment with ivermectin controls onchocerciasis as a public health problem, but it was not known if it could also interrupt transmission and eliminate the parasite in endemic foci in Africa where vectors are highly efficient. A longitudinal study was undertaken in three hyperendemic foci in Mali and Senegal with 15 to 17 years of annual or six-monthly ivermectin treatment in order to assess residual levels of infection and transmission, and test whether treatment could be safely stopped. This article reports the results of the final evaluations up to 5 years after the last treatment. METHODOLOGY/PRINCIPAL FINDINGS: Skin snip surveys were undertaken in 131 villages where 29,753 people were examined and 492,600 blackflies were analyzed for the presence of Onchocerca volvulus larva using a specific DNA probe. There was a declining trend in infection and transmission levels after the last treatment. In two sites the prevalence of microfilaria and vector infectivity rate were zero 3 to 4 years after the last treatment. In the third site, where infection levels were comparatively high before stopping treatment, there was also a consistent decline in infection and transmission to very low levels 3 to 5 years after stopping treatment. All infection and transmission indicators were below postulated thresholds for elimination. CONCLUSION/SIGNIFICANCE: The study has established the proof of principle that onchocerciasis elimination with ivermectin treatment is feasible in at least some endemic foci in Africa. The study results have been instrumental for the current evolution from onchocerciasis control to elimination in Africa