The Arthropods are present everywhere, on all the extent of the terrestrial globe but, their numbers and their species vary according to the ecological conditions. The current study has been ...conducted in theagronomic research station of Farako/Finkolo in Sikasso, Mali. The goal was to characterize the situation and to identify the main orders of arthropods, then to estimate their dynamics according to the dates of observations. A random collection design was set to collect every two days using traps and divers sexual attractive. Two (02) classes of arthropods of which ten (10) orders of insect and (01) one from arachnidahave been identified. Basically, the number of arthropods collected is very variable. The lowest level of collection has been foundin January while the highest number was collected in December. This study showed that the Dipterahave a preference for grazing, the beetles prefer the orchards whereas the hymenoptera was more frequent in the park of G. septum. Trichoptera, Dermoptera and some Nevroptera have also been identified.
The spread of SARS-CoV-2 cannot be well monitored and understood in areas without capacity for effective disease surveillance. Countries with a young population will have disproportionately large ...numbers of asymptomatic or pauci-symptomatic infections, further hindering detection of infection. Sero-surveillance on a country-wide scale by trained medical professionals may be limited in a resource-limited setting such as Mali. Novel ways of broadly sampling the human population in a non-invasive method would allow for large-scale surveillance at a reduced cost.
Here we evaluate the collection of naturally blood-fed mosquitoes to test for human anti-SARS-CoV-2 antibodies in the laboratory and at five field locations in Mali.
Immunoglobulin-G antibodies to multiple SARS-CoV-2 antigens were readily detected in mosquito bloodmeals by bead-based immunoassay through at least 10 h after feeding mean sensitivity of 0.92 (95% CI 0.78-1) and mean specificity of 0.98 (95% CI 0.88-1), indicating that most blood-fed mosquitoes collected indoors during early morning hours (and likely to have fed the previous night) are viable samples for analysis. We found that reactivity to four SARS-CoV-2 antigens rose during the pandemic from pre-pandemic levels. The crude seropositivity of blood sampled via mosquitoes was 6.3% in October and November 2020 across all sites, and increased to 25.1% overall by February 2021, with the most urban site reaching 46.7%, consistent with independent venous blood-based sero-surveillance estimates.
We have demonstrated that using mosquito bloodmeals, country-wide sero-surveillance of human diseases (both vector-borne and non-vector-borne) is possible in areas where human-biting mosquitoes are common, offering an informative, cost-effective, and non-invasive sampling option.
Tracking mosquitoes using current methods of mark–release–recapture are limited to small spatial and temporal scales exposing major gaps in understanding long‐range movements and extended survival. ...Novel approaches to track mosquitoes may yield fresh insights into their biology which improves intervention activities to reduce disease transmission. Stable isotope enrichment of natural mosquito breeding sites allows large‐scale marking of wild mosquitoes absent human handling. Mosquito larvae that develop in 2H‐enriched water are expected to be detectable for over 4 months using tissue mass fraction 2H measurements, providing opportunities for long‐term mark–capture studies on a large scale.
A laboratory study followed by a field experiment of mosquito larval habitat 2H enrichment was conducted in Mali, to evaluate potential labelling of wild mosquitoes. Twelve natural larval sites were enriched using 2H deuterium oxide (D2O, 99%). Enrichment level was maintained by supplementation following dilution by rains. Availability of 2H to mosquito larvae was enhanced by locally collected and cultured microorganisms (i.e. protozoa, algae and bacteria) reared in deuterated water, and provided as larval diet. Putative natural predators were removed from the larval sites and first instar larvae Anopheles gambiae s.l. larvae were added every other day. Emergence traps enabled collection of eclosing adults. Adult mosquitoes were kept at laboratory conditions for analysis of label attrition with age.
Deuterium enrichment of wild mosquitoes above background levels (maximum = 143.1 ppm) became apparent 5–6 days after initial exposure, after which 2H values increased steadily until c. 24 days later (to a mean of c. 220 ppm). Anopheles and Culex mosquitoes showed significantly different 2H values (211 and 194.2 ppm, respectively). Both genera exhibited exponential label attrition (e(‐x)) amounting to 21.6% by day 30 post‐emergence, after which attrition rate continuously decreased. Males of both taxa exhibited a higher mean 2H value compared to females.
Deuterium oxide proved useful in marking mosquitoes in their natural larval sites and although costly, may prove valuable for studies of mosquitoes and other aquatic insects. Based on our field study, we provide a protocol for marking mosquito larval sites using deuterium oxide.
Résumé
Suivre les moustiques dans la nature à l'aide des techniques actuelles de Marquage‐Lâcher‐Recapture est réservé à des études spatio‐temporelles à petites échelles, faisant ressortir de nombreuses insuffisances dans la compréhension des mouvements à longue distance et pour une survie prolongée. Des approches innovantes sur le suivi des moustiques peuvent fournir de nouvelles informations sur leur biologie enfin d’améliorer les activités d’intervention qui visent à réduire la transmission de la maladie. L'enrichissement en isotopes stables des gîtes larvaires naturels des moustiques permet un marquage à grande échelle des moustiques sauvages sans manipulation manuelle de l’homme. Les moustiques issus des larves qui se développent dans une eau enrichie en Deutérium (2H) sont supposés être identifiables pendant plus de quatre mois à l'aide des mesures du 2H dans la fraction de masse tissulaire, offrant ainsi des opportunités pour des études à grande échelle de Marquage‐Lâcher‐Recapture à long terme.
Une étude de laboratoire suivie d'expérimentations sur le terrain en vue d’enrichir les gîtes larvaires des moustiques en 2H a été menée au Mali afin d'évaluer un marquage potentiel des moustiques sauvages. Douze gîtes larvaires naturels ont été enrichis à l’aide d’oxyde de Deutérium 2H (D2O, 99%). Le niveau d'enrichissement a été maintenu par une compensation après dilution des gîtes par les eaux de pluies. Pour augmenter le niveau de marquage des larves, un régime alimentaire composé de microorganismes (protozoaires, algues et bactéries) collectés localement et élevés dans de l’eau très enrichie en Deutérium leur a été fournis. Les présumés prédateurs naturels ont été retirés des gîtes larvaires et un apport externe supplémentaire de larves de premier stade d’Anopheles gambiae s.l. a été fait tous les deux jours. Des pièges de capture après émergence ont permis la collecte des imagos. Les moustiques adultes collectés ont été maintenus au laboratoire pour des analyses de détection du niveau de marquage en fonction de l’âge.
L'enrichissement en Deutérium des moustiques sauvages au‐dessus du niveau référentiel (maximum = 143,1 ppm) est devenu apparent 5 à 6 jours après exposition, ensuite les valeurs de 2H ont régulièrement augmenté jusqu'à environ 24 jours au plus tard (où une moyenne d'environ 220 ppm est atteinte). Les Anophèles et Culex présentaient des valeurs de 2H significativement différentes (211 et 194,2 ppm respectivement). Les deux genres ont présenté une usure exponentielle des traces de marquage (e(‐x)) s'élevant à 21,6% au 30e jour après émergence, puis le taux d'usure du marquage a continuellement diminué. Les mâles des deux taxons présentaient une valeur moyenne de 2H supérieure à celle des femelles.
Malgré le coût, l'oxyde de Deutérium s'est montré efficace dans le marquage des moustiques dans leurs gîtes larvaires naturels ; cela serait d’une grande importance dans les études concernant les moustiques et autres insectes aquatiques. A partir de nos résultats sur terrain dans cette étude, nous venons de produire un protocole sur le marquage des gîtes larvaires de moustiques à l’oxyde de deutérium.
Les Culicidae, communément appelés moustiques, par leur large distribution et leur abondance, sont impliqués dans la transmission de nombreuses maladies humaines et animales. La lutte contre ces ...insectes nécessite la connaissance de leurs lieux de développement dans lequel évoluent les stades pré imaginaux. La présente étude vise à caractériser ces gîtes larvaires en vue d’identifier les indicateurs entomologiques et écologiques de production de larves dans ces milieux. Pour ce faire, le pH, la température, la conductivité, la teneur en oxygène dissout et la densité larvaire des culicidae ont été estimés à la suite des prospections des gîtes larvaires effectuées de juillet 2007 à mars 2018 à Saga, un quartier périurbain de la Ville de Niamey. Au total, 17 gîtes ont été identifiés dont cinq (5) gîtes permanents (29,41%). Les surfaces d’eau artificielles ont été plus abondantes (64,71%). L’étude sur la caractérisation des gîtes par la méthode ACP (Analyse par Composantes Principales) a permis de grouper les gîtes en trois (3) catégories: le groupe 1 constitué par des gîtes qui présentent un pH légèrement acide (6,075 à 7,035) et un taux d’oxygène dissout élevé (1,11 à 2,32). Le groupe 2 qui est constitué par des gites qui présentent une conductivité plus élevée (compris entre 0,97 à 1,08) ainsi qu’un pH légèrement alcalin (7,51 à 7,83). Quant aux gîtes du groupe 3, ils appartiennent en effet, à une zone de transition ou les trois (3) paramètres sont élevés à savoir le pH (8,02 à 8,36), le taux d’oxygène dissout (1,43 mg/l à 2,54 mg/l) et de la conductivité (1170 μS/cm à 1370 μS/cm). L’étude a mis en évidence des affinités entre les espèces de moustiques et les conditions physico-chimiques des gîtes larvaires. C’est ainsi que An. gambiae s.l abonde dans les gîtes caractérisés par une température moins élevée, un pH neutre un taux d’oxygène dissout élevé alors que Culex pipens présente une affinité aux gîtes à forte conductivité et à taux d’oxygène dissout faible.Mots clès : Culicidae, Paramètres physico-chimiques, gîtes larvaires, Saga, Niger.
English Title: Measurements of mosquito larvae proliferation indicators in the permanent and semi-permanent ponds of Saga, Niger
Culicidae, commonly known as mosquitoes, by their wide distribution and abundance, are involved in the transmission of many human and animal diseases. The fight against these insects requires knowledge of their places of development in which the pre-imaginary stages evolve. The present study aims to characterize these breeding sites in order to identify entomological and ecological indicators of larval production in these environments. To do this, the pH, temperature, conductivity, dissolved oxygen content and larval density of culicidae were estimated following surveys of the breeding sites carried out from July 2007 to March 2018 in Saga, a peri-urban area of the City of Niamey. In total, 17 lodgings have been identified, including five (5) permanent lodgings (29.41%). Artificial water surfaces were more abundant (64.71%). The study on the characterization of the deposits by the ACP method (Principal Component Analysis) made it possible to group the deposits in three (3) categories: group 1 consisting of deposits that have a slightly acidic pH (6.075 to 7.035) and a high dissolved oxygen level (1.11 to 2.32). Group 2 which consists of gites which have a higher conductivity (0.97 to 1.08) as well as a slightly alkaline pH (7.51 to 7.83). As for the group 3 deposits, they indeed belong to a transition zone where the three (3) parameters are high, namely the pH (8.02 to 8.36), the dissolved oxygen level (1.43 mg / l to 2.54 mg / l) and conductivity (1170 μS / cm to 1370 μS / cm). The study highlighted affinities between mosquito species and the physicochemical conditions of the breeding sites. This is how An. Gambiae sl abounds in deposits characterized by a lower temperature, a neutral pH a high dissolved oxygen level while Culex pipens has an affinity for deposits with high conductivity and low dissolved oxygen rate.Keywords: Culicidae, Physico-chemical parameters, breeding sites, Saga, Niger.
Reduced survival and future reproduction due to of current reproduction is a trade-off known as the cost of reproduction. Surprisingly, only a few studies have assessed the cost of reproduction in ...arthropod disease vectors, despite its effect on longevity, and thus on vectorial capacity. We evaluated the cost of reproduction on survival of Anopheles gambiae Giles by comparing mosquitoes that were denied exposure to the other sex, hereafter named virgins, and those that were allowed exposure to the other sex and mating, hereafter named mated. Merely 6 d of exposure to females with mating activity reduced male survival from a median of 17 d in virgins to 15 d in mated, indicating that male mating cost is substantial. The increase in mortality of mated males began several days after the exposure to females ended, indicating that mating is not associated with immediate mortality risk. Notably, body size was negatively correlated with male mortality in mated males, but not in virgins. The rate of insemination declined after 4 d of exposure to females, indicating that male mating capacity is limited and further supporting the hypothesis that mating is costly for males. Consistent with previous studies, female survival on sugar alone (median = 16 d) was shorter than on blood and sugar (median = 19 d), regardless if she was mated or virgin. Overall, survival of mated females was lower than that of virgins on a diet of blood and sugar, but no difference was found on a diet of sugar only. However, the cost of reproduction in females remains ambiguous because the difference in survival between virgin and mated females was driven by the difference between virgin (median = 19 d) and uninseminated females exposed to males (median = 17 d), rather than between virgin and inseminated females (median = 19 d). Accordingly, sperm and seminal fluid, egg development, and oviposition have negligible cost in terms of female survival. Only exposure to males without insemination decreased female survival, Nonetheless, if exposure to males under natural conditions is also associated with reduced survival, it might explain why females remain monogamous.
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