How reliable are light traps in estimating biting rates of adult Anopheles gambiae s.l. (Diptera: Culicidae) in the presence of treated bed nets?

The sampling efficiency of light trap catches relative to human bait catches in estimating biting rates of the mosquito Anopheles gambiae Giles was investigated in two types of community in southern Sierra Leone: (i) where most of the inhabitants slept under treated bed nets; and (ii) where most of the inhabitants slept without bed nets. The number of female A. gambiae mosquitoes caught in these communities by light trap was strongly correlated (r > or = 0.72) with those from corresponding human biting catches performed either on the same or adjacent nights. It was found that the relative sampling efficiency of light traps varied slightly but significantly with mosquito abundance in villages with treated bed nets, but not in those without them. Nevertheless, the relationship between relative sampling efficiency and mosquito abundance did not differ significantly between the two types of village. Overall, there was insufficient evidence to show that the presence of treated nets altered the relative efficiency of light traps and any bias was only slight, and unlikely to be of any practical importance. Hence, it was concluded that light traps can be used as a surrogate for human bait catches in estimating biting rates of A. gambiae mosquitoes in the two communities.     

Species Shifts in the Anopheles gambiae Complex: Do LLINs Successfully Control Anopheles arabiensis?

Introduction

High coverage of conventional and long-lasting insecticide treated nets (ITNs and LLINs) in parts of E Africa are associated with reductions in local malaria burdens. Shifts in malaria vector species ratio have coincided with the scale-up suggesting that some species are being controlled by ITNs/LLINs better than others.

Methods

Between 2005–2006 six experimental hut trials of ITNs and LLINs were conducted in parallel at two field stations in northeastern Tanzania; the first station was in Lower Moshi Rice Irrigation Zone, an area where An. arabiensis predominates, and the second was in coastal Muheza, where An. gambiae and An. funestus predominate. Five pyrethroids and one carbamate insecticide were evaluated on nets in terms of insecticide-induced mortality, blood-feeding inhibition and exiting rates.

Results

In the experimental hut trials mortality of An. arabiensis was consistently lower than that of An. gambiae and An. funestus. The mortality rates in trials with pyrethroid-treated nets ranged from 25–52% for An. arabiensis, 63–88% for An. gambiae s.s. and 53–78% for An. funestus. All pyrethroid-treated nets provided considerable protection for the occupants, despite being deliberately holed, with blood-feeding inhibition (percentage reduction in biting rates) being consistent between species. Veranda exiting rates did not differ between species. Percentage mortality of mosquitoes tested in cone bioassays on netting was similar for An. gambiae and An. arabiensis.

Conclusions

LLINs and ITNs treated with pyrethroids were more effective at killing An. gambiae and An. funestus than An. arabiensis. This could be a major contributing factor to the species shifts observed in East Africa following scale up of LLINs. With continued expansion of LLIN coverage in Africa An. arabiensis is likely to remain responsible for residual malaria transmission, and species shifts might be reported over larger areas. Supplementary control measures to LLINs may be necessary to control this vector species.     

A splice variant of PGRP-LC required for expression of antimicrobial peptides in Anopheles gambiae

Members of the peptidoglycan recognition protein （PGRP） family play essential roles in different manifestations of immune responses in insects. PGRP-LC, one of seven members of this family in the malaria vector Anopheles gambiae produced several spliced variants. Here we show that PGRP-LC, and not other members of the PGRP family nor the six members of the Gram-negative binding protein families, is required for the expression of antimicrobial peptide genes （such as CEC1 and GAM1） under the control of the Imd-Rel2 pathway in an A. gambiae cell line, 4a3A. PGRP-LC produces many splice variants that can be classified into three sub-groups （LC1, LC2 and LC3）, based on the carboxyl terminal sequences. RNA interference against one LC1 sub-group resulted in dramatic reduction of CEC1 and GAM1. Over-expression of LCla and to a lesser extent LC3a （a member of the LC1 and LC3 sub-group, respectively） in the 4a3A cell line enhances the expression of CEC1 and GAM1. These results demonstrate that the LC1-subgroup splice variants are essential for the expression of CEC1 and GAM1 in A. gambiae cell line.     

Can Anopheles gambiae be infected with Wolbachia pipientis? Insights from an in vitro system

Wolbachia pipientis are maternally inherited endosymbionts associated with cytoplasmic incompatibility, a potential mechanism to drive transgenic traits into Anopheles populations for malaria control. W. pipientis infections are common in many mosquito genera but have never been observed in any Anopheles species, leading to the hypothesis that Anopheles mosquitoes are incapable of harboring infection. We used an in vitro system to evaluate the ability of Anopheles gambiae cells to harbor diverse W. pipientis infections. We successfully established W. pipientis infections (strains wRi and wAlbB) in the immunocompetent Anopheles gambiae cell line Sua5B. Infection was confirmed by PCR, antibiotic curing, DNA sequencing, and direct observation using fluorescence in situ hybridization. The infections were maintained at high passage rates for >30 passages. Our results indicate that there is no intrinsic genetic block to W. pipientis infection in A. gambiae cells, suggesting that establishment of in vivo W. pipientis infections in Anopheles mosquitoes may be feasible.     

Cotton variant genomes—a breakthrough in population genetics analysis

正Cotton is not only an important cash crop for its fiber,but also an excellent model system for studying polyploidization,cell elongation and cell wall biosynthesis(Yang et al.,2014;Fang et al.,2017;Wang et al.,2016;Zou et al.,2016).A focus for scientists is to dissect the genetic basis underlying important agronomic traits(Gong et al.,2018;Huang et al.,2016).The advent of high-throughput sequencing technologies has boosted unveiling the cotton genome(Wang et al.,2012;Li et al.,2014;Li et al.,2015).High-throughput     

Three years of insecticide resistance monitoring in Anopheles gambiae in Burkina Faso: resistance on the rise?

ABSTRACT: Background and methods A longitudinal Anopheles gambiae s.l. insecticide-resistance monitoring programme was established in four sentinel sites in Burkina Faso. For three years, between 2008 and 2010, WHO diagnostic dose assays were used to measure the prevalence of resistance to all the major classes of insecticides at the beginning and end of the malaria transmission season. Species identification and genotyping for target site mutations was also performed and the sporozoite rate in adults determined. RESULTS: At the onset of the study, resistance to DDT and pyrethroids was already prevalent in An. gambiae s.l. from the south-west of the country but mosquitoes from the two sites in central Burkina Faso were largely susceptible. Within three years, DDT and permethrin resistance was established in all four sites. Carbamate and organophosphate resistance remains relatively rare and largely confined to the south-western areas although a small number of bendiocarb survivors were found in all sites by the final round of monitoring. The ace-1R target site resistance allele was present in all localities and its frequency exceeded 20% in 2010 in two of the sites. The frequency of the 1014 F kdr mutation increased throughout the three years and by 2010, the frequency of 1014 F in all sites combined was 0.02 in Anopheles arabiensis, 0.56 in An. gambiae M form and 0.96 in An. gambiae S form. This frequency did not differ significantly between the sites. The 1014 S kdr allele was only found in An. arabiensis but its frequency increased significantly throughout the study (P = 0.0003) and in 2010 the 1014 S allele frequency was 0.08 in An. arabiensis. Maximum sporozoite rates (12%) were observed in Soumousso in 2009 and the difference between sites is significant for each year. CONCLUSION: Pyrethroid and DDT resistance is now established in An. gambiae s.l. throughout Burkina Faso. Results from diagnostic dose assays are highly variable within and between rounds of testing, and hence it is important that resistance monitoring is carried out on more than one occasion before decisions on insecticide procurement for vector control are made. The presence of 1014 S in An. gambiae s.l., in addition to 1014 F, is not unexpected given the recent report of 1014 S in Benin but highlights the importance of monitoring for both mutations throughout the continent. Future research must now focus on the impact that this resistance is having on malaria control in Burkina Faso.     

Evolutionary determinants of population differences in population growth rate × habitat temperature interactions in Chironomus riparius

Little is known about intraspecific variation in fitness performance in response to thermal stress among natural populations and how this relates to evolutionary aspects of species ecology. In this study, population growth rate (PGR; a composite fitness measure) varied among five natural Chironomus riparius populations sampled across a climatic gradient when subjected to three temperature treatments reflecting the typical range of summer habitat temperatures (20, 24 and 28 °C). The variation could be explained by a complex model including effects of genetic drift, genetic diversity and adaptation to average temperature during the warmest month, in addition to experimental temperature. All populations suffered a decrease in PGR from 20 to 28 °C and ΔPGR was significantly correlated with the respective average habitat temperature in the warmest month—populations from warmer areas showing lower ΔPGR. This implies that long-term exposure to higher temperatures in the warmest month (the key reproductive period for C. riparius) is likely to be a key selective force influencing fitness at higher temperatures. A comparison of phenotypic divergence and neutral genetic differentiation revealed that one phenotypic trait—the number of fertile egg masses per female—appeared to be under positive selection in some populations. Our findings support a role for response to temperature selection along a climatic gradient and suggest population history is a key determinant of intraspecific fitness variation. We stress the importance of integrating different types of data (climatic, experimental, genetic) in order to understand the effects of global climate change on biodiversity.     

Holocene timber-line dynamics at Bachalpsee, a lake at 2265 m a.s.l. in the northern Swiss Alps

Palaeobotanical analysis and radiocarbon dating of lake sediments from Bachalpsee (2265 m a.s.l.), a small lake above the present-day timber-line in the northern Swiss Alps reveals that the region was already deglaciated during the Younger Dryas. The sediment record is dominated by long-distance transported pollen that originates from lowland vegetation but the plant macrofossils give evidence of the local vegetation development. Comparison with palaeobotanical results from three sites along an altitudinal transect permits the reconstruction of the regional timber-line history. Throughout the entire Holocene the catchment of Bachalpsee consisted of a mosaic of open meadows and dwarf shrubs (Salix, Vaccinium, Rhododendron). Chironomid and cladoceran assemblages suggest that the early to mid-Holocene was the warmest interval at Bachalpsee. Comparison of the palaeobotanical results with those from the mire “Feld” (2130 m a.s.l.) in the vicinity of Bachalpsee showed that during the mid-Holocene the timber-line was formed by Pinus cembra and Picea abies with some scattered Abies alba trees and was situated close to Bachalpsee but never reached its catchment. The maximum timber-line in the Northern Alps was reached between 6000 and 3000 cal b.p. which is several millennia later than in the Central Alps. The species composition of the tree-line (Abies alba, Pinus cembra and the absence of Larix decidua) points to less continental and moister climatic conditions compared with the central Alps during the early to mid-Holocene. From 3000 cal b.p. onwards the timber-line was lowered by human deforestation with the most intense pulses of human impact occurring since the Middle Ages. The catchment of Bachalpsee has been used as alpine pasture since the Bronze Age.     

Re-Visiting Insecticide Resistance Status in Anopheles gambiae from C?te d'Ivoire: A Nation-Wide Informative Survey

Insecticide resistance constitutes a major threat that may undermine current gain in malaria control in most endemic countries. National Malaria Control Programmes (NMCPs) need as much information as possible on the resistance status of malaria vectors and underlying mechanisms in order to implement the most relevant and efficient control strategy. Bioassays, biochemical and molecular analysis were performed on An. gambiae collected in six sentinel sites in Côte d''Ivoire. The sites were selected on the basis of their bioclimatic status and agricultural practices. An. gambiae populations across sites showed high levels of resistance to organochloride, pyrethroid and carbamate insecticides. The kdr and ace-1^R mutations were detected in almost all sentinel sites with mosquitoes on the coastal and cotton growing areas mostly affected by these mutations. At almost all sites, the levels of detoxifying enzymes (mixed-function oxidases (MFOs), non-specific esterases (NSE) and glutathione-S-transferases (GSTs)) in An. gambiae populations were significantly higher than the levels found in the susceptible strain Kisumu. Pre-exposure of mosquitoes to PBO, an inhibitor of MFOs and NSEs, significantly increased mortality rates to pyrethroids and carbamates in mosquitoes but resistance in most cases was not fully synergised by PBO, inferring a residual role of additional mechanisms, including kdr and ace-1 site insensitivity. The large distribution of resistance in Côte d''Ivoire raises an important question of whether to continue to deploy pyrethroid-based long-lasting insecticidal nets (LLINs) and insecticide residual spraying (IRS) towards which resistance continues to rise with no guarantee that the level of resistance would not compromise their efficacy. Innovative strategies that combine insecticide and synergists in LLINs or spatially LLIN and an effective non-pyrethroid insecticide for IRS could be in the short term the best practice for the NMCP to manage insecticide resistance in malaria vectors in Côte d''Ivoire and other endemic countries facing resistance.     

Male size does not affect mating success (of Anopheles gambiae in São Tomé)

Abstract For malaria control, the utility of transgenic vector Anopheles mosquitoes (Diptera: Culicidae) refractory to Plasmodium transmission, will depend on their interbreeding with the wild vector population. In many species, larger males are more successful in obtaining mates. In São Tomé island, we determined that size did not affect mating success of male Anopheles gambiae Giles sensu stricto, the main malaria vector in tropical Africa. Also we showed that larval intraspecific competition is probably insignificant in this population of An. gambiae. Thus, the potential success of transgenic An. gambiae is unlikely to be affected by size selection under field conditions.     

Echocardiographic chamber quantification in a healthy Dutch population

Aim

For accurate interpretation of echocardiographic measurements normative data are required, which are provided by guidelines. For this article, the hypothesis was that these cannot be extrapolated to the Dutch population, since in Dutch clinical practice often higher values are found, which may not be pathological but physiological. Therefore this study aimed to 1) obtain and propose normative values for cardiac chamber quantification in a healthy Dutch population and 2) determine influences of baseline characteristics on these measurements.

Methods

Prospectively recruited healthy subjects, aged 20–72 years (at least 28 subjects per age decade, equally distributed for gender) underwent physical examination and 2D and 3D echocardiography. Both ventricles and atria were assessed and volumes were calculated.

Results

147 subjects were included (age 44 ± 14 years, 50% female). Overall, feasibility was good for both linear and volumetric measurements. Linear and volumetric parameters were consistently higher than current guidelines recommend, while functional parameters were in line with the guidelines. This was more so in the older population. 3D volumes were higher than 2D volumes. Gender dependency was seen in all body surface area (BSA) corrected volumes and with increasing age, ejection fractions decreased.

Conclusion

This study provides 2D and 3D echocardiographic reference ranges for both ventricles and atria derived from a healthy Dutch population. BSA indexed volumes are gender-dependent, age did not influence ventricular volumes and a rise in blood pressure was independently associated with increased right ventricular volumes. The higher volumes found may be indicative for the Dutch population being the tallest in the world.

     

How can Populus euphratica cope with extremely dry growth conditions at 2,800 m a.s.l. on the northern Tibetan Plateau?

Euphrates poplar (Populus euphratica) is a key species of Tugai forests in the central Asian deserts and has been the topic of dendrochronological studies in west China since the 1980s. However, little is known about its growth performance at its highest occurrence in the southern Qaidam Basin of the northern Tibetan Plateau. Increment cores of the Euphrates poplar population there did well cross-date and thus showed a high dendrochronological potential. Its growth was persistently positively correlated with temperature from previous September to current August although not significant throughout. The annual precipitation of around 41 mm can not exert any significant effect on Euphrates poplar growth in view of the extremely high annual pan evaporation of 2,150 mm. Water in the nearby Tuolahai River is limited to the period from June–September. The positive correlation of tree growth with spring/early summer temperature indicates that the riparian Euphrates poplar trees may benefit from an increasing river runoff due to an advanced and accelerated snow and glacier melting under warmer conditions. An above-average autumn/early winter temperature in the preceding year may lead to an extended water flow in the river bed and hence to an increased tree growth in the next year. It is crucial to protect this invaluable natural forest from undue human activity.