Investigation of an Elevational Gradient Reveals Strong Differences Between Bacterial and Eukaryotic Communities Coinhabiting Nepenthes Phytotelmata.

Elevation is an important determinant of ecological community composition. It integrates several abiotic features and leads to strong, repeatable patterns of community structure, including changes in the abundance and richness of numerous taxa. However, the influence of elevational gradients on microbes is understudied relative to plants and animals. To compare the influence of elevation on multiple taxa simultaneously, we sampled phytotelm communities within a tropical pitcher plant (Nepenthes mindanaoensis) along a gradient from 400 to 1200 m a.s.l. We use a combination of metabarcoding and physical counts to assess diversity and richness of bacteria, micro-eukaryotes, and arthropods, and compare the effect of elevation on community structure to that of regulation by a number of plant factors. Patterns of community structure differed between bacteria and eukaryotes, despite their living together in the same aquatic microhabitats. Elevation influences community composition of eukaryotes to a significantly greater degree than it does bacteria. When examining pitcher characteristics, pitcher dimorphism has an effect on eukaryotes but not bacteria, while variation in pH levels strongly influences both taxa. Consistent with previous ecological studies, arthropod abundance in phytotelmata decreases with elevation, but some patterns of abundance differ between living inquilines and prey.

Genetic isolation within the malaria mosquito Anopheles melas.

Anopheles melas is a brackish water-breeding member of the Anopheles gambiae complex that is distributed along the coast of West Africa and is a major malaria vector within its range. Because little is known about the population structure of this species, we analysed 15 microsatellite markers and 1161 bp of mtDNA in 11 A. melas populations collected throughout its range. Compared with its sibling species A. gambiae, A. melas populations have a high level of genetic differentiation between them, representing its patchy distribution due to its fragmented larval habitat that is associated with mangroves and salt marsh grass. Populations clustered into three distinct groups representing Western Africa, Southern Africa and Bioko Island populations that appear to be mostly isolated. Fixed differences in the mtDNA are present between all three clusters, and a Bayesian clustering analysis of the microsatellite data found no evidence for migration from mainland to Bioko Island populations, and little migration was evident between the Southern to the Western cluster. Surprisingly, mtDNA divergence between the three A. melas clusters is on par with levels of divergence between other species of the A. gambiae complex, and no support for monophyly was observed in a maximum-likelihood phylogenetic analysis. Finally, an approximate Bayesian analysis of microsatellite data indicates that Bioko Island A. melas populations were connected to the mainland populations in the past, but became isolated, presumably when sea levels rose after the last glaciation period (≥10 000-11 000 bp). This study has exposed species-level genetic divergence within A. melas and also has implications for control of this malaria vector.

Outdoor host seeking behaviour of Anopheles gambiae mosquitoes following initiation of malaria vector control on Bioko Island, Equatorial Guinea.

BACKGROUND: Indoor-based anti-vector interventions remain the preferred means of reducing risk of malaria transmission in malaria endemic areas around the world. Despite demonstrated success in reducing human-mosquito interactions, these methods are effective solely against endophilic vectors. It may be that outdoor locations serve as an important venue of host seeking by Anopheles gambiae sensu lato (s.l.) mosquitoes where indoor vector suppression measures are employed. This paper describes the host seeking activity of anopheline mosquito vectors in the Punta Europa region of Bioko Island, Equatorial Guinea. In this area, An. gambiae sensu stricto (s.s.) is the primary malaria vector. The goal of the paper is to evaluate the importance of An gambiae s.l. outdoor host seeking behaviour and discuss its implications for anti-vector interventions. METHODS: The venue and temporal characteristics of host seeking by anopheline vectors in a hyperendemic setting was evaluated using human landing collections conducted inside and outside homes in three villages during both the wet and dry seasons in 2007 and 2008. Additionally, five bi-monthly human landing collections were conducted throughout 2009. Collections were segregated hourly to provide a time distribution of host-seeking behaviour. RESULTS: Surprisingly high levels of outdoor biting by An. gambiae senso stricto and An. melas vectors were observed throughout the night, including during the early evening and morning hours when human hosts are often outdoors. As reported previously, An. gambiae s.s. is the primary malaria vector in the Punta Europa region, where it seeks hosts outdoors at least as much as it does indoors. Further, approximately 40% of An. gambiae s.l. are feeding at times when people are often outdoors, where they are not protected by IRS or LLINs. Repeated sampling over two consecutive dry-wet season cycles indicates that this result is independent of seasonality. CONCLUSIONS: An. gambiae s.l. mosquitoes currently seek hosts in outdoor venues as much as indoors in the Punta Europa region of Bioko Island. This contrasts with an earlier pre-intervention observation of exclusive endophagy of An. gambiae in this region. In light of this finding, it is proposed that the long term indoor application of insecticides may have resulted in an adaptive shift toward outdoor host seeking in An. gambiae s.s. on Bioko Island.

NIH funding for vaccine readiness before the COVID-19 pandemic.

Rapid development of vaccines for COVID-19 has relied on the application of existing vaccine technologies. This work examines the maturity of ten technologies employed in candidate vaccines (as of July 2020) and NIH funding for published research on these technologies from 2000-2019. These technologies vary from established platforms, which have been used successfully in approved products, to emerging technologies with no prior clinical validation. A robust body of published research on vaccine technologies was supported by 16,358 fiscal years of NIH funding totaling $17.2 billion from 2000-2019. During this period, NIH funding for published vaccine research against specific pandemic threats such as coronavirus, Zika, Ebola, and dengue was not sustained. NIH funding contributed substantially to the advance of technologies available for rapid development of COVID-19 vaccines, suggesting the importance of sustained public sector funding for foundational technologies in the rapid response to emerging public health threats.

Early evening questing and oviposition activity by the Culex (Diptera: Culicidae) vectors of West Nile virus in northeastern North America.

To determine whether the Culex (Diptera: Culicidae) mosquitoes that transmit West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in the northeastern United States seek hosts and oviposit contemporaneously, we recorded when these mosquitoes attacked caged birds and when they deposited eggs. They traversed oviposition sites most frequently approximately 2 h after astronomical sunset, and eggs generally were deposited at that time. Although they most frequently approached avian hosts approximately 2 h after sunset during midsummer, they are more opportunistic during mid- to late fall. Because the Culex mosquitoes that serve as the main vectors of West Nile virus in the northeastern United States quest for hosts and seek to oviposit well after sunset, insecticidal aerosols would be most effective when applied at that time.

Efficacy of resmethrin aerosols applied from the road for suppressing Culex vectors of West Nile virus.

We determined whether aerosol applications of resmethrin, delivered from the road, suppress the reproductive activity of Culex pipiens pipiens and Cx. restuans mosquitoes in suburban sites located near Boston. Oviposition implies a prior blood-feeding event and hence a potential West Nile virus (WNV) transmission-related event. Droplet size, rate of delivery and meteorological conditions were monitored. The target populations proved to be fully susceptible to the insecticide that was used. The roads in the test sites generally gave adequate opportunity for insecticidal coverage. We found that the aerosol plume may have failed to contact the target mosquitoes and conclude that such insecticidal aerosols, delivered from the road, may not effectively reduce the force of transmission of WNV in our test sites.

New evidence of the effects of agro-ecologic change on malaria transmission.

Although maize pollen is known to provide nutrition for larval anopheline mosquitoes, the epidemiologic relationship between maize agriculture and malaria transmission has never been defined. To determine whether recent changes in malaria transmission in Ethiopia might be linked to the spread of maize as a commercial crop, we compared malaria transmission and maize cultivation intensity in 21 villages in the Bure District of northwestern Ethiopia where maize cultivation has recently expanded. The cumulative incidence in high maize cultivation areas was 9.5 times higher than in areas with less maize. A chi-square goodness-of-fit test results showed that malaria cases were not distributed evenly among categories of maize cultivation intensity, (chi2 = 1,578, P < 0.001). A Poisson regression suggested that the intensity of maize cultivation, controlled for differences in elevation between sites, was positively and significantly correlated with malaria incidence. Thus, the intensity of maize cultivation was associated with exacerbated human risk of malaria in Bure.

Laboratory experiments on stranding of Anopheles larvae under different shoreline environmental conditions.

BACKGROUND: One of the concerns for future malaria epidemiology is the elevated risks of malaria around an ever-increasing number of dam sites. Controlling larval populations around reservoirs behind dams by manipulating the water levels of reservoirs could be an effective and sustainable measure for suppressing malaria epidemics; however, the effectiveness of the water-level manipulation and the contributing mechanisms have been poorly studied. In this paper, we focus on how water recession may lead to larval stranding. METHODS: Larvae of An. albimanus were studied to assess their susceptibility to stranding under different conditions representing reservoir shoreline environments in an experimental tank (50 cm × 100 cm). The tank was initially seeded with 80 larvae uniformly, and the numbers of larvae stranded on land and remaining in water were counted (summed up to recovered larvae), following the recession of water. The vertical water drawdown rate and the proportion of stranded larvae to recovered larvae (p) were measured. Shoreline conditions tested were inclinations of shore slopes (2% and 4%) and surface types (smooth, vegetated, rough, ridged). RESULTS: For the 2% slopes, the proportions of stranded larvae (p) increased by about 0.002, 0.004, and 0.010 as the water drawdown rate increased by a centimeter per day on the smooth, rough, and vegetated surfaces, respectively. p for the 4% slopes were smaller than for the 2% slopes. Unlike other surface conditions, no significant correlation between p and the drawdown rate was observed on the ridged surface. CONCLUSIONS: Larger proportions of Anopheles larvae were stranded at higher water drawdown rates, on smaller reservoir slopes, and under rough or vegetated surface conditions. Three mechanisms of larval stranding were identified: falling behind shoreline recession; entrapment in small closed water bodies; and inhabitation in shallow areas. Depending on the local vectors of Anopheles mosquitoes, the conditions for their favorable breeding sites correspond to the conditions for large larval stranding. If these conditions are met, water-level manipulation could be an effective measure to control malaria along shorelines of reservoirs behind dams.

A review of the clinical and epidemiologic burdens of epidemic malaria.

The role of epidemic malaria as a distinct epidemiologic entity posing unique intervention challenges is reviewed from a global perspective. Epidemic malaria derives from particular interactions of vectors, parasites, and various environmental and anthropogenic determinants. Malaria epidemics generally afflict immunologically vulnerable populations, and their explosiveness can strain the capacity of health facilities, causing case fatality rates to increase five-fold or more during outbreaks. People of all ages remain susceptible to the full range of clinical effects. This flatter demographic profile may translate into larger economic consequences, although the full economic impact of epidemic malaria remains undefined. Specialized intervention approaches are recommended for epidemic-prone areas, including enhanced surveillance activities and intensified antivector interventions. Such considerations are particularly critical during a time when malaria epidemics are occurring more frequently in Africa and throughout the world.

Preprandial inhibition of re-mating in Ixodes ticks (Acari: Ixodidae).

Questing female blacklegged ticks, Ixodes scapularis, Say in Massachusetts rarely bear more than one endospermatophore in their reproductive tracts. We evaluated the cause of this nonrandom distribution by examining the stability of endospermatophore retention in females and the effect of prior insemination of females on the copulatory behavior of male ticks. Endospermatophores were retained without degradation in unfed female ticks for >1 yr at 5 degrees C and for at least 4 mo at 21 degrees C. Males were much more likely to abort preprandial (before feeding) copulations without inseminating females bearing endospermatophores. This remating inhibition activity persisted in unfed females for at least 2 mo after insemination. Perprandial (during feedng) copulations were less restrictive, particularly when females became partially engorged. Males were more likely to remain in copula with previously inseminated females that were engorged, but generally did not transfer spermatophores to them until their fifth day of attachment to a rabbit. Little inhibitory activity was evident during the final, rapid engorgement phase of feeding. Thus, remating inhibition appears to degrade as feeding progresses. In summary, an unknown factor associated with the previous insemination of females inhibits subsequent spermatophore transfer by causing mating pairs to interrupt copulation soon after initiation. Remating inhibition is strongest in unfed ticks and becomes less apparent as females become engorged.

Ecological succession and its impact on malaria vectors and their predators in borrow pits in western Ethiopia.

Soil pits excavated for home construction are important larval habitats for malaria vectors in certain parts of Africa. Borrow pits in diverse stages of ecological succession in a maize-farming region of Western Ethiopia were surveyed to assess the relationships between stage of succession and the structure and composition of invertebrate and plant communities, with particular attention to Anopheles gambiae s.l. and An. coustani, the primary local malaria vectors. An array of 82 borrow pits was identified in a multi-lobed drainage basin in the community of Woktola. Each pit was evaluated on its physical features and by faunal and floral surveys during August, 2011, at the height of the longer rainy season (kiremt). Anopheles gambiae s.l. and An. coustani were the sole immature anophelines collected, often coexisting with Culex spp. Sedges were the most common plants within these pits, and included Cyperus elegantulus, C. flavescens, C. erectus and C. assimilis. The legume Smithia abyssinica, Nile grass (Acroceras macrum), cutgrass (Leersia hexandra), clover (Trifolium spp.), and the edible herb Centella asiatica, were also common in these habitats. No plant species in particular was strongly and consistently predictive of the presence or absence of mosquito immatures, particularly with regard to An. coustani. The presence of An.gambiae s.l. immatures in borrow pit habitats was negatively correlated with the presence of backswimmers (Notonectidae) (Z = -2.34, P = 0.019). Young (freshly excavated) borrow pits more likely contained immature An. gambiae s.l. (Z =-2.86, P=0.004). Ecological succession was apparent in older pits, and as they aged, they became less likely to serve as habitats for An. gambiae s.l. (Z=0.26, P=0.796), and more likely to support An. coustani (Z=0.728, P=0.007). As borrow pits age they become less suitable for An. gambiae s.l. breeding and more likely to harbor An. coustani. The abundance of notonectids in habitats was a negative indicator for An. gambiae s.l. abundance. Plant species are not reliable indicators for the presence or absence of malaria vectors in borrow pits.

Insecticide resistance allele frequencies in Anopheles gambiae before and after anti-vector interventions in continental Equatorial Guinea.

Anti-malaria interventions that rely on insecticides can be compromised by insecticide-resistance alleles among malaria vectors. We examined frequency changes of resistance alleles at two loci, knockdown resistance (kdr) and acetylcholinesterase-1 (ace-1), which confer resistance to pyrethroids and DDT, and carbamates, respectively. A total of 7,059 Anopheles gambiae sensu stricto mosquitoes were analyzed from multiple sites across continental Equatorial Guinea. A subset of sites included samples collected pre-intervention (2007) and post-intervention (2009-2011). Both L1014S and L1014F resistance alleles were observed in almost all pre-intervention collections. In particular, L1014F was already at substantial frequencies in M form populations (17.6-74.6%), and at high frequencies (> 50%) in all but two S form populations. Comparison before and throughout anti-vector interventions showed drastic increases in L1014F, presumably caused by intensified selection pressure imposed by pyrethroids used in vector control efforts. In light of these findings, inclusion of other insecticide classes in any anti-vector intervention can be considered prudent.