Temperature effects on the dynamics of Aedes albopictus (Diptera : Culicidae) populations in the laboratory

We investigated how constant temperatures of 22, 24, and 26 degreesC experienced across the full life cycle affected the dynamics of caged populations of Aedes albopictus (Skuse). All cages were equipped with plastic beakers that served as sites for oviposition and larval development. We measured the per capita daily mortality and emergence rates of the adults and size of adult females, and estimated the intrinsic rate of increase (r) and asymptotic density (K) for each adult population. populations at 26 degreesC had greater intrinsic rates of increase and lower asymptotic densities than populations at 22 and 24 degreesC. Populations at high temperatures initially had greater daily. per capita emergence rates, and steeper. declines in per capita emergence rate as density increased over tire course of the experiment, There was no temperature effect on the size of adult females nor on the per capita daily mortality rate of adults. Results indicated that populations of Ae. albopictus occurring in regions with relatively high summer temperatures are likely to have hiyh rates of population growth with populations of adults peaking early in the season. These populations mn)l attain relatively. low peak densities of adults. Populations occurring in regions with low summer temperatures are likely to experience slow, steady production of adults throughout the season with population size peaking later in the season, and may attain higher peal, densities of adults. Nigh temperature conditions, associated with climate change, may increase the rate of spread of Ae, albopictus by increasing rates of increase and by. enhancing colonization due to rapid population growth

Precipitation and temperature effects on populations of Aedes albopictus (Diptera : Culicidae): Implications for range expansion

We investigated how temperature and precipitation regime encountered over the life cycle of Aedes albopictus (Skuse) affects populations. Caged populations of A. albopictus were maintained at 22, 26, and 30 degreesC. Cages were equipped with containers that served as sites for oviposition and larval development. All cages were assigned to one of three simulated precipitation regimes: (1) low fluctuation regime - water within the containers was allowed to evaporate to 90% of its maximum before being refilled, (2) high fluctuation regime - water was allowed to evaporate to 25% of its maximum before being refilled, and (3) drying regime - water was allowed to evaporate to complete container dryness before being refilled. Greater temperature and the absence of drying resulted in greater production of adults. Greater temperature in combination with drying were detrimental to adult production. These precipitation effects on adult production were absent at 22 C. Greater temperatures and drying treatments yielded higher and lower eclosion rates, respectively and, both yielded greater mortality. Development time and size of adults decreased with increased temperatures, and drying produced larger adults. Greater temperatures resulted in greater egg mortality. These results suggest that populations occurring in warmer regions are likely to produce more adults as long as containers do not dry completely. Populations in cooler regions are likely to produce fewer adults with the variability of precipitation contributing less to variation in adult production. Predicted climate change in North America is likely to extend the northern distribution of A. albopictus and to limit further its establishment in arid regions

Invertebrate carcasses as a resource for competing Aedes albopictus and Aedes aegypti (Diptera : Culicidae)

However, little is known of the role of these carcasses in other containers, which also receive leaf fall and stemflow inputs. This experiment investigated effects of accumulated invertebrate carcasses as a resource for two competing mosquitoes, Aedes albopictus (Skuse) and Aedes aegypti (L.) whether either species differentially benefited from accumulated carcasses, and if such a benefit affected interspecific competition. First, we measured accumulation of invertebrate carcasses in standard containers at a field site. We then used a replacement series with five different species ratios at the same total density: and varied the input of invertebrate carcasses [dead Drosophila melanogaster (Meigen) ] in three levels: none, the average input from our field site, or the maximum input recorded at our field site. Survivorship, development time, and mass were measured for each mosquito species as correlates of population growth, and were used to calculate a population performance index, lambda\u27. There were strong positive effects of invertebrate carcass additions on all growth correlates and lambda\u27. Differences in performance between species were pronounced in small or no carcass additions and absent in large inputs of invertebrate carcasses, but there was little evidence that inputs of invertebrate carcasses altered the competitive advantage in this system. These results suggest that terrestrial invertebrate carcasses may be an important resource for many types of container communities, and large accumulations of dead invertebrates may: reduce resource competition between these mosquitoes. thus favoring coexistence. We propose that the total amount of resource, including accumulated invertebrate carcasses, may explain observed patterns of replacement involving these mosquitoes

Culex tarsalis is a competent vector species for Cache Valley virus

Background: Cache Valley virus (CVV) is a mosquito-borne orthobunyavirus endemic in North America. The virus is an important agricultural pathogen leading to abortion and embryonic lethality in ruminant species, especially sheep. The importance of CVV in human public health has recently increased because of the report of severe neurotropic diseases. However, mosquito species responsible for transmission of the virus to humans remain to be determined. In this study, vector competence of three Culex species mosquitoes of public health importance, Culex pipiens, Cx. tarsalis and Cx. quinquefasciatus, was determined in order to identify potential bridge vector species responsible for the transmission of CVV from viremic vertebrate hosts to humans. Results: Variation of susceptibility to CVV was observed among selected Culex species mosquitoes tested in this study. Per os infection resulted in the establishment of infection and dissemination in Culex tarsalis, whereas Cx. pipiens and Cx. quinquefasciatus were highly refractory to CVV. Detection of viral RNA in saliva collected from infected Cx. tarsalis provided evidence supporting its role as a competent vector. Conclusions: Our study provided further understanding of the transmission cycles of CVV and identifies Cx. tarsalis as a competent vector

Linking Nutrient Stoichiometry to Zika Virus Transmission in a Mosquito

Food quality and quantity serve as the basis for cycling of key chemical elements in trophic interactions; yet the role of nutrient stoichiometry in shaping host–pathogen interactions is under appreciated. Most of the emergent mosquito-borne viruses affecting human health are transmitted by mosquitoes that inhabit container systems during their immature stages, where allochthonous input of detritus serves as the basal nutrients. Quantity and type of detritus (animal and plant) were manipulated in microcosms containing newly hatched Aedes aegypti mosquito larvae. Adult mosquitoes derived from these microcosms were allowed to ingest Zika virus-infected blood and then tested for disseminated infection, transmission, and total nutrients (percent carbon, percent nitrogen, ratio of carbon to nitrogen). Treatments lacking high-quality animal (insect) detritus significantly delayed development. Survivorship to adulthood was closely associated with the amount of insect detritus present. Insect detritus was positively correlated with percent nitrogen, which affected Zika virus infection. Disseminated infection and transmission decreased with increasing insect detritus and percent nitrogen. We provide the first definitive evidence linking nutrient stoichiometry to arbovirus infection and transmission in a mosquito using a model system of invasive Ae. aegypti and emergent Zika virus

Overexpression screen of interferon-stimulated genes identifies RARRES3 as a restrictor of Toxoplasma gondii infection

Toxoplasma gondii is an important human pathogen infecting an estimated one in three people worldwide. The cytokine interferon gamma (IFNγ) is induced during infection and is critical for restricting T. gondii growth in human cells. Growth restriction is presumed to be due to the induction of interferon-stimulated genes (ISGs) that are upregulated to protect the host from infection. Although there are hundreds of ISGs induced by IFNγ, their individual roles in restricting parasite growth in human cells remain somewhat elusive. To address this deficiency, we screened a library of 414 IFNγ induced ISGs to identify factors that impact T. gondii infection in human cells. In addition to IRF1, which likely acts through the induction of numerous downstream genes, we identified RARRES3 as a single factor that restricts T. gondii infection by inducing premature egress of the parasite in multiple human cell lines. Overall, while we successfully identified a novel IFNγ induced factor restricting T. gondii infection, the limited number of ISGs capable of restricting T. gondii infection when individually expressed suggests that IFNγ-mediated immunity to T. gondii infection is a complex, multifactorial process

A Pilot Trial of Universal School-Based Mental Health Screening in El Salvador: Traumatic Stress in an Underresourced School Environment

Salvadoran youth have an elevated risk of trauma exposure and related mental health problems. However, investigations of childhood trauma exposure and mental health sequelae in El Salvador are limited. The present study aimed to (a) explore the prevalence of exposure to potentially traumatic events and symptoms of posttraumatic stress, anxiety, and depression and (b) evaluate the associations between specific trauma types and emotional functioning among Salvadoran youth. A total of 1,296 youth aged 8–21 years from seven public schools completed self-report measures of trauma exposure, posttraumatic stress symptoms (PTSS), anxiety, and depression. Participants reported high levels of trauma exposure, endorsing an average of 3.62 (SD = 2.32) trauma types. In total, 34.5% of participants reported clinically elevated PTSS; fewer youths reported elevated depressive (8.7%) and anxiety symptoms (8.6%). Although boys reported exposure to more trauma types than girls, d = 0.22, girls were more likely to endorse elevated PTSS, V = .11; anxiety, V = .06; and depression, V = .10. Adolescents reported exposure to more trauma types than younger children, d = 0.23, and were more likely to endorse elevated PTSS, V = .07; anxiety, V = .13; and depression, V = .16. Undergoing a frightening medical procedure, OR = 2.30; female sex, OR = 1.92; witnessing domestic violence, OR = 1.70; and experiencing war between gangs, OR = 1.61, were strong predictors of elevated PTSS. This broad, school-based screening was a critical step toward better understanding the rate of trauma exposure and trauma-related symptoms among Salvadoran youth

Genome Sequence Analysis of Dengue Virus 1 Isolated in Key West, Florida

Dengue virus (DENV) is transmitted to humans through the bite of mosquitoes. In November 2010, a dengue outbreak was reported in Monroe County in southern Florida (FL), including greater than 20 confirmed human cases. The virus collected from the human cases was verified as DENV serotype 1 (DENV-1) and one isolate was provided for sequence analysis. RNA was extracted from the DENV-1 isolate and was used in reverse transcription polymerase chain reaction (RT-PCR) to amplify PCR fragments to sequence. Nucleic acid primers were designed to generate overlapping PCR fragments that covered the entire genome. The DENV-1 isolate found in Key West (KW), FL was sequenced for whole genome characterization. Sequence assembly, Genbank searches, and recombination analyses were performed to verify the identity of the genome sequences and to determine percent similarity to known DENV-1 sequences. We show that the KW DENV-1 strain is 99% identical to Nicaraguan and Mexican DENV-1 strains. Phylogenetic and recombination analyses suggest that the DENV-1 isolated in KW originated from Nicaragua (NI) and the KW strain may circulate in KW. Also, recombination analysis results detected recombination events in the KW strain compared to DENV-1 strains from Puerto Rico. We evaluate the relative growth of KW strain of DENV-1 compared to other dengue viruses to determine whether the underlying genetics of the strain is associated with a replicative advantage, an important consideration since local transmission of DENV may result because domestic tourism can spread DENVs

The type III effector EspF coordinates membrane trafficking by the spatiotemporal activation of two eukaryotic signaling pathways

Bacterial toxins and effector proteins hijack eukaryotic enzymes that are spatially localized and display rapid signaling kinetics. However, the molecular mechanisms by which virulence factors engage highly dynamic substrates in the host cell environment are poorly understood. Here, we demonstrate that the enteropathogenic Escherichia coli (EPEC) type III effector protein EspF nucleates a multiprotein signaling complex composed of eukaryotic sorting nexin 9 (SNX9) and neuronal Wiskott-Aldrich syndrome protein (N-WASP). We demonstrate that a specific and high affinity association between EspF and SNX9 induces membrane remodeling in host cells. These membrane-remodeling events are directly coupled to N-WASP/Arp2/3–mediated actin nucleation. In addition to providing a biochemical mechanism of EspF function, we find that EspF dynamically localizes to membrane-trafficking organelles in a spatiotemporal pattern that correlates with SNX9 and N-WASP activity in living cells. Thus, our findings suggest that the EspF-dependent assembly of SNX9 and N-WASP represents a novel form of signaling mimicry used to promote EPEC pathogenesis and gastrointestinal disease

Steady-state modulation of voltage-gated K+ channels in rat arterial smooth muscle by cyclic AMP-dependent protein kinase and protein phosphatase 2B

Voltage-gated potassium channels (Kv) are important regulators of membrane potential in vascular smooth muscle cells, which is integral to controlling intracellular Ca2+ concentration and regulating vascular tone. Previous work indicates that Kv channels can be modulated by receptor-driven alterations of cyclic AMP-dependent protein kinase (PKA) activity. Here, we demonstrate that Kv channel activity is maintained by tonic activity of PKA. Whole-cell recording was used to assess the effect of manipulating PKA signalling on Kv and ATP-dependent K+ channels of rat mesenteric artery smooth muscle cells. Application of PKA inhibitors, KT5720 or H89, caused a significant inhibition of Kv currents. Tonic PKA-mediated activation of Kv appears maximal as application of isoprenaline (a β-adrenoceptor agonist) or dibutyryl-cAMP failed to enhance Kv currents. We also show that this modulation of Kv by PKA can be reversed by protein phosphatase 2B/calcineurin (PP2B). PKA-dependent inhibition of Kv by KT5720 can be abrogated by pre-treatment with the PP2B inhibitor cyclosporin A, or inclusion of a PP2B auto-inhibitory peptide in the pipette solution. Finally, we demonstrate that tonic PKA-mediated modulation of Kv requires intact caveolae. Pre-treatment of the cells with methyl-β-cyclodextrin to deplete cellular cholesterol, or adding caveolin-scaffolding domain peptide to the pipette solution to disrupt caveolae-dependent signalling each attenuated PKA-mediated modulation of the Kv current. These findings highlight a novel, caveolae-dependent, tonic modulatory role of PKA on Kv channels providing new insight into mechanisms and the potential for pharmacological manipulation of vascular tone