scholarly journals Experimental Infection of Amblyomma americanum (Acari: Ixodidae) With Bourbon Virus (Orthomyxoviridae: Thogotovirus)

2020 ◽  
Author(s):  
Marvin S Godsey ◽  
Dominic Rose ◽  
Kristin L Burkhalter ◽  
Nicole Breuner ◽  
Angela M Bosco-Lauth ◽  
...  
Keyword(s):  
Infectious Virus ◽  
Vector Competence ◽  
Blood Feeding ◽  
Human Case ◽  
Amblyomma Americanum ◽  
Live Virus ◽  
Active Life ◽  
Series Of Experiments ◽  
Transstadial Transmission ◽  
Very High

Abstract Following the recent discovery of Bourbon virus (BRBV) as a human pathogen, and the isolation of the virus from Amblyomma americanum (L.) collected near the location of a fatal human case, we undertook a series of experiments to assess the laboratory vector competence of this tick species for BRBV. Larval ticks were infected using an immersion technique, and transstadial transmission of virus to the nymphal and then to the adult stages was demonstrated. Transstadially infected nymphs transmitted virus to adult ticks at very high rates during cofeeding, indicating the presence of infectious virus in the saliva of engorging ticks. Vertical transmission by transstadially infected females to their progeny occurred, but at a low rate. Rabbits fed on by infected ticks of all active life stages developed high titers of antibody to the virus, demonstrating host exposure to BRBV antigens/live virus during tick blood feeding. These results demonstrate that A. americanum is a competent vector of BRBV and indicate that cofeeding could be critical for enzootic maintenance.

scholarly journals Heartland Virus Epidemiology, Vector Association, and Disease Potential

Viruses ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 498 ◽  
Author(s):  
Aaron Brault ◽  
Harry Savage ◽  
Nisha Duggal ◽  
Rebecca Eisen ◽  
J. Staples
Keyword(s):  
Infection Rate ◽  
Disease Surveillance ◽  
Vector Competence ◽  
Amblyomma Americanum ◽  
Life Stages ◽  
Eastern United States ◽  
Transmission Cycle ◽  
Host Seeking ◽  
Transstadial Transmission ◽  
Severe Fever

First identified in two Missouri farmers exhibiting low white-blood-cell and platelet counts in 2009, Heartland virus (HRTV) is genetically closely related to severe fever with thrombocytopenia syndrome virus (SFTSV), a tick-borne phlebovirus producing similar symptoms in China, Korea, and Japan. Field isolations of HRTV from several life stages of unfed, host-seeking Amblyomma americanum, the lone star tick, implicated it as a putative vector capable of transstadial transmission. Laboratory vector competence assessments confirmed transstadial transmission of HRTV, demonstrated vertical infection, and showed co-feeding infection between A. americanum. A vertical infection rate of 33% from adult females to larvae in the laboratory was observed, while only one of 386 pools of molted nymphs (1930) reared from co-feeding larvae was positive for HRTV (maximum-likelihood estimate of infection rate = 0.52/1000). Over 35 human HRTV cases, all within the distribution range of A. americanum, have been documented. Serological testing of wildlife in areas near the index human cases, as well as in widely separated regions of the eastern United States where A. americanum occur, indicated many potential hosts such as raccoons and white-tailed deer. Attempts, however, to experimentally infect mice, rabbits, hamsters, chickens, raccoons, goats, and deer failed to produce detectable viremia. Immune-compromised mice and hamsters are the only susceptible models. Vertical infection augmented by co-feeding transmission could play a role in maintaining the virus in nature. A more complete assessment of the natural transmission cycle of HRTV coupled with serosurveys and enhanced HRTV disease surveillance are needed to better understand transmission dynamics and human health risks.

scholarly journals On the Average Coefficient of Dominance of Deleterious Spontaneous Mutations

Genetics ◽  
2000 ◽  
Vol 155 (4) ◽  
pp. 1991-2001 ◽  
Author(s):  
A García-Dorado ◽  
A Caballero
Keyword(s):  
Deleterious Mutations ◽  
Spontaneous Mutations ◽  
Partial Dominance ◽  
High Viability ◽  
Significant Difference ◽  
Plausible Hypothesis ◽  
Average Coefficient ◽  
Series Of Experiments ◽  
Very High ◽  
Balancer Chromosome

Abstract T. Mukai and co-workers in the late 1960s and O. Ohnishi in the 1970s carried out a series of experiments to obtain direct estimates of the average coefficient of dominance (h¯) of minor viability mutations in Drosophila melanogaster. The results of these experiments, although inconsistent, have been interpreted as indicating slight recessivity of deleterious mutations, with h¯≈0.4. Mukai obtained conflicting results depending on the type of heterozygotes used, some estimates suggesting overdominance and others partial dominance. Ohnishi's estimates, based on the ratio of heterozygous to homozygous viability declines, were more consistent, pointing to the above value. However, we have reanalyzed Ohnishi's data, estimating h¯ by the regression method, and obtained a much smaller estimate of ~0.1. This significant difference can be due partly to the different weighting implicit in the estimates, but we suggest that this is not the only explanation. We propose as a plausible hypothesis that a putative nonmutational decline in viability occurring in the first half of Ohnishi's experiment (affecting both homozygotes and heterozygotes) has biased upward the estimates from the ratio, while it would not bias the regression estimates. This hypothesis also explains the very high h¯≈0.7 observed in Ohnishi's high-viability chromosomes. By constructing a model of spontaneous mutations using parameters in the literature, we investigate the above possibility. The results indicate that a model of few mutations with moderately large effects and h¯≈0.2 is able to explain the observed estimates and the distributions of homozygous and heterozygous viabilities. Accounting for an expression of mutations in genotypes with the balancer chromosome Cy does not alter the conclusions qualitatively.

scholarly journals XIV. On the absorption of gases by solids

1881 ◽  
Vol 32 (212-215) ◽  
pp. 407-408
Keyword(s):  
Royal Society ◽  
Hydraulic Press ◽  
Careful Examination ◽  
Solid Matter ◽  
Chemical Action ◽  
High Pressure And Temperature ◽  
Solid Iron ◽  
Series Of Experiments ◽  
The Subject ◽  
Very High

During the progress of the investigations which I have from time to time had the honour of bringing under the notice of the Royal Society, I have again and again noticed the apparent disappearance of gases inclosed in vessels of various materials when the disappearance could not be accounted for upon the assumption of ordinary leakage. After a careful examination of the subject I found that the solids absorbed or dissolved the gases, giving rise to a striking example of the fixation of a gas in a solid without chemical action. In carrying out that most troublesome investigation, the crystalline separation of carbon from its compounds, the tubes used for experiment have been in nine cases out of ten found to be empty on opening them, and in most cases a careful testing by hydraulic press showed no leakage. The gases seemed to go through the solid iron, although it was 2 inches thick. A series of experiments with various linings were tried. The tube was electro-plated with copper, silver, and gold, but with no greater success. Siliceous linings were tried fusible enamels and glass—but still the' tubes refused to hold the contents. Out of thirty-four experiments made since my last results were published, only four contained any liquid or condensed gaseous matter after the furnacing. I became convinced that the solid matter at the very high pressure and temperature used must be pervious to gases.

scholarly journals Quantitative measurement of infectious virus in SARS-CoV-2 Alpha, Delta and Epsilon variants reveals higher infectivity (viral titer:RNA ratio) in clinical samples containing the Delta and Epsilon variants.

2021 ◽  
Author(s):  
Hannah W Despres ◽  
Margaret G Mills ◽  
David J Shirley ◽  
Madaline M Schmidt ◽  
Meei-Li Huang ◽  
...  
Keyword(s):  
Quantitative Measurement ◽  
Infectious Virus ◽  
Viral Rna ◽  
Clinical Samples ◽  
Rt Pcr ◽  
Genome Copy ◽  
Live Virus ◽  
High Degree ◽  
The Relationship ◽  
Rna Levels

ABSTRACT Background Novel SARS-CoV-2 Variants of Concern (VoC) pose a challenge to controlling the COVID-19 pandemic. Previous studies indicate that clinical samples collected from individuals infected with the Delta variant may contain higher levels of RNA than previous variants, but the relationship between viral RNA and infectious virus for individual variants is unknown. Methods We measured infectious viral titer (using a micro-focus forming assay) as well as total and subgenomic viral RNA levels (using RT-PCR) in a set of 165 clinical samples containing SARS-CoV-2 Alpha, Delta and Epsilon variants that were processed within two days of collection from the patient. Results We observed a high degree of variation in the relationship between viral titers and RNA levels. Despite the variability we observed for individual samples the overall infectivity differed among the three variants. Both Delta and Epsilon had significantly higher infectivity than Alpha, as measured by the number of infectious units per quantity of viral E gene RNA (6 and 4 times as much, p=0.0002 and 0.009 respectively) or subgenomic E RNA (11 and 7 times as much, p<0.0001 and 0.006 respectively). Conclusion In addition to higher viral RNA levels reported for the Delta variant, the infectivity (amount of replication competent virus per viral genome copy) may also be increased compared to Alpha. Measuring the relationship between live virus and viral RNA is an important step in assessing the infectivity of novel SARS-CoV-2 variants. An increase in the infectivity of the Delta variant may further explain increased spread and suggests a need for increased measures to prevent viral transmission.

scholarly journals Control of the lighting system using a genetic algorithm

2012 ◽  
Vol 16 (suppl. 1) ◽  
pp. 237-250 ◽  
Author(s):  
Velimir Congradac ◽  
Bosko Milosavljevic ◽  
Jovan Velickovic ◽  
Bogdan Prebiracevic
Keyword(s):  
Genetic Algorithm ◽  
Social Life ◽  
Electricity Consumption ◽  
Energetic Efficiency ◽  
Lighting System ◽  
Total Consumption ◽  
The Social ◽  
Series Of Experiments ◽  
The Mathematical Model ◽  
Very High

The manufacturing, distribution and use of electricity are of fundamental importance for the social life and they have the biggest influence on the environment associated with any human activity. The energy needed for building lighting makes up 20-40% of the total consumption. This paper displays the development of the mathematical model and genetic algorithm for the control of dimmable lighting on problems of regulating the level of internal lighting and increase of energetic efficiency using daylight. A series of experiments using the optimization algorithm on the realized model confirmed very high savings in electricity consumption.

Early Eocene simulations with three different palaeogeographic conditions

2021 ◽  
Author(s):  
Zijian Zhang ◽  
Zhongshi Zhang ◽  
Zhengtang Guo
Keyword(s):  
Early Eocene ◽  
Model Intercomparison ◽  
Warm Climate ◽  
Time Model ◽  
Deep Time ◽  
Climate Proxy ◽  
Proxy Records ◽  
Intercomparison Project ◽  
Series Of Experiments ◽  
Very High

&lt;p&gt;The early Eocene is a warm period with a very high atmosphere CO&lt;sub&gt;2&lt;/sub&gt; level in the Cenozoic. It &amp;#160;provides a good reference for our future climate under the Representative Concentration Pathway 8.5 scenario. Therefore, the early Eocene climate has received many attentions in &amp;#160;modeling&amp;#160;studies, for example, the Deep-Time Model Intercomparison Project (DeepMIP). However, the early Eocene palaeogeographic conditions show remarkable contrasts to the present conditions. Meanwhile, there are a few different reconstructions for the early Eocene palaeogeography, which may cause further model spreads in simulating the early Eocene warm climate. Here, we present a series of experiments carried out with the NorESM1-F, under the framework of DeepMIP. In these experiments, we consider three different palaeogeographic reconstructions for the&amp;#160;early Eocene. We also&amp;#160;compare&amp;#160;our simulations with climate proxy records, to validate which palaeogeographic reconstructions can reproduce simulations that agree better with the climate proxy records.&lt;/p&gt;

scholarly journals Transstadial Transmission and Replication Kinetics of West Nile Virus Lineage 1 in Laboratory Reared Ixodes ricinus Ticks

Pathogens ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 780
Author(s):  
Cristian Răileanu ◽  
Oliver Tauchmann ◽  
Ana Vasić ◽  
Ulrike Neumann ◽  
Birke Andrea Tews ◽  
...  
Keyword(s):  
West Nile Virus ◽  
Ixodes Ricinus ◽  
Tick Species ◽  
Vector Competence ◽  
Virus Transmission ◽  
Viral Agent ◽  
West Nile ◽  
Transstadial Transmission ◽  
Kinetics Of

West Nile virus (WNV) is a mosquito-borne agent that has also been isolated from several tick species. Vector competence of Ixodes ricinus, one of the most common tick species in Europe, has been poorly investigated for WNV to date. As such, to evaluate the vector competence, laboratory reared Ixodes ricinus nymphs were in vitro fed with WNV lineage 1 infectious blood, allowed to molt, and the resulting females artificially fed to study the virus transmission. Furthermore, we studied the kinetics of WNV replication in ticks after infecting nymphs using an automatic injector. Active replication of WNV was detected in injected nymphs from day 7 post-infection until 28 dpi. In the nymphs infected by artificial feeding, the transstadial transmission of WNV was confirmed molecularly in 46.7% of males, while virus transmission during in vitro feeding of I. ricinus females originating from infected nymphs was not registered. The long persistence of WNV in I. ricinus ticks did not correlate with the transmission of the virus and it is unlikely that I. ricinus represents a competent vector. However, there is a potential reservoir role that this tick species can play, with hosts potentially acquiring the viral agent after ingesting the infected ticks.

scholarly journals Tick-Borne Pathogens Shape the Native Microbiome Within Tick Vectors

2020 ◽  
Vol 8 (9) ◽  
pp. 1299
Author(s):  
Abdulsalam Adegoke ◽  
Deepak Kumar ◽  
Cailyn Bobo ◽  
Muhammad Imran Rashid ◽  
Aneela Zameer Durrani ◽  
...  
Keyword(s):  
Vector Competence ◽  
Bacterial Pathogen ◽  
Blood Feeding ◽  
Metagenomic Sequencing ◽  
Microbial Composition ◽  
Alpha And Beta Diversity ◽  
Operational Taxonomic Units ◽  
Diverse Community ◽  
Tick Vectors ◽  
Validation Experiments

Ticks are blood-feeding arthropods and transmit a variety of medically important viral, bacterial, protozoan pathogens to animals and humans. Ticks also harbor a diverse community of microbes linked to their biological processes, such as hematophagy, and hence affect vector competence. The interactions between bacterial and/or protozoan pathogens and the tick microbiome is a black-box, and therefore we tested the hypothesis that the presence of a protozoan or bacterial pathogen will alter the microbial composition within a tick. Hence, this study was designed to define the microbial composition of two tick species, Hyalomma (H.) anatolicum and Rhipicephalus (R.) microplus. We used a combination of PCR based pathogen (Anaplasma marginale and Theileria species) and symbiont (Wolbachia species) identification followed by metagenomic sequencing and comparison of the microbial communities in PCR positive and negative ticks. A total of 1786 operational taxonomic units was identified representing 25 phyla, 50 classes, and 342 genera. The phylum Proteobacteria, Firmicutes, Actinobacteriota, and Bacteroidota were the most represented bacteria group. Alpha and beta diversity were not significantly affected in the presence or absence of Theileria sp. and A. marginale as see with H. anatolicum ticks. Interestingly, bacterial communities were significantly reduced in Theileria sp. infected R. microplus ticks, while also exhibiting a significant reduction in microbial richness and evenness. Putting these observations together, we referred to the effect the presence of Theileria sp. has on R. microplus a “pathogen-induced dysbiosis”. We also identify the presence of Plasmodium falciparum, the causative agent of human malaria from the microbiome of both H. anatolicum and R. microplus ticks. These findings support the presence of a “pathogen-induced dysbiosis” within the tick and further validation experiments are required to investigate how they are important in the vector competence of ticks. Understanding the mechanism of “pathogen-induced dysbiosis” on tick microbial composition may aid the discovery of intervention strategies for the control of emerging tick-borne infections.

scholarly journals Microbial interactions in the mosquito gut determine Serratia colonization and blood-feeding propensity

2020 ◽  
Vol 15 (1) ◽  
pp. 93-108
Author(s):  
Elena V. Kozlova ◽  
Shivanand Hegde ◽  
Christopher M. Roundy ◽  
George Golovko ◽  
Miguel A. Saldaña ◽  
...  
Keyword(s):  
Vector Competence ◽  
Inverse Correlation ◽  
Blood Feeding ◽  
Microbial Interactions ◽  
Host Behavior ◽  
Microbiome Analysis ◽  
Microbe Interactions ◽  
Host Microbe Interactions ◽  
Native Host ◽  
Mosquito Behavior

AbstractHow microbe–microbe interactions dictate microbial complexity in the mosquito gut is unclear. Previously we found that, Serratia, a gut symbiont that alters vector competence and is being considered for vector control, poorly colonized Aedes aegypti yet was abundant in Culex quinquefasciatus reared under identical conditions. To investigate the incompatibility between Serratia and Ae. aegypti, we characterized two distinct strains of Serratia marcescens from Cx. quinquefasciatus and examined their ability to infect Ae. aegypti. Both Serratia strains poorly infected Ae. aegypti, but when microbiome homeostasis was disrupted, the prevalence and titers of Serratia were similar to the infection in its native host. Examination of multiple genetically diverse Ae. aegypti lines found microbial interference to S. marcescens was commonplace, however, one line of Ae. aegypti was susceptible to infection. Microbiome analysis of resistant and susceptible lines indicated an inverse correlation between Enterobacteriaceae bacteria and Serratia, and experimental co-infections in a gnotobiotic system recapitulated the interference phenotype. Furthermore, we observed an effect on host behavior; Serratia exposure to Ae. aegypti disrupted their feeding behavior, and this phenotype was also reliant on interactions with their native microbiota. Our work highlights the complexity of host–microbe interactions and provides evidence that microbial interactions influence mosquito behavior.

scholarly journals A Francisella tularensis Chitinase Contributes to Bacterial Persistence and Replication in Two Major U.S. Tick Vectors

Pathogens ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1037
Author(s):  
Brenden G. Tully ◽  
Jason F. Huntley
Keyword(s):  
Francisella Tularensis ◽  
Alternative Energy ◽  
Vector Competence ◽  
Chitinase Activity ◽  
Dermacentor Variabilis ◽  
Amblyomma Americanum ◽  
Haemaphysalis Longicornis ◽  
Order Of Magnitude ◽  
Transmission Studies

Nearly 100 years after the first report of tick-borne tularemia, questions remain about the tick vector(s) that pose the greatest risk for transmitting Francisella tularensis (Ft), the causative agent of tularemia. Additionally, few studies have identified genes/proteins required for Ft to infect, persist, and replicate in ticks. To answer questions about vector competence and Ft transmission by ticks, we infected Dermacentor variabilis (Dv),Amblyomma americanum (Aa), and Haemaphysalis longicornis (Hl; invasive species from Asia) ticks with Ft, finding that although Aa ticks initially become infected with 1 order of magnitude higher Ft, Ft replicated more robustly in Dv ticks, and did not persist in Hl ticks. In transmission studies, both Dv and Aa ticks efficiently transmitted Ft to naïve mice, causing disease in 57% and 46% of mice, respectively. Of four putative Ft chitinases, FTL1793 is the most conserved among Francisella sp. We generated a ΔFTL1793 mutant and found that ΔFTL1793 was deficient for infection, persistence, and replication in ticks. Recombinant FTL1793 exhibited chitinase activity in vitro, suggesting that FTL1793 may provide an alternative energy source for Ft in ticks. Taken together, Dv ticks appear to pose a greater risk for harboring and transmitting tularemia and FTL1793 plays a major role in promoting tick infections by Ft.

Sign in / Sign up

Export Citation Format

Share Document