Western Gulf Center of Excellence for Vector-borne Diseases Trainee Poster Session

University of Texas Medical Branch

More info: https://www.utmb.edu/wgcvbd/meetings/2021-annual-progress-meeting

Filter displayed posters (50 keywords)

Aedes aegypti 4 Culex quinquefasciatus 3 show more… Adulticide 1 Antiviral immunity 1 Arbovirus 1 Arboviruses 1 Biology 1 Disc Golf 1 Disease Ecology 1 Effective population size 1 Ehrlichia chaffeensis 1 Entomology 1 Field-cage test 1 Flea Surveillance 1 Human Monocytic Ehrlichiosis 1 Internship 1 Intervention 1 Lateral Flow Assays 1 Metabolic resistance 1 Microclimates 1 Permanone quantification 1 Point-of-Care Diagnostics 1 Point-of-care 1 Public Health 1 RNA interference 1 RPA-LF 1 Rickettsie 1 Risk Assessment 1 Serosurveillance 1 Tick surveillance 1 Tick-borne diseases 1 Truck spraying 1 Vector Borne Disease 1 Vector control 1 Vector-Borne Diseases 1 Virology 1 West Nile virus 1 White-tailed deer 1 antigen detection 1 chimeric protein 1 diagnostics 1 human monocytotropic ehrlichiosis 1 kdr 1 pyrethroid resistance 1 tick 1 ultrasensitive diagnosis 1 urban vector control 1 vaccine 1 vector-borne diseases 1 voltage-gated sodium channel 1

Poster: Detection of two co-occurring kdr mutations (V1016I, F1534C) and modeling factors influencing survivorship of Aedes aegypti (L.) from Harris County (Texas) after Permanone® field cage tests.

Detection of two co-occurring kdr mutations (V1016I, F1534C) and modeling factors influencing survivorship of Aedes aegypti (L.) from Harris County (Texas) after Permanone® field cage tests.

Jonathan Hernandez, Michael Longnecker, Chris Fredregill, Mustapha Debboun and Patricia Pietrantonio*

Abstract: Aedes aegypti is a vector of emerging arboviral diseases including Zika, dengue, and chikungunya. Mosquito population abatement with synthetic adulticides, including pyrethroids, is the most employed approach to control disease transmission. The selection of knockdown resistance (kdr) mutations in Ae. aegypti, including V1016I and F1534C, cause pyrethroid insensitivity in the voltage-gated sodium channel (VGSC), which may impede control efficacy. To assess the influence of these kdr mutations on vector control with pyrethroids, females of Ae. aegypti collected from eight mosquito control operational areas in Harris County were treated with the pyrethroid Permanone® 31-66 applied at the maximum operational rate at three distances in field-cage tests. Genomic DNA from these females was analyzed for the two kdr genotypes using melting curve PCR analyses. Females had low survivorship 25 ft from the pyrethroid source, while survivorship increased at further distances. Among mosquitoes analyzed, only 1.7% were the susceptible (VV/FF), while 77.3% of all females were double homozygous resistant (II/CC). These results indicate a widely distributed pyrethroid resistant mosquito population carrying kdr mutations in Harris County, as survivorship among the II/CC, VV/CC, and VV/FF genotypes was statistically different. A logistic regression model supported that area, distance from the treatment source, and cage within each distance influenced survivorship in field tests, but not genotype; this latter result is explained by very high variation among tests from different areas. We conclude that Harris County MVCD’s planned pyrethroid-based arboviral disease control against Ae. aegypti is threatened by the widespread pyrethroid-resistant mosquito population in Harris County.
Presented by: Jonathan Hernandez
Institution: Texas A&M University
Keywords: Aedes aegypti, pyrethroid resistance, kdr, urban vector control, voltage-gated sodium channel

Control your disc! Risk analysis of Ixodid tick Encounters While Disc Golfing

Jessie Merrifield, Michael Hoines

Abstract: Tick surveillance can help identify where and when people may be at the greatest risk for encountering a tick. For our project, we identified disc golf as an increasingly popular sport where tick encounters may be affected by a player's ability. We compared the abundance of questing ticks between the mowed and maintained fairways and the wooded or unmaintained peripheries of two Central Oklahoma disc golf courses. We found a much greater abundance of ticks around the periphery of the disc golf course, where a player with less experience may find their disc landing more frequently.
Presented by: Jessie Merrifield
Institution: University of Oklahoma, Department of Biology
Keywords: Risk Assessment, Disc Golf

Poster: Evaluation of truck-based adulticide spraying on Culex quinquefasciatus abundance and infection with West Nile virus in Harris County, Texas

Evaluation of truck-based adulticide spraying on Culex quinquefasciatus abundance and infection with West Nile virus in Harris County, Texas

Charlotte G. Rhodes, Luis F. Chaves, Maximea E. Vigilant, Mustapha Debboun, Rudy Bueno Jr., Chris Fredregill, Gabriel L. Hamer

Abstract: Since its introduction in 2002, West Nile virus (WNV) has been reported annually in Harris County, Texas. To mitigate infection, the Harris County Public Health Mosquito and Vector Control Division (HCPH MVCD) routinely conducts truck-based adulticide spraying. Previous studies in Harris County have investigated the development of insecticide resistance, insecticide class, and trap type. However, none have evaluated the long-term efficacy of adulticide application. This study utilizes a time series analysis to characterize the monthly and weekly influence of adulticide application on Culex quinquefasciatus abundance and infection over an eighteen-year period. We report preliminary findings from gravid trap data and note an association between Cx. quinquefasciatus abundance and infection with WNV six and three months post-spraying. However, these findings only address the long-term effects of adulticide application. As such, further analysis is needed before drawing any conclusions regarding the overall efficacy of Harris County’s truck-based adulticide program. Future studies should focus on the immediate effects of adulticide application, as opposed to the long-term effects, quantify reduction in abundance and WNV infection following spraying, and characterize the percent of area covered by a spraying event.
Presented by: Charlotte Rhodes
Institution: Texas A&M University
Keywords: Adulticide, Truck spraying, Culex quinquefasciatus, West Nile virus

Keeping Tabs on Ticks and Typhus in Texas and the Surrounding Areas

Mendell NL, Mastrud N, Teel PD, Bouyer DH, and WGCVBD Tick Group

Abstract: The infrastructure and continuity of tick-surveillance in the south-central and southwestern United States lags in comparison to areas with high incidences of Lyme disease. Due to the parcity of surveillance in this region, the true burden of disease caused by typhus group rickettsiae, spotted fever group rickettsiae, and ehrlichiae is not accurately known. Additionally, the presence of emerging viruses, such as Heartland and Bourbon virus has not been documented, and the distribution and prevalence of ticks infected with these pathogens or of fleas infected with R. typhi has not been determined. In order to address this deficiency, the Western Gulf Center of Excellence for Vector-Borne Diseases (WGCVBD) sought to create a surveillance program to determine the presence of vectors and their pathogens in this region. Through continuously expanding WGCVBD collaborations, ticks have been collected throughout Texas, Arkansas, Oklahoma, and New Mexico. Fleas have been collected along the Texas-Mexico border by collaborators from University of Texas El Paso and University of Texas Rio Grande Valley. Human sera and cord-plasma has been tested from Galveston and El Paso, respectively. The collection has expanded to include more than 25,965 ticks including: Amblyomma americanum, A. maculatum, A. mixtum, A. tenellum, Dermacentor albipictus, D. variabilis, I. scapularis, I. texanus, and R. sanguineus. The majority of tick species in the tick collection, comprising 89.9%, are A. americanum, which is the most common tick to parasitize humans in the southern United States. A. americanum, the lone star tick, is capable of transmitting pathogens that cause a multitude of diseases including ehrlichiosis, rickettsiosis, tularemia, and Heartland virus. In this study we have identified by molecular means the presence of Rickettsiae, Ehrlichiae, and Borrelia including endosymbionts, human pathogens, and those of unknown human consequence. This passive and active surveillance of arthropods will contribute to our understanding of the ecology of, and factors contributing to, the emergence of ticks, fleas, and their respective pathogens in the south-central United States with additional focus along the border region. Continued prospective clinical surveillance will give additional insight on the presence and prevalence of murine typhus, spotted fever group rickettsioses and ehrlichiosis on the Texas-Mexico border. Additionally, utilizing investigative methods of diagnosis in the research setting, such as cross-absorption serology, cultivation of Rickettsial isolates, PCR and sequencing will contribute to our understanding of the impact of these infectious diseases on the residents of these areas. Although the current surveillance is important and will contribute valuable knowledge to our understanding of ticks and fleas and their pathogens in the south-central United States, the networking and training of scientists and the public health community involved in this project is invaluable for continued surveillance.
Presented by: Nicole Mendell
Institution: University of Texas Medical Branch
Keywords: Tick surveillance, Flea Surveillance, Serosurveillance

Surveillance for Tick- and Flea- Borne Rickettsiacea Along the Texas-Mexico Border and Other Areas of Texas

Karen R. Valdez1; Azul Silveyra1; Ischack Morales1; Queenie trinh1; Celinda Crews1; Kenneth Waldrup, DVM, Ph.D.2; and Douglas M. Watts, Ph.D.1

Abstract: Abstract: Ticks and fleas are a global health concern due that they are vector and reservoirs of important pathogens that are the cause of severe and fatal diseases of man and animals. The only reported hard ticks that bite humans in the Chihuahuan Desert is Rhipicephalus sanguineus which can transmit Rickettsia rickettsi, Of the Spotted Fever Group, R. rickettsia is te cause of the most lethal disease. Little is known about flea distribution along the Texas- Mexico border and other areas of Texas. The goal of this research is to conduct tick and flea surveillance in the Chihuahuan desert to determine species diversity to better understand tick and flea species abundance and the geographic distribution of potential vectors. The information will provide a preliminary understanding of the public health risk based on existing information from other regions on the medical importance of potential vector species found in the West Texas region. Ticks and Fleas were collected from August 2019 through September 2021. Tick and Flea surveillance preliminary results show that the only tick species captured and identified is Rhipicephalus sanguineus. On the other hand, three flea species have been captured and identified: Ehidnophaga gallinacea, Pulex irritants and Ctenocephalides felis. These field collected samples were tested through Polymerase Chain Reaction (PCR) and the preliminary results were negative for the presence of the pathogen causing Rickettsia in El Paso, Texas. A total of 141 ticks were collected from feral swine in Travis County, Texas from 2018 to 2020 (83 Ixodes Scapularis, 58 Amblyomma americanum), 13 out of 53 pools were positive for Rickettsia using PCR assay. A total of 207 ticks were collected in Travis County, Texas from 2018 to 2020 (196 Ixodes scapularis 11 Dermacentor albipictus),24 out of 67 pools were positive for Rickettsia using PCR assay. All positive pools for Rickettsiae species will be verified by further analysis.
Presented by: Karen Valdez <kvaldez5@miners.utep.edu>
Institution: University of Texas El Paso
Keywords: Rickettsie, Tick-borne diseases, vector-borne diseases

Environmental Factors Influencing Aedes aegypti Populations in Two Communities Along the U.S.-Mexico Border

Adam J. Vera 1; Albert G. Soliz 1; Cindy Crews 1; Xiagang Su 2; Antonio De la Mora 3; Dourglas M. Watts 1

Abstract: The mosquito species, Aedes aegypti, is most commonly found in tropical and subtropical regions and is the primary vector of urban dengue, Chikungunya, Zika, and yellow fever viruses. However, the range currently extends into the temperate region, such as the Southern United States. While Ae. aegypti inhabits the communities of El Paso, Texas and Ciudad Juárez, Mexico, very little is known about the biology of this species. In anticipation dengue, Zika, and Chikungunya viruses could be introduced into these communities, this study was conducted to determine the environmental factors that influence Ae. aegypti populations in two unincorporated communities along the U.S.–Mexico border of Sparks in El Paso, Texas United States and Anapra, Ciudad Juárez, Chihuahua, Mexico to better asses potential spread of these mosquito-borne disease in this region. Two gravid traps were placed at each collection site (70 houses per community), one inside and one outside of the selected houses, for a 24-hour time period bi-weekly, from June to December 2016 to 2018. EasyLog data loggers and Davis Instruments weather station were used to record temperature, humidity, and rainfall to along with a Poisson Model with Mixed-Effects analysis was conducted to the compare mosquito abundance during weather fluctuations. Ae. aegypti were identified from the same trap night and trap-site. During this 3-year study the community of Sparks had a significant increase (p-value<0.05) during the rainy season of July – September. In addition, a decrease in temperature resulted in negative impacts on this mosquito population (p-value=0.07779). An increase in humidity in this community significantly increased the mosquito population (p-value<0.05). Similar to Sparks, the mosquito population increased in Anapra (p-value<0.05). Similarly, a decrease in temperature negatively impacted the mosquito population in Anapra (p-value=0.08441). Overall, an increase or decrease of either temperature or humidity alone did not exclusively result in population increases in both communities, a cumulation of various environmental factors occurring during the rainy season increased overall Ae. aegypti abundance.
Presented by: Adam J. Vera
Institution: 1) The University of Texas at El Paso, Department of Biological Sciences; 2) The University of Texas at El Paso, Department of Mathematical Sciences; 3) Universidad Autónoma de Ciudad Juárez, Departamento de Ciencias Biológicas
Keywords: Aedes aegypti, Vector-Borne Diseases, Disease Ecology

Project 6: Ultrasensitive Antibody and Antigen Detection for Human Ehrlichiosis

Jignesh Patel, Xiaofeng Zhang, Jonathan Schmitz, Richard Willson, David Walker, and Jere W. McBride

Abstract: Human monocytotropic ehrlichiosis (HME) is a tick-borne emerging disease and one of the most prevalent life-threatening zoonoses in the United States. HME results in patient hospitalization in 50-70% of cases and has a fatality rate of 3% due to inaccurate diagnosis and delays in treatment. HME is caused by an obligately intracellular bacterium, Ehrlichia chaffeensis (E.ch). Clinical diagnosis of HME is usually confirmed by detection of Ehrlichia-specific antibodies in patient sera using an indirect fluorescent antibody assay (IFA). Presently, there are no point-of-care (POC) antigen detection tests for HME diagnosis. Our laboratory has characterized secreted effector proteins including TRP120, TRP47 and TRP32 and reported that they are expressed at high levels during infection. Hence, TRPs are likely circulating in the peripheral blood and potential diagnostic biomarkers. In this study, we developed and optimized a sensitive colorimetric sandwich antigen capture ELISA, which can detect the presence of TRP32 and TRP120 antigens in the nanogram range (≤ 40 pg). We also developed an ultrasensitive chimeric protein by combining highly immuno-reactive epitopes of TRP32 and TRP120, which produced improved sensitivity compared to individual peptides. We also identified novel E.ch proteins which can detect antibodies in the acute HME patient sera. With these multiple ultrasensitive detection approaches, we anticipate that an assay that provides rapid, sensitive and specific detection of E. chaffeensis can be developed for POC and reference laboratory settings.
Presented by: Jignesh Patel
Institution: University of Texas Medical Branch, Department of Pathology
Keywords: ultrasensitive diagnosis, antigen detection, chimeric protein, human monocytotropic ehrlichiosis, Ehrlichia chaffeensis

Arbovirus-Entomology Internship

Cassandra Durden

Abstract: This summer, I applied for a funded student internship through the UTMB Western Gulf Center of Excellence for Vector Borne Diseases. I was ultimately selected as the intern for the Arbovirus-Entomology Laboratory at the Texas Department of State Health Services. In this position, I learned numerous methods of arboviral diagnostic testing as well as mosquito species identification and insecticide resistance testing. I was also exposed to the day-to-day life of a public health employee and learned about the background and experiences of my mentors. I am very thankful for this opportunity and am excited to apply the knowledge I learned throughout this experience in my graduate studies.
Presented by: Cassandra Durden
Institution: Texas A&M University
Keywords: Internship, Virology, Arbovirus, Public Health, Vector Borne Disease

Lateral Flow Assay Development for Point-of-Care Diagnosis of Human Monocytic Ehrlichiosis

Adheesha Danthanarayana(1), Jignesh Patel(4), Katerina Kourentzi(2), Binh Vu(2), Jakoah Brgoch(1), Jere McBride(4), Richard Willson(2,3)

Abstract: Human Monocytic Ehrlichiosis (HME) is an emerging life-threatening zoonosis caused by a type of bacteria known as Ehrlichia chaffeensis and it is transmitted to humans by the bite of the Lone Star tick. The number of cases reported to CDC has increased steadily since the first year of disease reporting and it has become the most prevalent life-threatening tick-borne disease in the US with a predominant prevalence in the South-eastern and South-central United States, from the East Coast extending westward to Texas. Symptoms include fever, headache, myalgia, nausea, confusion, chills, and rash at early stages, and meningitis, acute respiratory distress syndrome, and cardiac problems at late stages. Prompt diagnosis, therefore, is important to improve outcomes. We developed two different types of lateral flow assays (LFAs) for the point-of-care (POC) diagnosis of HME that can help in implementing appropriate treatment at earlier stages of the disease. Lateral flow assays are well known e.g., for their use in home pregnancy tests, due to their simple, rapid, affordable, and user-friendly nature. We first developed a direct antigen- detection lateral flow assay for the detection of Ehrlichia Tandem Repeat Proteins (TRPs), major immunoreactive secreted effector proteins that elicit protective immune responses. They are highly-expressed and abundantly secreted extracellularly and can serve as the target for POC diagnostics. A chemiluminescent reaction similar to that of glow sticks was used to detect fluorescent reporter particles bound in the LFA, and the resulting fluorescence imaged using a smartphone. This assay shows high sensitivity in 40% human serum with detection limits of 1 ng/mL and 5 ng/mL for TRP 32 and TRP 120, respectively. More recently, the McBride laboratory at UTMB also discovered that proteins expressed by E. chaffeensis in the tick host and injected into humans by tick bites can produce a detectable serological response early enough in the course of disease to be clinically- actionable. One of these tick-expressed proteins, A9, is being used to develop a serological lateral flow assay that can afford faster diagnosis and detect asymptomatic or latent infections. The enzyme-based colorimetric response of initial LFA can detect 1 µg/mL rabbit anti-A9 antibody in buffer and 100 µg/mL anti-A9 antibody in 40% human serum. Further optimization is in progress to improve the sensitivity of this assay for use in point-of-care settings.
Presented by: Adheesha Danthanarayana
Institution: (1) Department of Chemistry, University of Houston (2) Department of Chemical and Biomolecular Engineering, University of Houston (3) Department of Biology and Biochemistry, University of Houston (4) The University of Texas Medical Branch at Galveston
Keywords: Human Monocytic Ehrlichiosis, Point-of-Care Diagnostics, Lateral Flow Assays

The Effect of Vector Control on Mosquito Populations in Harris County: from Effective Population Size and Metabolic Resistance Profile

Xinyue Huang, Kendra Dagg*, Chris Fredregill* and Michel A Slotman

Abstract: Insecticide-based approaches play dominant roles in the control of vector-borne diseases. Culex quinquefasciatus is a principal vector of several mosquito-borne diseases. In Harris County, Texas, this mosquito is subjected to extensive insecticide-based control by the Harris County Public Health Department. This research is aimed to estimate the impact of vector control efforts on mosquito populations in Harris County from effective population size and metabolic resistance profile. The effective population size (Ne) of Houston C. quinquefaciatus population was estimated with approximate Bayesian computation (ABC) based method. The core idea of ABC based method is to calculate the posterior probabilities of different historical scenarios and the posterior distributions of the demographic parameters under a specific scenario. Posterior probabilities and distributions are determined by measuring the similarity between the observed dataset and millions of simulated datasets. C. quinquefaciatus were collected from two areas (area 415 and area 802) of Harris County. Adult mosquitoes were collected from 4 to 5 timepoints for 2016 and 2017 for both locations. There were extensive control efforts in area 802 during the summer of 2016, whereas no organized control was applied to area 415. 95 individuals were sampled for each timepoint per area. The genomic DNA of each sample was extracted. All samples were then genotyped for 15 previously published microsatellite loci. Formatted genotyping data were input DIYabc, a software package that allows comprehensive historical demographic analysis with microsatellite data. Many prior historical model settings were explored to infer the impact of extensive vector control applied in Harris County. Unfortunately, we were not able to get resolution to answer this question. In our current projects, there were basically four scenarios defined and tested, including bottleneck, expanding, contracting and constant. The change of Ne within one year was found following a population bottleneck at both two areas, specifically, expanding in summer and then contracting in winter. A 10-fold reduction in Ne was detected in area 415 while a 4-fold reduction was detected in area 802. Our results indicate that Ne of C. quinquefaciatus population in Houston is more likely to be affected by seasonal factor compared to vector control efforts. In order to assess to what extent C. quinquefasciatus has developed metabolic resistance against insecticides we conducted a gene expression analyses of detoxification gene families between susceptible and resistant mosquitoes. C. quinquefasciatus were sampled from Harris County in 2019. Mosquitoes were classified into ‘malathion resistant’ and ‘malathion susceptible’ groups based on a standard WHO bottle assay. RNAseq data was obtained for five pools of 10 mosquitoes for each group. In addition, RNAseq data was obtained for five pools of 10 field collected C. quinquefaciatus and susceptible Sebring colony samples. After filtering low-quality data, differential gene expression in EdgeR found more than 1,339 differential expressed genes in comparison between insecticide resistant and susceptible groups, and more than 1,915 differential expressed genes in comparison between wild and susceptible groups in Culex mosquito. We focus on 240 genes from three major gene families correlated with metabolic resistance, including P450, GST and esterase. Within these, we identified 14 candidates from the three gene families, some of which were also reported before (e.g., P4509AL1, P4509M12, P4509M10-de1b, P45012F9, P450325BC1 and P4504J20). Several of these candidate genes were implicated in insecticide resistance previously. For others we will validate their role in metabolic resistance using RNAi. This work will assist in planning future vector control work.
Presented by: Xinyue Huang
Institution: Texas A&M University, *Mosquito and vector control division, Harris County Public Health
Keywords: Culex quinquefasciatus, Vector control, Effective population size, Metabolic resistance

Population Dynamics of Hard Ticks in Southeastern Arkansas 2020-2021

Ty Say, Taylor Ludwig, Mark Hairston, Keith Blount

Abstract: Tick populations have increased, and their geographic range is expanding in the United States. At the start of this study in 2020, no other studies that met the definition of active surveillance had been completed in Arkansas for 9 years. The lone star tick, Amblyomma americanum, was the most abundant species collected with a total of 1796 ticks collected. Additional species observed was A. maculatum (67 ticks), Dermacentor variablis (127 ticks), and Ixodes scapularis (188 ticks). In this study we examined the prevalence of tick populations in southeast Arkansas over a period of 14 months. More research is needed to assess the populations in southeast Arkansas and well as surrounding areas.
Presented by: Ty Say
Institution: University of Arkansas at Monticello, Department of Biology
Keywords: Biology, Entomology

Poster: Testing the Immunogenicity of Tick Salivary Protein Vaccine Targets for White-tailed Deer (Odocoileus virginianus) targeting Ixodes scapularis

Testing the Immunogenicity of Tick Salivary Protein Vaccine Targets for White-tailed Deer (Odocoileus virginianus) targeting Ixodes scapularis

Alec Baker, Tammi Johnson, Albert Mulenga, Pia Olafson

Abstract: White-tailed deer (Odocoileus virginianus) are the primary host for adult blacklegged ticks (Ixodes scapularis). The population increase of white-tailed deer in the twentieth century has correlated with the rise of various tick-borne pathogens that are known to be spread by blacklegged ticks and other species of ticks. White-tailed deer play a vital role in the reproductive success of these ticks since they are the main bloodmeal host for the adult life stages. Previous studies targeting white-tailed deer for tick control suggest that deer-targeted interventions have the potential to decrease human tick-borne disease incidence. However, current methods of targeting white-tailed deer for tick control pose issues and are not sustainable options. Therefore, determining an effective immunization dosage of the candidate tick salivary antigen-based cocktail to develop an anti-tick vaccine that will only need to be administered to the host one-time has vital implications. Effective anti-tick immunization of white-tailed deer should be protective for the duration of the host’s life. Standard immunization protocols that require animals to be immunized more than once are not feasible when immunizing wildlife, as it is challenging to identify and capture individuals for a follow up vaccine booster. A single dose vaccine that can reduce tick feeding success and reduce tick fecundity has important implications for the human-wildlife disease interface and in future research and management targeting ticks and tick-borne disease in the livestock-wildlife interface.
Presented by: Alec Baker <abaker5569@tamu.edu>
Institution: Texas A&M University
Keywords: White-tailed deer, tick, vaccine

Aedes aegypti projects in the Rio Grande Valley, TX: ADS intervention, indoor quantification, (over)compensation

Nicole A. Scavo & Dr. Gabriel L. Hamer

Abstract
Presented by: Nicol Scavo
Institution: Texas A&M University, Department of Entomology
Keywords: Intervention, Aedes aegypti

Effect of cooler temperatures on the susceptibility of Aedes aegypti to Zika virus

Tyler D. Pohlenz, Zach N. Adelman, Byul Hur, Madhav Erranguntla, Martin Reyna, Mustapha Debboun, Chris Fredregill, Jeremey Vela, and Kevin M. Myles

Abstract: Our ability to develop predictive models capable of accurately forecasting epidemics of mosquito-borne viral diseases is limited by, among other things, a relatively poor understanding of the abiotic factors influencing the dynamics of virus transmission. In particular, there is a paucity of information regarding how the spatial temperature ranges occurring in the heterogeneous microclimate environments where ectothermic mosquitoes breed and rest affect vector competence. To begin exploring how the exposure of vector species to heterogeneous microclimates might influence disease transmission, we conducted a series of experiments to determine if Aedes aegypti held under different constant temperatures during various developmental stages exhibited evidence of an impaired RNA interference (RNAi) pathway, the primary antiviral defense of the insect. Interestingly, we demonstrated inhibition of RNAi in Ae. aegypti adults reared at temperatures similar to those commonly recorded in microhabitats near mosquito trap sites located throughout urban areas of Harris County, Texas. Further, exposure of only the aquatic pupal stage to lower temperatures significantly impaired the RNAi pathway in adults. As pupal development typically takes only a few days, and pupae are confined to a specific microclimate, typically a small container of water, these results may have significant implications for understanding how the thermal environment of the vector influences disease transmission. Overall, these results suggest that exposure of Ae. aegypti to low diurnal temperatures over relatively short durations, particularly during the relatively immobile aquatic stages of development, may compromise the antiviral immunity of this important disease vector, increasing the potential for virus transmission.
Presented by: Tyler Pohlenz
Institution: Texas A&M University
Keywords: RNA interference, Antiviral immunity, Aedes aegypti, Microclimates

Permanone® 31-66 quantification during Culex quinquefasciatus field-cage test

Han-Jung Lee, Michael Shield, Miguel Saldaña, Maximea Vigilant, Chris Fredregill and Patricia V. Pietrantonio

Abstract: Permanone® 31-66 is a pyrethroid-based adulticide applied to control Culex quinquefasciatus, a vector of West Nile Virus, in virus-positive areas of Harris County. To assess the field control efficacy of Permanone®, Harris County Public Health designed a field-cage test (FCT) simulating the field application scenario. In a previous study, our logistic regression model predicted that female survival probability was affected by “distance” from the spraying source and by “replicate” within the same distance in the FCT, but not by mosquito’s kdr genotypes (Lee et al., 2020). Therefore, we hypothesized that the variation of Permanone® quantities at different distances and replicates affected the female survival probability. To collect deposited Permanone® in the FCT, weighing boats were hung on replicates I-III from 100 to 300 feet from the source, and Permanone® from boats was quantified by GC/MS with a robust standard curve (R2=0.9952). The highest Permanone® quantity was detected at 100 feet where there were no female survivors, and quantities decreased with the increased distance from the source. Within the same distance, the variation of Permanone® quantities among replicates explained the female survival, i.e., at 200 feet, 237.6 ng/cm2 Permanone® detected from replicate I allowed 10-20% survival of field-collected females, while 343.6 ng/cm2 from replicate III killed all females. The methodology was sensitive to quantify the deposited Permanone® even at 300 feet, which varied from 10.77 to 45.84 ng/cm2 among replicates, congruent with their high female survivorship, from 100% to 21%. This result indicates the field mosquito control efficacy could be improved by modifying the field application methods to increase the amount of Permanone® deposited at 300 feet.
Presented by: Han Jung Lee
Institution: Texas A&M University, Department of Entomology
Keywords: Permanone quantification, Culex quinquefasciatus, Field-cage test

No evidence of SARS-CoV-2 associated with flies and cockroaches in COVID-19 positive households

Christopher M. Roundy, Sarah A. Hamer, Italo B. Zecca, Edward B. Davila, Lisa D. Auckland, Wendy Tang, Haley Gavranovic, Sonja L. Swiger, Jeffrey K. Tomberlin, Alex Pauvolid-Correa, Gabriel L. Hamer

Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 resulting in a pandemic of coronavirus disease (COVID-19), which continues to cause infections and mortalities worldwide. SARS-CoV-2 is transmitted via respiratory droplets and aerosol and has experimentally been found to be stable on surfaces for up to multiple days. Flies (Diptera) and other arthropods mechanically transmit a number of pathogens, including turkey coronavirus. A previous experimental study demonstrated house flies, Musca domestica, can mechanically transmit SARS-CoV-2 RNA, but the ability of flies in general to acquire and deposit this virus in the natural settings has not been explored. The purpose of this study was to evaluate the potential for using biting and non-biting flies a xenosurveillance tool for detection of SARS-CoV-2 and explore the possibility of mechanical transmission of the virus.
Presented by: Chris Roundy
Institution: Texas A&M, Department of Entomology
Keywords

A DIAGNOSTIC PLATFORM BASED ON RECOMBINASE-POLYMERASE AMPLIFICATION FOR DETECTION OF ARBOVIRAL INFECTIONS.

Shelite Thomas R(1), Aguilar Patricia(2), Pando Victoria(4), Abelardo Moncayo(5), Carlos Machain-Williams(6), Castellanos Alejandro(1), Melby Peter(1,2, 3), Travi Bruno(1,3).

Abstract: Vector-borne viral epidemics are becoming progressively frequent due to unplanned urbanization that favors vector-breeding sites and increased international mobility, which promotes virus introduction to new regions. The availability of rapid, easy to use molecular tests for diagnosing arboviral infections would lead to timely patient management. Our laboratory utilized isothermal recombinase-polymerase amplification (RPA) for detection of viral nucleic acids and reading of results with the naked eye using lateral flow (LF) strips. RPA-LF tests have potential as a point-of-care (POC) test because they do not require sophisticated equipment or complex laboratory infrastructure. We developed assays for viruses transmitted by mosquitoes (Chikungunya [CHIKV], Dengue [DENV], West Nile [WNV], and Zika [ZIKV]) or ticks (Heartland [HRTV]). The analytical sensitivity of each test was determined by serially diluting the viruses in human serum prior to RNA extraction and subsequent cDNA conversion. For assessing RPA-LF specificity, regionally relevant and genetically similar viruses were included in parallel RPA-LF assays. CHIKV spiked in serum detected as few as 1.8 pfu equivalents/100 µL of serum. The DENV assay for serotypes 1-3 had a limit of detection (LOD) of 1.43 pfu equivalents/reaction, while DENV 4 was less sensitive (13.73 pfu equivalents/reaction). The WNV RPA had an LOD of 3.13 pfu equivalents/reaction from spiked serum. The test achieved good sensitivity for ZIKV (0.462 pfu equivalent/100 µL of serum) and HRTV (1.54 pfu equivalent/100 µL of serum). All assays have 100% specificity as currently tested. We evaluated the diagnostic sensitivity of RPA-LFs using a small number of clinical samples positive for CHIKV (n= 6), HTRV (n= 6), and ZIKV (n= 3). We determined that CHIKV and ZIKV RPA-LF had 100% concordance with qPCR (reference test) while HRTV had 83.3% concordance. Further diagnostic validation of the tests using large numbers of clinical samples is still necessary. Nevertheless, the current results indicated that RPA-LF could be an alternative to diagnose arboviral infections in decentralized laboratories and have potential for implementation as POC tests.
Presented by: Tom Shelite
Institution: 1Department of Internal Medicine-Division of Infectious Diseases; 2Department of Pathology. 3Department of Microbiology and Immunology; University of Texas Medical Branch, Galveston (UTMB). 4Centro de Investigación sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, México. 5The Tennessee Department of Health. 6Laboratory of Arbovirology, Regional Research Center Dr. Hideyo Noguchi, Autonomous University of Yucatan, Mexico.
Keywords: Arboviruses, diagnostics, RPA-LF, Point-of-care