Biology subjects

Estep, A.

Publications and source records attributed to Estep, A..

3 recordsLinked to original sources

bioRxiv2025

Host usage in Aedes aegypti collected from Houston, Texas and Phoenix, Arizona using whole mosquito third-generation sequencing blood meal analysis

Aedes aegypti is the primary vector of several viruses of international public health concern, including Zika, dengue, yellow fever, and chikungunya. Their synanthropic ecology and establishment in tropical, sub-tropical, and temperate areas make Ae. aegypti one of the most medically relevant mosquito species. While they have been reported to be highly anthropophilic, several studies indicate a broader host range. They are also reported to take multiple blood meals between gonotrophic cycles. Consumption of multiple blood meals makes determination of host usage difficult when using common blood meal analysis methods. In this study, we examined host usage of Ae. aegypti in Harris County, Texas (Houston), and Maricopa County, Arizona (Phoenix), using a Nanopore-based third-generation sequencing protocol to successfully resolve host usage multiplicity and identify a broad range of host usage. Using this method, approximately 80% of samples from each location with evidence of blood feeding resulted in a blood meal species identification, with a single host blood meal in about 80% of samples and approximately 20% containing evidence of multiple blood meals. Overall, we observed a wide host range with human DNA the most prevalent followed by feline and canine. We also identified avian, rodent, ungulate and even ectotherm usage by Ae. aegypti from Maricopa County. The discovery of hosts other than humans expands the understanding of host usage dynamics in Ae. aegypti and their involvement in arbovirus transmission systems in highly urbanized areas such as Harris and Maricopa Counties. SynopsisThe yellow fever mosquito, Aedes aegypti, is a vector of several viral pathogens that frequently cause human disease in tropical and subtropical locations but many of these pathogens are not controlled by vaccination. As such, control of this mosquito is critical to reduce disease transmission and better understanding of the ecology of this species helps to improve the efficacy of operational control. In this study, researchers used a deep sequencing method to define patterns of host usage in two large US metropolitan areas, Houston, TX and Phoenix, AZ, with substantial Ae. aegypti infestations. Results identified frequent multiple blood feeding by individual mosquitoes and that the primary host sources were humans and their pets. Results from Phoenix indicated a broad host usage, including feeding on livestock, birds, and even reptiles. This may provide useful information about Ae. aegypti resting sites and could be used to improve treatment by operational personnel.

ecology↗

bioRxiv2022

Assessing pyrethroid resistance status in the Culex pipiens complex (Diptera: Culicidae) from the northwest suburbs of Chicago, Illinois using Cox regression of bottle bioassays and other detection tools

Culex pipiens complex is an important vector of epizootic and zoonotic pathogens, including West Nile virus. Chicago, Illinois and its suburbs have suffered high incidence of human West Nile virus infections in the past. This makes abatement programs in and around the Chicago area an essential service. The control of Cx. pipiens is often complicated by rapidly evolving resistance to pyrethroids, which are the most widely used chemical class in US mosquito abatement programs. The present study assessed Sumithrin(R) resistance in Cx. pipiens collected from five locations around Cook County, Illinois, neighboring the city limits of Chicago. According to CDC guidelines, samples from all five locations demonstrated some resistance to Sumithrin(R). When assessed with Anvil(R), a formulated product made of Sumithrin(R) synergized with piperonyl butoxide, susceptibility was rescued in mosquitoes from three out of the five locations, suggesting involvement of mixed-function oxidases and/or carboxylesterases in Sumithrin(R) resistance at these locations. Not all locations had susceptibility rescued by Anvil(R), but these locations had relatively low knockdown resistance allele frequencies, suggesting that mechanisms other than knockdown resistance may be involved. Enzyme activities did not reveal any marked trends that could be related back to mortality in the bottle bioassays, which highlights the need for multiple types of assays to infer enzymatic involvement in resistance. Future directions in pyrethroid resistance management in Chicago area Cx. pipiens are discussed.

pharmacology and toxicology↗

bioRxiv2018

Quantification of permethrin resistance and kdr alleles in Florida strains of Aedes aegypti (L.) and Aedes albopictus (Skuse)

Recent outbreaks of locally transmitted dengue and Zika viruses in Florida have placed more emphasis on the importance of integrated vector management plans for Aedes aegypti (L.) and Aedes albopictus Skuse. Adulticiding, primarily with pyrethroids, can be the best option available for the immediate control of potentially arbovirus-infected mosquitoes during outbreak situations. While pyrethroid resistance is common in Ae. aegypti worldwide and testing is recommended by CDC and WHO, resistance to this class of products has not been widely examined or quantified in Florida. To address this information gap, we performed the first study to quantify both pyrethroid resistance and genetic markers of pyrethroid resistance in Ae. aegypti and Ae. albopictus strains in Florida. Using direct topical application, we examined 21 Ae. aegypti strains from 9 counties and found permethrin resistance (resistance ratio (RR)=6-61-fold) in all strains when compared to the susceptible ORL1952 control strain. Permethrin resistance in five strains of Ae. albopictus was very low (RR<1.6) even when collected from the same containers producing resistant Ae. aegypti. Characterization of two sodium channel kdr alleles associated with pyrethroid-resistance showed widespread distribution in 62 strains of Ae. aegypti. The 1534 phenylalanine to cysteine (F1534C) single nucleotide polymorphism SNP was fixed or nearly fixed in all strains regardless of RR. We observed much more variation in the 1016 valine to isoleucine (V1016I) allele and observed that increasing frequency of the homozygous V1016I allele correlates strongly with increased RR (Pearson corr= 0.905). In agreement with previous studies, we observed a very low frequency of three kdr genotypes, IIFF, VIFF, and IIFC. In this study, we provide a statewide examination of pyrethroid resistance, and demonstrate that permethrin resistance and the genetic markers for resistance are widely present in FL Ae. aegypti. Resistance testing should be included in an effective management program.\n\nAuthor SummaryAedes aegypti and Aedes albopictus can vector a variety of arboviruses that cause diseases and are thus a public health concern. Pyrethroid insecticide resistance is common in Aedes aegypti in many locations worldwide and can adversely affect vector control operations. However, the resistance status of these vectors in Florida is largely unreported and recent local transmission of dengue and Zika viruses has made this information critical for effective control operations. In this study, we showed that permethrin resistance and two common SNPs of the voltage gated sodium channel (V1016I and F1534C) previously associated with pyrethroid resistance were widely present in Florida Aedes aegypti strains. We also observed a strong correlation between the IICC genotype and RR as determined by topical application, which suggests, as have others, that kdr frequency may be a useful indicator of resistance in Aedes aegypti.

genetics↗