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Blacklegged ticks (Ixodes scapularis Say) pose an enormous public health risk in eastern North America as the vector responsible for transmitting 7 human pathogens, including those causing the most common vector-borne disease in the United States, Lyme disease. Species distribution modeling is an increasingly popular method for predicting the potential distribution and subsequent risk of blacklegged ticks, however, the development of such models thus far is highly variable and would benefit from the use of standardized protocols. To identify where standardized protocols would most benefit current distribution models, we completed the “Overview, Data, Model, Assessment, and Prediction” (ODMAP) distribution modeling protocol for 21 publications reporting 22 blacklegged tick distribution models. We calculated an average adherence of 73.4% (SD ± 29%). Most prominently, we found that authors could better justify and connect their selection of variables and associated spatial scales to blacklegged tick ecology. In addition, the authors could provide clearer descriptions of model development, including checks for multicollinearity, spatial autocorrelation, and plausibility. Finally, authors could improve their reporting of variable effects to avoid undermining the models' utility in informing species–environment relationships. To enhance future model rigor and reproducibility, we recommend utilizing several resources including the ODMAP protocol, and suggest that journals make protocol compliance a publication prerequisite.
VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS
Musca flies (Diptera: Muscidae) have been found culpable in the mechanical transmission of several infectious agents, including viruses, bacteria, protozoans, and helminths, particularly in low-income settings in tropical regions. In large numbers, these flies can negatively impact the health of communities and their livestock through the transmission of pathogens. In some parts of the world, Musca sorbens is of particular importance because it has been linked with the transmission of trachoma, a leading cause of preventable and irreversible blindness or visual impairment caused by Chlamydia trachomatis, but the contribution these flies make to trachoma transmission has not been quantified and even less is known for other pathogens. Current tools for control and monitoring of house flies remain fairly rudimentary and have focused on the use of environmental management, insecticides, traps, and sticky papers. Given that the behaviors of flies are triggered by chemical cues from their environment, monitoring approaches may be improved by focusing on those activities that are associated with nuisance behaviors or with potential pathogen transmission, and there are opportunities to improve fly control by exploiting behaviors toward semiochemicals that act as attractants or repellents. We review current knowledge on the odor and visual cues that affect the behavior of M. sorbens and Musca domestica, with the aim of better understanding how these can be exploited to support disease monitoring and guide the development of more effective control strategies.
Anopheles coluzzii (Coetzee & Wilkerson) and its sibling species Anopheles gambiae s.s. (Giles) are highly anthropophilic and among the major malaria vectors in sub-Saharan Africa. Mosquitoes use various senses to find hosts, but rely primarily on olfaction. Therefore, the mosquito olfactory system has been studied extensively, including a variety of studies comparing chemosensory gene expression between An. coluzzii and its zoophilic sibling species Anopheles quadriannulatus (Theobald). These studies revealed species-specific chemosensory gene expression in the antennae and maxillary palps, which raised the question of a potential role for the palps in determining species-specific host preferences. To answer this question, we mechanically ablated the antennae, maxillary palps, and labella, and ran both control and ablated mosquitoes through a dual-port olfactometer. While we aimed to identify the organs responsible for vertebrate host choice, the ablated mosquitoes exclusively responded to human odor, so we were unable to do so. However, we were able to refine our understanding of the roles of these organs in host-seeking activation (leaving the release cage) as well as odor response (entering an odor port). As expected, the antennae are the most important organs to both behaviors: activation was roughly halved and vertebrate odor response was abolished in antennae-ablated mosquitoes. Maxillary palp ablation had little impact on activation, but reduced odor response to a similar degree as the exclusion of CO2. Finally, while labellar ablation dramatically reduced activation (probably associated with the inability to feed), it had little impact on odor response, suggesting that any labellar role in host choice is likely not olfactory.
Phlebotomine sand flies are important vectors of medical and veterinary importance, transmitting pathogens, such as the Leishmania parasites, responsible for 700,000 to 1 million new cases of leishmaniasis every year. The vast majority of the current sand fly surveillance and control tools are tailored against the adult stages, due to the limited knowledge on the ecology of the larval stages. Since vector control is primarily an ecological problem, an in-depth understanding of the behavior of the target insect pests across all the different life stages of their development is required prior to the development of effective control strategies. It is well known that chemical cues play an important role in insect behavior. While there are numerous studies investigating the behavior of adult sand flies in response to chemical sources, there is currently no information available on the response of their larval stages. In this study, novel bioassays were constructed to investigate the effect of chemical cues (gustatory and olfactory) on the behavior of Phlebotomus papatasi (Scopoli) sand fly larvae. The larvae exhibited a clear food preference within a few hours of exposure in a 2-choice bioassay, while, also, demonstrated positive chemotaxis in response to volatile stimuli emitted from their preferred food source. Identification of the specific chemical compounds (or the combination thereof) eliciting attractance response to sand fly immature stages could lead to the development of innovative, and targeted (larval-specific) tools for the surveillance, and management of these important public health pests.
This study aimed to explore the rate of decomposition of rabbit carcasses and the succession pattern of the associated dipteran flies outdoor, indoor, and on the roof of a 4-story building during the summer and winter. A total of 6,069 flies were recorded, with 30.91% reported as 2 waves outdoor and on the roof in the summer and 69.09% as 4 waves outdoor in the winter. The roof showed the most flies in the summer but the least in the winter, whereas the outdoor showed the most in the winter but the least in the summer. The ground and first floors showed the most indoor flies, while the second and third floors showed the least in both seasons. Indoor carcasses decomposed slower than those outdoor, and those on the second and third floors decomposed slower than those on the ground and first floors. Ten fly species from 8 families were identified in the winter, compared to 6 from 5 families in the summer. The most abundant species was Musca domestica Linnaeus (Muscidae) on the roof in the summer, while it was Chrysomya albiceps (Wiedemannn) (Calliphoridae) outdoor in the winter. The rare species (singletons) were Musca sp. (Muscidae) and Megaselia scalaris (Loew) (Phoridae) on the first floor in both seasons, Scaptomyza pallida (Zetterstedt) (Drosophilidae) on the ground floor in the summer, and Atherigona orientalis Schiner (Muscidae) outdoor in the winter. These data highlight the variance in carcass decomposition and fly composition across outdoor, indoor, and the roof of human dwellings, which could be of forensic importance.
Envenomation by terrestrial toxic animals is considered a serious risk to human health worldwide. Snakes, hymenopterans, spiders, and scorpions have mainly attracted the attention of medical literature. However, the relative importance of spiders has been studied only in a few countries. Here, we present the first retrospective study on the incidence of spider bites requiring hospital care in Spain, compared to bites or stings from snakes, hymenopterans, and scorpions. Using ICD9MC and ICD10 databases from the World Health Organization's International Classification of Diseases for the period 1997–2020, we quantified the cases of envenomation by spiders, compared to those by other terrestrial toxic animals, the demographic data of envenomation cases, the relative severity of spider bites, and the geographic distribution of envenomation cases. Overall, the incidence of acute intoxication by terrestrial toxic animals in Spain was ca. 1.23 cases per million inhabitants. In decreasing order of importance, cases were due to snakes, hymenopterans, spiders, scorpions, and myriapods. Fatal cases were extremely rare, caused mainly by hymenopterans. No fatalities were caused by spiders, scorpions, and myriapods. A greater incidence of snake bites occurred in northern Spain, but no geographical trends were found for spider bites or scorpion stings. Severe poisoning or life-threatening cases due to bites or stings from toxic terrestrial animals in Spain seems to be very low, especially for spiders, compared to other countries in the world. In general, spiders do not present a risk to human health and should not be considered a major driver of morbidity.
José Manuel Macário Rebêlo, Maria da Conceição Abreu Bandeira, Jorge Luiz Pinto Moraes, Itapotiara Vilas Boas, Raquel Silva Fonteles, Leonardo Dominici Cruz, Bruno Leite Rodrigues
Numerous sand fly species have been reported in Lençóis Maranhenses National Park (LMNP) in Northeast Brazil, including important Leishmania vectors, making the park an endemic area for tegumentary and visceral leishmaniasis. We evaluated sand fly abundance monthly over 7 years, correlating it with environmental variables and monthly tourist numbers in LMNP. Sand fly species were observed throughout the year, with Lutzomyia longipalpis Lutz & Neiva and Nyssomyia whitmani Antunes and Coutinho (Diptera: Psychodidae) being the most abundant species, especially from April to June. In addition to seasonal abundance patterns, Lu. longipalpis showed increasing abundance throughout 2013 until April 2014, whereas Ny. whitmani exhibited a consistent increase throughout the study period. Redundancy analysis indicated that monthly sand fly abundances increased with humidity but decreased with mean temperature and wind speed. Ecotourists mainly visit the park from May to September when interdune lagoons are full, coinciding with high-frequency vector activity during the rainy months (May–June). Tourists also visit in January and February during school holidays, when the rains begin and sand fly abundance increases, and in July, when sand fly abundance decreases. To date, no instances of infected tourists have been recorded, likely because visits to LMNP occur during the day when sand flies are inactive. However, there is a potential risk of vector exposure if tourists engage in nighttime cultural visits to villages around the park, where leishmaniasis cases occur annually.
Hiking is a popular recreational activity in North Carolina that may expose people to ticks and tick-borne pathogens. However, there is a lack of knowledge on how ticks are distributed on and near trails. Our study tested the hypothesis that ticks are more likely to be encountered when moving further away from trails by measuring differences in relative abundance at various distances. We tested 4 distances (middle of trail, edge of trail, 5 m, 20 m), as well as an on-trail and off-trail grouping. We collected significantly more ticks and ticks were more likely to be collected at our 20 m and 5 m sampling distances rather than directly on or adjacent to trails, and significantly more were collected during off-trail collections than on-trails. When looking only at Amblyomma americanum, post hoc comparisons revealed that significantly more juvenile stages were collected at 5 m and 20 m distances, but not for adults. Our monthly sampling also allowed us to describe the phenology of A. americanum in North Carolina, which is consistent with the phenology of this species in the southeastern United States with adults peaking May–Jun, nymphs Jun–Jul, and larvae in Jul–Aug. These results generally demonstrate the importance of utilizing established trails when hiking to decrease tick-borne disease risk and should be communicated to the public as a recommendation for reducing tick-encounter risk.
Silvânia Da Veiga Leal, Isaias Baptista Fernandes Varela, Davidson Daniel Sousa Monteiro, Celivianne Marisia Ramos de Sousa, Maria da Luz Lima Mendonça, Adilson José De Pina, Adéritow Augusto Lopes Macedo Gonçalves, Hugo Costa Osório
Mosquitoes play a critical role as vectors of pathogens affecting both humans and animals. Therefore, understanding their biodiversity and distribution is crucial to developing evidence-based vector control strategies. The current study updated the composition and distribution of mosquito species through a comprehensive survey of all municipalities of Cabo Verde. From October 2017 to September 2018, mosquito larvae and pupae were collected from 814 aquatic habitats. Anopheles gambiae (Giles, 1902) and Culex pipiens (Linnaeus, 1758) complexes were subjected to PCR-based techniques for sibling species identification. Ten mosquito species from 5 genera were identified: Aedes aegypti (Linnaeus, 1762), Aedes caspius (Pallas, 1771), Anopheles arabiensis (Patton, 1905), Anopheles pretoriensis (Theobald, 1903), Culex bitaeniorhynchus (Giles, 1901), Cx. pipiens, Culex quinquefasciatus (Say, 1823), Culex tritaeniorhynchus (Giles, 1901), Culiseta longiareolata (Macquart, 1838), and Lutzia tigripes (de Grandpre & de Charmoy, 1901). Santiago Island reported the highest number of species (n = 8). Ae. aegypti and Cx. quinquefasciatus were the most widely distributed species across the country. An. arabiensis was the sole species identified within the An. gambiae complex. The findings from our study will help guide health policy decisions to effectively control mosquito-borne diseases.
We studied chigger and gamasid mite loads on small mammals during the dry season in Vietnam and used both our field data and museum collections to estimate the influence of environmental factors on mite abundance and prevalence. Generalized linear (mixed effect) models were used to analyze the data. We examined 1,239 small mammal individuals, which were obtained from field expeditions and museum collections belonging to 59 species. In different localities, Rattus Fischer (Rodentia: Muridae), Niviventer Marshall (Rodentia: Muridae), and Maxomys Sody (Rodentia: Muridae) were the most common animals captured. The prevalence of chigger and gamasid mites in our expedition data was high: 72% and 62%, respectively. We found differences in the abundance of chigger mites between different populations of the same species of small mammals. Season and locality were the main factors that influenced chigger mite abundance and prevalence. The best model that predicted the abundance and prevalence of chigger mites included geography (province) as a predictor and host species and season as random effects. For the first time, we analyzed factors connected with climate and weather affecting chigger mites of small mammals in Vietnam.
Understanding the distribution patterns of medically significant sandflies is crucial for effective vector and disease control planning.This study focused on investigating the abundance and distribution of phlebotomine sandflies, specifically emphasizing Phlebotomus pedifer (Diptera: Psychodidae), the vector of Leishmania aethiopica responsible for cutaneous leishmaniasis in the highlands of southern Ethiopia.The study employed CDC light traps and sticky paper traps in various habitats, including human houses, farm fields, and rock cliffs, with and without the presence of hyraxes. The study was conducted along an altitudinal gradient in Kindo Didaye district, Wolaita Zone. A total of 7,994 sandflies belonging to 2 genera, Phlebotomus (26.1%) and Sergentomyia (73.9%), were collected. In the genus Phlebotomus, P. pedifer (74.1%) was the most abundant, followed by P. alexandri (18.05%) and P. gibiensis (7.85%). Altitude showed a strong positive association with the density and distribution of P. pedifer and a negative association with those of P. alexandri, P. gibiensis, and Sergentomyia spp. Furthermore, the study revealed distinct habitat preferences, with P. pedifer showing the highest mean density in hyrax dwellings, followed by human houses, and the lowest in farm fields.These findings provide valuable insights for planning targeted control measures against P. pedifer in both indoor and outdoor environments, particularly in the highland and midland areas of the study region.
Culex pipiens pallens Coquillett, 1898 (Diptera: Culicidae) was the dominant health threat to mosquito species in Beijing, and it is important to unravel the spatial distribution and environmental correlations of Cx. pipiens pallens in Beijing. 3S technology methods and spatial statistics were used to clarify the distribution pattern. Subsequently, linear and spatial regression were performed to detect the environmental factors linked with the density of Cx. pipiens pallens. The same “middle peak” spatial distribution pattern was observed for Cx. pipiens pallens density at the community, subdistrict, and loop area levels in our study area. In addition, there were various correlated environmental factors at the community and subdistrict scales. At the community scale, the summary values of the Modified Normalized Difference Water Index (MNDWI) in 2 km buffer zone (MNDWI_2K) were negatively correlated, and the summary values of Normalized Difference Built-up Index (NDBI) in 800 m buffer zone (NDBI_800) was positively correlated to the Cx. pipiens pallens density. However, the summary values of Normalized Difference Vegetation Index and Nighttime Light Index significantly affected Cx. pipiens pallens density at the subdistrict scale. Our findings provide insight into the spatial distribution pattern of Cx. pipiens pallens density and its associated environmental risk factors at different spatial scales in the Haidian district of Beijing for the first time. The results could be used to predict the Cx. pipiens pallens density as well as the risk of lymphatic filariasis (LF) infection, which would help implement prevention and control measures to prevent future risks of biting and LF transmission in Beijing.
We present an annotated checklist of fleas (Siphonaptera) known to occur in the state of Delaware based on an examination of Siphonaptera collections at the University of Delaware and the Carnegie Museum of Natural History, as well as new specimens of fleas we collected from wildlife, other hosts, and tick flags. We review published records and compile them herein with our new records, which include 3 species previously unreported from Delaware. With these additions, there are now 18 flea species from 19 avian and mammalian hosts documented from Delaware.
VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS
Based on increases in reported cases of tick-borne illnesses, expanding ranges of native ticks, and repeated documentation of arrivals of nonnative tick species, there is a clear need for their effective management in the United States. Synthetic acaricides have proven efficacious in tick management, but real/perceived negative impacts to the environment and nontarget, beneficial insects must be addressed. We sought to determine whether late fall synthetic acaricide application, when most susceptible beneficial insects are presumably dormant or have migrated, could effectively manage host-seeking spring Ixodes scapularis Say abundances as compared to traditional spring application. We compared results of delivery of Demand CS (lambda-cyhalothrin) via truck-mounted high-pressure spray and powered backpack blower as well as delivery of granular Demand G to experimental control (water) in peridomestic habitats in fall 2021, spring 2022, and combined fall 2021/spring 2022. High-pressure fall delivery of Demand CS and backpack delivery of Demand G significantly reduced host-seeking adult I. scapularis abundances within-season and the following spring combined by 100% and 94%, respectively. No host-seeking nymphal I. scapularis were documented in spring after fall only, spring only, or fall and spring combined delivery of Demand CS via high-pressure or powered backpack blower. No adult I. scapularis were documented at any time posttreatment on locations that received high-pressure delivery of Demand CS. We conclude that high-pressure delivery of Demand CS in late fall successfully eliminated multiple stages of host-seeking I. scapularis through the following spring while likely limiting exposure of beneficial insects to synthetic pyrethroids.
White-tailed deer, Odocoileus virginianus Zimmermann (Artiodactyla: Cervidae), are the primary wildlife host for adult stages of blacklegged ticks (Acari: Ixodidae: Ixodes scapularis Say) and an important host for lone star ticks (Acari: Ixodidae: Amblyomma americanum Linnaeus), both of which are vectors of numerous tick-borne pathogens. The 4-poster passive deer treatment device is a topical, host-targeted method to control free-living tick populations and has been proven to successfully reduce tick abundance in several states. Aggressive behavior of white-tailed deer at concentrated feeding stations is hypothesized to interfere with the effective use of 4-poster devices and deer contact with acaricide applicators. We analyzed images collected by camera traps at 4-poster feeding stations deployed at 3 sites in Maryland and found a negative relationship between some aggressive interactions and contact with applicators. Our results emphasize the need for further investigation into whether deer social dynamics can impact 4-poster efficacy for tick control. This study serves as a reminder that intraspecific interactions are important to consider when using host-targeted acaricide approaches.
The cosmopolitan ectoparasite humanheadlouse, Pediculus humanuscapitis (DeGeer)(Phthiraptera:Pediculidae), affects mostly school-aged children, with infestations reported every year mainly due to louse resistance to pyrethroids. One of the main resistance mechanisms of pyrethroids is the target site insensitivity (kdr), which is caused by single-nucleotide point mutations (SNPs) located in the voltage-sensitive sodium channel gene. In this study, we analyzed individual head lice toxicologically via the description of their susceptibility profile to permethrin and genetically through the genotypification of their kdr alleles as well as nuclear microsatellite loci. Lice were collected from 4 schools in the city of Buenos Aires, Argentina. The resistance ratios varied from 33.3% to 71.4%, with a frequency of the T917I kdr mutation of 87.31% and with 83.6% of the head lice being homozygous resistant to pyrethroids. Microsatellite data indicated that all the louse school populations had genotype proportions that deviated from Hardy–Weinberg expectations, with FIS > 0 reflecting a deficit of heterozygotes. Bottleneck analysis suggested that all louse school populations underwent a recent reduction in population sizes, while 3 of the 4 schools had gene flow values around 1, indicating ongoing gene flow among those schools. Our study suggests that school louse populations in the city of Buenos Aires may form a metapopulation, where each school represents a small population that undergoes extinction and recolonization processes under strong permethrin selection. This is the first multilevel analysis integrating toxicological, kdr-genotyping, and microsatellite data in human louse populations.
Control of African animal trypanosomosis is implemented through an integrated control strategy, with the sterile insect technique (SIT) as one of its components. The SIT requires mass rearing of tsetse fly colonies using an in vitro feeding system. The exposure of blood at 37 °C on heating plates over time can have an impact on the quality of fly productivity. In this study, we investigated the survival and fecundity of adult tsetse flies fed at 37 °C on 8 blood exposure times ranging from 30 min to 4 h with increments of 30 min (treatment 1, flies were fed 30 min after exposure to blood at 37 °C; treatment 2, 1 h and so on until treatment 8 [4 h after]) in order to determine the optimal exposure time. In addition, bacterial growth in blood from each treatment was assessed by agar culture at 37 °C for 72 h. The results showed that the adult female survival rates were similar regardless of the treatment. For males, only those of treatment 1 (30 min) showed a marginal lower survival than those of treatments 7 and 8 fed after 3 h 30 min and 4 h of blood exposure, respectively. Over the 4-h interval of blood exposure at 37 °C, the results showed that the number of pupae produced per initial female and pupal weight tended to increase with exposure time, but the differences were not significant. We discuss the implications of these results on tsetse mass rearing for the SIT program.
Gavin Maes, Giulia Tintorri, Irvane E. Nelson, Kobi A. Baker, Corey E. Seavey, Michele M. Rehbein, Gregory S. White, Ary Faraji, Bradley J. Willenberg, Christopher S. Bibbs
Propylene glycol (PG) demonstrates greater efficacy than other sugar polyols. However, the attributes it confers for toxicity and possible co-formulation with other ingredients are unknown. To evaluate this, α-glucosidase and glucose oxidase reactions were performed in Aedes aegypti (L.) (Diptera: Culicidae) to categorize if PG behaves similarly to prior studied sugar alcohols. A combination of no-choice and choice assays was used to determine effective ratios of PG and sucrose, competitiveness against a control of 10% sucrose, and whether mosquitoes recovered from PG consumption. The final trials included β-cyclodextrin encapsulated cinnamon leaf oil, clove stem oil, patchouli oil, garlic oil, cedarwood oil, and papaya seed oil formulated with 5% sucrose + 5% PG. PG functioned as a linear competitive inhibitor of α-glucosidase. The efficacy of PG was synergized by co-ingestion with equivalent ratios of sucrose. Unlike the high diuretic response to other sugar alcohols, PG resulted in diminished excretion regardless of being co-formulated with sucrose or terpenoids. PG is not especially competitive against unadulterated sugar meals but is likewise not clearly repellent. Although mosquitoes did not recover from ingestion of the glycol meals, there was no indication that mortality would continue to accumulate once the treatments were removed. Of the terpenoids tested, cinnamon and patchouli caused ∼50% or less mortality; garlic, cedarwood, and clove caused 80-90% mortality; and papaya seed caused 100% mortality, exceeding all other test groups and the formulation blank. PG is a useful supporting ingredient in attractive toxic sugar bait formulations with flexibility in formulation.
House flies (Musca domestica L.) (Diptera: Muscidae) are challenging pests to control. Biological control using Carcinops pumilio beetles may help to reduce house fly populations. However, it is unknown if C. pumilio beetles are compatible with Beauveria bassiana, another house fly biological control option. Five strains of commercially available (GHA, HF23, and L90) and newly discovered (NFH10 and PSU1) strains of B. bassiana were used to test the comparative susceptibility of adult house flies and adult C. pumilio using different laboratory exposure methods. Adult house flies were susceptible to B. bassiana in contact filter paper assays (89%–98% mortality) and immersion assays (100% mortality) at the same 108 conidia suspension using 0.1% CapSil as an aqueous surfactant. Carcinops pumilio were less susceptible than flies to B. bassiana infection using the contact and immersion assays at the same 108 conidial concentration, with 4.4%–12.2% and 8.3%–24.6% mortality, respectively. Immersion in an aqueous conidial suspension resulted in higher mortality compared to contact with treated filter papers at the same 108 concentration with house flies and beetles. We conclude that C. pumilio can safely be used as a biological control agent for house flies with B. bassiana in animal production systems.
The bed bug (Cimex lectularius L.) is one of the most prolific and burdensome indoor pests, and suppression of bed bug populations is a global priority. Understanding bed bug behavior is important to the development of new tactics for their control. Major gaps exist in our understanding of how host cues, insecticide resistance, and exposure modality impact the repellency of formulated products to bed bugs. Here, we validate the use of a binary choice olfactometer for assessing bed bug repellency behaviors using N,N-diethyl-3-methylbenzamide (DEET) in a dose-dependent manner, while considering the role of host-associated stimuli (with vs. without CO2), exposure modality (olfactory vs. olfactory and contact), and resistance status (susceptible vs. resistant) on repellency. We observed that host-seeking insecticide-susceptible bed bugs were repelled only when olfactorily exposed to high concentrations of DEET. However, exposure to DEET by contact repelled insecticide-susceptible bed bugs at 100-fold lower dose of DEET. Further, we demonstrate for the first time that insecticide-resistant bed bugs were significantly more responsive to DEET than susceptible bed bugs. We conclude that the 2-choice olfactometer is an effective tool for assessing the behavioral responses of bed bugs to spatial and contact repellents.
Ehrlichia chaffeensis is a bacterium belonging to the Anaplasmataceae family. In Mexico, only 2 species have been recorded in association with tick species and humans. The objective of the present study was to detect the presence of bacteria of the genus Ehrlichia in ticks collected from the Chamela-Cuixmala Biosphere Reserve, Jalisco, Mexico. The collected ticks were identified and analyzed individually by polymerase chain reaction to amplify a fragment of the Anaplasmataceae 16S rRNA gene and the Ehrlichia-specific dsb gene. A total of 204 ticks, corresponding to 5 species of Ixodidae and 1 of Argasidae, were collected from 147 mammals of 6 species and 4 orders; 57 ticks collected from vegetation were also included. Among the total ticks collected, 1.47% (3/204) was positive for Ehrlichia sp. DNA was obtained using the primers EHR 16SD and EHR 16SR for 16S rRNA and DSB-330 and DSB-728 for dsb. The positive samples corresponded to a larva (Amblyomma sp.) associated with Didelphis virginiana and 2 nymphs (Amblyomma cf. oblongoguttatum) infesting Nasua narica. None of the ticks collected from the vegetation tested positive for Ehrlichia sp. DNA on the basis of the 16S rRNA and dsb genes. The sequences from the larvae of Amblyomma sp. and the nymphs of A. cf. oblongoguttatum were similar to those of E. chaffeensis. The phylogenetic analysis inferred with maximum likelihood corroborated the identity as E. chaffeensis. Although the role of these tick species as vectors of E. chaffeensis is still undetermined, the presence of infected ticks in the area indicates a potential zoonotic risk.
Demodex folliculorum (Simon, 1842) has been associated with various dermatological conditions. This study aimed to assess the prevalence of Demodex infestation in medical students with facial dermatoses compared with healthy medical students serving as controls. A total of 250 participants were enrolled, including 150 individuals with facial dermatoses and 100 healthy controls. Sampling was performed based on the standardized skin surface biopsy method. Demographic characteristics, specifically gender and age, were not statistically different between the patient and control groups. Among the facial dermatosis patients, 25 out of 150 (16.6%) were found to have Demodex infestation, while only three out of the 100 healthy controls (3%) exhibited infestations. The only identified species was D. folliculorum. The rates of Demodex infestation were significantly higher in the patients compared to the control groups. These findings indicate a higher prevalence of Demodex infestation among medical students with facial dermatosis, particularly in those diagnosed with folliculitis, acne vulgaris, and inflammatory papule, when compared to healthy controls. A better understanding of the relationship between D. folliculorum infestation and these dermatological conditions may lead to improved diagnostic and treatment strategies in the future.
Nicholas A. Panella, William L. Nicholson, Nicholas Komar, Kristen L. Burkhalter, Holly R. Hughes, David P. Theuret, Bessie H. Blocher, Christopher Sexton, Roxanne Connelly, Laura Rothfeldt, Joan L. Kenney
The recovery of a Haemaphysalis longicornis Neumann (Acari: Ixodidae) tick from a dog in Benton County, Arkansas, in 2018 triggered a significant environmental sampling effort in Hobbs State Park Conservation Area. The objective of the investigation was to assess the tick population density and diversity, as well as identify potential tick-borne pathogens that could pose a risk to public health. During a week-long sampling period in August of 2018, a total of 6,154 ticks were collected, with the majority identified as Amblyomma americanum (L), (Acari: Ixodidae) commonly known as the lone star tick. No H. longicornis ticks were found despite the initial detection of this species in the area. This discrepancy highlights the importance of continued monitoring efforts to understand the dynamics of tick populations and their movements. The investigation also focused on pathogen detection, with ticks being pooled by species, age, and sex before being processed with various bioassays. The results revealed the presence of several tick-borne pathogens, including agents associated with ehrlichiosis (n = 12), tularemia (n = 2), and Bourbon virus (BRBV) disease (n = 1), as well as nonpathogenic rickettsial and anaplasmosis organisms. These findings emphasize the importance of public health messaging to raise awareness of the risks associated with exposure to tick-borne pathogens. Prevention measures, such as wearing protective clothing, using insect repellent, and conducting regular tick checks, should be emphasized to reduce the risk of tick-borne diseases. Continued surveillance efforts and research are also essential to improve our understanding of tick-borne disease epidemiology and develop effective control strategies.
Since the introduction of West Nile virus (WNV) to the United States over 20 years ago, thousands of cases of human disease and death have been reported. Yearly seasonal outbreaks continue to persist, and the city and suburbs of Chicago, Illinois, is considered a “hot spot” for WNV activity. To interrupt WNV transmission, ground ultra-low volume (ULV) adulticide applications are regularly used to reduce Culex pipiens L. and Culex restuans Theobold (Diptera: Culicidae) abundance and infection. The real-world effectiveness of adulticide applications has not been comprehensively assessed, and prior studies, including our own investigation, have yielded inconclusive or conflicting results. Therefore, we expanded our prior work and evaluated the effects of 5 sequential weekly truck-mounted ULV adulticide applications in large residential areas in the northern suburbs of Chicago, Illinois, in 2019 and 2020. Each day, Cx. pipiens and Cx. restuans host-seeking and gravid mosquitoes were collected to assess abundance, age structure, and WNV infection rates. Adulticide applications resulted in significant reductions of both host-seeking and gravid abundance on the night of treatment. The reduction in host-seeking mosquitoes was followed by a reduction in gravid mosquitoes trapped 3 and 4 days after adulticide application and an increase in the proportion of nulliparous mosquitoes. WNV infection rates were significantly reduced in treatment sites as compared to untreated sites when infection rates were higher in 2020. This large-scale study provides comprehensive evidence that ground ULV adulticide applications are an effective tool in an integrated mosquito management program for combating WNV vectors and infection risk.
We conducted surveys of New Jersey mosquito control and public health agencies to determine their willingness and ability to expand or create and maintain publicly funded tick and tick-borne disease (T/TBD) management programs. Nearly all (86%) of 21 county mosquito control agencies (MCAs) completed the survey, while only 25% of the 102 health departments (HDs) responded, probably reflecting traditional agency responsibilities. Although few of either group had formal programs, many were engaged inT/TBD-related activities. Many MCAs rated their ability to assumeT/TBD responsibilities as high or moderate, while most HDs rated their capabilities as low.With the exceptions of lack of sustainable funding and possible legal constraints, the groups differed regarding perceived barriers to program creation and maintenance. Both groups envisioned comprehensive programs emphasizing public education, but program priorities differed between the groups. MCAs were willing to include most program activities, while HDs felt that some activities should be the responsibility of other agencies. MCAs were generally more familiar than HDs with tick control methods and while both groups would include control in a comprehensive program, both would limit control to public lands. Estimated program costs varied widely, probably reflecting responding agency size and complexity of envisioned programs. These results in a state with a system of existing agencies staffed by highly competent professionals suggest that more than simply additional funding (e.g., established guidelines for tick control and surveillance) is needed to create a network of practice necessary to address the growing incidence of TBD.
Female mosquitoes undergo multiple rounds of reproduction known as gonotrophic cycles (GC). A gonotrophic cycle spans the period from blood meal intake to egg laying. Nutrients from vertebrate host blood are necessary for completing egg development. During oogenesis, a female prepackages mRNA into her oocytes, and these maternal transcripts drive the first 2 h of embryonic development prior to zygotic genome activation. In this study, we profiled transcriptional changes in 1–2 h of Aedes aegypti (Diptera: Culicidae) embryos across 2 GC. We found that homeotic genes which are regulators of embryogenesis are downregulated in embryos from the second gonotrophic cycle. Interestingly, embryos produced by Ae. aegypti females progressively reduced their ability to hatch as the number of GC increased. We show that this fertility decline is due to increased reproductive output and not the mosquitoes' age. Moreover, we found a similar decline in fertility and fecundity across 3 GC in Aedes albopictus. Our results are useful for predicting mosquito population dynamics to inform vector control efforts.
Eleanor Fausett, Oscar D. Kirstein, Stephanie Bellman, Audrey Long, Isabella Roeske, Chun Cheng, Anne Piantadosi, Tavis K. Anderson, Gonzalo M. Vazquez-Prokopec
The invasion of the Asian longhorned tick, Haemaphysalis longicornis Neumann, into the United States poses a significant ecological, veterinarian, and public health threat. We conducted a comprehensive tick survey using standard tick flagging protocol for collection over 3 field seasons, March–August, and 56 surveyed sites to identify the presence of H. longicornis in the native ecosystem and prove its establishment according to USDA criteria. Of the total 56 state parks and wildlife management areas (WMA) surveyed, only one was found to be invaded by H. longicornis; detection of H. longicornis occurred at Buck Shoals Wildlife Management area in White County, GA. This site is maintained by the state of Georgia, has no agricultural animals present, and hosts a large white-tailed deer population. After the initial detection of H. longicornis in 2022, an additional field season occurred in 2023, where H. longicornis was confirmed as established based on USDA criteria. The increase in H. longicornis populations from 2021 to 2023 at Buck Shoals WMA points to the rapid spread of this tick within the environment. Our findings provide evidence of the rapid establishment of H. longicornis in the southern edge of suitability for this tick and within the native ecosystem beyond farmlands and private land.
Recent studies on invasive Aedes koreicus (Edwards 1917) have been conducted to elucidate the source population introduced to Europe. However, current information about the native range of Ae. koreicus is not consistent. The purpose of this study is to resolve confusion in the native distribution of Ae. koreicus by reviewing available literature from the first description of the species in its native range in 1917 to the first invasion in Europe in 2008. Aedes koreicus have been recorded in China, Japan, Korea, and eastern Russia. The 2 existing records of Ae. koreicus from Hokkaido, Japan, however, is likely due to the misidentification of 2 different morphologically similar species, Ae. koreicoides (Sasa, Kano & Hayashi 1950) and Aedes japonicus (Theobald 1901). Upon re-examination of published records, we conclude that the native distribution of Ae. koreicus is confined to continental eastern Asian regions, specifically China, Korea, and eastern Russia.
Amblyomma maculatum Koch, the Gulf Coast tick, is expanding northward from its original range in the southeastern United States. In 2013, its most northern collection was in Delaware. Amblyomma maculatum has since been found in Connecticut, Illinois, and New York. It is the vector of the human pathogen Rickettsia parkeri, the causative agent of R. parkeri rickettsiosis. We report the first finding of an established population of A. maculatum in Salem County, NJ, with a R. parkeri infection prevalence rate of 23.8%. Our finding of A. maculatum is consistent with other recent findings in the northeastern United States in that specimens were found in open areas devoid of tree canopy. This discovery demonstrates the importance of tick surveillance in order to identify expanding tick populations and the pathogens they may transmit.
Brooke L. Coder, Keith J. Price, Deepanker Tewari, Bryn J. Witmier, Holly A. Chapman, Michael S. Chroscinski, Jason Long, Julia L. Livengood, Christian N. Boyer
Borrelia miyamotoi disease is an emerging tick-borne human illness in the United States caused by Borrelia miyamotoi (Spirochaetales: Spirochaetaceae) bacterium. With Pennsylvania reporting thousands of tick-borne disease cases annually, determining the minimum infection rate (MIR) of B. miyamotoi in Ixodes scapularis (Say, Acari: Ixodidae) adults within Pennsylvania is of utmost importance. Active surveillance was performed from October 2019 to April 2020 to collect a minimum of 50 I. scapularis ticks from every county within Pennsylvania and then screened for B. miyamotoi via qPCR. Ticks were collected from all 67 counties with the majority of those being adult I. scapularis. Additional ticks collected were Dermacentor albipictus (Packard, Acari: Ixodidae), Haemaphysalis longicornis (Neumann, Acari: Ixodidae), and immature I. scapularis. Adult I. scapularis were pooled and tested for B. miyamotoi. MIR for positive B. miyamotoi pools and density of infected adult I. scapularis varied by county, with positive pools from 38 Pennsylvania counties. This is the first statewide evaluation of B. miyamotoi in Pennsylvania in questing adult I. scapularis. These prevalence and distribution data will aid health care practitioners within the state of Pennsylvania and the northeast United States to understand potential risk and bring awareness to the lesser known human Borrelia illness, Borrelia miyamotoi disease.
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