Journal of medical entomology最新文献

This project documents the expanded zoogeographic ranges of the blacklegged tick (Ixodes scapularis Say) and lone star tick (Amblyomma americanum Linnaeus) within eastern South Dakota. The research involves 2 steps. First, tick surveillance was conducted in the eastern counties of South Dakota, spanning March 2021 through August 2022. Surveillance took place along the edge habitat at any accessible natural areas that could be identified as suitable tick habitat. All life stages and species of ticks were collected using a white cloth tick drag, preserved in ethanol, and frozen. Second, the collection of data was contextualized by comparison with prior data in the region to determine if, and to what extent, range expansion had occurred. Distribution maps were created for each year to represent areas where I. scapularis and A. americanum were reported, and changes in species establishment were displayed. This study focused primarily on the Southeastern region of the state, near where I. scapularis populations exist in bordering Minnesota, and A. americanum in Nebraska and Iowa. As of the 2022 sampling season, the only counties where I. scapularis and A. americanum appear to have overlapping ranges are Clay County and Union County. This study also yielded a state record for another human disease vector, the Gulf Coast tick (Amblyomma maculatum Koch) in 2021 and 2022. Target species of tick were detected in nine counties in eastern South Dakota.

Phlebotomine sand flies are important vectors of pathogens affecting both humans and animals and are widely distributed geographically. In Cabo Verde, research on vector-borne diseases has focused primarily on mosquitoes, leaving other potential vectors understudied. As part of the ONESVEC surveillance project, we conducted a preliminary assessment to determine the presence of sand flies in Cabo Verde. From February to December 2024, entomological surveys using BioGents-Sentinel traps were carried out in five neighborhoods of Praia, Santiago Island: Achada Eugénio de Lima, Ponta de Água, Taiti, Vale do Palmarejo, and Vila Nova. Male specimens were slide-mounted for morphological identification, and randomly selected individuals underwent mitochondrial cytochrome c oxidase subunit I (COI) gene sequencing. Haplotype diversity and species delimitation (DnaSP, ASAP) were also assessed. A total of 367 sand flies (184 males, 173 females) were collected, of which 168 males were successfully identified. Most specimens were Sergentomyia fallax, found in all neighborhoods, while S. squamipleuris was identified in Taiti and Vale do Palmarejo. Phylogenetic analysis showed Cabo Verde S. fallax forming a well-supported monophyletic group, distinct from North African and Cyprus-Saudi Arabian lineages. Haplotype analysis revealed high haplotype but low nucleotide diversity, suggesting a genetically diverse yet stable or expanding population. In contrast, S. squamipleuris sequences clustered with Kenyan isolates in separate subclades, consistent with higher nucleotide diversity. ASAP species delimitation supported the phylogenetic analysis. This study provides the first confirmed record of phlebotomine sand flies in Cabo Verde and highlights the need for expanded surveillance and pathogen screening across the archipelago.

Toward a more detailed understanding of the Eastern equine encephalitis virus (EEEV) cycle, individual blood-fed Culiseta melanura (Coquillett) mosquitoes were collected at an enzootic focus in New York State. Blooded females were tested for EEEV by multiplex real-time quantitative reverse transcription polymerase chain reaction, qRT-PCR. Host bloodmeals were identified using DNA amplification and sequencing of the cytochrome B gene. In 2018, 577 individual mosquitoes were tested. Virus was detected in the bodies of 16, of which two had the virus in their legs. In 2022, 606 individual mosquitoes were tested, and the virus was detected in the bodies of six, of which one had the virus in its legs. Virus in the legs suggested a disseminated infection. The qRT-PCR cycle threshold (Ct) values for individual bodies ranged from 17.6 to 38.3, and for legs, 22.8 to 28.1. Host sources for 17 of the 22 were: Passeriformes, Bombycillidae, cedar waxwings (Bombycilla cedrorum); Icteridae, red-winged blackbird (Agelaius phoeniceus); Turdidae, American robin (Turdus migratorius), veery (Catharus fuscescens), and wood thrush (Hylocichla mustelina); Vireonidae, yellow-throated vireo (Vireo flavifrons); Passerellidae, song sparrow (Melospiza melodia), and field sparrow (Spizella pusilla); Parulidae, American redstart (Setophaga ruticilla); and Gruiformes, Rallidae, American coot (Fulica americana). In both years, red-winged blackbirds were a source of blood for Cs. melanura in the earliest 2 d after EEEV was detected. Annually, the earliest detection of the virus was in blooded-gravid mosquitoes before non-blooded mosquitoes in 15 of 17 yr. These results support the thesis that birds contribute to the introduction and re-emergence of EEEV to this enzootic focus.

The Chicago metropolitan area is a hotspot for human West Nile virus (WNV) cases. Despite extensive surveillance and research, predicting WNV cases in Chicago on a local scale is a major challenge. Most studies and mosquito surveillance efforts do not differentiate between the cryptic species Culex pipiens Linnaeus and Culex restuans (Theobald), key vectors of WNV, due to the challenge of distinguishing them morphologically. This obscures each species' respective role in transmission and may blunt the accuracy of local case forecasting. We used species-specific PCR diagnosis to identify Chicago mosquitoes across 21 sites in July and August of 2021 and 2022. We found that the percentage of collected Cx. restuans declined between July and August, with Culex pipiens often being the sole species recorded from sites in August. We found that the relative proportions of our target species varied by site, sometimes dramatically, across years. Following species identification, we pooled our specimens and determined infection prevalence using reverse transcription quantitative polymerase chain reaction (RT-qPCR). We found that both species were infected with WNV and observed no significant difference in their infection rates between months. We also assessed the accuracy of a human case prediction model, and we found no evidence to support the molecular separation of these species in routine Chicago WNV surveillance.

The German cockroach, an obligate indoor pest, produces potent aeroallergens whose presence, along with endotoxins, are often reported as important indoor predictors of increased risk of morbidity in sensitized asthmatic children. In our recent analysis, we found significantly higher endotoxin concentrations in household dust from cockroach-infested homes than from uninfested homes in the same communities. We also found that both female and male cockroaches excreted large amounts of endotoxin in their feces. In this study, we hypothesized that if the cockroach gut microbiota is the major source of endotoxin, then all life stages would be expected to excrete endotoxin in relation to their gut microbial abundance. Using the kinetic Limulus amebocyte lysate assay, we found high levels of endotoxin in the feces of all life stages of the cockroach. In both laboratory-maintained and recently field-collected cockroaches, adult females produced 2.5- to 3-fold more endotoxin than males, consistent with their larger body mass and greater food consumption. Nymphs produced less endotoxin than adults, but the endotoxin concentration (endotoxin per mg) was higher in nymph feces than in adult feces. We found trace amounts of endotoxin in the feces of adults with axenic guts lacking microbiota. Lastly, endotoxin in fecal residues remained stable for at least 30 days at ambient room temperature. These results reveal that cockroaches expose sensitized people to a mix of allergens that are potent asthma triggers and endotoxins that can exacerbate the allergic response. Further research is warranted to understand their combined effects on asthma sensitization and exacerbation.

Aedes aegypti (L.) and Aedes albopictus (Skuse) are significant urban pests and disease vectors. In addition to small containers, the urban storm drains serve as an extensive production ground. Management of these species is notoriously challenging due to numerous reasons, such as lack of optimal larvicide products. A larvicide, Sumilarv 0.5G Sachet, containing 0.5% pyriproxyfen, a juvenile hormone analog (JHA), was evaluated for its bioactivity and efficacy in simulated storm drain catch basins. In bioassays, high bioactivity in inhibition of emergence (IE) was observed with no significant differences between test materials or species. Against Ae. aegypti, the IE10, IE50 and IE90, respectively, measured 0.011, 0.028, and 0.122 ppb for the technical grade, and 0.016, 0.036, and 0.161 ppb for the formulated granules from the sachet. A similar bioactivity was observed in Ae. albopictus. The IE10, IE50, and IE90, respectively, amounted 0.013, 0.033, and 0.142 ppb for the technical grade, and 0.015, 0.038, and 0.151 ppb for the formulated product. In simulated storm drain catch basins, application of Sumilarv 0.5G Sachet at three sachets (25 g each) per 151.4 L of water provided sustained control of Ae. aegypti (91.1% to 100%) and Ae. albopictus (91.0% and 100%) for up to 22 wk, despite poor water quality and low detectable pyriproxyfen concentrations. These results demonstrate that Sumilarv 0.5G Sachet is a highly effective and reliable larvicide for long-term control of invasive Aedes mosquitoes in urban storm drain systems.

Ticks present a significant risk to people in the southern United States, particularly those who spend time outdoors, as ticks can transmit agents that cause various diseases. This study evaluated the risk of exposure to ticks positive for spotted fever group (SFG) Rickettsia species among forestry workers. From 2017 to 2021, forestry workers passively collected ticks during field surveys for the USDA Forest Service's Forest Inventory and Analysis program. We screened 1395 ticks for SFG-Rickettsia, including Amblyomma americanum (51.5% positive, N = 1,279), A. maculatum (40% positive, N = 10), and Dermacentor variabilis (22.6%, N = 106). The agent of Rocky Mountain spotted fever, R. rickettsii, was not detected; however, 7 different SFG Rickettsia species were identified. Rickettsia amblyommatis was the most common, present in 95.7% of A. americanum ticks. The pathogenic R. parkeri was rare, detected in 2 A. americanum nymphs and 2 A. maculatum males only. Several Rickettsia species, such as R. montanensis, R. monacensis, Candidatus R. andeanae, and R. tamurae subsp. buchneri, were identified in D. variabilis. Some of these species are suspected to be pathogenic. Rickettsia-positive ticks were detected year-round, with the highest prevalence in Tennessee and Kentucky, possibly due to larger sample submissions, which may have increased detection rates. Dermacentor variabilis were less likely to be Rickettsia-positive compared to A. americanum. Male ticks were less likely to carry Rickettsia than females and nymphs. The presence of Rickettsia-positive ticks found in this study poses a risk to forestry workers, emphasizing the importance of ongoing surveillance and education to prevent tick-borne infections.

Within recent decades, the northeastern United States has experienced milder winters, supporting an increase in blacklegged tick (Ixodes scapularis) densities and concomitant increase in reported cases of tick-borne disease. While numerous laboratory and field studies have investigated impacts of cold temperatures on tick overwinter survival, temperature variability also may contribute to tick longevity and remains largely underexplored. In this study, we conducted three experiments. First, we carried out a laboratory experiment in which blacklegged tick nymphs were exposed to different low temperatures and cycles of temperatures typical of the northern geographic range of the blacklegged tick and survival was measured. We found that tick survival was highest under a high temperature, low variability regime (in which ticks were exposed to -5 °C for nine days followed by 4 °C for one day) compared to both lower temperature and higher variability regimes. Second, in a parallel field experiment, we tested overwinter survival of captive nymphal blacklegged ticks held in outdoor enclosures spanning a natural ambient temperature gradient and manipulated snowpack conditions. Again, we found that tick survival was highest at the warmer field site and when snow was allowed to accumulate over the enclosure, which reduced temperature variability. Finally, we conducted an assay to measure ticks' energy usage over the course of two winters and established a link between survival and percent lipid content. We propose that tick mortality may be driven by repeated freeze-thaw cycles, causing ticks to rapidly expend energy. Overall, we anticipate that understanding the interacting effects of cold temperature and temperature variability can aid in forecasting range shift of the blacklegged tick under climate change.

Host-vector contact is central to mosquito-borne disease transmission, during which pathogens are transmitted via saliva injection or blood feeding. Biting persistence, defined as the number of repeated biting attempt when interrupted, is an understudied trait that may influence transmission risk. Currently it is unknown how temperature may influence biting persistence. We tested the effect of ambient temperature on biting persistence in Aedes aegypti (Linnaeus), under controlled laboratory conditions. Individual mosquitoes (n = 141) were assayed at four temperatures (18, 23, 28, and 33 °C). Biting persistence was measured as the number of landings over a 1-h period on the experimenter's arm when probing was repeatedly prevented. Results showed that persistence differed significantly across temperature treatments, peaking at 28 °C and declining at 18 and 33 °C. Temporal analysis showed that biting persistence declined steadily during the 1-h assay period. To control for experimental variations in relative humidity, mosquito age, wing size, assay time, starvation period, and acclimation period, multivariate models were fitted with temperature included as both linear and quadratic terms. Model comparisons and other robustness tests supported that temperature significantly affected biting persistence; and suggested a thermal optimum at intermediate conditions. While this study focused specifically on temperature effects, in natural settings other factors such as host defensive behaviors, mosquito learning and memory, and additional environmental variables such as humidity may also shape biting persistence. Because pathogen transmission can occur even during interrupted feeding attempts, biting persistence may contribute to increased transmission risk, likely near thermal optima.