Journal of medical entomology最新文献

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.

The smallest hematophagous insects in the world belong to the genus Culicoides Latreille, which are vectors of various diseases. These insects are frequent pests on sandy beaches, with immature stages often found in flooded upper areas, edges of brackish waters, and intertidal zones of mangroves, mainly concentrated above the mean water level. In this study we investigated the presence of Culicoides larvae across extensive distances in the intertidal zone of an Amazonian sandy beach-a challenging, high energy, and macrotidal environment with fine sediment. Local community reports link biting midge infestations to neap tides. Hence, this study aimed to determine whether larvae found across the beach intertidal area were associated with these infestations and their periodicity. Samples were collected daily over a two-week period spanning a semidiurnal tidal cycle, down to 150 m below the mean high-tide line, at three distances (every 50 m). Immature individuals occurred at all levels, with abundance about three times higher at 50 m below the waterline. Interestingly, larval abundance was significantly higher during spring tides than during neap tides (when none were recorded), despite the harsh nature of this high-energy, macrotidal environment-especially during spring tides. The tidal cycle pattern of immatures was opposite to that observed in adults and consistent with local community reports. Adults that emerged from reared immatures, as well as those collected using human bait, were identified as C. phlebotomus. This information may benefit further studies and tourism management by helping visitors plan trips to avoid periods of peak biting midge activity.

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.

We investigated the sand fly fauna and the presence of Leishmania spp. DNA in collected specimens, domestic animals, and military personnel. The 4th Mechanized Cavalry Brigade of Dourados, Mato Grosso do Sul, Brazil is located in an area that has characteristics conducive to the life cycle of Leishmania spp. An epidemiological questionnaire applied to military personnel, and whole blood samples were collected from them and domestic animals. Using the collected blood samples, PCR (Polymerase Chain Reaction) and serology tests were performed to detect Leishmania spp. DNA and anti-Leishmania antibodies, respectively. Additionally, CDC (Center on Disease Control) traps were installed at eight points over 12 months. In total, 652 sand flies belonging to 9 genera and 19 species were collected. Lutzomyia longipalpis, which is the main vector of Leishmania infantum, the etiological agent of visceral leishmaniasis was present in half of the collection points. The DNA detection rate of Leishmania spp. was 0.31% (one pool of Psathyromyia aragaoi and one pool of Brumptomyia spp.). We analyzed 35 animals (dogs and horses) and 235 military personnel. Analysis of samples from animals and soldiers was negative for Leishmania spp. About 30.2% (n = 71) of military personnel did not know about leishmaniasis. Although some vector species were found, no Leishmania spp. DNA was identified in species of medical and veterinary importance. The area investigated showed characteristics that can contribute to the proliferation of the vector and the spread of the disease. Long-term monitoring studies and activities that increase awareness in the population should be encouraged by research funding bodies and leishmaniasis surveillance and control programs.

Hemotrophic Mycoplasma, or hemoplasma, is a group of bacteria that cause infectious anemia in mammals, including pigs. These pathogens can potentially be mechanically transmitted by mosquitoes. However, limited data exist on hemoplasma transmission within pig farms via mosquitoes. This study involved monthly mosquito surveillance on a pig farm in Erawan District, Loei Province, Thailand, from November 2021 to October 2022. CO2-baited CDC light traps were used to collect mosquitoes over 2 consecutive days each month. Pig blood samples were collected every other month. Female mosquitoes were sorted under a stereomicroscope, pooled by species, complex or group, and kept individually if blood-fed. All mosquito and pig samples were tested for hemoplasma using PCR targeting the 16S rRNA gene. Positive samples were further analyzed by amplifying a partial 23S rRNA gene fragment, followed by sequencing. Sequences were analyzed using DnaSP6, BLASTn, phylogenetic trees, and network analysis. In total, 5,797 female mosquitoes were collected, representing 5 genera (Aedes, Anopheles, Armigeres, Culex, and Mansonia). Hemoplasma DNA was detected in 18.40% (85/462) of blood-fed mosquitoes, 2.17% (5/230) of mosquito pools, and 21.61% (51/236) of pig blood samples. Sequences from 36 mosquitoes across 4 species and 31 pig samples were recovered. At least 6 hemoplasma species were identified; 4 (Mycoplasma suis, Mycoplasma sp., Mycoplasma parvum, and Mycoplasma wenyonii) were found in both pigs and mosquitoes. These findings suggest mosquitoes may act as mechanical vectors, while other mammals like buffalo may serve as additional reservoirs for hemoplasma in pig farms.

North Carolina reports high incidences of spotted fever group rickettsiosis (SFGR) and ehrlichiosis, with cases concentrated in the more urban and suburban central area of the state. To define the spatial distribution of ticks and the prevalence of tick-borne pathogens in this region, tick surveillance was conducted via (1) drag sampling and (2) passive canine surveillance. Drag sampling was conducted in 18 suburban green spaces (eg, parks, sports fields) in Chatham and Orange counties between June and August 2022. During the same timeframe, animal shelters and veterinary clinics in these counties also submitted ticks found attached to dogs. One hundred eight ticks were collected, 40 of which were from suburban green spaces and 68 from canine sampling, with Amblyomma americanum (L.) ticks comprising the majority of each subgroup. Ehrlichia chaffeensis and Ehrlichia ewingii were largely concentrated in the canine sample and were present in 12% and 41% of A. americanum ticks, respectively. Rickettsia amblyommatis was the most frequently encountered pathogen overall and was detected in 30% of A. americanum from green spaces and 50% of the canine sample. In suburban green spaces, 50% of Amblyomma maculatum (Koch) ticks were positive for Rickettsia parkeri, while none of the Dermacentor variabilis (Say) ticks were positive for Rickettsia rickettsii. These results suggest that the risk of acquiring SFGR or ehrlichiosis may extend beyond rural risk factors (ie, camping, hunting, hiking) and into routine exposures in suburban counties.

Mosquito-borne disease and nuisance biting from mosquitoes have severe health and economic consequences. Conventional fabrics are typically not effective at providing protection against mosquito bites, and fabrics treated with repellents and/or insecticides are limited by rising insecticide resistance, risk of significant dermatologic and neurologic side effects, and decreased efficacy with washing and time. The goal of this study was to identify commercially available, repellent/insecticide-free, comfortable fabrics that block bites from three genera of mosquitoes that are known to transmit dangerous infectious diseases with widespread distribution: Aedes, Anopheles, and Culex. To do this, we evaluated fabrics from Ripstop By the Roll LLC in a step-wise series of mouse blood-feeding and behavioral bioassays. Out of 88 fabrics, 53 were found to be blood-feed-proof. These fabrics were more likely to have a higher areal weight density (AWD) and a polyurethane coating than blood-feed-susceptible fabrics. Of the six most comfortable fabrics by subjective hand-feel testing, five were definitively bite-proof during behavioral bioassays. These five fabrics varied substantially in AWD, thickness, finish/coating, and fiber pattern. None of them had a polyurethane coating. Three of them were breathable, making them appropriate for active-wear clothing. Overall, the bite-proof fabrics identified in this study have the potential to significantly reduce mosquito biting and the transmission of mosquito-borne diseases.

miRNA-mRNA interactions regulate mite physiology and behavior, especially in response to growth- and reproduction-affecting environmental factors. Despite being a major source of allergens, gender-specific mRNA and miRNA expression in allergic mites has not yet been explored. Male and female Dermatophagoides farinae mites were manually selected under a stereomicroscope and used for library preparation for mRNA and small RNA sequencing, following standard Illumina protocols. Differential expressions of mRNA and miRNAs were analyzed separately and validated by qRT-PCR. An mRNA-miRNA regulatory network was then constructed using computational target prediction algorithms, with further validation through a dual-luciferase reporter assay. Compared to female mites, male mites exhibited 321 upregulated and 430 downregulated genes. GO analysis revealed significant differences in gene sets associated with DNA replication, RNA polymerase complexes, and sex differentiation between the two sexes. A total of 130 miRNAs showed differential expression, with 51 miRNAs upregulated in male mites. Integrated analysis of mRNA and miRNA sequencing data predicted 29 specific miRNAs targeting distinct mRNAs, with key genes and miRNAs further validated by qRT-PCR. Additionally, dual-luciferase reporter assays confirmed that PC-5p-65423_75 regulates the developmental processes of male and female mites by targeting Sex Comb on Midleg Like-2 (SCML2). This study provides a comprehensive analysis of the transcriptome and small RNA sequencing of D. farinae. We identified key miRNAs and their target genes, offering valuable insights into the reproductive and growth strategies of allergic mites.

American tegumentary leishmaniasis (ATL) constitutes an infectious, non-contagious pathology that manifests as ulcerative lesions on the integumentary system and mucosal surfaces. The causative agents are parasites belonging to the genus Leishmania (Protozoa: Kinetoplastida: Trypanosomatidae). In Brazil, the principal ATL agents include Leishmania (Leishmania) amazonensis, Leishmania (Viannia) guyanensis, and Leishmania (Viannia) braziliensis. ATL transmission to humans occurs via the hematophagous activity of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae). Despite the endemic status of ATL in Brazil, a notable outbreak occurred in the municipality of Montes Claros (Minas Gerais state), yielding 509 documented cases over a triannual period (from 2019 to 2021). In light of the absence of contemporary entomological data in that region, a survey was performed involving monthly collections over 1-yr (from June 2022 to May 2023) across 6 sylvan environments within the peri-urban area of the city, where ATL cases were reported. A total of 3,342 phlebotomine sand flies, representing 10 genera and 29 species, were collected and identified to the species level. Three ATL vectors were identified with the following relative abundances: Nyssomyia intermedia (Lutz & Neiva, 1912) (8.53%), Nyssomyia whitmani (Antunes & Coutinho, 1939) (1.74%), and Migonemyia migonei (França, 1920) (0.45%). The presence of Leishmania DNA was assessed through quantitative PCR in female phlebotomine sand flies across 26 species. Although no positive samples were detected, the registration of autochthonous cases and the presence of proficient vectors establishes the essential conditions for ATL transmission and emphasizes the necessity for ongoing surveillance of its incidence within Montes Claros.