Journal of medical entomology最新文献

Tick-borne pathogen infections are an increasing occurrence globally, yet many aspects of pathogen maintenance and host-tick interactions remain poorly understood. Here we consider the potential role of eastern cottontails (Sylvilagus floridanus) in the enzootic cycles of tick-borne pathogens of medical importance in Virginia. Over a 3-year period, ticks and blood were collected from rabbits acquired through passive surveillance in 21 counties in Virginia. Seven hundred seventy ticks were collected from 90 of the 121 rabbits examined in this study. Tick species collected from the rabbits included Haemaphysalis leporispalustris, Haemaphysalis longicornis, Amblyomma americanum, Dermacentor variabilis, and Ixodes spp. Ticks identified as Ixodes spp. and H. leporispalustris were tested in pools for Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, and Powassan virus (POWV). Borrelia burgdorferi and A. phagocytophilum were detected in several Ixodes spp. pools yielding a pooled infection rate of 4.6% and 3.7%, respectively. These bacterial pathogens along with POWV were detected in pools of H. leporispalustris yielding pooled infection rates of 0.2%, 0.2%, and 0.5%, respectively. In addition, 3 rabbits were found to have neutralizing antibodies against POWV indicating exposure to this tick-borne flavivirus. We describe the presence of infected ticks (including juvenile ticks that could bite humans as adults) utilizing rabbits as hosts, as well as evidence of POWV infection (1.75% seroprevalence) in rabbit sera. These results provide useful information about the role of rabbits as hosts to infected ticks, though cannot ascertain their role in the maintenance or the transfer of pathogens from the rabbits to naïve ticks. Future studies are warranted to explore any additional roles these and other lagomorphs may be playing in the enzootic cycle of tick-borne pathogens.

Culicoides (Diptera: Ceratopogonidae) Latreille biting midges are the vectors of several viruses of veterinary significance. The larvae of some biting midge species develop in semiaquatic habitats that are affected by the activity of vertebrates. However, the importance of vertebrate animal activity in biting midge density has not been satisfactorily quantified. The goal of this study was to investigate the impact that three different hooved animals representing agricultural (cattle), wild (cervids), and intermediate (bison) animal populations have on the density and emergence of Culicoides from larval habitats. Trail cameras recorded vertebrate activity at eight sites at the Konza Prairie Biological Station with cattle, cervids, and/or bison, which was paired with larval substrate sampling to investigate midge density. The total time spent by all 3 target animals over the previous month and the average time spent by bison were significantly positively correlated with overall biting midge emergence. Species-specific analyses revealed significant positive associations of C. crepuscularis Malloch with several cattle variables including number of cattle days and events and average number of cattle, while more bison variables were found to be significant for C. haematopotus Malloch (bison days and bison events, negative associations) and C. variipennis Coquillett (negative associations for bison days and average number of bison; positive relationship with average bison time). Significant results for cervids included negative associations of C. crepuscularis with average cervid time and C. variipennis with cervid days. These results show that different ungulates impact midge abundance and emergence in different ways, improving our understanding of midge population drivers.

The long-horned tick, Haemaphysalis longicornis Neumann (Ixodida: Ixodidae) was recently introduced to the United States from its native range in Asia. Although H. longicornis transmits numerous disease-causing pathogens in its native range, it is unclear to what extent H. longicornis will act as a disease vector in the United States. The ability of H. longicornis to acquire pathogens likely depends on overlap with resident tick species in both habitat and pathogens transmitted within its introduced range. To assess the potential overlap in habitat and pathogens between invasive H. longicornis and resident tick species, we field-collected ticks across southeastern Pennsylvania and tested them for pathogens. We then contextualized the risk of pathogen transmission to and by H. longicornis at sites where it overlaps with the current vector species using a network of vectored pathogens. None of the collected H. longicornis individuals tested positive for any pathogens. However, we found significant overlap in habitat use among H. longicornis and resident tick nymphs, as well as several overlaps in the pathogens vectored by resident ticks and those carried by H. longicornis in Asia. These findings indicate a high but yet-to-be-realized potential for H. longicornis to acquire North American tick-borne pathogens.

Mosquito control using pyrethrins and synthetic pyrethroids (PSP) is important for preventing vector-borne diseases. Although the benefits associated with PSP use are well-documented, public concern exists regarding potential human adverse health effects. The aim of this scoping review was to describe adverse human health effects associated with PSP use for community adult mosquito control. A literature search using the databases MEDLINE, EMBASE, Agricultural and Environmental Science Collection, CAB Abstracts, and Scopus obtained 6,154 original peer-reviewed articles published during 1 January 2000 to 22 May 2024. Articles were independently reviewed for inclusion using predetermined exclusion and inclusion criteria. Data were extracted from 10 included articles. Study designs included cohort (n = 5), cross-sectional (n = 2), and risk assessment (n = 4). One article included 2 study designs. Of the cohort studies, one was prospective and the remainder were retrospective. A causal relationship between PSP application for adult mosquito control and adverse human health impacts was not identified. No increases in acute health manifestations were reported. The 4 risk assessments estimated that PSP exposures were not above the regulatory level of concern; a meta-analysis determined the likelihood of PSP exposures exceeding the regulatory level of concern was <0.0001. The limited evidence indicated that PSP applied appropriately for control of nuisance mosquitoes or mosquitoes that transmit arboviruses do not pose acute or chronic human health risks. Continued investigation into potential human health impacts of PSP would help inform guidelines for adult mosquito control and help inform public health decision making.

Aedes aegypti (Linnaeus) is the principal mosquito vector for many of the most medically significant arboviruses that threaten global public health. A better understanding of time-of-day variation in insecticide resistance mediated by detoxifying enzymes in Ae. aegypti could allow for targeted insecticide applications when susceptibility is highest and the upregulation of detoxification enzymes is lowest. Using a susceptible and metabolically resistant field Ae. aegypti strain from Florida, we investigated simulated photoperiodic changes in permethrin susceptibility and upregulation of detoxification enzymes by measuring permethrin LD50 and expression of detoxification genes (GSTE7, GSTE2, CCEae3A, CYP9J28, and CYPBB2) for both strains every 4 h over a 24 h (12:12 h light: dark) cycle. We found that in both Ae. aegypti strains, permethrin susceptibility was lower during the day as compared to evening, with susceptibility lowest at dusk (18:00) and highest between 02:00 and 14:00. Although no significant changes in gene expression over time were observed in the susceptible Ae. aegypti strain, we documented increased expression of all investigated detoxification genes in the metabolically resistant field Ae. aegypti strain during the night (18:00 to 02:00) as compared to the day (06:00 to 14:00). These data suggest that permethrin applications made between midnight and dawn (06:00) may be more effective against Ae. aegypti as compared to applications made at dusk (approximately 18:00).

A comprehensive study was conducted on the life history parameters of an important vector Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae), to standardize potential rearing procedures. Data on life history traits and rearing conditions are crucial for establishing laboratory colony and conducting vector competence-based studies utilizing specimens with a known rearing history. Six different substrate compositions were used to rear the larvae: S1: habitat mud containing cattle manure + nutrient broth + yeast, S2: yeast, S3: habitat mud containing cattle manure + nutrient broth, S4: nutrient broth, S5: sterile (habitat mud consisting cattle manure + nutrient broth + yeast) and S6: tap water. Gravid females preferred ovipositing on beds moistened with tap water compared to distilled water. Egg hatching recorded minimal (3%) in the sterile substrate (S5), hinting at the role of live microbial load. Progression of larval instars got disrupted at 1st instars in S5 and S6. Larval survival and adult emergence were the highest in S1 and the lowest in S4, indicating that S1 is highly effective in the rearing of this species. The life cycle parameters and duration between transitional stages were evaluated at 15 °C, 20 °C, 26 °C, 30 °C, and 35 °C using rearing substrate S1. The highest larval survival (>70%) and adult emergence (69%) were achieved at 26 °C. The duration from egg to adult was 16 to 20 d at 35 °C, 18 to 24 d at 26 °C, but up to 36 d at 15 °C. Elucidating the effective rearing conditionalities of this important vector species will be helpful to study the transmission cycles of pathogens.

Myiasis is a parasitic infestation of soft vertebrate tissues by larval stages of Diptera. We briefly described the lesion-causing genus Cordylobia Grünberg (Diptera: Calliphoridae). Three Polish travelers to Uganda, Gambia, and Senegal returned with furuncular myiasis. To identify the third-instar larvae removed from their skin, we examined the morphological features of the 3 specimens and sequenced a 5' barcoding fragment of the cytochrome c oxidase subunit I gene (COI-5P). One larva was identified as C. rodhaini Gedoelst, and 2 larvae were identified as C. anthropophaga (Blanchard). We were the first to submit the COI-5P of C. rodhaini to GenBank and the Barcode of Life Database. This is the first record of the importation of C. anthropophaga and the second record of the importation of C. rodhaini to Poland.

Filarial nematodes are parasitic roundworms transmitted by mosquitoes that can cause morbidity and mortality for their human and animal hosts. The filariae community, specifically infection prevalence of heartworm, Dirofilaria immitis (Filarioidea: Onchocercidae) (Leidy), and its primary mosquito vector species, has not been described in Connecticut since 1977. In light of the recent invasion and establishment of an important filariasis vector, Aedes albopictus (Diptera: Culicidae) (Skuse), we used molecular-based sequencing methods to identify filarial species infecting field-caught mosquitoes in Connecticut, United States. The filarial parasites identified include D. immitis, Aproctella sp., and Setaria sp. (Filarioidea: Setariidae). The total minimum infection rate for D. immitis for all mosquito species tested in 2020 was 0.97 [0.56 to 1.56] and in 2021 was 1.48 [0.93 to 2.24]. Aedes albopictus had the highest infection prevalence compared to other species during both years. We determined a low but persistent mosquito infection prevalence for D. immitis and suggest that Ae. albopictus is likely to be the primary vector in the region. Aproctella sp. and Setaria sp. had lower burdens compared to D. immitis. Persistent mosquito infection with filarial parasites, particularly in invasive species, poses a risk to veterinary and public health.

Dirofilariasis is a globally significant emerging-zoonotic-disease caused by nematode parasites belonging to the genus Dirofilaria (Rhabditida: Onchocercidae) and is transmitted by mosquitoes (Diptera: Culicidae) of the Culicidae family. A recent study on molecular prevalence of Dirofilaria sp. "hongkongensis" To, 2012 (nomen nudum) among the dog population in Kerala indicated a high infection rate. However, no data are currently available on the vectors involved in the transmission of this disease. In this study, an entomological survey was conducted to detect natural infection and to characterize the Dirofilaria parasite from Kani tribal settlements in Thiruvananthapuram, India. A total of 356 mosquitoes were collected, morphologically identified, and analyzed for natural infection of Dirofilaria from 4 different villages in the study area. The species composition of the collected mosquito specimens comprised 10 species belonging to 6 genera, namely Anopheles, Aedes, Armigeres, Culex, Uranotaenia, and Heizmannia. Aedes albopictus (Skuse, 1895) was found to be the predominant species, followed by Armigeres subalbatus Coquillett, 1898. Out of these, 200 female mosquitoes were grouped by species into 31 pools, for genomic DNA extraction. Detection of the nematode parasite was performed using nematode-specific primers via conventional PCR, and the species was subsequently confirmed by sanger sequencing. Natural-infection of Dirofilaria sp. "hongkongensis" was identified in Ae. albopictus and Ar. subalbatus, with a minimum infection rate of 17.6% and 13.3%, respectively. This study represents the first report of natural-infection of Dirofilaria sp. among field-collected mosquitoes in India. These findings underscore the need for robust entomological-surveillance system to prevent potential future outbreaks.

Comparative studies of the microbiota in whole-body mosquitoes from natural populations and laboratory-reared specimens are scarce, particularly in tropical countries like Colombia, where understanding microbial patterns is critical for effective disease control and vector management. This study examines the bacterial microbiota of Aedes aegypti by comparing field-collected mosquitoes from 3 Colombian regions (Southern Amazon, Central Andean region, and Northern Caribbean coast) with laboratory strains (Rockefeller, Otanche, and Tolima). These regions are highly endemic for dengue and are associated with lineage 1 of Ae. aegypti, known for its elevated vector competence. Using next-generation sequencing of the 16S rRNA gene with Illumina technology, we found that field-collected mosquitoes exhibited significantly higher alpha and beta diversity compared to laboratory-reared specimens. Field mosquitoes were enriched with bacterial families such as Acetobacteraceae, Lactobacillaceae, and Bacillaceae, while laboratory mosquitoes showed a greater abundance of Enterobacteriaceae. Differential abundance analysis revealed that Acetobacter and Bacillus predominated in field mosquitoes, whereas Asaia, Cedacea, and Chryseobacterium were more common in laboratory specimens. Notably, Pseudomonas and Acinetobacter were consistently abundant across all samples. Our findings suggest that environmental factors, such as habitat and diet, significantly influence the bacterial composition and diversity of Ae. aegypti in Colombia. Future research should further explore how these factors, alongside genetic components, shape mosquito-microbiota interactions and their implications for disease transmission and vector competence.