Journal of medical entomology最新文献

Malaria continues to be a major public health issue in Ghana, contributing significantly to hospital outpatient visits. Vector control remains central to malaria prevention; however, the growing resistance of malaria vectors to insecticides presents a major obstacle to control and elimination efforts. This review examined the evolution of insecticide resistance in Ghana from 2001 to 2024, summarising resistance mechanisms across the country's bioclimatic zones to inform evidence-based vector control strategies aligned with Ghana's malaria elimination goals. A systematic literature search was conducted using PubMed, Google Scholar, and Scopus databases to identify studies on insecticide resistance in major malaria vectors. A total of 41 articles were retrieved, and data were analysed using Microsoft Excel 365 and GraphPad Prism v.9.1.2. Pyrethroids were the most frequently studied insecticides, particularly in the Coastal (48%, n = 17), Forest (37.1%, n = 13), and Sahel (14.3%, n = 5) zones. An increasing trend of pyrethroid resistance in Anopheles gambiae s.l. was observed across all transmission zones, with the vgsc-L995F mutation being the most reported resistance mechanism. Temporal analysis revealed significant differences in resistance levels over time across all zones. Resistance to dual-active ingredients (piperonyl butoxide + pyrethroid) was also detected nationwide. Notably, there are limited studies on An. funestus susceptibility and metabolic resistance driven by copy number polymorphisms or vgsc variants. Given these gaps, the application of genomic surveillance and whole genome sequencing is essential for identifying locally relevant resistance mechanisms to guide future vector control interventions in support of Ghana's malaria elimination efforts.

Arachnophobia is a widespread phenomenon, despite the fact that the vast majority of spiders pose no meaningful threat to people. The introduction and spread of an invasive spider (Trichonephila clavata L. Koch, 1878) to the United States has prompted questions about whether it should be considered dangerous. These questions are particularly relevant because the spider is large, builds webs on and near human structures, and has been documented to consume small vertebrate prey. To understand the realistic threat this species represents, we examined spider-human interactions in the field with escalating levels of contact intensity. During these interactions, spiders primarily moved to avoid human contact, and bites were incredibly rare, mainly occurring when spiders were forcibly restrained. To assess the medical significance of a bite by T. clavata, we conducted what we believe to be the first controlled study of spider bites. Spiders were induced to bite volunteers under controlled laboratory conditions while supervised by medical staff. Subjects who were bitten reported reliably low levels of pain and only localized physical symptoms (eg redness and swelling) that attenuated quickly. It is clear that this spider is unlikely to bite someone who encounters it in nature, and the symptoms are minor and fleeting in the event of a bite. Although T. clavata is spreading quickly in the United States, the risk of its bite or resulting symptoms should not be cause for fear.

The United States Centers for Disease Control and Prevention introduced the National Tick Surveillance Program in 2018 to better define areas of acarologic risk in response to the increasing burden of blacklegged tick (Ixodes scapularis, Acari: Ixodidae)-associated infections. The program coordinates surveillance efforts conducted by state and local public health programs and collates acarological data in the ArboNET Tick Module national database. Among the metrics collected, the density of infected host-seeking nymphs (DIN) is believed to be most closely correlated with the reported occurrence of tick-borne diseases. Here, we assess the completeness and geographic representativeness of pathogen-specific DIN data collected from 2004 to 2023 and reported to the ArboNET Tick Module. We summarize county, state, and regional variation in the density of host-seeking I. scapularis nymphs infected with 6 human pathogens: Borrelia burgdorfieri sensu stricto (Spirochaetales: Spirochaetaceae), Borrelia mayonii (Spirochaetales: Spirochaetaceae), Borrelia miyamotoi (Spirochaetales: Spirochaetaceae), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), Ehrlichia muris eauclairensis (Rickettsiales: Ehrlichiaceae), and Babesia microti (Piroplasmida:Babesiidae). Although DIN data submissions have increased from the first to the second decade of surveillance in some regions (Northeast, Ohio Valley, Northern Rockies and Plains), they have decreased in other regions (South, Southeast). For a majority of counties across all regions, county DIN estimates were largely based on only a single annual DIN estimate per pathogen over the nearly 20 yr of surveillance. Despite the sparseness of DIN records in ArboNET, we show that acarological risk for Lyme disease has expanded geographically over the past 2 decades, and we present acarological risk maps for other I. scapularis-borne infections across the eastern United States.

Dermacentor albipictus (Packard), the winter tick, is a one-host tick often found in high numbers on horses, moose, elk, and deer in the northern United States and parts of Canada. In Mississippi, there have been very few collections of D. albipictus. Herein we report the collection and molecular screening of 5 male specimens and 3 nymphs of the winter tick for rickettsial organisms. Broad PCR screening using a PanRickettsia TaqMan PCR assay targeting a portion of the 23 s gene was utilized, and a family-wide Anaplasmataceae SYBR real-time PCR assay was chosen for initial screening of tick eluates. PanRickettsia PCR-positive samples were then amplified using a conventional PCR targeting the citrate synthase (gltA) gene for species identification. One resultant amplicon was 99.75% identical to Rickettsia felis DNA. This is the first report of R. felis in the winter tick, D. albipictus.

Chagas disease is caused by Trypanosoma cruzi Chagas, a parasite with a life cycle involving hematophagous triatomines and vertebrate mammals as hosts. The parasite's metapopulation is nested within its biological habitat patches, or hosts. In anthropogenic landscapes, the hierarchical arrangement of territorial units (locality, block, property) complicates the identification of an appropriate geographic patch size to assess parasite and host persistence. In this study, we evaluated local spatial co-occurrence patterns among Triatoma dimidiata (sensu lato) (Latreille), Didelphis virginiana Allen, and T. cruzi using 3 distinct patch sizes: (i) property area (x¯=3115 ± 1.01 m2), (ii) perceptual range of D. virginiana (x¯=16241 ± 5.29 m2), and (3) urban block area (x¯=36473 ± 4.89 m2) averages, replicated across 10 localities in Yucatán, Mexico. A total of 1,437 host individuals were sampled, with infection prevalence reaching 12% in triatomines and 50.1% in opossums. We delineated over 13,000 spatial patches for assessing parasite-host dynamics. Our results showed that block-sized patches had a higher density of hosts and stronger host-parasite interactions, resulting in increased parasite occupancy in a smaller number of patches. While interactions varied more across localities in these patches, most localities exhibited significant spatial autocorrelation in patches defined by the perceptual range of D. virginiana. Co-occurrence patterns were best captured at the urban block scale. Increasing patch size led to a higher probability of non-random spatial co-occurrence, indicating that geographic patch size is a key factor in understanding how the spatial ecology of its hosts affects the distribution and persistence of T. cruzi.

The Aedes aegypti (Linnaeus, 1762) is the principal vector of dengue, chikungunya, Zika, and yellow fever viruses, worldwide. The rate of infected people notifications, have risen in recent years in of Brazil, especially dengue, reinforces the need for the genetic monitoring of these populations, to provide insights into the population dynamics of this vector. So, a population study has been conducted using sequences of 2 mitochondrial genes in Ae. aegypti 22 populations from northeastern Brazil. The analyses identified 33 and 28 haplotypes of ND4 and COI, respectively, with high levels of genetic diversity (ND4; Hd = 0.644, COI; Hd = 0.646) and the existence of two genetic clusters (k = 2). F  ST values and AMOVA indicated that most of the genetic variation is intra-population (ND4-56.17%, F  ST = 0. 43834; COI-60.76%, F  ST = 0.39242). The genetic distances between the locations ranged from moderate (ND4 = 0.095 and COI = 0.106; P < 0.05) to high (ND4 = 1.00 and COI = 0.951; P < 0.05). In contrast, the genetic structure observed cannot be explained by the isolation-by-distance model (ND4-r = 0.0151, P = 0.114; COI-r = 0.0005, P = 0.415). The phylogenetic analysis identified that some of the obtained haplotypes grouped themselves with haplotypes from West African and East African samples, the mosquito's bionomics were fundamental to the adaptation and expansion of the species worldwide. This information extends the knowledge about the effects of ecological relationships in the genetic diversity of Ae. aegypti in Brazil, being a key factor understanding its adaptability, vector competence and resistance, essential information for planning public policies and to control the of arboviruses.

Aedes aegypti (L.) is the primary vector of several arboviruses, including chikungunya, dengue, Zika, and yellow fever viruses. While models have predicted a low likelihood for establishment of Ae. aegypti in the arid climate of the Las Vegas Metropolitan (Statistical) Area, United States, surveillance indicates it is established. Since its initial detection in 2017, its distribution has spread over the Las Vegas metro area, which has low precipitation and hot summers. We mapped the spread of Ae. aegypti over 5 yr using adult catches. A total of 407 census tracts in metro Las Vegas were surveyed at least once for a total of 8,895 trap nights. In 2017, 5 of 117 (4%) surveyed census tracts were positive. By 2023, the number of positive census tracts increased to 147 of 276 (53%). Our study highlights the need for effective vector control measures and public health strategies to mitigate the growing risk of vector-borne diseases in Las Vegas and other urban areas experiencing similar introductions of Ae. aegypti.

Vector-borne viruses like Bluetongue (BTV) and Schmallenberg virus (SBV) pose an ongoing threat to livestock health across Europe. Transmitted by Culicoides biting midges, these pathogens can circulate silently, escaping early detection. In this study, we investigated the presence and infection status of Culicoides on 2 cattle farms in northwestern Italy, where congenital malformations and abortions had previously been reported. Between June and October 2023, over 4,000 Culicoides were captured using UV-light suction traps; over 95% belonged to the C. obsoletus complex. Molecular screening of pooled insects revealed a low viral prevalence (0.5%) for both BTV and SBV. Notably, no official outbreaks were recorded in the area during 2023, suggesting a silent viral circulation without clinical signs in animals. The persistence of BTV in vectors and possible animal reservoirs, including wildlife, may have contributed to its reemergence in 2024 when a new BTV outbreak occurred in northern Italy. Our findings highlight the critical role of continuous entomological and virological surveillance in anticipating and mitigating future outbreaks.

Bait trapping is a common practice throughout the field of entomology to target specific groups of insects for research interests like surveys of presence, abundance, and distribution. This technique can also be used to capture live insects to use in further research studies or to establish laboratory colonies. This study investigated the effectiveness of different types of bait, levels of bait decomposition, and environmental effects for live traps targeting carrion-associated families Calliphoridae and Sarcophagidae. Trapping was conducted over a 3-mo period in the summer in Stephens County, Texas. Model selection was used to analyze the effects of bait type, decomposition level, temperature, and relative humidity on overall trap capture at the family level for Calliphoridae and Sarcophagidae, and the species level for Lucilia mexicana Macquart (Diptera: Calliphoridae). Though the data were highly variable and did not show high R2 in the best models, relative humidity was always included in the best models and may play an important role in the number of flies captured during bait trapping. There is also evidence of an interaction between relative humidity and bait type present in some models describing the number of Calliphoridae collected. The results of this study indicate a need for further research into the interactions between environmental variables like relative humidity on bait types commonly used in field trapping for carrion-associated flies.

Aedes albopictus (Skuse), the Asian tiger mosquito, is an efficient arbovirus vector adapted to suburban and forested environments, including rubber plantations. Effective surveillance requires reliable sampling techniques to assess mosquito abundance and transmission risk of mosquito-borne diseases. This study evaluated the efficacy of moving-sweep net collection (MSC) relative to human landing catch (HLC) for collecting Ae. albopictus during peak biting periods and estimated their parity rates, mosquito longevity, and vectorial capacity (VC). Both methods were evaluated in 3 rubber tree plots by rotating collectors' positions with respect to methods and plots over 24 d, with daily collection conducted from 07:00 to 10:00 and from 14:00 to 17:00. A Generalized Linear Mixed Model analysis with negative binomial distribution revealed HLC generally outperformed MSC in morning collections. However, afternoon collections consistently yielded higher mosquito counts across both methods and specific plots, with MSC occasionally showing higher efficiency in the afternoon. Both MSC and HLC significantly affect the age structure estimation of Ae. albopictus, particularly in the morning, where MSC captured a greater proportion of parous and older females. These differences in collection efficacy and parity rates influenced survival and infective lifespan, leading to MSC-collected mosquitoes showing a slightly higher estimation of VC than HLC. While HLC is practical for small areas, it is less effective for sampling spatially scattered mosquitoes. Whereas MSC is a reliable, efficient, and rapid sampling technique for representative sampling of mosquitoes in large, heterogeneous areas. Integrating standardized sampling methods such as MSC and HLC with age-grading techniques can improve vector surveillance and disease risk assessment.