Medical and Veterinary Entomology最新文献

Culicoides (Diptera, Ceratopogonidae) biting midges serve as vectors of viruses, bacteria, filaria, and protozoans, such as dixenous avian blood parasites (Trypanosomatidae). Additionally, these insects can harbour insect-specific flagellates—monoxenous trypanosomatids—which are generally considered harmless commensals; however, in certain cases, they can increase mortality or reduce the fitness of their insect hosts. Recent studies indicate that the prevalence of trypanosomatids in wild-caught biting midges can reach up to 11.1%, while in experimentally infected individuals, infection rates can be even higher. This study explores the diversity of trypanosomatids detected in Culicoides biting midges worldwide and supplements current knowledge with new records of avian Trypanosoma occurrence in these insects from the Curonian Spit, Lithuania. Wild-caught biting midges collected in 2020–2022 using UV light traps were tested for the presence of trypanosomatids using polymerase chain reaction (PCR)-based methods. Both morphological and molecular methods were used for Culicoides species identification. Four species of Trypanosoma were determined in biting midges belonging to eight different species. Avian trypanosomes from the T. bennetti group, T. avium, and T. culicavium were detected in C. pallidicornis/subfascipennis, C. segnis, C. kibunensis, C. festivipennis, C. pictipennis, C. duddingstoni, C. impunctatus, and biting midges of the C. obsoletus group. Additionally, mammal-infecting Trypanosoma from the T. theileri group were detected in C. pictipennis. Monoxenous Herpetomonas ztiplika and Sergeia podlipaevi were found in C. obsoletus group, C. segnis, C. pallidicornis/subfascipennis, C. kibunensis, C. pictipennis, C. festivipennis, and C. impunctatus biting midges as well. This study reports, for the first time, the presence of avian Trypanosoma in C. duddingstoni females and also reviews previous research data on the prevalence of both monoxenous and dixenous trypanosomatids in different Culicoides species. Our results enhance the understanding of trypanosomatid diversity in Culicoides biting midges and update the list of Culicoides species that should be considered in research on their role as potential vectors of avian Trypanosoma.

The Ceratopogonidae family, comprising over 6000 described species, includes the genus Leptoconops, which has been understudied despite its ecological significance and biting nuisance to humans. Here, we document the presence of inland Leptoconops noei populations for the first time in Italy in an area previously considered environmentally atypical for this species. Our findings expand the known range of L. noei, traditionally confined to coastal areas, and highlight its potential to colonise diverse habitats. Interestingly, despite the thorough morphological and molecular identification of sampled individuals and their clear assignment to the species L. noei, a notable morphological variability was observed in the sensory structures of the maxillary palps, suggesting the possibility of a new morphotype or environment-driven adaptations. Phylogenetic analyses of COX1 sequences revealed negligible genetic differentiation between the newly discovered inland population and coastal populations, suggesting recent separation or gene-flow connection. These findings underscore the ecological adaptability of L. noei, which poses risks of human-biting nuisance, allergic reactions and even possible economic losses in recreative areas, in a range of locations wider than previously assumed. Additionally, this study reports the first complete mitochondrial genome for the genus Leptoconops, offering valuable genetic insights for taxonomic clarification, evolutionary studies and future research on the biology of Ceratopogonidae.

Aedes aegypti mosquitoes account for the highest number of infections among vector-borne diseases and continue to present a formidable global health challenge. Due to the nonavailability of direct treatment of dengue, vector control relies on the use of insecticides currently dominated by pyrethroids. Recurring applications of these insecticides lead to transgenerational impacts on their fitness and resistance dynamics. This study investigates the threat to vector control techniques by altered biological fitness, metabolic and molecular properties after selection with permethrin exposure. Populations of Ae. aegypti were treated with a sublethal dose of permethrin (LC₅₀) in each generation, and their resistance status, together with its effect on biological fitness and transgenerational features, were analysed. To understand the different mechanisms of resistance development, detoxifying enzyme activity, the presence of kdr mutation and cuticular thickness were also analysed. Throughout the study, a prolonged larval and pupal stage was noted with reduced fecundity and hatchability. Moreover, biochemical assays revealed a major role of cytochrome P450 monooxygenases behind permethrin resistance, which was supported by a piperonyl butoxide assay. Major kdr mutations F1534C and V1016G were also found. Overall, reduction in life traits of resistant populations may seem in favour of vector management but this may be the manipulative strategy of Ae. aegypti to divert the essential fuels away from these features and invest it towards the maintenance of insecticide resistance. Therefore, to effectively combat resistance, insecticides must be used judiciously as part of a comprehensive strategy that includes non-insecticide methods and regular surveillance.

Ticks are key ectoparasites for the One Health approach, as they are vectors of pathogens that infect humans, domestic and wild animals. The bacteria Rickettsia rickettsii and R. parkeri are the aetiological agents of tick-borne spotted fever (SF) in South America, where Amblyomma sculptum, A. aureolatum, A. ovale and A. triste are the main vectors. Studies in the medical and biological fields show that artificial intelligence, through machine learning, has great potential to assist researchers and health professionals in image identification practices. The aim of this study was to evaluate the performance of the Convolutional Neural Networks (CNN) AlexNet, ResNet-50 and MobileNetV2 for identifying tick species transmitting SF bioagents. We organised an image database with the following groups: females (368), males (458), dorsal (423), ventral (403), low resolution (328), high resolution (498) and all together (sex+position+resolution = 826), to identify the three main vectors of SF bioagents (Amblyomma aureolatum, A. ovale and A. sculptum), two other possible vectors (A. triste and A. dubitatum) and the species A. cajennense sensu stricto (s.s.), which has similar morphology to A. sculptum but no known vectorial capacity. To evaluate the network's performance, we measured accuracy, sensitivity and specificity. We used Grad-CAM to highlight the regions of the images most relevant to the predictions. CNNs achieved accuracy rates of ~90% in identifying ticks and showed sensitivities of 59%–100% according to species, sex, position or image resolution. When considering all images, both AlexNet and MobileNetV2 recorded the best sensitivity and specificity values in identifying SF vectors. The most relevant areas for classifying species varied according to algorithms. Our results support the idea of using CNNs for the automated identification of tick species transmitting SF bioagents in South America. Our database could support the development of tick identification apps to aid public health surveillance and contribute to citizen science.

In California, public health disease surveillance data for flea-borne typhus (FBT) are generated by healthcare providers and laboratories who are responsible for notifying local health jurisdictions when the disease is detected. When accounting for the associations between socioeconomic status (SES) factors (age, race and ethnicity, poverty, unemployment, housing status and land use), R. typhi reservoir host presence (e.g., rats, cats, opossums), and healthcare-seeking behaviours, it is reasonable to consider whether these factors also lead to under-reporting of FBT surveillance and distorted estimations of incidence. This study aimed to evaluate population-level associations between SES factors and FBT surveillance reporting using a Bayesian hierarchical model including a spatially autocorrelated random effect. Census tract-level covariates were sourced from the American Community Survey and Healthy Places Index (HPI). Specifying a zero-inflated Poisson distribution to FBT surveillance report counts, we estimated spatially smoothed, census tract-level estimates of FBT surveillance report rates and attributed variability in report rates to census tract characteristics. Socioeconomic advantage, as measured by the HPI, had the largest effect (IRR = 1.34 [1.07, 1.69]), corresponding to a 34% increase in FBT surveillance reporting for every point increase in HPI score for census tracts. The results herein suggest that FBT surveillance may be biased in its ascertainment of surveillance data, which may be helpful in contextualising and interpreting current trends in FBT epidemiology.

The emergence of insecticide resistance is one of the major challenges vector control programmes face worldwide. For Chagas disease and its main vector Triatoma infestans, pyrethroid-resistant foci have severely compromised vector control and elimination efforts across sections of northern Argentina and Bolivia. We assessed the status and spatiotemporal distribution of pyrethroid resistance in T. infestans populations in Castelli (Argentine Chaco), where it had reached record levels, and tested whether the village-level prevalence of house infestation was associated with pyrethroid resistance. We also monitored the infestation and pyrethroid resistance status of a reinfested (index) house in an adjacent municipality (Pampa del Indio) under sustained triatomine surveillance and control. Eighty-three georeferenced populations of T. infestans collected in 13 villages over 2018-2024 were tested for susceptibility to deltamethrin by discriminant-dose assays. Widespread pyrethroid resistance occurred in 12 villages; 45% of the tested bug populations had very low mortality (<45%). Pyrethroid resistance levels were spatially heterogeneous between and within villages, were negatively associated with house infestation at the village level and reached record resistance ratios (RR₅₀ > 2400). Pampa del Indio's index house remained persistently infested with high resistance levels despite pyrethroid applications and other interventions (i.e., repeated control failures) over a 7-year period. Castelli's highly resistant focus has persisted for >10 year despite the near absence of government-sponsored pyrethroid applications. Alternative insecticides effective against pyrethroid-resistant T. infestans populations are urgently needed to suppress them and curtail their propagation. Sustainable triatomine control in this high-risk scenario requires an integrated vector management framework including housing and peridomestic modifications combined with community-based triatomine surveillance.

Synanthropic rodents, due to their close contact with humans, have always been a concern because of their substantial impact on both the economy and public health. This study aims to investigate the presence of ectoparasites in rodents captured during pest control campaigns in various Italian provinces (Bologna, Forlì-Cesena, Rimini, Ravenna, Arezzo) in northern-central Italy. We examined a total of 140 carcasses of brown rats (Rattus norvegicus – 81 samples), black rats (Rattus rattus – 49 samples) and house mice (Mus musculus – 10 samples). Skin samples were collected, digested in sodium hydroxide and microscopically examined after the enrichment method. The results revealed the presence of Polyplax spinulosa lice in 44 subjects (31.4%), Myobiidae mites in 13 subjects (9.3%), Laelaps echidninus and Notoedres muris in 7 subjects respectively (5%) and mesostigmata mites in 3 (2.1%). A specimen of Rattus norvegicus was positive for the flea Nosopsyllus fasciatus. The conducted research has provided an overview of the arthropods present on the fur and skin of synanthropic mice and rats in the surveyed provinces. This study represents a baseline investigation, particularly considering the lack of nationwide and scarce European data.

As most malaria parasites of humans are strict anthroponoses, mosquito preference for human blood strongly influences transmission intensity and intervention strategy. Here, retrospective analyses of observational entomological data assessed the attraction of Anopheles arabiensis and Anopheles quadriannulatus (Diptera: Culicidae) to humans by comparing their abundance in larval and adult samples collected across an ecologically heterogeneous landscape in southern Tanzania. Surveys of mosquito larvae and adults were conducted across a landscape mosaic of different habitat types, with a gradient of land use practices ranging from comprehensive conversion to agriculture and human settlement through to essentially intact natural ecosystems inside well-protected conservation areas. Larvae were collected from all water bodies within a 2 km radius of each of 40 mobile camping locations, while adults were surveyed using four light traps and one interception netting barrier trap at each transient camp. Light traps were placed at defined locations, specifically beside a human-occupied tent, near the camp, in a nearby streambed, and in an open natural glade, while the barrier trap was also placed in an open natural glade. Almost all adult Anopheles gambiae complex mosquitoes caught were unfed and presumably host-seeking. Breaking this complex down by sibling species, two to four times more An. arabiensis were caught in the light traps placed beside human-occupied tents, although barrier traps achieved somewhat higher capture rates again. In contrast, An. quadriannulatus catches were consistently low across all traps, even in wild areas where it dominated larval populations, but were highest in open glades away from the camp location and activities. The overall proportion of An. arabiensis in adult collections was higher than in larval samples (98.7% vs. 78.3%, p < 0.0001) and adults caught beside human-occupied tents had 20 times higher odds of being An. arabiensis, rather than An. quadriannulatus. Similarly, the barrier trap placed away from the camp, but frequently visited by human researchers, exhibited 22-fold enrichment of An. arabiensis. These results confirm strong attraction of An. arabiensis to humans, contrasting with complete non-responsiveness of the non-vector An. quadriannulatus. Light traps beside human-occupied tents efficiently capture anthropophagic mosquitoes outdoors, suggesting those occupants act as de facto bait hosts. In contrast, traps farthest from people give apparently unbiased representations of larval population composition, albeit with very low efficiency. However, frequent collector visits to netting barriers appear to attract anthropophagic mosquitoes, turning them into human-baited traps in practical terms.

Culex mosquitoes are assumed to be secondary vectors of Rift Valley fever virus (RVFV), with Aedes being the most important for initiating outbreaks. However, environmental change may be affecting the role Culex species play in transmission. We aimed to curate a collection of published studies from Tanzania and Kenya, identify gaps in research concerning Culex communities and establish whether sufficient spatio-temporal published data may be available for future meta-analysis. This presents a first step in leveraging published data to better understand the role of Culex in maintaining RVFV transmission. We carried out a systematic search of the published literature using Web of Science for studies that sampled Culex in Tanzania or Kenya, up until the 28th April 2023. We determined motivations for studies, their duration and the geographic coverage in relation to an RVFV risk map. We then assessed species identification methods and how these may have impacted results. Of 275 studies, 17 explicitly stated the motivation for the study was RVFV. Despite most studies being motivated by other topics, there was good coverage of studies reporting mosquito sampling in areas associated with the risk of RVFV outbreaks. Fifty studies were at least 12 months in duration. In terms of species identification, studies were c. 14 times more likely to have identified more species than just the Culex pipiens complex if they stated that they used a Culex specific key. Although the majority of published studies sampling Culex in Kenya and/or Tanzania did not state RVFV explicitly as a key motivation for research, we propose that drawing on the data contained within these wider studies may still be of value for understanding how RVFV transmission is maintained. Our work here presents a first step to this end.

Dermacentor reticulatus ticks play a crucial role in the circulation and maintenance of tick-borne pathogens (TBPs) foci in the environment. From a medical perspective, this species is particularly significant in transmitting TBPs classified within the spotted fever group rickettsiae (SFGR), primarily Rickettsia slovaca and R. raoultii. Moreover, in recent years, notable changes in the distribution of the species have been observed across various countries, including Poland. We hypothesized that south-central Poland, particularly the Świętokrzyskie Voivodeship, represents the current southern boundary of the continuous range of D. reticulatus ticks in the country. Our aim was to assess the population density and the prevalence of Rickettsia spp. in ticks collected from the studied area. For this purpose, 34 research sites were designated for field surveys. In total, 910 adult D. reticulatus ticks were collected and identified. Molecular analysis for the detection of Rickettsia spp. was conducted on a randomly selected subset of individual ticks. Selected PCR-positive samples underwent phylogenetic analysis. Using a random forest model, we explored the relative importance of environmental factors driving tick density. The model revealed that altitude, followed by humidity, were the primary determinants of tick density, while temperature and seasonality had negligible impacts. The mean density of D. reticulatus within its contiguous range was 3.3 ± 5.0 specimens per 100 m² (0.00–16.7/100 m²). Surveyed tick populations showed a high prevalence of Rickettsia spp. (24.00%–74.19%). Sequencing of the gltA gene in the selected PCR-positive samples confirmed that the analyzed strains belonged to the SFGR. In conclusion, our findings suggest that south-central Poland currently forms the boundary of the contiguous range of the D. reticulatus population, which is characterized by moderate density and a high prevalence of Rickettsia spp. This study underscores the influence of ecological factors on tick distribution and highlights the need for continued surveillance of this medically significant vector and its associated pathogens.