Medical and Veterinary Entomology最新文献

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.

Anopheles (Anopheles) pseudopunctipennis, involved in seasonal malaria transmission in the Andean foothills and American coastal areas, was previously proposed as a species complex based on cross-mating experiments and population genetic analyses. In this work, a fragment of the mitochondrial gene cytochrome c oxidase subunit I or COI barcode region, and the nuclear second internal transcribed spacer (ITS2) were analysed in Colombian An. pseudopunctipennis s.l. specimens; the obtained sequences were compared to publicly available data using phylogeny and distance-based species delimitation approaches. Assemble Species by Automatic Partitioning (ASAP) and coalescent-based approaches provided strong evidence of at least two putative species on the American mainland, here designated as the North-Central and Southern lineages. The North-Central lineage is primarily found in southern/southwestern United States, Central America (Mexico and Honduras) and northwestern Colombia, while the Southern lineage is mainly detected in the Colombian Pacific and Argentina; there were some co-occurrences of these lineages in the Colombian regions. The definition of these putative species is crucial for understanding their bionomy, ecology and potential role in malaria transmission. Further research, including a more comprehensive sampling and population genetic analysis, is needed to fully elucidate their evolutionary history and demographic dynamics.

Maintaining fitness is an important consideration when mosquitoes are mass-reared for the deployment of genetic interventions that are designed to suppress populations because released mosquitoes need to compete with wild-type mosquitoes. Late-hatching mosquitoes are more suitable for transportation to remote field sites. Here, we investigated the fitness of late-hatching phenotypes in Anopheles coluzzii. Selected lines of the VK strain (from Burkina Faso) were created through bidirectional selection for early and late hatching, over 20 generations. These were compared with each other and the established Mopti reference strain from Mali, reared in the lab for >16 years. Significant differences in life-history traits were found between Mopti and VK strains but few differences were found between the selected VK lines. Considering that late-hatching VK lines showed no evidence of fitness costs, our results suggest that the late selected VK lines, which start hatching after 4 days, are an alternative option for egg shipment for mass mosquito releases over the well-established Mopti that hatches within 2 days and has lower adult survival.

Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), the human head louse, is a parasitic insect responsible for pediculosis, a global health concern. In a previous study, we demonstrated that this hematophagous insect is attracted to a solvent extract from its faeces. In this study, we evaluated the head louse attraction towards mixtures of the three main components present in faeces (uric acid, hypoxanthine and guanine). A basic uric acid:hypoxanthine:guanine (10:10:1) mixture in 0.2 M produced significant attraction towards head lice in behavioural bioassays. In another approach, we evaluated the aggregation response of groups of head lice around collected fresh faeces and around the main components of the synthetic blend. In both studies, we found a significant aggregation of head lice. Finally, we studied the effect of the addition of the attractant blend on the mortality produced by malathion and permethrin, and found an increased mortality effect for both insecticides. We concluded that the blend of the main components of the louse faeces produces both attraction and aggregation of head lice, and increases the insecticide mortality effect of malathion and permethrin insecticides. These findings can contribute to the development of new strategies for pediculosis control.

Climate change is projected to profoundly alter global biodiversity with significant implications for vector-borne disease dynamics. In tropical regions, rising temperatures and shifting precipitation patterns influence the distribution and behaviour of insect disease vectors, thereby affecting disease transmission cycles. Chagas disease, caused by the Trypanosoma cruzi and transmitted by triatomine bugs, is a major public health concern in Latin America. Brazil is particularly vulnerable to climate-driven vector redistribution due to its vast land area, diverse ecosystems and rapid land-use changes. Using ecological niche modelling and 11,640 unique occurrence records, we assessed the potential geographic displacement of 55 triatomine species under two climate scenarios: a moderate warming scenario (SSP2-4.5) and a high-emissions scenario (SSP5-8.5) for 2050 and 2080. While projections for 2050 suggest stability in vector distributions, our models indicate a substantial shift by 2080, with increasing suitability for vector populations in the Brazilian Amazon, particularly in the deforestation arc. This expansion could exacerbate Chagas disease risk in previously unaffected regions, where socioeconomically vulnerable populations face poor housing conditions that facilitate vector-human contact. Our findings underscore the urgent need for proactive vector surveillance, public health interventions and climate-adaptive disease prevention strategies to mitigate potential epidemiological risks associated with climate change.

Defecation is one of the posterior-station transmission routes for pathogens in haematophagous insects. Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) are the proven vectors of many arboviruses, most importantly bluetongue virus, protozoa, and filarial nematodes of livestock. Duration of blood feeding and defecation vary according to species. Culicoides females take blood from their hosts to acquire additional protein to develop their eggs. This study investigates the bacterial communities in defecated contents and gut of the field-collected post-defecated females of C. peregrinus and C. oxystoma. To observe the defecation period and pathogenic bacteria in their defecated contents, engorged females of both species were investigated. The females were transferred to the glass vials containing moistened cotton beds at the bottom and kept in an environmental test chamber. The females defecated within 48 h of post-blood meal intake. The defecated contents discharged by C. peregrinus contained the following bacterial species: Bacillus cereus, Bacillus flexus, Enterococcus faecium, Proteus vulgaris, and C. oxystoma: B. cereus, E. faecium, and Alcaligenes faecalis. Bacillus cereus, B. flexus, Paenibacillus sp., E. faecium, A. faecalis, and Brevundimonas sp. were obtained from the gut of post-defecated females of C. peregrinus, and B. cereus, Lysinibacillus sp., and Paenibacillus sp. were identified from the gut contents of post-defecated females of C. oxystoma. Within the defecated contents, the following pathogenic bacteria, B. cereus, P. vulgaris, and A. faecalis, were detected, which raises the chances of zoonotic posterior transmission to their hosts that should be investigated.

The house fly (Musca domestica Linnaeus, 1758) has developed resistance to several pesticides, necessitating innovative approaches for effective control. This study explores the synergistic effects of benzyl alcohol (BA) on the toxicity of deltamethrin (D) against various life stages of M. domestica larvae, pupae and adults. Additionally, molecular docking analyses were conducted to investigate interactions with the acetylcholinesterase enzyme (AChE) and voltage-sensitive sodium channel (Vssc). Two formulations of deltamethrin were tested: deltamethrin + benzyl alcohol (DBA) mix (D 5% dissolved in ethyl alcohol, then mixed with BA at its LC₅₀ concentration) and DBA combination (D 5% dissolved directly in pure BA). In vitro testing revealed significant synergistic effects. For larvae, the LC₅₀ of deltamethrin alone was 0.95 mg/mL, while the DBA mix reduced it to 0.09 mg/mL, yielding a synergism factor of 10.56. For pupae, deltamethrin's LC₅₀ was 1.32 mg/mL, compared with 0.104 mg/mL for the DBA mix, with a synergism factor of 12.69. The DBA combination also exhibited notable toxicity, with LC₅₀ values of 0.14 mg/mL for larvae and 0.16 mg/mL for pupae, corresponding to synergism factors of 6.79 and 8.80, respectively. Against adult flies, the DBA mix and DBA combination demonstrated high fumigant toxicity, with LC₅₀ values of 0.08 mg/L and 0.09 mg/L air, respectively, and synergism factors of 9.31 and 8.11. Docking analyses showed that deltamethrin exhibited a strong binding affinity to AChE, forming two hydrogen bonds with Lys480 and a pi-sigma interaction with Met351. BA occupied a separate binding pocket in AChE, forming two hydrogen bonds with Met309 and Lys335. Both compounds demonstrated strong, distinct binding affinities, confirming their synergistic inhibition of AChE. Against Vssc, deltamethrin (ΔG = -5.90 kcal/mol) formed a pi-pi interaction with Phe78 and a hydrogen bond with Lys79, while BA (ΔG = -3.79 kcal/mol) interacted with a different pocket via hydrophobic interactions. These findings highlight the potential of combining BA with deltamethrin to overcome insecticide resistance in house fly populations, offering a promising strategy to enhance pest control effectiveness.

The monoxenous Ixodid tick Rhipicephalus microplus is an economically important pest infesting cattle populations worldwide. Apart from being a vector of various diseases, they cause substantial production losses. The control against this tick is mostly through chemical acaricides, which have been undermined by problems of resistance as well as toxic residues in the environment and living beings. In spite of the development of two commercial vaccines against the tick way back in the 1990s, the anticipated results were not recorded in field conditions. The search for vaccine antigens has led to the identification of subolesin, serpins, lipocains and proteoses showing protective immune response. The efficacy of these candidate antigens is mostly assessed by the mortality of adult and larval stages and effect on reproductive performance. Similarly, the use of plant extracts, nano encapsulation of plant extracts and entomopathogenic fungi have been widely subjected to in vitro and in vivo trials to offer a cost-effective and green solution to tick infestation. In recent years, the use of modern technologies like RNA interference, in silico docking and CRISPR technology have accelerated the identification of potent antigens and active fractions of plant extracts. Integrated tick management is a good option for the eradication of R. microplus. However, the integration of chemical and non-chemical control strategies still remains a challenge. The present review article is focused on the ongoing and emerging control strategies against the tick that will help researchers evolve a sustainable solution against R. microplus infestation.