Journal of medical entomology最新文献

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.

Growing of insecticide resistance in Aedes aegypti underscores the need for alternative vector control tools. Ivermectin, an endectocide with mosquitocidal properties, is currently evaluated against Anopheles for residual malaria control. Its potential use against Ae. aegypti within integrated strategies also warrants investigation. This study assessed the effects of ivermectin-treated cattle blood on the survival and reproductive parameters of two Ae. aegypti strains: Bora Bora (insecticide susceptible) and Bobo (insecticide resistant). Laboratory-reared females were fed on cattle treated with ivermectin at doses of 0.6, 0.8, and 1 mg/kg. Blood meals were offered at 0, 2, 7, 14, 21, and 28 days after injection (DAI). Daily mortality, oviposition probability, egg production, and egg hatching rates were recorded and compared to mosquitoes fed on untreated cattle. For the Bora Bora strain, all ivermectin doses significantly reduced mosquito survival and reproductive outputs. The 1 mg/kg dose reduced survival by 66% at 2 DAI and 30% at 14 DAI. Oviposition probability declined by up to 51.9%, and egg production by 42.9%. For the Bobo strain, survival was significantly affected by the 1 mg/kg dose only (-14% at 7 DPI), though all doses led to reduced hatching rates (up to -50.7%). These findings confirm that injectable ivermectin can impair Aedes aegypti survival and fertility, particularly in susceptible populations. However, it's reduced efficacy against resistant strains and short-time toxicity limits its effectiveness in field settings. Developing a formulation that can maintain mosquitocidal concentrations over extended periods will be essential to enhance impact, cost-effectiveness, and operational feasibility.

Temperature is a key environmental factor influencing the development, survival, and transmission potential of malaria vectors. While most laboratory studies use constant temperature (CT) regimes, mosquitoes in natural habitats experience fluctuating temperatures (FTs), which may affect their life-history traits. We investigated the effects of CT (27 °C) and FT (27 ± 3 °C) on larval and adult traits of 2 major malaria vectors, Anopheles gambiae and An. coluzzii, under laboratory conditions. We measured larval survival, development time, adult body size, and adult survival, using survival and mixed-effects models. Species-specific and stage-specific responses to temperature regimes were observed. An. gambiae larvae exhibited higher survival under FT, while An. coluzzii larvae survived better under CTs. However, this pattern reversed in adulthood: An. coluzzii adults showed increased survival and larger body size under FT, whereas An. gambiae adults performed better under CT. Development time was slightly longer under FT for both species, with An. coluzzii pupating faster overall. These opposing patterns suggest that differential larval survival under FTs may influence adult fitness in a species-specific manner. The contrasting and reversed responses of An. gambiae and An. coluzzii across life stages might reflect their ecological adaptations: An. gambiae, found in small and thermally variable habitats, performed better under FT during larval stages, while An. coluzzii, associated with larger, more thermally stable habitats, showed improved adult performance under FT. These findings underscore the importance of incorporating species-specific, stage-dependent thermal responses into models of vector dynamics and control strategies under climate change.

The interceptor G2, a newly recommended dual-ingredient long-lasting insecticidal net (LLIN) by the World Health Organization (WHO), contains chlorfenapyr (pyrrole) and alpha-cypermethrin (pyrethroid), demonstrating efficacy against malaria vectors in Africa. Despite the extensive deployment of LLINs for malaria vector control across sub-Saharan Africa, there is limited understanding of their impact on non-target hematophagous pests sharing similar ecological habitats. Through contact bioassays, a total of 28 Cimex hemipterus (F.) strains from 7 regions in Ghana were tested against chlorfenapyr, alphacypermethrin, and a combined mixture at recommended label rate of Interceptor G2. We found that chlorfenapyr showed significantly lower survival times and higher mortality within 48 h post-exposure (24/28 strains ≥ 80% mortality) compared to alpha-cypermethrin (4/22 strains ≥ 80% mortality) when tested independently, indicating widespread resistance to pyrethroids. The chlorfenapyr/alpha-cypermethrin combination had comparable effectiveness (23/24 strains ≥ 80% mortality) to chlorfenapyr, and synergistic interactions between the active ingredients became more apparent at 48 h post-exposure. Late instar nymphs displayed a similar susceptibility trend to adults, but survival times were variable and often longer in the nymphs than adults. These results suggest that the deployment of Interceptor G2 nets may provide incidental but beneficial control of bed bug populations, including those resistant to pyrethroids. However, prolonged exposure to chlorfenapyr may result in resistance to chlorfenapyr in the future. This work sets a baseline for monitoring the risk and understanding the evolution of insecticide resistance in bed bugs especially to chlorfenapyr under selective pressure from future widespread use of Interceptor G2 in Africa.

Chagas disease is one of the most important vector-borne diseases in Mexico. Triatoma longipennis (Usinger. 1939) is one of the most epidemiologically important vector species of Trypanosoma cruzi (Chagas, 1909), the etiological agent of Chagas disease. This study reports the third collection of T. longipennis from the state of Hidalgo, Mexico. This paper evaluates and compares feeding and defecation behaviors for each instar of two populations of T. longipennis recently detected in Hidalgo, Mexico. No significant differences were noted between the two populations in the mean time to initiate feeding (immediate "attack"), feeding times (> 10 min), and defecation delay (when feeding or immediately after feeding: 77% to 99% vs 84.5% to 100%). These observed behaviors in the two populations of T. longipennis from Hidalgo align with the characteristics of an effective transmitter of T. cruzi. Given these results, the recently detected populations of T. longipennis could be considered significant potential vectors of T. cruzi to human populations and may replace key triatomine species within their new distribution area.