Medical and Veterinary Entomology最新文献

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.

Aedes aegypti L. (Diptera, Culicidae), the key vector of viral diseases to humans in the tropics, is susceptible to infection by entomopathogenic fungi. Self-grooming behaviour, which remains largely unstudied for mosquitoes, may possibly interfere with fungal infection through the cuticle. In this study, self-grooming by A. aegypti adults exposed to Metarhizium humberi Luz, Rocha & Delalibera 2019 (Hypocreales, Clavicipitaceae) conidia supplemented or not with micronized carnauba wax (MCW) led to a decrease of non-germinated conidia and of early germinative stages from their body surface up to 24 h after exposure to a fungus-treated surface. Self-grooming behaviours by adults distinctly showed increased low-level, spontaneous and stimulus-independent self-grooming after exposure to conidia with or without added MCW or only to MCW. The first pair of legs simultaneously scraped the proboscis, antennae and wings; in three separate actions, the third pair of legs scraped (a) each other, (b) the first and second legs and (c) the gonapophyses. Immediately after exposure, conidia, a conidial/MCW mixture or MCW (without fungus) was readily detectable on tarsi, tibias and femurs (especially of the first and second leg pairs), gonapophyses, proboscis, antennae and wings. In mobile adults, mean conidial numbers dropped approximately fivefold during the 24 h immediately after exposure, but especially during the first 6 h, regardless of the conidial preparation and then, to a lesser extent, in the remaining 18 h. For cold-immobilized adults, during the first day post-exposure, conidial losses were distinctly lower or insignificant. MCW neither increased the number nor enhanced the retention time of conidia on the cuticle during the time tested. These findings strengthen the importance of considering self-grooming of mosquitoes – particularly regarding A. aegypti, the vector examined here – when developing specific fungal formulations for use in biological control.

The Aedes aegypti mosquito is generally associated with arboviruses that cause yellow fever, dengue, zika and chikungunya. The most efficient way to control their populations is through application in breeding sites of highly toxic insecticides that can also impact non-target organisms and generate resistant populations. Therefore, the use of compounds is desirable. Morin hydrate has broad pharmacological applications based on its antioxidant potential, in addition to not having negative effects on mammals. Therefore, the objective of the present study was to investigate the effects of morin hydrate on A. aegypti survival, pupation rate, egg laying, triacylglycerol reserves and expression of proteins related to lipid metabolism 24 h after exposure of larvae. For this, rearing media containing A. aegypti larvae with different concentrations of morin hydrate were formulated to evaluate the lethal concentration. Calculation of the expected lethal concentrations showed LC₂₅ of 52.692 μM, LC₄₀ of 111.121 μM, LC₅₀ of 174.775 μM, LC₇₅ of 575.083 μM and LC₉₀ of 1685.936 μM. Twenty-four hours after treatment with morin hydrate, surviving larvae were transferred to morin-free water with food, and their pupation rate and fertility were evaluated. We observed that an increase in the concentration of morin hydrate induced a dose-dependent reduction in survival, doubled pupation time in survivors and reduced the number of eggs laid by treated females during the larval stage by approximately 30% at concentrations exceeding 100 μM. From this, the impact of 24 h on the triacylglycerol (TAG) stock was evaluated, in addition to evaluating the expression of proteins involved in lipid metabolism. Larvae 24 h after treatment with 100 μM morin showed a reduction in TAG reserves of approximately 17%, while at 175 μM, there was a reduction of more than 33% in stocks, and at 500 μM there was a reduction of 61%. Furthermore, the lipolytic proteins TAGL1 and HSL were upregulated, while the lipogenic proteins FAS1, DGAT1 and GPAT1 were downregulated. Insulin-like receptors were also downregulated, unlike AKHr, which was also upregulated. These data demonstrate that morin hydrate reduces the survival and fertility of A. aegypti by affecting its lipid metabolism. Morin hydrate did not exhibit toxicity toward non-target organisms, demonstrating interesting potential for the control of mosquito populations.

The Amblyomma cajennense (Fabricius) complex (Acari: Ixodidae) is represented by six species of hard ticks widely distributed from southern Texas in the United States to northern Argentina. Species within the complex feed on a variety of vertebrate hosts, primarily mammals, including humans. These ticks are the main vector of the bacterium Rickettsia rickettsii (Brumpt; Rickettsiales: Rickettsiaceae) and have been associated with the transmission of several arboviruses. In Colombia, one of the most ecologically diverse countries of the Neotropics, two species of the complex have been recorded with sympatric distribution in the northwestern part of the country: Amblyomma mixtum (Koch) and Amblyomma patinoi (Labruna, Nava & Beati). The latter is of medical importance as it has been confirmed as a competent vector of R. rickettsii in inter-Andean valleys of Colombia. Here, we assessed the current distribution of A. patinoi and predicted changes in its distribution over the century under different climate change scenarios. Additionally, we incorporated new records, delved deeper into the distribution of A. patinoi and interpreted model results using the climate classification and ecoregions for the Neotropical region. The results showed the presence of A. patinoi in 79 localities distributed across 34 municipalities and seven departments of the Caribbean and Andean regions of Colombia. In addition, new records were identified in two additional departments (Valle del Cauca and Caquetá) of the Andean and Amazon regions, as well as additional records in the department of Cundinamarca, especially in the inter-Andean Magdalena River basin. A. patinoi has been recorded in five ecoregions (Cauca Valley Dry Forests, Guajira-Barranquilla Moist Forests, Magdalena Valley Dry Forests and Magdalena-Urabá Moist Forests) and is associated with horses, cattle, dogs and humans. Its elevational range extends from 8 to 645 m a.s.l. in the Caribbean region and from 497 to 1712 m a.s.l. in the Andean region and inter-Andean valleys. The potential distribution models suggest that A. patinoi presents high climatic suitability in the Caribbean areas and inter-Andean valleys. Under climate change scenarios a possible expansion of the species distribution is observed in areas currently not recorded in the Neotropics, in countries such as Brazil, Peru and Venezuela. However, geographical conditions, such as elevation, could limit its distribution at higher elevations.