Medical and Veterinary Entomology最新文献

The control of zoonotic and vector-borne pathogens is challenging due to the limited availability of intervention tools. West Nile virus (WNV) is an example of a globally distributed zoonotic arbovirus that circulates between Culex species (Diptera: Culicidae) mosquitoes and avian hosts, with spillover transmission to humans, resulting in disease cases. Interventions delivering systemic insecticides to vertebrate hosts used by vector species, known as xenointoxication, are potential tools for managing vector populations by creating toxic bloodmeals. In this study, we evaluated the impact of two systemic pesticides (ivermectin; Ivomec® Pour-On and fluralaner; Bravecto®), and one anthelmintic (fenbendazole; Safe-Guard® Aquasol) on the mortality of Cx. quinquefasciatus Say (Diptera: Culicidae). We found no significant difference in the feeding rates of mosquitoes that fed on treated chickens compared with those fed on untreated chickens, suggesting that the treatment did not repel mosquitoes. The mortality of Cx. quinquefasciatus mosquitoes feeding on fluralaner-treated chickens was significantly higher (p < 0.01) than those fed on control chickens at 3 and 7 days post-treatment, but this effect was not observed in mosquitoes fed on chickens treated with fenbendazole or ivermectin. No differences in mortality were observed among the groups at 14, 26 or 56 days post-treatment. These data support fluralaner as a xenointoxication tool to control Cx. quinquefasciatus populations and decrease the risk of human exposure to their associated pathogens.

Ground water tanks are known to be preferred Aedes aegypti oviposition places providing opportunities for adult and larvae control. Therefore, a dual-effect insecticidal coating (IC) (alphacypermethrin/ pyriproxyfen) with a slow-release mechanism and safe for users could be applied within Aedes spp. breeding sites, representing a promising option. Bioassays were designed to determine the mortality and sterilizing effects on gravid mosquitoes exposed to IC. The effect of inhibition of emergence was evaluated in eggs, larvae and pupae exposed in different containers. For the water safety assessment concentrations of active ingredients were determined by reverse phase high performance liquid chromatography (RP-HPLC) and the health risk was calculated. The IC applied to the interior walls of water-holding containers showed efficacy against Ae. aegypti in terms of high gravid-female mortality (81% at 24 h, p < 0.01), sterilizing effect (inhibition of oviposition by 63%, p < 0.01) and emergence inhibition (100% in eggs, L3 and L4; 97% in pupae). The offspring rate was reduced [only 0.15 (38/250) new adults emerged per exposed gravid females as against 11.90 per unexposed female (2976/250) at baseline]. Emergence inhibition was recorded up to 12 months and adult mortality >80% up to 6 months. The use of water stored in treated containers, either for washing or drinking, is not expected to pose a health risk to users. IC applied to domestic water containers has dual and complementary action that reduces Ae. aegypti densities (immature and adult stages). This represents baseline information for a cluster randomized efficacy trial in Colombia.

Culex species, such as Culex quinquefasciatus and Culex nigripalpus display a range of feeding habits and act as vectors for pathogens that can cause diseases in both humans and animals. Understanding their feeding habits is pivotal for enhancing disease prevention strategies. The present study introduces the application of two multiplex real-time PCR (qPCR) followed by high-resolution melting (HRM) as a cost-effective and time-efficient alternative. This investigation involved the development of two multiplex qPCR-HRM: assay 1 detects human, dog and chicken, while assay 2 detects cat, cattle and horse in Culex sp. engorged female mosquitoes. The qPCR-HRM reactions showed a detection limit of one copy of genomic DNA when performed as single and multiplex qPCR-HRM. The reaction efficiencies were 97.96% for human, 100.60% for dog, 99.03% for chicken, 99.92% for feline, 99.18% for cattle and 97.68% for horse. The qPCR-HRM method, employing multiplex 1 and 2, was applied to field-collected mosquitoes and demonstrated the ability to detect DNA from multiple blood sources within a single sample. By analysing both multiplexes, it was possible to identify up to five distinct blood sources in Cx. quinquefasciatus and Cx. nigripalpus, and up to two sources in Culex coronatus. Sequencing corroborated the qPCR-HRM results, confirming the presence of DNA from one to four different blood sources with 100% accuracy. The development of these molecular methods may contribute for identification of blood-feeding patterns in mosquitoes. It contributes to studies on the dissemination and transmission of pathogens among various animals and humans, thereby bridging the gap between epidemiology and vector monitoring.

The diversity and abundance of vectors are essential parameters in the transmission dynamics of West Nile virus (WNV) between its avian reservoirs and clinically susceptible mammalian species. Knowing the determinants of vector abundance could be thus useful in preventing West Nile fever (WNF) cases and associated socio-economic impact. We designed a survey at the wildlife–livestock interface to test the hypothesis that variations in environmental favourability between anthropized and wild scenarios modulate WNV vector abundance and transmission risk. In a continental Mediterranean region where WNF has recently emerged, we selected nine sampling sites and allocated three areas to every site with a decreasing gradient of wildlife–livestock interaction: A₁—a horse farm where interaction is maximal; A₂—a zone of intermediate interaction 500–1000 m from the farm; and A₃—an entirely wild zone of low interaction 1–5 km from the farm. At a fortnightly frequency, we estimated mosquito abundance at each of the 27 study sites in May–December 2018 and April–July 2019. We estimated bird and mammal abundance, collected meteorological information and characterised mosquito habitat at the site scale. Thereafter, we studied the determinants of Culex spp., Culex pipiens sensu lato (s.l.) Linnaeus, 1758 (Diptera: Culicidae) and Culex theileri  Theobald, 1903 abundance by constructing negative binomial generalised linear mixed models. We identified 20 mosquito species, with a notable predominance of Culex spp. and, particularly, of Cx. pipiens s.l. We found differences in the spatiotemporal distribution of Culex spp. abundance and confirmed our hypothesis by finding important effects of local environmental variations in abundance. The accumulated rainfall in fortnights 4–14 and the mean temperature of the two fortnights before sampling were positively and statistically significantly associated with the abundance of Cx. pipiens s.l. (Z = 13.09, p < 0.001, and Z = 9.91, p < 0. 001, respectively) and Culex spp. (Z = 13.35, p < 0.001, and Z = 6.99, p < 0.001, respectively), while the mean temperature of the two previous fortnights was a positive statistically significant predictor (Z = 14.69, p < 0.001) of the abundance of Cx. theileri. The farm environment was the most conducive predictor to hosting Culex spp. compared with wild settings. Our results indicate that continental Mediterranean environments are favourable for WNV circulation and maintenance, especially the environment of anthropized rural settings such as farms. These results will have an impact on the spatiotemporal risk prediction of WNF emergence in continental Mediterranean environments.

This study aimed to assess the presence of Anaplasma, Ehrlichia and Rickettsia species infecting wild birds and their associated ticks in two localities: Moconá Provincial Park (MPP) and Piñalito Provincial Park (PPP), within the Atlantic rainforest ecoregion of Argentina. A total of 142 birds were captured representing 34 species, 28 genera, 15 families and five orders. Ticks were collected from 33 of these birds, comprising 19 species, 14 genera and one order. A total of 59 ticks were collected and identified as Amblyomma calcaratum (13 larvae and four nymphs), Amblyomma longirostre (31 larvae and four nymphs), Amblyomma ovale (one larva and one nymph) and Haemaphysalis leporispalustris (five larvae). All samples were screened for detection of Anaplasma, Ehrlichia and Rickettsia DNA by polymerase chain reaction (PCR) assay. Four bird species tested positive for Anaplasmataceae, with three closely related to Anaplasma and Ehrlichia species previously reported in A. calcaratum adults from a site 15 km away from MPP. The fourth Anaplasmataceae agent was phylogenetically related to Ehrlichia strains reported in Amblyomma triste from the Delta and Parana Islands ecoregion. Additionally, two Rickettsia species were detected and molecularly identified within ticks collected from birds: Rickettsia amblyommatis in A. longirostre larvae and Rickettsia rhipicephali in H. leporispalustris larvae. These findings suggest that birds may play a significant role in the spread of ticks and their associated tick-borne pathogens across diverse biomes.

It is often necessary to use motorised transport to move live mosquitoes from distant field collection points into a central insectary, so that their behavioural and/or physiological phenotypes can be assessed under carefully controlled conditions. However, a survey of heritable insecticide susceptibility traits among wild-caught Anopheles arabiensis mosquitoes, collected across an extensive study area composed largely of wilderness in southern Tanzania, necessitated that live mosquitoes were carried on foot over distances up to 25 km per day because most of the area was impassable by car, motorcycle or even bicycle during the rains. A self-cooling, self-humidifying carrier backpack was therefore developed that allows live adult mosquito specimens to be transported across rugged miombo woodland and floodplain terrain throughout the year. This wettable backpack was fabricated from stitched Tanzanian kitenge cotton fabric and polyvinyl chloride–coated fibreglass netting that allows easy circulation of air in and out. An outer cover flap made of cotton towelling embedded inside a kitenge envelope overhangs the fibreglass netting upper body of the bag, to protect mosquitoes from direct sunlight, and can be soaked with water to maintain low temperature and high humidity inside. Mean survival of insectary-reared female An. arabiensis transported through nine different mobile camps inside the 509 km² Ifakara-Lupiro-Mang'ula wildlife management area (ILUMA WMA), over up to 143 km and 25 days, was statistically indistinguishable from those left in the field insectary over the same period. Although considerable variance of survival was observed between different batches of mosquitoes from the insectary and between individual cups of mosquitoes, the different levels and positions inside the backpack had no influence on this outcome. Temperature and humidity inside the backpack were maintained at standard insectary conditions throughout, despite much more extreme conditions immediately outside. When the backpack was used to transport wild An. arabiensis and Anopheles quadriannulatus across a much larger study area of >4000 km², encompassing the ILUMA WMA, some nearby villages and adjacent parts of Nyerere National Park (NNP), it achieved a mean survival rate of 58.2% (95% confidence interval 47.5–68.2). Encouragingly, no difference in survival was observed between ILUMA WMA and NNP even though transport back from NNP involves much longer distances, sometimes involving lengthy journeys by car or boat. Overall, this mosquito carrier backpack prototype appears to represent a viable and effective method for transporting live wild-caught mosquitoes on foot across otherwise impassable terrain under challenging weather conditions with minimal detrimental impact on their survival.

Culicoides biting midges (Diptera: Ceratopogonidae) are known vectors of multiple arboviruses of veterinary and medical importance, as well as avian haemosporidian parasites. Despite their significant role as vectors, the distribution of Culicoides species in non-farmland habitats remains largely unknown. We conducted a study to assess the species community composition, abundance, and host feeding patterns of Culicoides biting midges in urban ecosystems in northern Spain. Light-baited suction traps were operated biweekly for 6 months across six urban landscapes (three cemeteries and three green areas). In total, 181 Culicoides specimens of 18 species were morphologically identified, with the Obsoletus complex being predominant (43.% of the total catches), followed by Culicoides kibunensis (21.5%). Culicoides midges peaked in early June in green areas and in May in cemeteries. Host feeding patterns revealed avian preferences (mainly Turdus spp.) in four Culicoides species. Despite the low overall number of specimens collected, a high diversity of biting midge species was recorded. These findings offer critical insights into Culicoides ecology and their interactions with hosts in urban settings, which are vital for disease surveillance and management strategies.

Vector-borne diseases pose a significant threat to human and animal health worldwide, with arthropods, including fleas and lice, acting as key vectors for transmitting various pathogens. In Uzbekistan, where millions of domestic dogs coexist with humans, the diversity of vector-borne pathogens carried by ectoparasites remains largely unexplored. This study aimed to investigate the diversity and prevalence of lice and pathogens carried by fleas and lice collected from domestic dogs in Uzbekistan. Ectoparasites were collected from 77 dogs across five regions and subjected to morphological identification and molecular analysis. The 47 lice collected were identified as Trichodectes canis Fabricius, 1780 (Psocodea: Trichodectidae), Linognathus africanus Kellogg and Paine, 1911 (Psocodea: Linognathidae) and Bovicola bovis Linnaeus, 1758 (Phthiraptera: Trichodectidae), alongside with 197 fleas. Notably, L. africanus was detected for the first time on dogs worldwide. Molecular screening detected Rickettsia spp. in 27.9% fleas and 44.7% lice, Dipylidium caninum Linnaeus, 1758 (Cyclophyllidea: Dipylidiidae) in 1.5% of fleas and Bartonella spp. in 0.5% of fleas. Sequencing confirmed Rickettsia asembonensisMaina et al., 2016 (Rickettsiales: Rickettsiaceae), Rickettsia helvetica Beati et al., 1993 (Rickettsiales: Rickettsiaceae), Rickettsia monacensis Simser et al., 2019 (Rickettsiales: Rickettsiaceae), D. caninum and Bartonella clarridgeiae Lawson and Collins, 1996 (Hyphomicrobiales: Bartonellaceae). These findings highlight the potential role of dogs as reservoirs for vector-borne pathogens and emphasises the need for further research to inform effective disease control strategies.

The cattle tick Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Ixodida, Ixodidae) is responsible for significant economic losses in bovine production in tropical and subtropical regions worldwide. Control of this tick predominantly involves the use of chemical acaricides; however, their indiscriminate use has led to the selection of resistant populations. A survey on tick populations was conducted in the state of Rio Grande do Sul, in Brazil, to assess the prevalence of multiple resistance to acaricides in cattle farms. Additionally, questionnaires were administered to identify potential risk factors associated with multiple resistance to acaricides. In total, 176 farms with a bovine population of ≥40 cattle were randomly assigned for tick sampling. The resistance to six acaricidal compounds was investigated by bioassays. A larval packet test was performed for amitraz, chlorpyrifos, cypermethrin, fipronil and ivermectin. Fluazuron was screened using an adult immersion test. Multiple resistance to acaricides (i.e., resistance to three or more compounds) was detected in 173 samples, representing 98% of the total samples. Among these samples, 125 (71%) showed resistance to all six compounds tested. Additionally, we classified the resistance intensity into four levels (I to IV) based on the quartile distribution of the bioassay data. Ten samples (6%) showed high and very high levels (III and IV) of resistance to all six compounds tested. Three variables were significantly associated with multiple resistance to the six acaricides tested: (i) use of injectable acaricides to control ticks, (ii) application of more than five acaricide treatments per year, and (iii) farms with larger herds (≥232 animals). These results regarding widespread resistance and the emergence of multiple resistance to acaricides ticks are alarming and highlight the significant challenge of tick control in southern Brazil.

In Mexico, Triatoma pallidipennis is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease. Current efforts are focused on developing attractants to control these vectors, using volatile substances derived from vertebrate hosts or compounds known to attract hematophagous insects. However, the efficacy of these compounds in attracting parasite-infected triatomines remains to be evaluated. In this study, we assessed the attractant activity of octenol (1-octen-3-ol), nonanal and a mixture of odorants consisting of ammonium hydroxide, lactic acid and hexanoic acid (in a ratio of 1:0.2:0.4 respectively), at concentrations of 1, 10 and 100 ng on the N3, N4 and N5 nymphal stages of T. pallidipennis, both infected and non-infected with T. cruzi. We also evaluated the synergistic effect of the most effective compounds and doses. All experiments were performed in a laboratory using a Y-type glass olfactometer. We found that both infected and non-infected N3 and N4 nymphs were attracted to low doses of octenol, nonanal and the odorant mixture. Particularly noteworthy was the synergistic effect observed between the odorant mixture and nonanal, which significantly increased attraction of T. cruzi–infected individuals. These findings contribute to the development of baited traps utilising these compounds for monitoring triatomines in epidemiological studies or for mass trapping to control these vectors.