Medical and Veterinary Entomology最新文献

The Borrelia burgdorferi sensu lato (s.l.) complex includes a group of spirochete bacteria that are involved in transmission cycles with vertebrates and the ticks associated with them. Rodents play an essential role in the ecoepidemiology of Borrelia, acting as reservoirs for the bacteria and hosts for ticks. To identify potential reservoir vertebrate hosts of Borrelia spirochetes in Argentina, we conducted molecular analyses on tissues obtained from a population of Sigmodontinae rodents inhabiting the Delta and Parana Islands ecoregion. We report the presence of B. burgdorferi s.l. complex genotypes infecting Akodon azarae and Oxymycterus rufus in this ecoregion. Phylogenetic analysis revealed at least three flaB haplotypes related to 'Candidatus Borrelia paulista' and Borrelia sp. strain Pampa from Brazil and to several Borrelia haplotypes from Uruguay. Additionally, we identified different alleles of the plasmid-borne gene ospC in B. burgdorferi s.l. infecting A. azarae and Ox. rufus. The ospC allele present in Borrelia from Ox. rufus was also detected in Borrelia from Oligoryzomys mattogrossae, indicating the ability of Borrelia harbouring this ospC allele to infect multiple Sigmodontinae species, whereas the ospC allele from Borrelia infecting A. azarae represents a novel variant. Further research is needed to determine host specificity of ospC alleles present in South America.

We explored how the ratio of blood-feeding behaviour—nonfeeding, bird feeding (ornithophily) and mammal feeding (mammalophily)—and voltinism (univoltine and multivoltine) vary over a latitudinal gradient from Alaska to Florida. These two fixed species traits were divided into five mutually exclusive combinations of trait states—nonfeeding/univoltine, ornithophilic/univoltine, mammalophilic/univoltine, ornithophilic/multivoltine and mammalophilic/multivoltine—within each of three datasets (north, east and west). We found a significant association between location (north, east and west) and trait state, which was driven by the large percentage of nonfeeding females in the north. When this trait state was removed, no significant differences were found for the remaining trait states and locations. Although the distribution of trait states did not differ between east and west datasets, the distribution with relation to 1° changes in latitude within each of these datasets showed distinct differences. In the east, both ornithophilic/univoltine and mammalophilic/univoltine species significantly increased with latitude, in proportion to the total species present. In contrast, the proportion of mammalophilic/multivoltine species decreased as latitude increased. Ornithophilic/multivoltine species in the east and the trait states in the west did not show any significant relationship to latitude.

Mosquitoes occupy a wide range of habitats where they experience various environmental conditions. The ability of some species, such as the tiger mosquito, Aedes albopictus, to adapt to local conditions certainly contributes to their invasive success. Among traits that remain to be examined, mosquitoes' ability to time their activity with that of the local host population has been suggested to be of significant epidemiological importance. However, whether different populations display heritable differences in their chronotype has not been examined. Here, we compared laboratory strains originating from eight populations from three continents, monitored their spontaneous locomotor activity patterns and analysed their sleep-like states. Overall, all strains showed conserved diurnal activity concentrated in the hours preceding the crepuscule. Similarly, they all showed increased sleep levels during the morning and night hours. However, we observed strain-specific differences in the activity levels at each phase of the day. We also observed differences in the fraction of time that each strain spends in a sleep-like state, explained by variations in the sleep architecture across strains. Human population density and the latitude of the site of the geographic origin of the tested strain showed significant effects on sleep and activity patterns. Altogether, these results suggest that Ae. albopictus mosquitoes adapt to local environmental conditions via heritable adaptations of their chronotype.

Aedes aegypti is an important mosquito vector of human disease with a wide distribution across the globe. Climatic conditions and ecological pressure drive differences in the biology of several populations of this mosquito species, including blood-feeding behaviour and vector competence. However, no study has compared activity and/or sleep among different populations/lineages of Ae. aegypti. Having recently established sleep-like states in three mosquito species with observable differences in timing and amount of sleep among species, we investigated differences in activity and sleep levels among 17 Ae. aegypti lines drawn from both its native range in Africa and its invasive range across the global tropics. Activity monitoring indicates that all the lines show consistent diurnal activity, but significant differences in activity level, sleep amount, number of sleep bouts and bout duration were observed among the lines. The variation in day activity was associated with differences in host preference and ancestry for the lineages collected in Africa. This study provides evidence that the diurnal sleep and activity profiles for Ae. aegypti are consistent, but there are significant population differences for Ae. aegypti sleep and activity levels and interactions with host species may significantly impact mosquito activity.

Pyrethroid resistance and mechanisms for resistance for Anopheles gambiae sensus lato (s.l.) (Diptera: Culicidae) Giles, were assessed in three urban areas (vegetable farming, industrial and residential) of Abidjan. Susceptibility to pyrethroids (deltamethrin, permethrin and alphacypermethrin), with and without piperonyl butoxide (PBO) pre-exposure was evaluated. Anopheles gambiae complex members were identified using Short Interspersed Nuclear Elements PCR (SINE PCR), and resistance mechanisms (kdr-west, kdr-east and ace-1) and metabolic gene expression (CYP6P5, CYP6M2, CYP6P3, CYP6P4) were determined by real-time polymerase chain reaction (PCR). High resistance to deltamethrin, permethrin and alphacypermethrin was observed in Port-Bouet (vegetable farming) and Treichville (industrial site), whereas moderate resistance to deltamethrin and high resistance to alphacypermethrin and permethrin were found in Abobo (residential site). Pre-exposure to PBO with pyrethroid increased mortalities in all sites. In Treichville, pre-exposure to PBO restored susceptibility to deltamethrin, but not in Port-Bouet or Abobo. In Treichville, An. gambiae Giles sensu stricto (s.s.) was predominant (92.9%), whereas in Abobo and Port-Bouet, An. coluzzii Giles was predominant (73.6% and 66.4%, respectively). The highest kdr-west mutation frequency was in An. gambiae s.s. (42.8%) from Abobo, followed by An. gambiae s.s. (40%) from Port-Bouet and An. gambiae s.s. (35.6%) from Treichville. In An. coluzzii, the highest kdr-west mutation frequency was in Port-Bouet (48.2%), followed by Abobo (28.00%) and Treichville (21.4%). Mutation frequencies of kdr-east were lower in An. gambiae s.s. from Treichville (4.1%) and Port-Bouet (2.1%) and absent in An. gambiae from Abobo. In industrial and vegetable farming areas, CYP6P3 and CYP6M2 were overexpressed compared with Kisumu. The study suggests An. gambiae s.l. distribution and pyrethroid resistance are influenced by human activities. Treichville's industrial area favoured An. gambiae s.s., whereas Abobo's residential and Port-Bouet's vegetable farming areas were dominated by An. coluzzii. Resistance in Treichville and Port-Bouet was associated with kdr (west and east) genes and metabolic genes, whereas in residential areas, only kdr-west genes were observed. These data suggest that PBO + deltamethrin impregnated nets could aid malaria control, benefiting industrial areas of Côte d'Ivoire and other African cities.

Sand flies (Diptera: Psychodidae: Phlebotominae) are blood-feeding insects that transmit the protozoan parasites Leishmania spp. and various arboviruses. The Balkan region, including the Republic of Kosovo, harbours a diverse sand fly fauna. Vector species of Leishmania infantum as well as phleboviruses are endemic; however, recent data are scarce. We performed a cross-sectional study to update the current sand fly distribution in Kosovo and assess biological as well as environmental factors associated with sand fly presence. CDC light trapping was conducted at 46 locations in 2022 and 2023, specifically targeting understudied regions in Kosovo. Individual morphological species identification was supported by molecular barcoding. The occurrence data of sand flies was used to create distribution maps and perform environmental analyses, taking elevation, wind speed and climate-related factors into account. In addition, PCR-based blood meal analysis and pathogen screening were conducted. Overall, 303 specimens of six sand fly species were trapped, predominated by Phlebotomus neglectus (97%). Barcodes from eight of nine known endemic sand fly species were obtained. Combining our data with previous surveys, we mapped the currently known sand fly distribution based on more than 4000 specimens at 177 data points, identifying Ph. neglectus and Ph. perfiliewi as the predominant species. Environmental analyses depicted two geographical groups of sand flies in Kosovo, with notable differences between the species. In total, 223 blood meals of five sand fly species were analysed. Of seven identified host species, the predominant blood meal source was observed to be cattle, but the DNA of dogs and humans, among others, was also detected. This study assessed biological as well as ecological factors of sand fly occurrence, which should help better understand and evaluate potential hot spots of disease transmission in Kosovo.

South Africa is a frontline country for malaria elimination in the southern African region. It has three malaria-endemic provinces, each with its own transmission pattern. The elimination of malaria depends, in part, on controlling and/or eliminating vectors responsible for transmission. Sustained entomological surveillance is an important factor to consider when shifting from a control to elimination framework. The Ehlanzeni district in Mpumalanga province is a key entomological sentinel surveillance area. It is one of the malaria-endemic districts in South Africa with higher rates of malaria incidences. As such, entomological data about the Anopheles gambiae Giles (Diptera: Culicidae) complex have been collected in this province over a substantial period. These data are stored in a pre-existing institutional database. An analysis of the trends that can be observed from this database has not been performed before. This retrospective (longitudinal) analysis provides a summary of the An. gambiae complex vector composition in this region from 2009 to 2021. Routine surveillance data were correlated with climatic data (obtained from the NASA LaRC POWER project database) for the same period to assess the role of climatic factors in vector dynamics. This review also identifies a number of limitations in the data collection process across the sampling period and provides recommendations on how to strengthen the database going forward. The most abundant member of the An. gambiae complex since 2009 in the province was An. merus Dönitz followed by An. arabiensis Patton. Collection methods used showed that human landing catches were successful for collecting An. arabiensis, while pit traps were the most effective in collecting An. merus and An. quadriannulatus Theobald. The latter two species were mainly collected in spring, whereas An. arabiensis abundance was larger during autumn collections. Vector abundance was not significantly correlated with annual climatic data. The information gained from this database provides insights into the vector dynamics of the Ehlanzeni district of the Mpumalanga province.