Medical and Veterinary Entomology最新文献

Mass ivermectin (IVM) treatment of livestock (MITL) is under consideration as a malaria control tool as IVM-treated livestock are lethal to blood-feeding Anopheles mosquitoes. MITL is routinely used as a prophylaxis in livestock to reduce the burden and transmission of helminth infections. Recently, there has been a shift in the veterinary IVM market in Southeast Asia wherein nearly all standard IVM formulations are now co-formulated with clorsulon (CLO). CLO is used to treat the trematode liver fluke, Fasciola hepatica. Thus, the co-administration of IVM and CLO simultaneously targets multiple livestock infections. Additionally, F. hepatica frequently afflicts human populations in endemic areas, making control of F. hepatica in livestock beneficial for One Health. CLO interrupts glycolysis in F. hepatica, but its potential effect against Anopheles mosquitoes has never been evaluated. Anopheles dirus mosquitoes were blood-fed CLO across a range of concentrations (1-10,000 nM; 0.38-3807 ng/mL), and mosquito survival was monitored for 10 days. Co-feeding experiments were also performed with An. dirus blood-fed on IVM at two concentrations (4 and 6 ng/mL) without and with CLO corresponding to peak concentration in cattle (C_max) (2700 ng/mL) and five times the C_max (13,500 ng/mL), and mosquito survival was monitored for 10 days. CLO had no mosquito-lethal effect on An. dirus. The IVM and CLO co-feed experiment did not indicate any altered effect of IVM on mosquito survival when co-fed with CLO. IVM-CLO livestock co-formulations would not likely alter the Anopheles mosquito-lethal effect of MITL. The use of MITL-CLO for malaria control would have health benefits for livestock, treating helminth and liver fluke infections, and additional One Health benefits by reducing transmission risk of liver flukes to humans.

Land use and cover changes lead to fragmentation of the natural habitats of sand flies and modify the epidemiological profile of leishmaniasis. This process contributes to the infestation of adjacent rural settlements by vector sand fly species with different degrees of adaptation, promoting leishmaniasis outbreaks. This study aimed to assess land use and cover changes over a 12-year period and investigate the diversity and abundance of sand fly assemblages in the rural area of Codó, Maranhão State, Brazil. Temporal analysis of land use and cover changes was conducted using Sentinel-2 satellite imagery treated in QGIS software (free version 3.10) and classified using Orfeo Toolbox. Sand flies were sampled in alternate months between August 2022 and June 2023 using Centers for Disease Control and Prevention (CDC) light traps and white and black Shannon traps installed in peridomestic and extradomestic environments. Map images showed that the predominant land covers in 2012 and 2014 were dense and sparse vegetation, with few buildings. In 2021 and 2023, areas of sparse and dense vegetation were fragmented as new settlements were established. The entomological survey resulted in the capture of 3375 sand flies (CDC = 856, white Shannon = 650, black Shannon = 1969) belonging to 20 species. The most abundant species were Psychodopygus wellcomei Fraiha, Shaw & Lainson, 1971 (78.19%), followed by Nyssomyia whitmani (Antunes & Coutinho, 1939) (7.53%). Additionally, Ny. whitmani was the most abundant species (84.97%) in peridomestic environments, whereas Ps. wellcomei was the most abundant species (96.51%) in extradomestic environments. The sand fly assemblage was highly diverse, with a high abundance of competent vectors of Leishmania spp. These findings can promote community participation in surveillance and control efforts to prevent leishmaniasis cases.

Ticks continue to invade new regions spreading pathogens of zoonotic and veterinary importance. Diverse tick species have been reported in Ghana due to the continuous trade of livestock. In this study, ticks were collected from cattle in three sites within Southern Ghana. The 1489 ticks collected were morphologically identified and further confirmed using a molecular assay that amplifies the 660-bp segment of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene. These ticks were pooled and screened for pathogens of zoonotic importance. From the 215 tick pools screened, Rickettsia DNA was detected in 34 (15.81%). Sanger sequencing revealed the occurrence of Rickettsia africae (14.42%), the causative agent of African tick-bite fever, and Rickettsia aeschlimannii (1.39%). Regular monitoring of tick populations is essential to generate data for creating effective control and preventive measures.

Culicoides biting midges adversely impact animal health through transmission of multiple orbiviruses, such as bluetongue virus (BTV). This study used light trapping data collected in the Southeastern United States for three Culicoides midge species that are confirmed or suspected BTV vectors: Culicoides insignis, Culicoides stellifer and Culicoides venustus. Midge presence datasets were combined with meteorological data and ecological data to model habitat suitability for each species. Logistic regression and machine learning models were used to generate individual species distribution models (SDMs). Results for each SDM method were combined in an ensemble model to create a distribution model for each midge species. Based on overlay analyses of livestock populations and midge suitable habitat, there is extensive overlap of cattle and goat populations and suitable habitat for C. insignis in Florida. Suitable habitat for C. stellifer intersects with cattle and goat populations in various counties in Alabama, Arkansas, the Carolinas, Florida, Georgia, Louisiana and Tennessee; and suitable habitat for C. venustus intersects with cattle and goat populations in the same states as C. stellifer, except for Florida. It is critical for orbivirus and midge surveillance to continue in the Southeastern United States as the habitat of all three midge species intersect with livestock populations.

Aedes albopictus (Skuse) and Aedes aegypti L. (Diptera: Culicidae) are invasive species known for their notable expansion capacity, which makes them relevant in the context of public health due to their role as vectors. In Argentina, these species coexist in a limited subtropical area in Northeastern part of the country. Because of the limited knowledge existing about these species in this region, the present study aims to investigate the determinants of the presence and abundance of both vectors at the larval habitat scale (presence and abundance) and neighbourhood scale (House, Container and Breteau Indices; abundance; and number of pupae). For this purpose, preimaginal stages of Ae. albopictus and Ae. aegypti were sampled in households from areas with variable urbanisation degrees (in rural, vegetated urban and non-vegetated urban) located in the province of Misiones, Argentina. The analyses considered the association with meteorological variables (temperature and precipitation), environmental variables (type of urbanisation), biotic variables (presence of predator species) and container characteristics (size and water volume). At the larval habitat scale, Ae. albopictus was associated with precipitation, temperature and rural environments. In contrast, Ae. aegypti was positively associated with urban environments and negatively with predator presence. At the neighbourhood scale, Ae. albopictus was primarily associated with precipitation and temperature, whereas Ae. aegypti showed a negative association with predator presence and positive associations with urban environments and, to a lesser degree, meteorological variables. These results indicate that in Argentina, meteorological, biotic and environmental factors have differential influences on Ae. albopictus and Ae. aegypti, underscoring the need to consider them for the development of effective public health strategies.

The nocturnal behaviour and reproduction patterns of Sarcophagidae species during the scotophase are largely unexplored for species in the Neotropical region. The aim of this study was to assess the light regimes under which females of Peckia (Peckia) chrysostoma (Wiedemann, 1830) and Peckia (Sarcodexia) lambens (Wiedemann, 1830) would larviposit and understand how these variables influence intrauterine development in these flies. The experiments were conducted in an experimental room (lux = 100) in two independent experiments: I. Larviposition test: Females mated with males of over 8 days old. II. Intrauterine development test: females over 8 days old and mated were individually isolated. Both experiments were performed under photophases (L:D) of 0:24, 6:18; 12:12; 18:6 and 24:0 for a period of 96 h. Larviposition occurred in total darkness for P. (P.) chrysostoma and P. (S.) lambens in all treatments, without significant differences among photophase treatments (p > 0.05). Photophase influenced the timing of larviposition, occurring as early as 24 h in 12:12 L:D conditions, while no larviposition was observed in the first 24 h in the 0:24 treatment for either species. The light duration significantly affected the percentage of gravid females of both species (p < 0.05), with higher percentages of gravid females in treatments of longer light duration. Females at the initial and intermediate stages of egg development were more strongly associated with treatments of continuous darkness (0:24) or short photophase (6:18), whereas females with an advanced stage of egg development were more prevalent in the 12:12 treatment. The implications of these findings for forensic entomology are profound, challenging conventional knowledge by revealing that necrophagous insects are not limited to diurnal activity patterns.

The aim of this work was to analyse the spatiotemporal heterogeneity of Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae) resistance to chemical acaricides at intra-farm level under different environmental (favourable and unfavourable areas for tick development) and management (different schemes of acaricides applications) conditions using ivermectin as a model. The in vitro larval immersion test (LIT) was used to determine quantitatively the levels of resistance to ivermectin in the different populations and subpopulations of R. microplus analysed. In the first case study, differences in resistance levels among tick samples within the same paddock across time and among tick samples from different paddocks were recorded. These results stress the importance of taking successive samples so that they represent the spatial and temporal variabilities in the levels of resistance that can occur within the same farm. In a second case study, the evolution of resistance in R. microplus subpopulations subjected to strategic and threshold control methods based on the application of three annual treatments with alternation of chemical groups was compared. No changes in resistance/susceptibility status were observed in both tick subpopulations. These results show that the application of a particular drug once a year within a scheme of alternation with other chemical groups could be an appropriate strategy to delay the development of resistance. Data of the third case study showed that environmental constraints is not only a key modulator of R. microplus abundance but could also affect the evolution of resistance in the tick populations. The decreasing trend of LC₅₀ values in the tick subpopulation not exposed to chemical treatments but also in that subpopulation exposed to three annual chemical treatments under unfavourable environmental conditions allow us to hypothesise that environmental constraints can modify the levels of resistance in a tick population because it can constitute a stronger selection factor than the treatments themselves.

Vector-borne diseases represent various sicknesses that are increasingly significant in human and veterinary health. Among the zoonotic agents transmitted by ticks, infections caused by the intracellular pathogens from the Anaplasmataceae family and piroplasmids (Babesia/Theileria spp.) are particularly notable due to the substantial economic losses they cause in the livestock sector. A study was carried out to assess the prevalence of these pathogens in ticks from ruminants in the province of Valencia (Eastern Iberian Peninsula). Between 2019 and 2022, 1674 ticks were collected from 163 domestic and wild ruminants. The tick species were identified using molecular and morphological features and included Rhipicephalus spp. (Rhipicephalus bursa and Rhipicephalus sanguineus) (88.7%), Haemaphysalis sulcata (5.9%), Ixodes ricinus (3.6%) and Dermacentor marginatum (1.2%). The Spanish ibex (Capra pyrenaica) was found to be at greater risk of infestation by Haemaphysalis compared to other ruminants. Polimerase Chain Reaction (PCR) analysis was performed on 108 individual ticks from different hosts, with 16.7% testing positive for members of the Anaplasmataceae family and 39.8% for Theileria spp. Sequencing of 10 positive samples from each pathogen group revealed the presence of Anaplasma ovis, Anaplasma platys, Ehrlichia spp., Theileria ovis and Theileria capreoli. No Anaplasma phagocytophilum or Babesia spp. were detected. Further research is essential for improved management of ticks and the diseases they transmit in the study area.

Aedes albopictus (Diptera: Culicidae), commonly known as the Asian tiger mosquito, is an important vector transmitting dangerous arboviruses to humans. This study investigated the phenotypic and genetic variation of this species in Thailand through wing geometric morphometric (GM) and mitochondrial cytochrome c oxidase subunit I (COI) gene sequence analyses. A total of 236 Ae. albopictus specimens from 12 populations in Thailand and 89 specimens from invasive populations in Florida, Hawaii and Brazil underwent wing GM analysis. The centroid size (CS) of Ae. albopictus populations in Thailand ranged from 2.00 mm in Bangkok to 2.36 mm in Chanthaburi, while in invasive populations, CS varied from 2.25 mm in Brazil to 2.47 mm in Florida. Pairwise comparisons of wing shape revealed significant differences for most population pairs, with distances ranging from 1.63 to 10.02. The clustering tree indicated distant relationships in wing shape between native and invasive populations. Additionally, partial COI gene sequences were amplified from 108 specimens, revealing a mean haplotype diversity of 0.842 ± 0.025 and a mean nucleotide diversity of 0.002 ± 0.001. The results from neutral Tajima's D and Fu's Fs tests indicated negative and statistically significant values (-2.159 and -33.846, respectively), suggesting population expansion. Further examination of haplotype relationships between Thailand and other countries identified two distinct groups: a Southeast Asia group, with Thai haplotypes clustered exclusively within it, and a non-Southeast Asia group. These findings highlight the phenotypic and genetic variation of Ae. albopictus in Thailand, providing essential insights for disease control strategies and tracing the mosquito's origins across regions.

The 158 bug species that make up the subfamily Triatominae are the potential vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Despite recent progress in developing a picture-based automated system for identification of triatomines, an extensive and diverse image database is required for a broadly useful automated application for identifying these vectors. We evaluated performance of a deep-learning network (AlexNet) for identifying triatomine species from a database of dorsal images of adult insects. We used a sample of photos of 6397 triatomines belonging to seven genera and 65 species from 27 countries. AlexNet had an accuracy of ~0.93 (95% confidence interval [CI], 0.91-0.94) for identifying triatomine species from pictures of varying resolutions. Highest specific accuracy was observed for 21 species in the genera Rhodnius and Panstrongylus. AlexNet performance improved to ~0.95 (95% CI, 0.93-0.96) when only the species with highest vectorial capacity were considered. These results show that AlexNet, when trained with a large, diverse, and well-structured picture set, exhibits excellent performance for identifying triatomine species. This study contributed to the development of an automated Chagas disease vector identification system.