Medical and Veterinary Entomology最新文献

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.

The soft tick Ornithodoros turicata Duges (Acari: Argasidae) is a potential vector of African swine fever virus (ASFV). We evaluated the efficacy of two methods to collect soft ticks rapidly and efficiently from gopher tortoise (Gopherus polyphemus) burrows, which are ubiquitous throughout large regions of the southeastern United States and their burrows are a known microhabitat of O. turicata. Burrow vacuuming was an effective and efficient tick collection method; no tick was captured employing CO₂ trapping. Using an occupancy modelling framework, we estimated that the probability of detecting ticks from an infested burrow each time a sample was taken with this method was 58% and increased with the average relative humidity. With the occupancy model, we estimated that 70% of the burrows in the study area were infested with O. turicata. Manual sifting of the burrow material yielded more ticks (6.6 individuals/sample) than using a set of three sieves (2.9 individuals/sample), yet the probability of detecting the species was not different between the two methods (Pval = 0.7). These methods can inform the development of ASF vector surveillance and outbreak response plans in areas of high risk for ASFV introduction in the region.

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.

Culicoides biting midge species (Diptera: Ceratopogonidae) of the Obsoletus Group and the Pulicaris Complex are considered the major vectors of bluetongue and Schmallenberg viruses in Europe. Overwintering strategies of these arboviruses are controversially discussed, with the ongoing activity of vector species and a non-disrupted transmission cycle during winter being a plausible explanation. Although data on Culicoides winter activity are relatively scant, a seasonal vector-free period (SVFP), during which adult Culicoides are not or hardly active, is questionable. To determine winter activity and define SVFPs according to the EU Commission Regulation No 1266/2007, adult Culicoides were trapped weekly with UV-light traps from October to April 2019/2020 and 2020/2021 inside and outside stables on 16 farms throughout Germany. Temperature measurements were taken regularly at each trapping site since the temperature is a known driver of biting midge activity. In 960 indoor and outdoor catches, 32,377 Culicoides were trapped, with 90.9% of them belonging to the Obsoletus Group, 6.1% to the Pulicaris Complex and 3.0% to ‘other Culicoides’ according to morphological identification. The majority (61.3%) of Culicoides were trapped indoors, with substantial numbers of specimens collected from October to December, in March and in April, and only a few or no specimens in January and February. Obsoletus Group biting midges were active indoors for almost the entire winter. Outdoors, Culicoides numbers decreased from October to December, few or no specimens were caught from January to March, and high numbers were captured in April. Of the collected Culicoides, 2028 were blood-fed, of which 94.6% were trapped in the stables. The indoor SVFP, although calculated for blood-fed instead of parous females, lasted for almost 4 months (late November until mid-March) in winter 2019/2020 and 2 months (January and February) in winter 2020/2021. The outdoor SVFPs covered almost the entire study period in both winters, with slight differences between the onsets and the ends. The Culicoides activity significantly depended on temperature. Specimens of the Obsoletus Group were caught at an average temperature of 7.4°C (minimum 0.3°C) and of the Pulicaris Complex at an average temperature of 10.3°C (minimum 1.2°C). These temperatures were reached inside the stables over more extended periods than outside. The average indoor temperatures were 1.2 K higher than the average outdoor temperatures, although absolute temperature differences of up to 9.0 K were recorded. Based on Culicoides activity, the results of the present study indicate an almost continuous potential for virus transmission in winter within livestock houses.

Research into various bacterial pathogens that can be transmitted between different animals and may have zoonotic potential has led to the discovery of different strains of Bartonella sp. in bats and their associated ectoparasites. Despite their enormous species diversity, only a few studies have focussed on the detection of bacterial pathogens in insectivorous bats of boreal forests and their associated Macronyssidae and Spinturnicidae mites. We collected and molecularly analysed mite samples from forest-dwelling bat species distributed all along the boreal belt of the Palearctic, from Central Europe to Far East. Ectoparasitic mites were pooled for DNA extraction and DNA amplification polymerase chain reaction (PCRs) were conducted to detect the presence of various bacterial (Anaplasmataceae, Bartonella sp., Rickettsia sp., Mycoplasma sp.) and protozoal (Hepatozoon sp.) pathogens. Bartonella sp. DNA was detected in four different mite species (Macronyssidae: Steatonyssus periblepharus and Spinturnicidae: Spinturnix acuminata, Sp. myoti and Sp. mystacinus), with different prevalences of the targeted gene (gltA, 16-23S ribosomal RNA intergenic spacer and ftsZ). Larger pools (>5 samples pooled) were more likely to harbour Bartonella sp. DNA, than smaller ones. In addition, cave-dwelling bat hosts and host generalist mite species are more associated with Bartonella spp. presence. Spinturnicidae mites may transmit several distinct Bartonella strains, which cluster phylogenetically close to Bartonella species known to cause diseases in humans and livestock. Mites with ubiquitous presence may facilitate the long-term maintenance (and even local recurrence) of Bartonella-infestations inside local bat populations, thus acting as continuous reservoirs for Bartonella spp in bats.

Chagas disease is considered one of the most important human parasitosis in the United States. This disease is mainly transmitted by insects of the subfamily Triatominae. The chemical vector control is the main tool for reducing the incidence of the disease. However, the presence of triatomines after pyrethroids spraying has been reported in some regions, as in the case of Triatoma infestans in Argentina and Bolivia. The presence of insects can be explained by the colonization from neighbouring areas, the reduction of insecticide dose to sublethal levels due to environmental factors, and/or by the evolution of insecticide resistance. In the last two scenarios, a proportion of the insects is not killed by insecticide and gives rise to residual populations. This article focuses on the toxicological processes associated with these scenarios in triatomines. Sublethal doses may have different effects on insect biology, that is, sublethal effects, which may contribute to the control. In addition, for insect disease vectors, sublethal doses could have negative effects on disease transmission. The study of sublethal effects in triatomines has focused primarily on the sequence of symptoms associated with nervous intoxication. However, the effects of sublethal doses on excretion, reproduction and morphology have also been studied. Rhodnius prolixus and T. infestans and pyrethroids insecticides were the triatomine species and insecticides, respectively, mainly studied. Insecticide resistance is an evolutionary phenomenon in which the insecticide acts as a selective force, concentrating on the insect population's pre-existing traits that confer resistance. This leads to a reduction in the susceptibility to the insecticide, which was previously effective in controlling this species. The evolution of resistance in triatomines received little attention before the 2000s, but after the detection of the first focus of resistance associated with chemical control failures in T. infestans from Argentina in 2002, the study of resistance increased remarkably. A significant number of works have studied the geographical distribution, the resistance mechanisms, the biological modifications associated with resistance, the environmental influences and the genetic of T. infestans resistant to pyrethroid insecticides. Currently, studies of insecticide resistance are gradually being extended to other areas and other species. The aim of this article was to review the knowledge on both phenomena (sublethal effects and insecticide resistance) in triatomines. For a better understanding of this article, some concepts and processes related to insect-insecticide interactions, individual and population toxicology and evolutionary biology are briefly reviewed. Finally, possible future lines of research in triatomine toxicology are discussed.

Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) has been vectoring several arboviruses, protozoa and nematodes, leading to mortality and morbidity of livestock and wild ruminants in the tropics and subtropics. Insight into the bacterial communities associated with the vector species must be worked out. This work tries to inventorize the bacterial communities associated with this important vector species. Acquisition of gut microbiota may be the parental origin, while some are obtained through feeding during larval stages. Culicoides oxystoma possesses semi-aquatic life cycle strategies for egg-laying and larval survival. The bacteria associated with C. oxystoma were compared throughout (i) life stages: egg, larval instars, pupa, adult: male and female obtained from laboratory colony; (ii) field-collected adult: male and age-graded females; and (iii) natural breeding substrate and artificial rearing substrate. The culture-dependent bacteria were identified by Sanger sequencing of 16S rRNA, and haemolytic bacteria were screened on blood agar. Results show that Firmicutes and Proteobacteria are the predominant Phyla, of which Bacillus spp. was the most abundant across the life stages. Across the life history, Bacillus cereus, Bacillus pumilus, Bacillus tropicus, Lysinibacillus sp. and Paenibacillus sp. were retrieved routinely. Bacillus cereus and Alcaligenes faecalis were detected in the lab-reared specimens and shared between the natural breeding site and rearing medium. From the adults trapped across two locations, B. cereus, Bacillus flexus, A. faecalis, Enterococcus faecium and Pseudomonas sp. were isolated. The bacterial species associated with this vector may influence various physiological traits, such as vectorial capacity, digestion and larval development, which need further investigation.

Most blow flies (Diptera: Calliphoridae) species are sarcosaprophagous during the larval stage, primarily feeding on the soft tissues of carcasses during the early stages of decomposition, making them valuable forensic indicators for minimum post-mortem interval (minPMI) estimations. Like other insects, their developmental rates are strongly influenced by the environmental temperature. Although several studies have examined the influence of temperature on the development of different blow fly species, the impact of cold temperatures remains largely unstudied, despite its potential forensic implications. The present study investigates the effect of three cold temperatures (0, −2.5 and −5°C) on the survival of Calliphora vicina embryos of five different ages (0%, 20%, 40%, 60% and 80% of the total embryonic development) and two exposure times (6 and 24 h). Our results revealed significant differences in egg survival at the earliest embryonic stages (0% and 20% of the total embryonic development), resulting in high mortality rates. While at 20% of the total embryonic development high mortality was only observed under −5°C, at 0% of the total embryonic development high mortality rates were observed at all the temperatures tested. Although C. vicina embryos demonstrate tolerance to cold temperatures once they have completed the first 20% of the total embryonic development, potentially mitigating the impact of cold weather events, the possibility of minPMI underestimations due to the death of the first egg batches should not be disregarded. Additionally, considering that the embryonic development stages may last for several days under low temperatures, caution should be taken in the analysis of entomological evidence if a cadaver is discovered following cold weather episodes.

Investigations of host feeding behaviour in haematophagous insects are critical to assess transmission routes of vector-borne diseases. Understanding if a certain species has ornithophilic or mammalophilic feeding behaviour can facilitate future studies focused on pathogens transmission to and from certain host species. Culicoides Latreille (Diptera: Ceratopogonidae) are vectors of several pathogens, which include arboviruses, bacteria and parasites to a considerable diversity of vertebrate hosts. However, most of the studies focused on feeding habits target Culicoides species that could transmit the Bluetongue virus, consequently with a mammalophilic feeding behaviour, leaving aside the Culicoides species that are involved in the transmission of vector-borne parasites to birds, such as Haemoproteus Kruse (Haemosporida: Haemoproteidae). This study aimed to investigate the source of blood meals of wild-caught Culicoides using molecular-based methods and to correlate our findings with the reports of Haemoproteus parasites in Culicoides species. Engorged Culicoides females were collected using ultraviolet (UV)-light traps at seven different localities in Lithuania in 2021–2023. Biting midges were dissected, and the abdomens of engorged females were used for molecular investigation of the blood meal source. A polymerase chain reaction (PCR) protocol that amplifies a fragment of the Cytochrome B gene of vertebrates was used. Obtained sequences were compared to available information in GenBank database to confirm the source of the blood meal. In total, 258 engorged Culicoides females, representing nine different species, were analysed. The source of blood meal was identified in 29.1% of them with most of the insects having fed on birds (74.7%) and the remaining on mammals (25.3%). Culicoides segnis Campbell, Pelham-Clinton was the only species to feed exclusively on birds; Culicoides from the Obsoletus group, C. pallidicornis Kieffer and C. punctatus Latreille were found to feed exclusively on mammals; C. festivipennis Kieffer, C. kibunensis Tokunaga and C. pictipennis Staeger had an opportunistic feeding behaviour, with the first two preferably feeding on birds. Due to their feeding behaviour and the presence of Haemoproteus parasites reported in the literature, C. festivipennis, C. kibunensis, C. pictipennis, and C. segnis play an important role in the transmission of those avian vector-borne parasite in the wild. These Culicoides species were already confirmed as being able to support the development of several Haemoproteus species and lineages. Future studies focused on understanding the epidemiology of avian pathogens transmitted by Culicoides should target these species.