Life remained far from normal as we completed the first year of the Covid-19 pandemic and entered a second year. Despite the challenges faced worldwide, together we continue to move the field of Medical Entomology forward. Here, I reflect on parallels between control of Covid-19 and vector-borne disease control, discuss the advantages and caveats of using new genotyping technologies for the study of invasive species, and proceed to highlight papers that were published between 2020 and 2021 with a focus on those related to mosquito surveillance and population genetics of mosquito vectors.

In this study, a systematic investigation was performed to estimate the prevalence of head lice infestation, and to determine the factors affecting the prevalence of heterogeneity among primary school-aged children in Iran. A comprehensive search was fulfilled in international databases, including MEDLINE, Scopus, Web of Science, and Embase, to identify the articles on the prevalence of pediculosis. So, all the cross-sectional epidemiological studies evaluating the prevalence of pediculosis were covered without any restrictions. A random-effects model was used to assess the pooled prevalence. A meta-regression method was applied to determine the factors affecting the heterogeneity among the studied population. An analysis was performed on 67 studies with a total sample size of 358,053. The total pooled estimate for the prevalence of pediculosis in boys and girls was 7.52% (95% CI: 6.15–9.03), 1.99% (95% CI: 1.25–2.89), and 8.97% (95% CI: 721–10.91), respectively. The highest and lowest pooled prevalence was in Hormozgan (southern Iran) (29.21%; 95% CI: 8.89–55.34) and Isfahan (Central Iran) (0.69%; 95% CI: 0.59–0.80), respectively. Based on the results of the univariate meta-regression, gender and father's job showed a significant direct association with the prevalence of pediculosis, but the sample size had significant inverse relations with the prevalence of pediculosis. This study demonstrated that pediculosis is a common public health problem affecting school-aged children with a relatively high prevalence in Iran, especially among girls.

The study of Acari associated with cricetid rodents in Mexico began at the end of the 1930s. Despite efforts to gathering the information, only listings were built, but none of these studies present an analysis of the available data. A search was made through electronic databases; in addition, some not published records contained at Collection of Laboratorio de Acarología, Facultad de Ciencias, Universidad Nacional Autónoma de México were included in the inventory. Combining the literature records and those deposited in the collection, the total number of species of Acari associated with this family of rodents is 165, distributed in two superorders, four orders, 15 families, and 57 genera. Of the 15 families registered, the richest is Trombiculidae (70 nominal species and 75 taxa), followed by Laelapidae (39 and 42, respectively), Ixodidae (13 nominal and 16 taxa), and Leewenhoekiidae (13 nominal and taxa). From the bibliographic searches, a total of 76 papers were recovered with information on the association between Acari and cricetid rodents in Mexico. The main detected approach in the literature was taxonomic (75 works) and one on detection of pathogens. From the 145 known species of cricetids recorded in Mexico, only 72 (distributed in 18 genera) have been studied and found to host Acari. The use of regionalization of Mexico in provinces allowed us to map the records of Acari associated to cricetids in the most natural approximation of their distribution. We recognize and discuss seven factors that favor the scarcity and asymmetry of acarological studies in Mexico.

Graphical Abstract

The yellow fever virus is estimated to cause 30,000 deaths each year worldwide, with the majority of cases and deaths occurring in Africa. The virus is also endemic to Central and South America, including northern and western Brazil. The sylvatic cycle of the virus is related to wild and rural areas, with nonhuman primates as the primary host and wild mosquitoes, specifically from the genera Haemagogus, as vectors. The diversity of the mosquito community plays a significant role in the increase of pathogen transmission to humans. In the present study, we detected fluctuation in populations of vector mosquitoes using ovitraps for Culicidae egg collection. The study area is a forest fragment of the Atlantic Forest, one of the most threatened biomes in Brazil. This biome has been suffering significant deforestation due to anthropic activity. Worryingly, the proximity of human populations to forest environments increases the risk of spreading disease from forest fragments to urban areas. Our findings showed that the highest egg abundance occurred in December 2019, with a significant difference (p = 0.005) between rainy and dry seasons. Most eggs were collected during the rainy period. Subsequent quantification of specimens from epidemiologically relevant species hatched from field-collected eggs resulted in 1,131 (86%) Haemagogus leucocelaenus (Dyar & Shannon, 1924), 111 (8%) Aedes terrens (Walker, 1856), 47 (4%) Aedes albopictus (Skuse, 1894), and 21 (2%) Haemagogus janthinomys (Dyar, 1921). Finally, we assessed the behavior of different vector species performing oviposition on the same breeding site. The highest correlation coefficient was observed between Ae. albopictus and Ae. terrens (rho = 0.52) concerning other Culicidae species. Therefore, we believe that Culicidae population surveillance is crucial for disease monitoring since the increase in specimens of a number of vector species influences the emergence of yellow fever cases in nonhuman primates and human populations.

The common bed bug (Cimex lectularius L.) is a hematophagous pest species that lives in close proximity to humans. Following a blood meal, bed bugs deposit fecal material indoors. The feces contain a variety of compounds, including histamine, which serves as a component of their aggregation pheromone. Histamine is a pivotal mammalian immune modulator, and recently it was shown to be present in high concentrations in household dust from homes infested with bed bugs. To better understand the dynamics of histamine excretion, we analyzed bed bug fecal material from different life stages and populations, along with fecal material collected at different post-feeding times and from bed bugs fed on different diets. Our analysis showed significant variation in histamine excretion among life stages, with mated females excreting the most histamine and first instar nymphs excreting the least histamine. However, when histamine excretion was normalized for blood consumption, males were found to excrete more histamine than the other life stages. There was no difference in histamine excretion among laboratory and recently home-collected bed bug populations. Further, we found histamine excretion continued for at least 14 d post-feeding, with the highest amount of histamine excreted 3–4 d after a bloodmeal. Overall, this work demonstrates that bed bugs excrete histamine across all feeding life stages, populations, and at various times after feeding, and that histamine excretion is directly related to blood feeding. These results will be used to better understand the health risks associated with histamine excretion and potential mitigation strategies of environmental histamine.

We assessed the influence of diet on the development and survival in the immature stages of the necrophagous beetle Oiceoptoma thoracicum (Linnaeus, 1758). The species is frequently observed on large cadavers, including humans, and thus can be of potential forensic relevance. We compared multiple meat tissues from three animal sources, and detected the optimal diet for rearing the species for further entomological and forensic objectives. We reared 203 individuals to adulthood at the constant temperature of 20°C. Our results represent the first robust data set of the development time for this species. They further confirmed a significant relationship between survival and the type of diet, as the highest survival rates were detected in larvae fed with both pork liver and pork muscle.

Triatoma dimidiata (Latreille 1811) is considered the second most important vector of the Trypanosa cruzi etiological agent of Chagas disease in Colombia. It has a life cycle that involves a domiciled, peridomiciled, and wild distribution. The study of feeding behavior and its influence on the survival of sylvatic and peridomestic populations can help identify a possible differential risk in the transmission of Chagas disease to humans, mainly in northwestern and east-central Colombia. We characterize the main parameters of feeding behavior and their influence on the longevity and survival of two rat-fed populations of T. dimidiata from Colombia, one in the north-west (from palms in a tropical dry forest area) and the other in the center-east (peridomiciliated), under controlled environmental conditions. The palm population took considerably longer than the peridomestic population to complete its life cycle under experimental laboratory conditions, being both populations univoltine since they have only one life cycle per year. Statistically significant differences were evidenced using Box-Cox model between the survival rates of T. dimidiata populations when the parameters related to blood intake and behavior were incorporated, in contrast to the survival models in which the origin only was considered as a factor. Our results could be used to generate recommendations to guide prevention strategies in communities near sylvatic and peridomiciliated populations of T. dimidiata.

The flesh fly, Sarcophaga crassipalpis Macquart 1839 (Diptera: Sarcophagidae), colonizes estimation of the minimum post-mortem interval (min-PMI). This study examined the effects of different types of tissues and temperature on the development of S. crassipalpis. To the best of our knowledge, the present study is the first to investigate the effects of life-history information of S. crassipalpis. Larvae were reared on three tissue types, chicken heart, bovine minced meat, and bovine tongue, at five temperatures, 15, 20, 25, 30, and 32°C. Pupal and larval development time, adult weight, and pupal and larval survival differed significantly for tissue type and temperature. Temperature had a significant effect on pupal weight but tissue type did not significantly affect pupal weight. The duration of the larval and pupal stages (except of chicken heart, 30°C) decreased with increasing temperature, except for 32°C, in all tissue types. Larval survival was lowest at 32°C in bovine minced meat, bovine tongue, and chicken heart, and at 32°C, all pupae failed to reach the adult stage in minced meat. The results of this study highlight the necessity of considering larval diet and temperature in forensic investigations.

This study investigates the impacts of three different heavy metals at different concentrations on some life-history traits of Lucilia sericata (Meigen 1826) (Diptera: Calliphoridae). First-instar larvae of L. sericata were reared on a diet containing four concentrations (0.25, 0.50, 1, and 2 µg/g) of the heavy metals (cadmium, zinc copper). The parameters measured were larval and pupal mortality, larval length, adult, pupal, and larval weight, and development time. Larval and pupal survival decreased as heavy metal concentrations increased. Pupal weight was significantly different among heavy metals andc oncentrations, but the adult weight was not significantly different among heavy metals and concentrations. The larval length was significantly different among concentrations and heavy metals. This study reveals that the presence of heavy metal in carrion or the carrion environment should be inconsidered when estimating the time of colonization in forensic investigations.

Exposure to mosquito-borne diseases is influenced by landscape patterns and microclimates associated with land cover. These influences can be particularly strong in heterogeneous urban landscapes where human populations are concentrated. We investigated how land cover and climate influenced abundances of Ae. albopictus (Skuse) (Diptera: Culicidae) and Cx. quinquefasciatus (Say) (Diptera: Culicidae) in Norman, Oklahoma (United States). From June–October 2019 and May–October 2020 we sampled mosquitoes along an urban-rural gradient using CO₂ baited BG Sentinel traps. Microclimate sensors at these sites measured temperature and humidity. We mapped environmental variables using satellite images from Landsat, Sentinel-2, and VIIRS, and the CHIRPS rainfall dataset. We also obtained meteorological data from the closest weather station. We compared statistical models of mosquito abundance based on microclimate, satellite, weather station, and land cover data. Mosquitoes were more abundant on trap days with higher temperature and relative humidity. Rainfall 2 wk prior to the trap day negatively affected mosquito abundances. Impervious surface cover was positively associated with Cx. quinquefasciatus and tree cover was negatively associated with Ae. albopictus. Among the data sources, models based on satellite variables and land cover data had the best fits for Ae. albopictus (R² = 0.7) and Cx. quinquefasciatus (R² = 0.51). Models based on weather station or microclimate data had weaker fits (R² between 0.09 and 0.17) but were improved by adding land cover variables (R² between 0.44 and 0.61). These results demonstrate the potential for using satellite remote sensing for mosquito habitat analyses in urban areas.

While the number of human cases of mosquito-borne diseases has increased in North America in the last decade, accurate modeling of mosquito population density has remained a challenge. Longitudinal mosquito trap data over the many years needed for model calibration, and validation is relatively rare. In particular, capturing the relative changes in mosquito abundance across seasons is necessary for predicting the risk of disease spread as it varies from year to year. We developed a discrete, semi-stochastic, mechanistic process-based mosquito population model that captures life-cycle egg, larva, pupa, adult stages, and diapause for Culex pipiens (Diptera, Culicidae) and Culex restuans (Diptera, Culicidae) mosquito populations. This model combines known models for development and survival into a fully connected age-structured model that can reproduce mosquito population dynamics. Mosquito development through these stages is a function of time, temperature, daylight hours, and aquatic habitat availability. The time-dependent parameters are informed by both laboratory studies and mosquito trap data from the Greater Toronto Area. The model incorporates citywide water-body gauge and precipitation data as a proxy for aquatic habitat. This approach accounts for the nonlinear interaction of temperature and aquatic habitat variability on the mosquito life stages. We demonstrate that the full model predicts the yearly variations in mosquito populations better than a statistical model using the same data sources. This improvement in modeling mosquito abundance can help guide interventions for reducing mosquito abundance in mitigating mosquito-borne diseases like West Nile virus.

Recent focus on Culicoides species diversity in Thailand was prompted by a need to identify vectors responsible for the transmission of African Horse Sickness in that country. To assist rapid genetic identification of species, we sampled mitochondrial cytochrome c oxidase subunit I (COI) DNA barcodes (N = 78) from 40 species of Culicoides biting midge from Thailand, including 17 species for which DNA barcodes were previously unavailable. The DNA barcodes were assigned to 39 Barcode Identification Numbers (BINs) representing terminal genetic clusters at the Barcode of Life Data systems (BOLD). BINs assisted with comparisons to published conspecific DNA barcodes and allowed partial barcodes obtained from seven specimens to be associated with BINs by their similarity. Some taxonomic issues were revealed and attributed to the possible misidentification of earlier reported specimens as well as a potential synonymy of C. elbeli Wirth & Hubert and C. menglaensis Chu & Liu. Comparison with published BINs also revealed genetic evidence of divergent population processes and or potentially cryptic species in 16 described taxa, flagged by their high levels of COI sequence difference among conspecifics. We recommend the BOLD BIN system to researchers preparing DNA barcodes of vouchered species for public release. This will alert them to taxonomic incongruencies between their records and publicly released DNA barcodes, and also flag genetically deep and potentially novel diversity in described species.

Ants (Hymenoptera: Formicidae) are among the largest and most widespread families of terrestrial insects and are valuable to medical and ecological investigations. The mitochondrial genome has been widely used as a reliable genetic marker for species identification and phylogenetic analyses. To further understand the mitogenome-level characteristics of the congeneric Formicidae species, the complete mitogenome of Formica sinae (Hymenoptera: Formicidae) was sequenced, annotated, and compared with other 48 Formicidae species. The results showed that gene composition, content, and codon usage were conserved. The complete mitochondrial genome of F. sinae was 17,432 bp, including 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and one control region located between rrnS and trnM, which was 1,256 bp long, the longest of all sequenced species. Gene rearrangement was not detected in Formica species (Hymenoptera: Formicidae). All PCGs of F. sinae were initiated with ATN codons and terminated with the TAA codon. The overall nucleotide composition of F. sinae was AT-biased (83.51%), being 80.58% in PCGs, 86.68% in tRNAs, 87.10% in rRNAs, and 88.70% in the control region. Phylogenetic analyses indicated that each subfamily formed a strongly monophyletic group. Furthermore, F. sinae clustered with Formica fusca (Hymenoptera: Formicidae) and Formica selysi (Hymenoptera: Formicidae). This work enhances the genetic data of Formicidae and contributes to our understanding of their phylogenic relationship, evolution, and utilization.

Chewing lice comprise a large group of ectoparasites that colonize and adversely affect several domestic and wild birds including pigeons. In Saudi Arabia, there is a lack of studies describing such ectoparasites and their infestation rates. Through this work, a new record, Columbicola, tschulyschman Eichler (C. tschulyschman Eichler) was collected from domestic pigeons (Columba livia domestica, Linnaeus). The collected C. tschulyschman Eichler was morphologically identified based on specific taxonomic keys. Mitochondrial (COI) and nuclear (EF-1α) gene fragments were used for molecular identification and phylogenetic reconstruction. In this study, the C. tschulyschman Eichler accounted for around 69.40%. To our knowledge, this is the first report of C. tschulyschman Eichler in Riyadh, Saudi Arabia. To improve the tree topology and differentiate between genera, further studies should utilize the 16s rRNA.

Haemaphysalis Koch, 1844, is the largest genus of ticks in Southeast Asia, but little information is available concerning the species present in Laos. Recent research has yielded records for 10 Haemaphysalis species in Laos, including 5 new records, as well as 3 morphological entities of uncertain status. Further morphological and molecular studies are needed to clarify our taxonomic understanding of this genus in Southeast Asia.

To better understand tick ecology in Virginia and the increasing Lyme disease incidence in western Virginia, a comparative phenological study was conducted in which monthly collections were performed at twelve sampling locations in southwestern Virginia (high Lyme disease incidence) and 18 equivalent sampling locations in southeastern Virginia (low Lyme disease incidence) for one year. In western Virginia, we also explored the effect of elevation on collection rates of Ixodes scapularis Say (Acari: Ixodidae) and Amblyomma americanum (L.) (Acari: Ixodidae). In total, 35,438 ticks were collected (33,106 A. americanum; 2,052 I. scapularis; 134 Ixodes affinis Neumann [Acari: Ixodidae]; 84 Dermacentor variabilis [Say] [Acari: Ixodidae]; 49 Dermacentor albipictus [Packard] [Acari: Ixodidae]; 10 Haemaphysalis leporispalustris [Packard] [Acari: Ixodidae]; 2 Ixodes brunneus Koch [Acari: Ixodidae]; 1 Haemaphysalis longicornis Neumann [Acari: Ixodidae]). Within southwestern Virginia, Ixodes scapularis collection rates were not influenced by elevation, unlike A. americanum which were collected more frequently at lower elevations (e.g., below 500 m). Notably, I. scapularis larvae and nymphs were commonly collected in southwestern Virginia (indicating that they were questing on or above the leaf litter) but not in southeastern Virginia. Questing on or above the leaf litter is primarily associated with northern populations of I. scapularis. These findings may support the hypothesis that I. scapularis from the northeastern United States are migrating into western Virginia and contributing to the higher incidence of Lyme disease in this region. This comparative phenological study underscores the value of these types of studies and the need for additional research to further understand the rapidly changing tick-borne disease dynamics in Virginia.

Muscid flies, especially house flies (Musca domestica L.) (Diptera: Muscidae), are a major pest of poultry layer facilities. Augmentative biological control of muscid flies with pteromalid wasps has gained increased attention in recent years. Knowing which pteromalid species are present in a specific area could produce more effective filth fly control. The purpose of this project was to survey parasitoid populations in poultry layer facilities in central and southeastern Pennsylvania from June through September. Two genera of parasitoids, Spalangia and Trichomalopsis, were collected over the course of the survey. Overall, out of 3,724 parasitized pupae the species collected in order of most to least common were Spalangia cameroni Perkins, Spalangia nigroaenea Curtis, Trichomalopsis spp., and Spalangia endius Walker. House fly parasitism overall and by each parasitoid species varied by location and over the four study months. A second objective was to evaluate a new parasitoid trap for surveying parasitoid wasp populations. This device uses a combination of house fly third instars and development media. This was compared to a more traditional method, the sentinel bag, which uses only fly pupae. A higher proportion of Spalangia spp. emerged from the new trap design and more Trichomalopsis spp. emerged from the sentinel bag. This suggests that using this new device alongside the traditional collection method may result in more accurate sampling of pteromalid populations.

Knowledge of the hibernation site preferences and the factors which influence winter survival in these hibernation sites may enhance understanding of mosquito population dynamics after winter and how arboviruses persist in temperate regions. Our study quantified the number of adult overwintering mosquitoes in cellars and aboveground constructions and analyzed survival rates in relation to the environmental conditions in these sites. During the winters 2016/2017 and 2018/2019, 149 different constructions in Northwest Germany were sampled for mosquitoes. Mosquitoes were detected in 44% of the cellars and in 33% of the aboveground constructions. Culex p. pipiens Linnaeus was the most abundant species in cellars, whereas high numbers of Anopheles messeae Falleroni were collected from a single barn. Subsequently, an enclosure study was conducted during 2019/2020. Overwintering field-collected Cx. p. pipiens and An. messeae were divided into groups with or without fructose availability, and placed in cages with different man-made hibernations sites, where temperature and relative humidity were recorded hourly. For both species, increasing mean temperatures (5–16°C) but not mean relative humidity (58–94%) were correlated with winter mortality rates of the mosquitoes. The lipid measurements were greater and mortality rates were lower when both species were provided fructose. Larger specimens (determined by wing length) stored more lipids, and in Cx. p pipiens, but not in An. messeae, survival probability of large specimens was significantly greater than for small females. Mosquitoes showed a distinct pattern in the selection of overwintering sites, while temperature was an important driver for survival.

Nonpathogenic bacteria likely play important roles in the biology and vector competence of ticks and other arthropods. Coxiella, a gram-negative gammaproteobacterium, is one of the most commonly reported maternally inherited endosymbionts in ticks and has been associated with over 40 tick species. Species-specific Coxiella-like endosymbionts (CLEs) have been reported in the brown dog tick, Rhipicephalus sanguineus sensu lato (Acari: Ixodidae), throughout the world, while recent research suggests low Coxiella diversity among tick species. We investigated CLE diversity among R. sanguineus s.l. ticks across Arizona. We detected 37 recurrent sequence variants (SVs) of the symbiont, indicating greater diversity in these symbiotic bacteria than previously reported. However, two SVs accounted for the vast majority of 16S rRNA amplicon reads. These two dominant CLEs were both closely related to Candidatus C. mudrowiae, an identified symbiont of Rhipicephalus turanicus ticks. One strain strongly associated with the tropical lineage of R. sanguineus s.l. while the other was found almost exclusively in the temperate lineage, supporting the conclusion that CLEs are primarily vertically transmitted. However, occasional mismatches between tick lineage and symbiont SV indicate that horizontal symbiont transfer may occur, perhaps via cofeeding of ticks from different lineages on the same dog. This study advances our understanding of CLE diversity in Rh. sanguineus s.l.

The Amazonian region is composed by many kinds of environments, including the Amazonian savannas, which comprise about 5% of the Amazon biome in Brazil. The biota of Amazonian savannas is poorly known, especially for insects. In this study, we performed a faunistic inventory of flesh flies (Diptera: Sarcophagidae) of four Brazilian Amazon savannas, where we recorded two subfamilies, 16 genera, and 40 species, two of which are described as new to science: Lepidodexia (Notochaeta) helenae sp. nov. and Lipoptilocnema augustoi sp. nov. Oxysarcodexia graminifolia Souza, Pape & Thyssen, 2020 is recorded for the first time for Brazil. Dexosarcophaga paulistana Lopes (1982), Helicobia biplagiata Dodge, 1966, Helicobia cearensisTibana, 1976, Oxysarcodexia simplicoides (Lopes, 1933), and Oxyvinia excisa (Lopes, 1950) are newly recorded for the Brazilian Amazon. Oxysarcodexia nitida Soares & Mello-Patiu, 2010 is a new record for the state of Pará. The species D. paulistana is redescribed, and photographs and detailed illustrations of male terminalia are provided.

Fleas have rarely been reported from the puma, Puma concolor (Linnaeus, 1771), despite its vast geographic range, its breadth of habitat use, and its diverse diet, all of which bring it into contact with many other species of mammals and potentially their fleas. We review the reported occurrence of 8 species of fleas from pumas, 7 of these species being from wild hosts and 1 species from a host in captivity, and we correct the mistaken report of 1 other flea species from the puma. We present 10 new records of 4 species of fleas from the puma in Utah and Texas. 2 of these flea species, Cediopsylla inaequalis inaequalis (Baker, 1895) and Odontopsyllus dentatus (Baker, 1904), represent new host records, and 1 species, Chaetopsylla setosa Rothschild, 1906, is a new state record for Utah as well as being 1 of the 2 southernmost known localities for this species. At least 7 of the 9 flea species now known from free-ranging pumas are species that are acquired by pumas from their prey. Pumas may be primary hosts of 2 flea species, but even these fleas may be from prey. Some of the flea species that parasitize pumas transmit sylvatic plague, and, since pumas are highly vagile and are known to become infected with plague, they may spread the disease through their dispersal of infected fleas. Pumas and their fleas also may be involved in the ecology of several other bacterial zoonoses, which are discussed.

In the southeastern United States, biting midges transmit agents of hemorrhagic diseases that are enzootic among white-tailed deer (Odocoileus virginianus (Zimmermann), Artiodactyla: Cervidae). Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), the only confirmed vector of epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) in the United States, is rarely collected in the Southeast, implying that other Culicoides Latreille species act as vectors. Despite multiple surveillance studies, the influence of trapping habitat and light wavelength on Culicoides sampling has yet to be investigated in Alabama. This study sampled Culicoides species at a deer research facility using CO₂-baited CDC light traps with three distinct wavelengths. Traps were rotated within three habitats to examine impacts of habitat type and light wavelength on Culicoides abundance and parity status. For most species, midges were more abundant in a pine forest compared to a hardwood-forest riparian zone or a lightly wooded area adjacent to a seasonal pond. The pine forest generally had negative effects on parity status, suggesting that most females in this habitat were foraging for their first bloodmeal. Ultraviolet (UV) black-light (350 nm–360 nm) attracted more midges than incandescent light or UV LED light (385 nm–395 nm), but wavelength had less of an effect on parity than habitat. This study indicates that light wavelength and habitat significantly influence Culicoides sampling outcomes, and that when collecting parous females is desired (e.g., EHDV/BTV surveillance), targeting areas around oviposition sites may be a better strategy than trapping where midges are most abundant.

The house fly (Musca domestica L.) is a cosmopolitan and synanthropic pest fly commonly associated with confined animal facilities, known to mechanically vector numerous disease-causing pathogens. Control of adult house flies often relies on insecticides formulated into insecticidal baits, though many baits have failed due to insecticide resistance. House fly resistance to imidacloprid, the most widely used neonicotinoid insecticide available for fly control, has evolved through physiological and behavioral mechanisms in field populations. Behavioral resistance to imidacloprid was documented in field populations of flies from southern California dairies. Lab colonies of these flies were established and behavioral resistance to imidacloprid was selected over several generations. The current study examined the ability of these lab-selected flies to feed on varying concentrations of imidacloprid formulated in sucrose, and if these flies would demonstrate a feeding preference for different concentrations of imidacloprid when exposed in bioassays. Behaviorally resistant flies preferred to feed on untreated sucrose as opposed to treated sucrose at concentrations greater than 25 µg/g imidacloprid when provided sucrose treated with and without imidacloprid. When provisioned with only sucrose treated with a low and high imidacloprid concentration, flies fed on the low concentrations (≤100 µg/g) imidacloprid but reduced feeding on either treatment when concentrations were >100 µg/g imidacloprid. The current study extends the body of knowledge on house fly behavioral resistance to imidacloprid, which could provide insights into future failures of granular fly baits.

The emergence of West Nile virus and Usutu virus in Europe poses a significant risk to public health. In the absence of efficient antiviral therapy or vaccine candidates, the only strategy to control these arboviruses is to target the Culex (Diptera: Culicidae) mosquito vector. However, the selection pressure caused by exposure to insecticides for vector control or agricultural pest control can lead to insecticide resistance, thereby reducing the efficacy of insecticide-based vector control interventions. In Culex mosquitoes, two of the most common amino acid substitutions associated with insecticide resistance are the kdr L1014F in voltage gated sodium channels and G119S in acetylcholinesterase. In this study, Culex pipiens biotype pipiens, Culex torrentium, and Culex modestus were sampled from 2019 to 2021 in three distinct environmental habitats (urban, peri-urban, and agricultural) in and around the city of Leuven, Belgium. Individual mosquitoes were screened for two mutations resulting in L1014F and G119S amino acid substitutions. Both mutations were observed in Cx. pipiens and Cx. modestus but not in Cx. torrentium mosquitoes across the four collection sites. Furthermore, multi-resistance or cross-resistance in Cx. pipiens could be a threat in these areas, as both mutations were observed at low frequencies. These results provide the first report of kdr L1014F and ace-1 G119S resistance mutations in Cx. pipiens and Cx. modestus mosquitoes from Belgium, highlighting the importance of mosquito surveillance to design effective arbovirus outbreak control strategies.

Graphical Abstract

The development of interventions that reduce Lyme disease incidence remains a challenge. Reservoir-targeted approaches aiming to reduce tick densities or tick infection prevalence with Borrelia burgdorferi have emerged as promising ways to reduce the density of infected ticks. Acaricides of the isoxazoline family offer high potential for reducing infestation of ticks on small mammals as they have high efficacy at killing feeding ticks for a long period. Fluralaner baits were recently demonstrated as effective, in the laboratory, at killing Ixodes scapularis larvae infesting Peromyscus mice, the main reservoir for B. burgdorferi in northeastern North America. Here, effectiveness of this approach for reducing the infestation of small mammals by immature stages of I. scapularis was tested in a natural environment. Two densities of fluralaner baits (2.1 baits/1,000 m² and 4.4 baits/1,000 m²) were used during three years in forest plots. The number of I. scapularis larvae and nymphs per mouse from treated and control plots were compared. Fluralaner baiting reduced the number of larvae per mouse by 68% (CI95: 51–79%) at 2.1 baits/1,000 m² and by 86% (CI95: 77–92%) at 4.4 baits/1,000 m². The number of nymphs per mouse was reduced by 72% (CI95: 22–90%) at 4.4 baits/1,000 m² but was not significantly reduced at 2.1 baits/1,000 m². Reduction of Peromyscus mouse infestation by immature stages of I. scapularis supports the hypothesis that an approach targeting reservoirs of B. burgdorferi with isoxazolines has the potential to reduce tick-borne disease risk by decreasing the density of infected ticks in the environment.

The most widespread arboviral diseases such as Dengue, Chikungunya, and Zika are transmitted mainly by Aedes mosquitoes. Due to the lack of effective therapeutics for most of these diseases, vector control remains the most effective preventative and control measure. This study investigated and compared the species composition, insecticide susceptibility, and resistance mechanisms in Aedes mosquito populations from a forest reserve converted to an eco-park and a peri-domestic sites in urban Accra, Ghana. Immature Aedes were sampled from the study sites, raised to adults, and exposed to deltamethrin, permethrin, DDT, fenitrothion, bendiocarb, permethrin + PBO, and deltamethrin + PBO using WHO tube assays. Melting curve analyses were performed for F1536C, V1016I, and V410L genetic mutations in surviving and dead mosquitoes following exposure to deltamethrin and permethrin. Microplate assay was used to access enzyme activity levels in adult mosquitoes from both populations. Aedes aegypti was found to be the dominant species from both study populations. The susceptibility test results revealed a high frequency of resistance to all the insecticides except fenitrothion. F1534C mutations were observed in 100% and 97% of mosquitoes from the peri-domestic and forest population, respectively but were associated with pyrethroid resistance only in the forest population (P < 0.0001). For the first time in Aedes mosquitoes in Ghana, we report the existence V410L mutations, mostly under selection only in the forest population (HWE P < 0.0001) and conclude that Aedes vectors in urban Accra have developed resistance to many commonly used insecticides. This information is important for the formulation of vector control strategies for Aedes control in Ghana.

Dengue vector control strategies are mostly based on chemicals use against Aedes aegypti populations. The current study aimed at investigating the insecticidal effects of essential oils (EOs) obtained from five plant species, Cymbopogon citrates (D. C.) Stapf. (Poaceae), Cymbopogon nardus (Linn.) Rendle (Poaceae), Eucalyptus camaldulensis Linn. (Myrtaceae), Lippia multiflora Moldenke (Verbenaceae), and Ocimum americanum Linn. Lamiaceae, and combinations of Cymbopogon nardus and Ocimum americanum on Ae. aegypti populations from Bobo-Dioulasso. For this purpose, adults of the susceptible and field strains of Ae. aegypti were tested in WHO tubes with EO alone and binary combinations of O. americanum (OA) and C. nardus (CN; scored from C1 to C9). The extraction of the essential oils was done by hydrodistillation, and their components were determined by GC/MS. Among the 5 EOs tested, L. multiflora essential oil was the most efficient, with KDT₅₀ values below 60 min on all Ae. aegypti strains tested, and also with a rate of mortality up to 100 and 85% for Bora Bora and Bobo-Dioulasso strains, respectively. This efficacy may be due to its major compounds which are with major compounds as β-caryophyllene, p-cymene, thymol acetate, and 1.8 cineol. Interestingly, on all strains, C8 combination showed a synergistic effect, while C2 showed an additive effect. These combinations exhibit a rate of mortality varying from 80 to 100%. Their toxicity would be due to the major compounds and the putative combined effects of some major and minor compounds. More importanly, L. multiflora EO and combinations of C. nardus and O. americanum EO, may be used as alternatives against pyrethroid resistant of Ae. aegypti.

To reduce the risk of zoonoses, it is necessary to understand the infection process, including the ecology of animals and vectors (i.e., the ‘One Health’ approach). In temperate climates, ticks are the major vectors of zoonoses, so factors determining their abundance, such as host mammal abundance and microhabitat conditions, should be clarified. Sika deer (Cervus nippon) are a major tick host and are rapidly expanding their distribution in Japan. We established 12 plots along a gradient of sika deer abundance in Tochigi Prefecture, Japan. We monitored the occurrence of mammal species with camera traps and sampled questing ticks on a monthly basis by flagging along three transects (center of a trail, forest edge, and forest interior) at each site from April to November 2018. The camera traps recorded 12 mammal species, predominantly sika deer. Five Haemaphysalis species and three Ixodes species were sampled. The numbers of ticks sampled were explained by the photographic frequency of sika deer, and partly by that of other mammal species, depending on tick species and their developmental stages. The numbers of sampled adult and nymphal ticks were the highest at the forest edge, where vegetation cover was greatest. Thus, vegetation management in tick habitats and the control of sika deer populations may reduce tick abundance.

Northern Morocco is endemic for cutaneous and visceral leishmaniasis. Our entomological investigations aim to evaluate the risk of Leishmania transmission by determining the species composition, the density, and seasonal fluctuation of sand fly populations in endemic and nonendemic areas of leishmaniasis in Tetouan province (North-Western Morocco). Using Sticky-paper traps, 8,370 specimens were collected between May and November 2015 in two localities: peri-urban area of Tetouan city, where leishmaniasis is endemic and that of the Oued Laou village where no cases of leishmaniasis have been recorded. Six sand fly species were identified. The genus Phebotomus was represented by five species: Phlebotomus ariasi, Phlebotomus. longicuspis, Phlebotomus perniciosus, Phlebotomus kazeruni, and Phlebotomus sergenti, while the genus Sergentomyia was represented by only one species Sergentomyia minuta. Phlebotomus perniciosus was dominant in the nonendemic area (47%) while Phlebotomus sergenti was dominant in the endemic area (51%). The spatio-temporal distribution of sand fly populations is discussed according to biotic and abiotic variables. Seasonal fluctuation in sand fly density showed a bimodal pattern for the subgenus Larroussius and a unimodal pattern for the subgenus Paraphlebotomus in Tetouan city. But, in Oued Laou village, a unimodal density distribution for species of the Larroussius subgenus and a bimodal seasonal distribution for species of the subgenus Paraphlebotomus were identified. We affirm the coexistence, in the study area, of vectors of both cutaneous and visceral leishmaniasis, namely P. ariasi, P. longicuspis and P. perniciosus vectors of Leishmania infantum and P. sergenti vector of L. tropica. However, the geographic distribution, the specific abundance, and the activity reveal significant differences between endemic and nonendemic areas in the region.

Entomological indicators of onchocerciasis transmission and the effect of climatic variables on the vector population dynamics were investigated in two first-line villages after more than two decades of mass drug administration with ivermectin. Female blackflies were collected in two villages (Bayomen and Biatsota) using human landing method for a period of 12 months. Blackflies were dissected and entomological indices were computed. Monthly temperature, precipitation, and humidity were collected and the Spearman correlation rank test was used to assess the relationship between biting rates and climatic variables. The highest biting rates (62,280 bites/human/month in Bayomen and 42,090 bites/human/month in Biatsota) were recorded during the long rainy season (November). The Onchocerca volvulus transmission was greater during the long dry season in both villages, with a peak at the beginning of the long dry season in Biatsota (100 infective larvae/human/month), and at the middle of the long dry season in Bayomen (92 infective larvae/human/month). No correlation was found between biting rates and selected climatic variables in the two villages. This study revealed that onchocerciasis transmission is ongoing in the study area despite almost 25 years of Community-Directed Treatment with Ivermectin. In accordance with WHO recommendations, vector control should be used in combination with mass drug administration to accelerate transmission interruption of onchocerciasis. To be optimal, this vector control should be implemented during the long dry season (November to March) when water volumes are low and transmission potentials are high.

The performances of the human-baited double net trap (HDNT) and the human-baited host decoy trap (HDT) methods were compared against the outdoor human landing catch (OHLC) method in Thailand and Vietnam. Two study sites were selected in each country: a rural village and a nearby forest setting. The three outdoor trap methods were rotated nightly between three set trapping positions, in a pre-assigned Latin square design. Volunteers were rotated following the trap rotation to avoid bias. The greatest number of adult mosquitoes was collected from the forest sites in both countries, showing Anopheles minimus (s.s.)Theobald (96.54%) and Anopheles dirus (s.s.) Peyton & Harrison (25.71%) as the primary malaria vectors in Thailand and Vietnam, respectively. At theThai forest site, OHLC collected significantly more anopheline mosquitoes per trap night than HDNT and HDT, with mean ± standard error values of 14.17 ± 4.42, 4.83 ± 1.56, and 4.44 ± 1.45, respectively, whilst HDNT and HDT were significantly less productive at 0.34 times and 0.31 times, respectively, than OHLC in capturing anopheline mosquitoes. However, there were no significant differences among the three methods of trapping malaria vectors for the village site. At the Vietnamese forest site, HDNT achieved the highest performance in collecting Anopheline mosquitoes at 1.54 times compared to OHLC, but there was no significant difference between the two traps. The results suggested HDNT could be a possible alternative trap to OHLC in this area. Although HDT was less efficient at attracting Anopheline mosquitoes, it was highly efficient at trapping culicine mosquitoes.

Here, we report a new record of Triatoma infestans (Klug) in Mexico after 50 years and provide a brief description of the discovery area. Fifty-nine specimens (71.2% adults) of the introduced species were collected from the peridomestic areas of a single house in the port of Manzanillo in the state of Colima, Mexico. Thirty-one specimens (52.5%) were collected from the exterior walls of the house and were apparently attracted to light. The other specimens (47.5%) were associated with chickens. No specimen was infected with Trypanosoma cruzi Chagas, the causative agent of Chagas disease, possibly because they were feeding on chickens. We speculate that the introduced species travelled from South America to Mexico via seed shipment in a twenty-foot equivalent unit (TEU) maritime container. Because Mexican phytosanitary regulations demand only the cargo to be inspected, the triatomines could have escaped notice during inspection. Subsequently, as the cargo was unloaded and the TEU was stored, the triatomines likely flew to and invaded the nearby residential areas. The rediscovery of this domestic vector of T. cruzi in Mexico warrants further investigation owing to the potential risk of transmission to the inhabitants of the study area.

Graphical Abstract

Triatoma infestans was found after 50 years in Mexico. The possible introduction of some specimens of that species via seed shipment from a South American country in a twenty-foot equivalent unit (TEU) maritime container is hypothesized. The rediscovery of this invasive domestic vector of T. cruzi in Mexico warrants further investigation owing to the potential risk of transmission to the inhabitants of the study area.

Increasing incidence of tick-borne human diseases and geographic range expansion of tick vectors elevates the importance of research on characteristics of tick species that transmit pathogens. Despite their global distribution and role as vectors of pathogens such as Rickettsia spp., ticks in the genus Dermacentor Koch, 1844 (Acari: Ixodidae) have recently received less attention than ticks in the genus Ixodes Latreille, 1795 (Acari: Ixodidae). To address this knowledge gap, we compiled an extensive database of Dermacentor tick traits, including morphological characteristics, host range, and geographic distribution. Zoonotic vector status was determined by compiling information about zoonotic pathogens found in Dermacentor species derived from primary literature and data repositories. We trained a machine learning algorithm on this data set to assess which traits were the most important predictors of zoonotic vector status. Our model successfully classified vector species with ∼84% accuracy (mean AUC) and identified two additional Dermacentor species as potential zoonotic vectors. Our results suggest that Dermacentor species that are most likely to be zoonotic vectors are broad ranging, both in terms of the range of hosts they infest and the range of ecoregions across which they are found, and also tend to have large hypostomes and be small-bodied as immature ticks. Beyond the patterns we observed, high spatial and species-level resolution of this new, synthetic dataset has the potential to support future analyses of public health relevance, including species distribution modeling and predictive analytics, to draw attention to emerging or newly identified Dermacentor species that warrant closer monitoring for zoonotic pathogens.

Pale-banded variants of Culex territans Walker larvae were found in southern New Jersey in 2016 and in subsequent years. The larvae lacked pigmentation on the prothoracic and mesothoracic segments as well as on abdominal segment (IV). The amount of pigmentation varied between populations. Specimens were found in six locations within a 5-yr period; of which, two locations recurred within the same season and in subsequent seasons. This is the first report in the State of New Jersey despite extensive larval surveillance over many years among the study area.

Visceral leishmaniasis is not endemic in West Africa, but prevalence of canine leishmaniasis and seroprevalence of Leishmania infantum infection in humans are high in the Mont Rolland community (Thiès region, Senegal). Previous studies in this area showed that Sergentomyia schwetzi could be the potential vector of Le. infantum. To precisely describe the biology and population structure of this potential vector, we identified eight novel microsatellite loci to characterize Se. schwetzi populations. We tested these loci in Se. schwetzi populations from five locations at Mont Rolland (Thiès, Senegal). All the loci were polymorphic, with a mean of 17.25 alleles (observed heterozygosity: 0.455). We did not detect any evidence of scoring errors due to stuttering and large allele dropout. Moreover, several of these loci were also amplified in six other sand fly species (Sergentomyia magna, Sergentomyia dubia, Sergentomyia minuta, Phlebotomus duboscqi, Phlebotomus perniciosus, and Phlebotomus ariasi). These preliminary results demonstrate the utility of these microsatellite markers for Se. schwetzi (and for the other sand fly species) population genetic studies.

The Asian longhorned tick (Haemaphysalis longicornis Neumann), native to East Asia, was first reported in the United States in 2017 and is now established in at least 17 states. Haemaphysalis longicornis feeds on birds in its range outside of the United States, and migratory birds disperse this tick and tick-borne pathogens. However, early studies in the United States did not find H. longicornis on migrating passerine birds. The transport of the parthenogenetic H. longicornis on birds has the potential to greatly expand its range. We report the first discovery of H. longicornis on migratory passerine birds in the Americas.

Lyme disease (LD), caused by the bacterium Borrelia burgdorferi, is transmitted to humans in California through the bite of infected blacklegged ticks (Ixodes pacificus). Overall, the incidence of LD in California is low: approximately 0.2 confirmed cases per 100,000 population. However, California's unique ecological diversity results in wide variation in local risk, including regions with local foci at elevated risk of human disease. The diagnosis of LD can be challenging in California because the prior probability of infection for individual patients is generally low. Combined with nonspecific symptoms and complicated laboratory testing, California physicians need a high level of awareness of LD in California to recognize and diagnose LD efficiently. This research addresses an under-studied area of physicians' knowledge and practice of the testing and treatment of LD in a low-incidence state. We assessed knowledge and practices related to LD diagnosis using an electronic survey distributed to physicians practicing in California through mixed sampling methods. Overall, responding physicians in California had a general awareness of Lyme disease and were knowledgeable regarding diagnosis and treatment. However, we found that physicians in California could benefit from further education to improve test-ordering practices, test interpretation, and awareness of California's disease ecology with elevated levels of focal endemicity, to improve recognition, diagnosis, and treatment of LD in California patients.