Mosquito-borne diseases (MBDs) are emerging in response to climate and land use changes. As mosquito (Diptera: Culicidae) habitat selection is often contingent on water availability for egg and larval development, studies have recognized water quality also influences larval habitats. However, underlying species-, genera-, and mosquito level preferences for water quality conditions are varied. This systematic review and meta-analysis aimed to identify, characterize, appraise, and synthesize available global data on the relationships between water quality and mosquito presence and abundance (MPA); with the goal to further our understanding of the geographic expansion of MBD risks. A systematic review was conducted to identify studies investigating the relationships between water quality properties and MPA. Where appropriate, random-effects meta-analyses were conducted to provide pooled estimates for the association between the most reported water quality properties and MPA. The most reported water quality parameters were pH (87%), nitrogen concentrations (56%), turbidity (56%), electrical conductivity (54%), dissolved oxygen (43%), phosphorus concentrations (30%), and alkalinity (10%). Overall, pH (P = 0.05), turbidity (P < 0.0001), electrical conductivity (P = 0.005), dissolved oxygen (P < 0.0001), nitrogen (P < 0.0001), and phosphorus (P < 0.0001) showed significantly positive pooled correlations with MPA, while alkalinity showed a nonsignificant null pooled correlation (P = 0.85). We observed high heterogeneity in most meta-analyses, and climate zonation was shown to influence the pooled estimates. Linkages between MPA and water quality properties will enhance our capacity to predict MBD risks under changing environmental and land use changes.

Graphical Abstract

Rearing common bed bugs (Cimex lectularius L.) and other hematophagous insects is essential for basic, medical, and pest-control research. Logistically, acquiring fresh blood can be a challenge, while biologically, the eventual effects of different rearing and blood preparation protocols on bed bug genotype and phenotype pose a risk of biased research results. Using bed bug populations that are either bat- (BL) or human-related (HL), we tested the short- and long-term effects of rearing bugs on live bats or human volunteers, or artificially on CPDA (citrate phosphate dextrose, adenine)-treated blood, measuring meal size, body size, and fertility. We found that artificial feeding did not affect meal size compared with feeding on natural hosts. Long-term rearing across many generations of HL on CPDA-preserved blood led to reduced body size and fertility compared with populations reared on human volunteers. Blood preservatives increased the proportion of sterile eggs even after a single feed. Finally, our results indicated that laboratory reared bed bugs were smaller, regardless of the blood source, than wild bugs. Similar effects of artificial feeding or laboratory rearing alone should be considered in future studies using bed bug cultures to choose an appropriate rearing protocol. With regard to switching between bat and human hosts, HL took smaller meals and BL had lower fertility when fed on bats than when fed on humans. We attribute these results to methodological constrains, specifically the inconsistency of bat feeding, rather than to host specialization. Nevertheless, BL can be easily reared using human blood and artificial feeding systems.

The geographical range of the American dog tick, Dermacentor variabilis (Say), in Canada continues to expand northwards into areas with colder winter temperatures. Understanding what influences the off-host survival of D. variabilis over winter is important for predicting the northern distributional limit of this species. A field experiment was conducted to determine the effect of snow cover on the off-host survival of unfed D. variabilis larvae from a population situated near the northern distributional limit in Saskatchewan, Canada. Ticks were placed in tubes within 1 of 9 field enclosures (tickaria) in early fall. The 9 tickaria were divided into 3 equal treatment groups: no snow cover, natural snow cover (maximum depth of 25 cm) and extra snow cover (maximum depth of 32 cm). Tick survival was measured in mid-winter and in early spring (i.e., ∼17 and ∼26 wk after start of experiment). The results showed that snow cover had a significant impact on the relative humidity, but not temperature, in the tickaria. Larvae in tickaria with no snow cover had a higher mortality rate (27%) than larvae in tickaria with natural snow cover (6%) or extra snow cover (4%). Although snow cover enhanced off-host survival, many individuals were able to survive in sub-zero temperatures under leaf litter in the absence of continuous snow cover for a period of 108 days. These findings have implications for the construction of predictive models to determine the northern distributional limits of D. variabilis, a species that is an important vector of several pathogens.

Necrophagous insect species are widely used during death investigations primarily for the estimation of the minimum postmortem interval, since these species use decomposing organic matter for feeding, oviposition, and larval development. The development stages and successional colonization patterns provide important information for shorter or longer postmortem time intervals. Diptera species are the predominant taxa recovered from decomposed bodies. The temperature variance/seasonality is the main factor affecting the time presence and activity of these species. Other factors, such as geographical location, antemortem conditions, and cause of death, can influence the presence and succession of necrophagous entomofauna. Consequently, successional studies and information regarding species colonization patterns are needed for each geographical region to be used as reference data during death investigations. This study addressed the need to collect forensic entomological data for the State of North Dakota, within the first necrophagous entomofauna diversity report for the month of July 2022, using pig carcasses as human analogs. During the experimental period, 18 species of Diptera and Coleoptera were identified, with 10 new state records, while Calliphoridae was found to be the predominant family. The resulted data on necrophagous insect species diversity and dynamics from exposed pig carcasses will strengthen the current knowledge on forensic entomology in North Dakota and will serve as reference data to be used during death investigations in the Great Plains region.

Musca domestica (Linnaeus, 1758) (Diptera: Muscidae), popularly known as “housefly”, is a highly synanthropic species, with economic, medical-sanitary, veterinary, and forensic importance. It is able to cause damage to health, transmit pathogenic agents, cause infection in domestic animals, and, in its immature stage, cause secondary myiasis. The scavenging habit of its immature stages makes these flies pioneers in colonizing both human and animal carcasses, from the initial stages of corpse decomposition to the final stages. Intrapuparial development studies of all stages of the biological cycle of these insects help estimate pupal age, being useful to forensic entomology to aid in determining the minimum postmortem interval (_minPMI). This study describes, morphologically, the external structures of the pupae, under temperatures of 23, 27, and 30 ± 1 °C aiming to identify the characteristics that define their developmental stages and estimation of the pupae age of M. domestica. The whole experiment was carried out under laboratory conditions, with relative humidity 60 ± 10% and 12 hours of photoperiod. The process of pupariation and pupation including pre-pupae phases were observed; larvae pupae apolysis; early cryptocephalic pupae; late cryptocephalic pupae; phanerocephalic pupae; pharate adult, discriminated by eye color (transparent eyes, pink eyes, and red eyes); and the emergency of adults, which occurred in the intervals of 162–180; 138–144, and 96–102 hr, respectively, being described throughout the metamorphosis of the external morphological characteristics of the pupal stage of M. domestica.

Musca domestica (Linnaeus, 1758) (Diptera: Muscidae), conhecida popularmente como “mosca doméstica”, é uma espécie altamente sinantrópica, com importância econômica, médica-sanitária, veterinária e forense, podendo causar danos à saúde, ao veicular e transmitir agentes patogênicos, ser espoliadora dos animais domésticos e, em seu estágio imaturo, causar miíase secundária. Seu hábito necrófago na fase imatura faz dela uma espécie pioneira na colonização de carcaças tanto de humanos quanto de animais, desde os estágios iniciais de decomposição cadavérica até os estágios finais. O estudo de seu desenvolvimento intrapuparial, permite conhecer todos os estágios do ciclo biológico destes insetos, de modo a auxiliar a entomologia forense no Intervalo Pós-Morte Mínimo (IPMmín). Esse estudo objetivou, descrever morfologicamente, as estruturas externas das pupas, visando a identificação das características que definem as fases de seu desenvolvimento e estimativa da idade pupal de M. domestica, sob as temperaturas de 23, 27 e 30 ± 1°C. Todo o experimento foi realizado em condições de laboratório, com umidade relativa de 60 ± 10% e 12 horas de fotoperíodo. Foram observados o processo de pupariação e pupação com as fases pré-pupa; apólise larva-pupa; pupa criptocefálica anterior; pupa criptocefálica posterior; pupa fanerocefálica; adulto farado, (olhos transparentes, olhos rosados e olhos vermelhos); e emergência do adulto, que ocorreu nos intervalos de 162–180 h; 138-144 h e 96–102 h, respectivamente e sendo descritas durante toda a metamorfose das características morfológicas externas do estágio de pupa de M. domestica.

Females of some mosquito species are anthropophilic, as they feed on human blood to support egg production and, hence, are forensically valuable if found at a crime scene. The present study investigated the blood meal digestion process in Culex pipiens L. both with and without heroin and proposed a method for estimating the post-feeding interval (PFI). Mosquitoes were fed on a control mouse, a heroin-injected mouse, or in vitro heroin-treated mouse blood. The blood meal digestion was then investigated at different hours post-feeding. Data showed that the blood meal size ingested by control mosquitoes was 0.681 ± 0.04 mg/mosquito and was completely digested within 45 h post-feeding. An estimation of the PFI was proposed in terms of the rate of hemoglobin (Hb) digestion. The blood meal size of the mosquitoes fed on the in vitro heroin-treated blood and the heroin-injected mouse was 0.96 ± 0.06 and 0.79 ± 0.01 mg/mosquito and was completely digested within 50 and 55 h post-feeding, respectively. The digestion of Hb started similarly in all experimental mosquitoes until 10 h post-feeding, after which it significantly decreased in heroin-treated blood meals compared with the control ones. This may suggest that heroin impacted the digestion process, as it took an extra 5–10 h to complete. These findings could be valuable in the forensic context since an estimation of PFI is proposed as a potential estimation of the postmortem interval (PMI). However, care should be taken as heroin in the host blood has significantly impacted the overall digestion process and, hence, may bias the PFI/PMI estimation.

Nyssorhynchus (Nyssorhynchus) ibiapabaensis (Sant'Ana & Sallum n. sp.) and Ny. (Nys.) untii (Sant'Ana & Sallum n. sp.) are new species of the Arthuri Complex of the Strodei Subgroup. The new species are described and validated using morphological characters of the male, female, and immature stages. The description of the male, female, fourth-instar larva and pupa of Ny. arthuri (Unti, 1941) and Ny. albertoi (Unti, 1941) are provided for the first time.To avoid nomenclature instability, neotypes are designated for both species. All life stages of Ny. strodei (Root, 1926) employing specimens collected in the Agua Limpa District, Juiz de Fora, Minas Gerais, Brazil are redescribed.

Ticks are blood-feeding arthropods responsible for the transmission of disease-causing pathogens to a wide range of vertebrate hosts, including livestock and humans. Tick-borne diseases have been implicated in significant economic losses to livestock production, and this threat will increase as these obligate parasites widen their geographical ranges. Similar to other ectotherms, thermal stress due to changing global temperatures has been shown to influence tick survival and distribution. However, studies on the influence of extreme temperatures in ticks have focused on advanced, mobile stages, ignoring immobile stages that cannot move to more favorable microhabitats. In this study, low- and high-temperature regimens were assessed in relation to egg viability for hard tick species—Amblyomma maculatum (Gulf Coast tick), Ixodes scapularis (black-legged tick), Dermacentor variabilis (American dog tick), and Rhipicephalus sanguineus (Brown dog tick). Tick eggs exposed early in development (freshly laid during early embryo development) were significantly more susceptible to thermal stress when compared with those exposed later in development (late embryo development denoted by a fecal spot). Based on our studies, differences in egg hatching success among treatments were greater than in hatching success when comparing species. Lastly, there was evidence of extreme thermal exposure significantly altering the hatching times of tick eggs for specific treatments. These results provide insights into the critical period for tick egg viability in relation to thermal exposure and tick survival associated with stress and climate change.

Mortality imposed on a population can interact with negatively density-dependent mortality to produce overcompensation, wherein added mortality results in more survivors. Experimental mortality can cause overcompensation in mosquito larvae, which would be counterproductive if it resulted from mosquito control in nature. We tested for different demographic responses to mortality among 3 container Aedes species when impacted by density dependence. We imposed 48.2% mortality on cohorts of larvae 2, 6, or 8 days after hatching and compared adult production, development times, and female size to those variables for controls without mortality. Mortality significantly increased adult production compared to controls, but the 3 species varied in the details of that response. Aedes albopictus (Skuse) produced more adults with mortality on day 2 primarily because of greater production of males. Aedes triseriatus (Say) yielded more adults with mortality on day 2 primarily because of greater production of females. Aedes aegypti (L.) adult production was not significantly affected by mortality, but development times for both sexes were significantly shorter with mortality on day 8. There were no effects of mortality on female wing length. None of our mortality treatments yielded significant reductions of adults for any species. These species responses to mortality are not the same, despite their similar ecologies and life histories. Thus, we cannot assume that killing almost half the larvae present in a dense population will reduce adult production, nor can we assume that different Aedes species will respond to mortality in the same way.

Prey populations that encounter predators experience density-mediated effects through lethality and associated numerical changes in the population. Prey also exhibit trait-mediated effects through nonlethal alterations in phenotypic traits associated with exposure to predators. Immature stages of mosquitoes commonly co-occur in habitats along with predators, a natural source of mortality and potential biocontrol agent. Toxorhynchites rutilus Coquillett 1896 is a natural source of mortality with potential as a biological control agent. Previous studies have shown that predation and the mere presence of Tx. rutilus (predator cues) can alter the life-history traits of Aedes aegypti (L. 1762). In addition to observed reductions in recruitment of adults (lethality), exposure to Tx. rutilus without consumption resulted in adult Ae. aegypti females with altered growth and reduced lifespan. To determine the influence of predation on the reproductive biology of Ae. aegypti, we tested the hypothesis that predation, or exposure to predator cues, will compromise the reproduction of adult survivors through reductions in fecundity (egg batch size) and fertility (hatch rate). We observed that for both female and male Ae. aegypti, survival to adulthood was the lowest and development time the shortest in treatments containing prey removal effects, attributable to predation and treatment manipulations of density reduction. There were effects of Ae. aegypti weight, but not predation treatments, on fecundity and fertility. Results suggest that predator-mediated effects on Ae. aegypti derive from lethal effects due to consumption and alterations in other phenotypic traits of survivors, including development, weight, lifespan of adults, and population growth, but not reproductive parameters measured here.

Bichromomyia flaviscutellata (Mangabeira, 1942) sensu stricto (Diptera: Psychodidae) has been recognized as the main vector of Leishmania amazonensis in the Brazilian Amazon. For this reason, it is of paramount importance to understand the distribution of genetic diversity of populations of this vector, particularly the genetic structure and gene flow, for its management and control efforts. This study investigated the phylogeographic structure of five B. flaviscutellata s.s. populations from the central Brazilian Amazon region by analyzing 1,141 bp fragment of the 3′ region of the COI gene. A total of 85 specimens of B. flaviscutellata s.s. were sequenced from Manaus (14), Rio Preto da Eva (10), Pitinga (14), Novo Airão (21), and Autazes (26); all in the state of Amazonas. The dataset yielded 59 haplotypes, most of them connected to each other in the main network. There were high levels of intrapopulation genetic variability (h = 0.945 ± 0.035 – 0.978 ± 0.054). The genetic distance values among populations varied from moderate (0.0873) to very high (0.3535), and all comparisons were significant, as well as the hierarchical analysis (Φ_ST = 0.2145). In contrast, these comparisons revealed a high number of shared sites (S_s = 6–34) and no difference in fixed sites (S_f = 0) among populations indicating absence of historical isolation. The Mantel test indicated that 67.92% (r = 0.6792; P = 0.06) of the genetic structure observed in B. flaviscutellata s.s. cannot be explained by the isolation-by-distance (IBD) model. This genetic structure, weakly explained by the IBD, may be due mainly by the forest habitat fragmentation and the low dispersal (flight) capacity of sand flies. Both factors could lead to population fragmentation and isolation, which promote genetic differentiation. Taken together, these findings suggest that the genetic structure observed in the studied populations of B. flaviscutellata s.s. is likely generated by microevolutionary processes acting at the population level at the present time and, therefore, evolutionary lineages were not recognized among the populations analyzed.

Available methods to census exophilic tick populations have limitations in estimating true population size due to their inability to capture a high proportion of the actual tick population. We currently ignore the efficacy of these methods to capture questing Hyalomma spp. ticks, vectors of the Crimean-Congo hemorrhagic fever virus. To address the need of accurately estimating questing densities of Hyalomma spp., we designed a field experiment to test the efficacy of blanket dragging, blanket flagging, CO₂-baited traps, and an ad hoc designed method, absolute surface counts, in capturing adult Hyalommalusitanicum ticks from known numbers of preset fluorescent-marked ticks.The experiment was designed in 2 stages to estimate the point (1-day sampling) and cumulative (3-day serial sampling) efficacy of the methods under varying sampling effort and habitat. Tick survival, host interference, and weather effects on efficacy were controlled for in multiple regression models. There was high variability in method efficacy for capturing ticks, which was also modulated by effort, habitat, tick density, hosts, and soil temperature. The most effective method was absolute surface counts for both point estimates (39%) and cumulative efficacy (83%). CO₂-baited traps reached a maximum efficacy of 37%, while blanket dragging and blanket flagging captured a maximum of the 8% of the marked ticks. Our results reveal the strengths and weaknesses of the different tick capture methods applied to adult H. lusitanicum and lay the groundwork for more accurate inferences about the true size of exophilic tick populations.

Graphical Abstract

Control of mosquito vector populations is primarily intended to reduce the transmission of pathogens they transmit. Use of chemical controls, such as larvicides, can have unforeseen consequences on adult traits if not applied properly. The consequences of under application of larvicides are little studied, specifically the impacts on pathogen infection and transmission by the vectors that survive exposure to larvicides. We compared vector susceptibility of Aedes aegypti (L.) for dengue virus, serotype 1 (DENV-1) previously exposed as larvae to an LC₅₀ of different classes of insecticides as formulated larvicides. Larval exposure to insect growth regulators (methoprene and pyriproxyfen) significantly increased susceptibility to infection of DENV-1 in Ae. aegypti adults but did not alter disseminated infection or transmission. Larval exposure to temephos, spinosad, and Bti did not increase infection, disseminated infection, or transmission of DENV-1. Our findings describe a previously under observed phenomenon, the latent effects of select larvicides on mosquito vector susceptibility for arboviruses. These data suggest that there are unintended consequences of sublethal exposure to select larvicides that can influence susceptibility of Ae. aegypti to DENV infection, and indicates the need for further investigation of sublethal effects of insecticides on other aspects of mosquito biology, especially those parameters relevant to a mosquitoes ability to transmit arboviruses (life span, biting behavior, extrinsic incubation period).

St. Tammany Parish Mosquito Abatement District relies on ultra-low volume (ULV) insecticides to manage adult Culex quinquefasciatus (Say 1823), the primary vector of West Nile virus in Louisiana, but abundance rarely declines post-treatment. Three field ULV applications each of adulticides containing deltamethrin, naled, or resmethrin were conducted from May through October 2022 to measure efficacy against free-flying Cx. quinquefasciatus. Female mosquitoes trapped before and after treatment were identified, counted, and age-graded by parity dissection. No insecticide applications reduced Cx. quinquefasciatus abundance, but trials with deltamethrin and naled significantly lowered average mosquito age in the area post-treatment. No trials with resmethrin reduced mosquito age, which corroborates laboratory susceptibility data indicating local resistance toward the pyrethroid. These trials establish parity dissections and relative age gradation as a means of measuring treatment success against Cx. quinquefasciatus.

Volatile pyrethroids exert a range of both lethal and behavioral effects on mosquitoes through the passive release of insecticides into the atmosphere. We investigated the protective efficacy (PE) of transfluthrin-treated jute (TI-jute) and cotton (TI-cotton) fabrics, worn at the back of a protective black vest, against laboratory-reared pyrethroid susceptible and resistant strains of Aedes aegypti (L.) in a semifield system (SFS). Each fabric (1,029 cm²) was treated with 1.79 mg/cm² of transfluthrin as the intervention. Human landing collections were conducted by 2 collectors seated in designated treatment and control compartments of the SFS. The trials were conducted for 41 days, with 16 days partitioned into morning and evening phases. Furthermore, we examined blood feeding behavior and fecundity of the surviving mosquitoes post-exposure. Results showed that in the morning, the PE of TI-jute (49.4%) was higher than that of TI-cotton (36.8%). TI-jute demonstrated a lower PE of 9.6% against the transfluthrin-resistant strain. Remarkably, a significantly higher number of eggs were laid by the transfluthrin-resistant mosquitoes that survived the intervention (36.5 eggs/female) compared to the control group (11.8 eggs/female). These findings suggest that TI-jute can help protect against bites and alter the life traits of Ae. aegypti. The study highlights that the timing of the intervention during the day affected the efficacy of TI-jute and TI-cotton, while sublethal exposure to transfluthrin stimulated egg production in the resistant strain. These are critical challenges that warrant attention in vector control strategies. Investigating this phenomenon in mosquito reproduction necessitates future research at a molecular level.

Curcuma longa L. (Zingiberales: Zingiberaceae) leaf and rhizome essential oils were evaluated for their toxicity and repellency against invasive fire ants: red imported fire ants (RIFA), Solenopsis invicta Buren, black imported fire ants (BIFA), Solenopsis richteri Forel, and a reproductively functional hybrid (HIFA). Ar-turmerone was the major constituent of leaf (42.4%) and rhizome (40.4%) essential oils. A range of concentrations starting from 156 µg/g until the failure of treatment were used. Removal of treated sand in digging bioassay was used as a criterion for repellency. Leaf essential oil showed significantly higher repellency at concentrations of 19.5, 9.8, and 4.9 µg/g against RIFA, BIFA, and HIFA workers, respectively, as compared with control whereas rhizome essential oil was active at 39, 19.5, and 4.9 µg/g against BIFA, RIFA, and HIFA, respectively. Ar-turmerone exhibited repellency at 19.5 µg/g against HIFA workers whereas DEET (N,N-diethyl-meta-toluamide) failed at 39 µg/g. Leaf essential oil showed LC₅₀ values of 85.8, 97.7, and 182.7µg/g against RIFA, BIFA and HIFA workers, whereas the rhizome essential oil had LC₅₀ values of 127, 109.9, and 151.2 µg/g against these species, respectively. Ar-turmerone, tested only against HIFA, with LC₅₀ value of 57.2 was the most active compound. Bifenthrin, a commonly used pyrethroid, with LC₅₀ of 0.03, 0.32, and 0.018 µg/g was toxic against RIFA, BIFA, and HIFA workers, respectively. Both the essential oils and ar-turmerone showed toxicity and repellency against imported fire ants. Different formulations of these natural products will be tested to explore the use potential of these natural products under field conditions.

Graphical Abstract

Plague is a zoonotic vector-borne disease caused by the bacterium Yersinia pestis. In Madagascar, it persists in identified foci, where it is a threat to public health generally from September to April. A more complete understanding of how the disease persists could guide control strategies. Fleas are the main vector for transmission between small mammal hosts and humans, and fleas likely play a role in the maintenance of plague. This study characterized the dynamics of flea populations in plague foci alongside the occurrence of human cases. From 2018 to 2020, small mammals were trapped at sites in the central Highlands of Madagascar. A total of 2,762 small mammals were captured and 5,295 fleas were collected. The analysis examines 2 plague vector species in Madagascar (Synopsyllus fonquerniei and Xenopsylla cheopis). Generalized linear models were used to relate flea abundance to abiotic factors, with adjustments for trap location and flea species. We observed significant effects of abiotic factors on the abundance, intensity, and infestation rate by the outdoor-associated flea species, S. fonquerniei, but weak seasonality for the indoor-associated flea species, X. cheopis. A difference in the timing of peak abundance was observed between the 2 flea species during and outside the plague season. While the present study did not identify a clear link between flea population dynamics and plague maintenance, as only one collected X. cheopis was infected, the results presented herein can be used by local health authorities to improve monitoring and control strategies of plague vector fleas in Madagascar.

The abundance of hard ticks can be determined by abiotic factors and the presence of suitable hosts. Since deer represent important hosts for many tick species, it is imperative to investigate whether deer introduction will increase the number of ticks, which can transmit a wide variety of pathogens. The sika deer (Cervus nippon) was introduced to Green Island, Taiwan, to supply velvet antlers, a traditional Chinese medicine. However, they were later released into the wild after a steep decline in antler prices. We conducted surveys for questing ticks, ticks on rodents and shrews, and the fecal pellet groups of ungulates (deer and goats) in 31 transects within 3 habitat types (forest, grassland, and roadside) on Green Island every 2 months in 2019. A total of 5,321 questing ticks were collected. All collected ticks were Haemaphysalis mageshimaensis Saito and Hoogstraal, a species first identified on an island with an abundance of sika deer. Additionally, 48 ticks collected from 126 trapped rodents and shrews were almost invariably Ixodes granulatus (except for 1 larval Haemaphysalis sp.). We did not find a positive correlation between the number of questing ticks and the number of fecal pellet groups, suggesting that factors other than ungulate abundance affect tick abundance. Nevertheless, large populations of questing ticks along some roadsides suggest a high risk of tick-borne diseases to tourists on this tropical island.

Senegal has experienced periodic epidemics of dengue in urban areas with increased incidence in recent years. However, few data are available on the local ecology of the epidemic vectors. In October 2021, a dengue outbreak was reported in northern Senegal to the Institute Pasteur de Dakar. Entomologic investigations then were undertaken to identify the areas at risk of transmission and to identify the vector(s). Adult mosquitoes were collected indoors and outdoors at selected households, while containers with water were inspected for mosquito larvae. All the Aedes aegypti (L.) collected were tested for dengue virus NS1 protein using a rapid diagnostic test (RDT), and positive samples were confirmed by real-time RT–PCR. The qRT–PCR positive samples were subjected to whole genome sequencing using Nanopore technology. The majority of the larvae-positive containers (83.1%) were used for water storage. The Breteau and Container indices exceeded the WHO-recommended thresholds for the risk of dengue virus transmission except at 2 localities. Ae. aegypti, the only reputed dengue vector, was collected resting indoors as well as outdoors and biting during the day and night. The NS1 protein was detected in 22 mosquito pools, including one pool of females emerging from field-collected larvae. All NS1-positive results were confirmed by RT-PCR. Virus serotyping showed that the outbreak was caused by DENV-1. This study demonstrates the need for continuous control of adult and aquatic stages of Ae. aegypti to prevent future dengue epidemics in Senegal. RDTs appear to be a promising tool for dengue diagnostics and surveillance.

Graphical Abstract

Urbanization alters abiotic conditions, vegetation, and wildlife populations in ways that affect tick abundance and tick-borne disease prevalence. Likely due to such changes, tick abundance has increased in many US urban areas. Despite growing public health importance of tick-borne diseases, little is known about how ticks are influenced by urbanization in North America, especially in the central United States where several pathogens occur at or near their highest incidences. To identify factors influencing tick abundance across a gradient of urbanization intensity, we used CO₂ traps and flagging to sample ticks at 16 parks across Oklahoma City, Oklahoma, USA over 2 yr, conducted vegetation surveys, and used trail cameras to estimate a deer abundance index. Our results indicate there is a risk of encountering ticks across the entire urbanization gradient from exurban areas to the urban core, although some species (Dermacentor variabilis (Say)) appear less-common in heavily-urbanized areas. Vegetation variables were also associated with tick abundance. For example, Amblyomma maculatum Koch decreased with increasing woody plant and leaf litter cover, and there was a weak positive relationship between D. variabilis abundance and cover of understory eastern redcedar (Juniperus virginiana L.), indicating this native encroaching tree may increase tick populations in urban areas of the Great Plains. The deer abundance index was positively correlated with A. maculatum and D. variabilis abundance but unrelated to A. americanum (L.) abundance. Public health officials and land managers can use such information about parks/greenspaces and their surroundings to focus public education and land management efforts designed to reduce tick-borne disease prevalence.

White-tailed deer Odocoileus virginianus (Zimmermann) (Artiodactyla: Cervidae) are the main host for adult Ixodes scapularis Say (Acari: Ixodidae) (blacklegged tick) and all stages of Amblyomma americanum Linnaeus (Acari: Ixodidae) (lone star tick). However, literature describing the feeding and reproductive parameters of these tick species when feeding on this host is limited. We experimentally infested white-tailed deer with adult pairs of either I. scapularis or A. americanum to improve our understanding of these tick–host relationships. Our study used tick-naïve white-tailed deer and restricted host grooming throughout the infestation. For I. scapularis, the days to repletion (mean ± SE, 6.04 ± 0.07), engorgement weight of replete females (0.20 ± 0.0032 g), duration of oviposition (32 ± 0.45 d), egg mass weight (0.10 ± 0.0027 g), and number of eggs laid per tick (1,803.00 ± 49.00) were recorded. Data from A. americanum were also recorded, including days to repletion (11.00 ± 0.063), engorgement weight of replete females (0.63 ± 0.025 g), duration of oviposition (37.00 ± 1.30 d), egg mass weight (0.34 ± 0.017 g), and number of eggs laid per tick (5,873.00 ± 291.00). These biological parameter data could be used as variables in models (e.g., LYMESIM 2.0) to determine how white-tailed deer influence I. scapularis and A. americanum populations in nature, and to evaluate the protective efficacy of tick-antigen-based antitick vaccines.

Wolbachia (Hertig 1936) (Rickettsiales: Ehrlichiaceae) has emerged as a valuable biocontrol tool in the fight against dengue by suppressing the transmission of the virus through mosquitoes. Monitoring the dynamics of Wolbachia is crucial for evaluating the effectiveness of release programs. Mitochondrial (mtDNA) markers serve as important tools for molecular tracking of infected mitochondrial backgrounds over time but require an understanding of the variation in release sites. In this study, we investigated the mitochondrial lineages of Aedes aegypti (Linnaeus 1762) in Jeddah, Saudi Arabia, which is a prospective release site for the “wAlbB^Q” Wolbachia-infected strain of this mosquito species. We employed a combination of comprehensive mitogenomic analysis (including all protein-coding genes) and mtDNA marker analysis (cox1 and nad5) using data collected from Jeddah. We combined our mitogenome and mtDNA marker data with those from previous studies to place mitochondrial variation in Saudi Arabia into a broader global context. Our findings revealed the presence of 4 subclades that can be broadly categorized into 2 major mitochondrial lineages. Ae. aegypti mosquitoes from Jeddah belonged to both major lineages. Whilst mitogenomic data offered a higher resolution for distinguishing Jeddah mosquitoes from the wAlbB^Q strain, the combination of cox1 and nad5 mtDNA markers alone proved to be sufficient. This study provides the first important characterization of Ae. aegypti mitochondrial lineages in Saudi Arabia and offers essential baseline information for planning future molecular monitoring efforts during the release of Wolbachia-infected mosquitoes.

Some of the most prevalent arthropod-borne pathogens impacting humans in the United States are transmitted by Ixodes ticks. However, little is known regarding the Rickettsia species that inhabit Ixodes scapularis in the United States. The aim of this study was to screen adult I. scapularis collected in central Oklahoma over an 8-yr period for the presence of tick-borne rickettsial pathogens or potential pathogens. During 2014–2021, 112 adult specimens of I. scapularis were collected from central Oklahoma. Amplicons for Rickettsia spp. were amplified from 53 (47.3%) of the samples. Of the positive ticks, 42 (79.2%) amplicon-positive Rickettsia samples were 100% identical to Rickettsia buchneri, 10 (18.9%) were 100% identical to R. tillamookensis strain Tillamook 23, and 1 (1.9%) specimen showed high identity for Rickettsia amblyommatis. This study highlights the importance of considering Rickettsia-specific assays when assessing Ixodes species ticks for potential pathogens.

Female sand fleas (Tunga penetrans Linnaeus, 1758, Siphonaptera: Tungidae) cause a severe parasitic skin disease known as tungiasis. T. penetrans is a small flea, measuring less than 1 mm in length. The females of this species burrow into the skin of human and animal hosts and mostly affect the feet. This has led to the anecdotal assumption that T. penetrans, unlike its relatives in the Siphonaptera family, would have a limited jumping ability potentially not reaching higher body parts. However, there is no data supporting this. This study evaluated the jumping capabilities of T. penetrans for height and distance using sticky tapes. The vertical jump of the female T. penetrans ranged from 4.5 to 100 mm with a mean of 40 mm whereas the vertical jump of the male T. penetrans ranged from 1.2 to 138 mm with a mean of 46 mm. The horizontal jump of the female T. penetrans ranged from 18 to 138 mm with a mean of 64 mm and that of the male ranged from 9 to 251 mm with a mean of 80 mm. Based on the literature, fleas of various species have been described as jumping vertically 50–100 times their size and horizontally 5–100 times their size. In this respect, sand fleas appear to have equal expert jumping abilities to their relatives. Their aggregation on people's feet is not likely a result of their poor jumping ability but might be an adaptation to the host's behavior which would require further investigations.