Many farmers house livestock in open pens or sheds that offer no physical protection against biting flies, with protection relying heavily on the use of residual or on-animal insecticides. Insecticidal barriers can offer an alternative or additional option to managing pestiferous biting flies near livestock but they need to be evaluated in the field. We assessed the efficacy of a deltamethrin-incorporated net to reduce contact of Culicoides and mosquitoes with livestock. On cervid farms, reduction of biting-midges in light traps was assessed for traps surrounded by deltamethrin-treated nets, untreated nets, or no-net controls. Significantly fewer Culicoides were collected in pens surrounded by untreated nets compared to no-net, and further significant reductions were achieved with deltamethrin-treated nets. Similar results were observed on a subsistence poultry and swine farm. Total Culicoides and mosquito abundance and abundance of blood-fed females was significantly reduced in light-trap collections after surrounding livestock units with a deltamethrin-treated net. These results suggest the use of insecticidal nets at a 2 m height can reduce contact between livestock and some biting flies in open areas or sheds.
Lutzia vorax Theobald (Diptera: Culicidae) is a ferocious predator of small container habitats in the forests and rural areas of the eastern Palearctic and Oriental regions. Owing to its consumption of various invertebrates, including mosquito larvae, it is considered a potential biological control agent of vector species. However, studies on the general biology of Lt. vorax are scarce; thus, our understanding of its role in natural habitats is limited. To elucidate its ecological role with regard to its interaction with vector species populations, we conducted field monitoring surveys in two different deciduous forests in South Korea, using tire traps for larvae in 2023. Community samples of mosquito larvae were collected every three weeks (July to September, 2023) from each trap, which replicated the natural container environment in forest areas. Then, community structures were compared based on the presence or absence of Lt. vorax. Communities with Lt. vorax larvae exhibited distinct structures characterized by lower species richness, diversity, and vector species density. Furthermore, non-metric multidimensional scaling results showed that the group structure differed depending on the presence of Lt. vorax larvae. Gut content analysis of the predaceous larvae supported the evidence of top-down regulation of Lt. vorax with considerable predation rates on other mosquito larvae in each habitat: 63.92 ± 30.72% in Site A and 72.85 ± 18.03% in Site B (mean ± SD). Thus, we suggest that Lt. vorax serves as both a significant natural enemy and key predator species in container habitats in the forested areas of Korea.
In Peru, since the beginning of the 20th century, 18 mosquito species (Diptera: Culicidae) and three forms have been discovered by previous authors: Anopheles acanthotorynus, An. calderoni, An. peruvianus, Chagasia ablusa, Ae. (Howardina) Iquitos form, Aedes epinolus, Haemagogus obscurescens, Hg. (Conopostegus) Peruvian highland form, Hg. (Con.) Peruvian lowland form, Culex archegus, Cx. debilis, Cx. diplophyllum, Cx. escomeli, Cx. raymondii, Onirion aenigma, On. celatum, Sabethes idiogenes, Trichoprosopon hyperlecum, Tr. subsplendens, Wyeomyia baltae, and Wy. paucartamboensis. Of these, seven species were later synonymized under the name of other species, the rest remain as valid species, one of them is placed in Nomen dubium, and the forms continue retained without specific status. With the intention of updating the checklist of mosquito species in Peru, historical and recent species-records were reviewed and mosquito collections were conducted in specific sites of Peru, resulting in the confirmation of the presence of Hg. anastasionis, Hg. capricornii, Psorophora dimidiata, Ps. cilipes, Cx. usquatissimus, Cx. dunni, Mansonia wilsoni, Johnbelkinia leucopus, Limatus pseudomethysticus, Tr. compressum, and Uranotaenia socialis. Additionally, Ae. aurivittatus, Ae. terrens/zavortinki, Cx. acharistus, Cx. dolosus, and Cx. surinamensis are reported for the first time in Peru, while An. apicimacula, An. mediopunctatus, Ae. condolescens, Cx. bihaicolus, and Sa. tarsopus are removed from the Peruvian mosquito fauna. An updated list of 198 nominal species and four forms of mosquitoes from Peru is presented.
Tick-borne pathogens pose an ongoing threat to human health in the southeastern United States, where tick and host abundances are high. In North Carolina, several medically important tick species are present, but in the Piedmont region, Amblyomma americanum is particularly abundant and associated with multiple human pathogens, including Rickettsia amblyommatis, a hypothesized human pathogen. In this study, we build on recent tick surveillance efforts across several North Carolina counties by screening A. americanum for Ehrlichia ewingii, Ehrlichia chaffeensis, and R. amblyommatis while also analyzing tick abundance, pathogen prevalence, and county-level human disease case data from the North Carolina Department of Health to assess potential correlations. Our results reveal variation in pathogen prevalence across counties, with Chatham County consistently emerging as a high-risk area due to high tick abundance and elevated infection rates. However, we did not observe a strong correlation between tick abundance or pathogen prevalence and reported human disease cases at the county level. These findings highlight counties of elevated risk in a region experiencing an increasing burden of tick-borne disease and contribute to our understanding of ongoing public health trends.
The subtropical coastal plain of Deep South Texas provides a wildlife corridor for hosts of disease-transmitting ixodid species, including the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini). Wind tides and storm surges push hypersaline Lower Laguna Madre water inland on occasion, creating substantial areas of saline soil dominated by sea ox-eye daisy, Borrichia frutescens (L.) DC, and inhabited by numerous mud flat fiddler crabs, Uca rapax (Smith). Ixodid populations, especially larvae, in the saline areas are mostly negligible because of saltwater toxicity to eggs, desiccation, and predators. Soil salinity, U. rapax populations, and ant foraging activity were determined for areas dominated by B. frutescens, areas with intermediate stands, and areas without the plant. Borrichia frutescens density and U. rapax populations were moderately correlated with soil salinity, but predatory ant foraging was not correlated with soil salinity, B. frutescens density, and U. rapax abundance. Borrichia frutescens stand density, however, was strongly correlated with numbers of U. rapax holes, hence, the plant is an indicator of negligible ixodid activity. GIS mapping of high-Borrichia habitats might be useful for refining surveillance of ixodid populations, particularly one-host ixodids, such as R. (B.) microplus.
In 2021, Japanese encephalitis virus (JEV) reverse transcription quantitative RT-qPCR testing of mosquitoes was used for the first time in the Northern Territory (NT) in an attempt to determine the presence of circulating JEV and identify probable vector mosquito species. All test results for 2021 and 2022 returned negative for JEV. Testing resumed in January, 2023, with mosquitoes also tested for Murray Valley encephalitis virus (MVEV) following an outbreak resulting in eight confirmed human cases. Mosquito pools tested positive by RT-qPCR for both viruses on several occasions, confirming the suitability of this method for flavivirus surveillance. Culex annulirostris (Skuse) and Cx. gelidus (Theobald) tested RT-qPCR positive for both viruses in 2023, incriminating them as JEV and MVEV vectors in the NT. Aedes normanensis (Taylor) also tested positive for JEV and MVEV, identifying this species as a probable vector species for both viruses in the NT. While Cx. annulirostris is known to be the principal MVEV vector in the NT, the fact that all three vector mosquito species potentially play a part in the JEV transmission cycle is of major public health concern. While Cx. tritaeniorhynchus (Giles) did not test positive to JEV in 2023, this species is the principal JEV vector in SE Asia and could potentially play a role in JEV transmission in the NT. Genotyping of viruses from the NT mosquitoes confirmed the continued circulation of genotype IV JEV and showed that both genotypes 1A and 2 of MVEV were co-circulating in the NT in 2023.
Dermacentor reticulatus is a widely distributed tick species in Europe, whose rapid range expansion and importance as a vector of multiple pathogens have increased scientific interest in its genetic diversity and population structure. The Baltic States region, which has been experiencing D. reticulatus tick migration into northern areas over the last two decades, with its unique ecological and climatic conditions, could offer valuable insights into tick distribution patterns and their genetic structure in northern European ranges. This study aimed to investigate the genetic variation of D. reticulatus across its European range, including new data from the Baltic States. Genetic variability of 83 D. reticulatus tick samples from 42 locations across the Baltic states, central, western, and southeastern Europe was assessed using mitochondrial (12S rRNA, 16S rRNA) and nuclear (ITS2) markers. The study revealed low genetic variability in D. reticulatus populations across Europe, characterized by a dominant haplotype present in the Baltic states as well as central and western Europe. Unique haplotypes discovered in the Baltic region may be associated with environmental factors and the recent range expansion of the species. The presence of unique haplotypes and genetic variability among northern D. reticulatus populations suggests ongoing local adaptation driven by environmental pressures, including regional climate and landscape heterogeneity in newly colonized habitats.
The increasing prevalence of insecticide resistance in Aedes mosquitoes necessitates development of alternative control methods. This study evaluated adulticidal efficacy of essential oils from Litsea cubeba, Syzygium aromaticum, and Cinnamomum porrectum against laboratory and field populations of Aedes aegypti and Aedes albopictus. Discriminating concentrations (DCs) were established using WHO tube tests. L. cubeba showed the lowest DCs (6.21% v/v for Ae. aegypti, 9.68% v/v for Ae. albopictus), followed by C. porrectum (9.70%, 15.55%) and S. aromaticum (19.40%, 24.33%). At these DCs, all oils demonstrated 98-100% knockdown and 99-100% mortality against field populations. Aedes albopictus required higher DCs than Ae. aegypti, suggesting species-specific susceptibility differences. Essential oils showed superior efficacy against field-collected Ae. aegypti compared to cypermethrin. Results indicate potential of these oils as effective botanical insecticides, particularly where conventional insecticide resistance occurs.
We investigated the association between water physicochemical parameters and polarized light patterns with mosquito oviposition in central coast urban areas of Peru. Water samples from diverse locations were analyzed, assessing key parameters, including conductivity, total dissolved solids, hardness, pH, alkalinity, phosphate, and nitrate levels. Principal component analysis revealed that conductivity, total dissolved solids, and hardness were significantly associated with the presence of mosquito oviposition. These findings were corroborated by generalized linear mixed models, which highlighted location-specific effects and seasonal variations in physicochemical parameters associated with oviposition. Our study also explored polarized light as a potential oviposition cue. While a direct causal link between polarized light patterns and oviposition requires further investigation, a positive correlation between pH levels and circularly polarized light patterns suggests a potential interaction between water chemistry and this optical cue. These findings underscore the complex interplay of environmental factors associated with mosquito oviposition. Our results suggest an association between physicochemical cues, particularly conductivity, total dissolved solids, and hardness, and the presence of mosquito oviposition, with polarized light potentially playing a role.
This field study describes the abundance of ticks and the prevalence of tick-borne pathogens in two hiking areas, Stebbins Cold Canyon (SCC) and Skyline Wilderness Park (SKY), in northern California. These areas have experienced extreme weather events, including wildfire, drought, and heavy rainfall, which have changed the environment. Questing ticks were collected over nine months, identified to species, and screened for tick-borne pathogens using qPCR. Four hundred and fifty-nine ticks were collected, including 54 adults from SCC and 405 from SKY, consisting of 279 (68.9%) larvae, 2 (0.5%) nymphs, and 124 (30.6%) adults. At SCC, Ixodes pacificus and Dermacentor occidentalis accounted for 92.6% (50/54) and 7.4% (4/54), respectively. At SKY, I. pacificus (16.8%, 68/405), D. occidentalis (12.3%, 50/405), D. similis (0.7%, 3/405), and D. albipictus (70.4%, 285/405) were collected. Overall, the prevalence of tick-borne pathogens was low in the collected ticks. Borrelia burgdorferi sl (0.8%, 1/121) and Rickettsia rhipicephali (1.7%, 2/121) were found at SKY. Rickettsia tillamookensis was identified at SCC and SKY with a prevalence of 3.7% (2/54) and 1.7% (2/121), respectively. Babesia duncani was identified in 3.7% (2/54) and 1.2% (5/405) of ticks at SCC and SKY, respectively. These findings suggest that multiple tick species can withstand extreme weather events, providing further data regarding the effects of weather extremes and climate change on tick populations and pathogen prevalence. This study is one of the first to report B. duncani in I. pacificus ticks in California, particularly in Solano County.
We investigated the abundance and distribution of Aedes aegypti and Aedes albopictus mosquitoes in urban parks in the eastern zone of the city of São Paulo, where the highest number of autochthonous dengue cases during the major 2015-2016 epidemic was reported. The association of climatic and environmental factors with the spatiotemporal distribution of species in relation to vegetation cover and human proximity was examined. Twelve geo-referenced ovitraps were randomly installed in each park, covering areas with varying degrees of vegetation and human activity from September, 2018 to February, 2020, during three weeks each season. A total of 57,604 Aedes aegypti or Aedes albopictus eggs were collected, identifying 10,228 Ae. aegypti and 23,764 Ae. albopictus larvae. Seasonal variations showed distinct patterns with higher mosquito abundances during warmer and rainier seasons. The association between abundance and climatic factors was more evident at the level of the aedini assemblies than at the level of the local populations. Aedes aegypti was predominantly found in peripheral and transitional areas with higher human activity during rainy and warmer seasons. In contrast, Ae. albopictus thrived in inner park areas with greater vegetation cover and lower human activity during drier and milder seasons. The abundance of Ae. aegypti and Ae. albopictus was influenced by climatic factors and park-specific microhabitats. These findings underscore the importance of targeted vector control strategies in urban park settings during seasons favorable for mosquito reproduction. Understanding the interaction between ecological factors and these mosquitoes in urban environments is critical for effective public health interventions.
The CDC light trap with incandescent light is the most commonly used method for conducting sand fly surveillance. However, new trap models that use LED lights might provide a more cost-effective alternative. This study compared the efficacy of a modified commercial Katchy light trap with two CDC light trap models in capturing sand flies in the Amazonian rainforest of Peru. Using a 3 x 3 randomized Latin square design, the light traps were compared based on phlebotomine sand fly species total abundance, species richness, sex-specific collections, and efficiency in capturing potential vector species. A total of 1,184 sand flies were collected, representing nine genera and 25 species, including three species that had not been previously reported in the Cusco department. Significant differences in sand fly collections based on trap type were found, with the modified Katchy light trap capturing significantly higher total abundance and species richness compared to CDC light traps. This pattern held for both female and male sand flies, with the modified Katchy trap also collecting more potential vector species in terms of both abundance and species richness, although differences in potential vector species richness were only significant compared to the incandescent CDC light trap. These results suggest that the modified Katchy trap is a viable, cost-effective alternative for sand fly surveillance, offering potential improvements in leishmaniasis vector monitoring.
Knowledge of the utilization by mosquito species of different habitats is critical for determining risk for the transmission of mosquito-borne pathogens. The Great Plains region of the United States is experiencing a biome-level change as grasslands are being converted to forests through the process of woody plant encroachment by eastern redcedar (ERC). There is a need to evaluate how mosquitoes respond to fine scale habitat characteristics within areas experiencing ERC encroachment. This study examined the influence of fine-scale vegetation differences on mosquito abundance, bloodmeal hosts, and infection with West Nile virus (WNV) in eight ERC-encroached sites across Oklahoma. Mosquito traps were placed in three unique habitats in ERC-encroached sites. Ae. albopictus, Ae. vexans, An. punctipennis, Cx. erraticus, and Cx. tarsalis were most abundant in the ecotone and/or forested areas of ERC trees compared with grass. Ps. columbiae was more abundant in grassland than in forest. Blood meal analysis indicated that mosquitoes fed primarily on mammals, and we detected Anaplasma species in several blood meals. These results suggest that important mosquito vectors may occur throughout much of ERC-encroached areas, a finding that has consequences for blood meal acquisition, pathogen transmission, and thus public health and land management programs throughout the Great Plains.
Culicoides midges are vectors of bluetongue virus (BTV), an arbovirus affecting wild and domestic ruminants. Bluetongue distribution generally overlaps with vector range, so understanding the vector's ecology is necessary for predicting BTV risk. Culicoides require moist substrate for development, and C. sonorensis, the primary recognized vector in the western United States, is classically associated with livestock wastewater ponds. However, it is well-known that BTV can be found outside of livestock areas, with transmission occurring in natural settings. To better classify development habitat, we conducted a broad biweekly survey of moist and wet habitats from June to September of 2022 in northern Colorado at ten sites, including large livestock operations, non-commercial domestic operations, and natural spaces. Samples were maintained in the insectary for 11 weeks and monitored for emergence of adult midges. Standing water substrates displayed higher presence and abundance of midges than running or transient habitats, though all microhabitats showed emergence. Additionally, livestock sites did not produce more midges than other site types, and in fact more midges were observed in natural spaces per sample and overall. Livestock spaces did, however, show significantly higher proportions of C. sonorensis midges, which are thought to be the most competent vectors of BTV in this region, as opposed to other Culicoides species. These results suggest that development sites in natural areas may play an important role in maintaining vector populations in the western U.S. outside of previously implicated livestock operations, and that differences in larval habitat lead to differences in vector species composition.
Ticks and tick-borne diseases are of increasing concern in the United States, and understanding tick behavior could be crucial to limiting the exposure of humans and other animals to ticks. Here, we wanted to understand the drivers of questing and burrowing in Amblyomma americanum and A. maculatum. We used a factorial design to assess the effects of substrate (sand, soil, and rock), temperature (16° and 22° C), tick species (A. maculatum and A. americanum), and competition (homogenous or heterogenous mixture of ticks in the arena) on tick behavior in laboratory arenas. Questing varied significantly between tick species, with 61% of A. americanum questing compared to 35% of A. maculatum. Substrate similarly affected questing, with most ticks questing in the arenas with sand (83%) compared to arenas with rock (35%) or soil (25%). Burrowing behavior was also influenced by substrate; every tick in the arenas with rock (100%) and nearly all in the arenas with soil (98%) exhibited burrowing, whereas only 10% burrowed in sand. A. americanum traveled longer distances than A. maculatum (23 ± 2.8 cm vs 9.7 ± 2.3 cm). The disparity in laboratory behavior between sand and rock/soil substrates might warrant further consideration in a field setting, as understanding factors that inhibit host-seeking behaviors of ticks can inform management of public spaces and potentially help mitigate tick-exposure.
This study examined the presence and characteristics of microplastics (MPs) in water collected from potential mosquito oviposition habitats in Lubbock, TX. Water samples ranging from 10 to 1000 mL were collected from 36 suspected artificial and natural oviposition habitats, and sites were categorized as artificial containers, tires, or natural sites. Samples were filtered through a series of stainless-steel sieves and isopore membrane filters, and MPs were imaged and counted using a stereo microscope. MPs were classified by shape into fragments, fibers, films, spheres, and foams. Scanning Electron Microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA)were employed to characterize the size, morphology, and polymer type of MPs collected from a subset of oviposition habitats. Results suggest MPs are commonly found in artificial containers and tires, and at higher concentrations than natural sites. Furthermore, MPs found in all potential oviposition sites were predominantly fragments and fibers. SEM analysis revealed diverse morphologies and indicated potential microbial colonization on MP surfaces. Ultimately, this study provides insights into the distribution and characteristics of MPs in mosquito oviposition habitats, highlighting the potential impact of MP pollution and the potential effects on mosquito biology, and serves as a foundation for further research on the ecological implications of MPs in mosquito oviposition habitats.
Musca domestica salivary gland hypertrophy virus (MdSGHV) affects house flies by enlarging salivary glands, impeding ovary development in females, and mating behavior in both males and females. It is not known if this virus impacts the quantity of saliva produced by house flies. This study aimed to establish baseline saliva quantities in healthy M. domestica across sexes and ages and examine how MdSGHV infection influences saliva output in 5-day-old males. Results reveal that healthy female Musca domestica produce more saliva on average than males and that saliva production among both sexes decreases with age. A comparison of infected, PBS-injected, and healthy flies shows significantly higher saliva quantities in infected individuals, suggesting MdSGHV enhances saliva production to improve transmission. These findings provide insights into MdSGHV transmission dynamics, which may provide for a better understanding of how other vector-borne diseases like Zika and Dengue virus interact in the infected salivary glands of the host vector.
Murine typhus, caused by Rickettsia typhi, is re-emerging in many parts of the world. The disease is also called endemic typhus to differentiate from epidemic typhus (caused by Rickettsia prowazekii), and sometimes also named flea-borne typhus. Occasionally, literature sources will include Rickettsia felis as a causative agent of flea-borne typhus, but illnesses caused by R. felis are actually flea-borne spotted fever. Murine typhus occurs in warm, coastal areas worldwide. In the United States, most cases are reported from California, Texas, and Hawaii. Murine typhus is usually a self-limited febrile illness but about onequarter of patients suffer organ complications. The disease is only infrequently fatal. Regarding disease ecology, the historical paradigm is that rats (Rattus rattus and R. norvegicus) are reservoirs of R. typhi worldwide, with rat fleas (Xenopsylla cheopis) as primary vectors. More recently, researchers have proposed an alternative suburban murine typhus transmission cycle involving opossums, cat fleas, cats, and dogs in Texas, California, and rural Mexico. Because cat fleas feed on a variety of mammals, there may be other avenues for R. typhi transmission, including stray or feral cats bringing cat fleas and other infected fleas into proximity with humans and possible aerosolization of infected flea feces. Additional fleas, ticks, lice, and mites may play a role in various areas throughout the world, but a striking lack of fundamental research on this topic makes drawing conclusions difficult. This review provides an overview of the history, epidemiology, diagnosis, and treatment of murine typhus, with special emphasis on its disease ecology. Journal of Vector Ecology 50 (1): 1-13. 2025.
