Journal of medical entomology最新文献

Female ticks deposit large egg clusters that range in size from hundreds to thousands. These egg clusters are restricted to a deposition site as they are stationary, usually under leaf litter and other debris. In some habitats, these sites can be exposed to periodic flooding. When the clusters of tick eggs are disturbed, they may float to the surface or remain underneath organic debris entirely submerged underwater. Here, we examined the viability of egg clusters from winter ticks, Dermacentor albipictus, and lone star ticks, Amblyomma americanum, when partially or fully submerged in water and in relation to the developmental stages of the eggs under lab conditions. In general, egg clusters that were older and partially submerged had a higher viability than fully submerged, younger eggs. Of the two species, A. americanum was more resistant to water exposure. These studies highlight that egg clusters for certain tick species can remain viable when exposed to water for at least two weeks. These results also suggest that distribution by flooding of egg clusters could occur for some species and water submersion will differentially impact tick egg survival based on the specific developmental stage of exposure and species.

Developmental data for necrophagous Diptera are frequently used in medico-legal investigations to estimate portions of the postmortem interval and interpret periods of insect activity. These applications require baseline developmental data for local populations from geographic locations of interest. For the widely distributed blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), detailed developmental data does not exist for many locations in the mid-Atlantic region of the United States. This study examined development of C. vicina collected from a large, metropolitan city (Baltimore) in Maryland utilizing 11 ambient temperatures. The developmental threshold and thermal range of growth and tolerance were also estimated, as well as critical thermal minima and maxima based on thermal injury. For this population, linear growth was observed between 10°C and 25°C, whereas flies failed to complete development at temperatures below 7°C or above 28°C. Growth at low temperatures was not curvilinear, which contrasts with other developmental studies using C. vicina and other calliphorids. The lower developmental threshold was estimated to be 5.9°C and corresponds closely with experimental observations. The implications of these result in reference to phenotypic plasticity in populations of C. vicina and applications in forensic entomology are discussed.

Mosquito-borne disease (MBD) incidence is increasing in the United States (U.S.), presenting an evolving health threat. Assessments of public perceptions have revealed limited awareness of MBDs among the U.S. population. Our team used focus groups to gain an in-depth understanding of risk perceptions regarding mosquito exposure and pesticide use, and benefit perceptions and motivators for bite prevention strategies. A total of 37 individuals participated in focus groups across 3 states: New Jersey (n = 14), New York (n = 15), and Massachusetts (n = 8). Most participants were unfamiliar with public mosquito control services and felt they were not at high exposure risk to any MBDs. Overall, participants were supportive of investing public funds for mosquito surveillance. However, participants across all focus groups expressed concerns over ecosystem health and long-term consequences of pesticide use for mosquito control. Participants in every focus group referenced a risk assessment that weighed the risk of MBD exposure against the use of chemical control: once participants perceived MBDs as negatively impacting human and/or animal health in their area, sentiment swung largely to supporting the use of pesticides. In the absence of an obvious MBD threat, participants preferred nonchemical control interventions. Participants felt communication from mosquito control agencies should be accessible, disseminated across multiple venues, and should include instructions for the public during spray events, resources for individual bite prevention, and information on control products used. Our research results can inform the development of improved, evidence-based MBD outreach and educational resources that are acceptable, actionable, and relevant to Northeast communities.

Insecticide formulations with safer environmental profiles and limited off-target effects are desirable to manage medical and veterinary pests. Silver nanoparticles are insecticidal against mosquitos, nonbiting midges, and other insects. The biting midge, Culicoides sonorensis Wirth and Jones, is a vector of agriculturally important pathogens in much of the United States, and this study aimed to examine the insecticidal properties of silver nanoparticles in larvae of this species. Mortality of third-instar larvae was assessed daily for 7 days after exposure to concentrations of silver nanoparticles, sorghum polymer particles, and hybrid silver-sorghum polymer particles. Both silver nanoparticles and silver-sorghum polymer particles were insecticidal, but sorghum polymer particles alone did not significantly contribute to larval mortality. Concentrations of 100 mg/liter of silver nanoparticles achieved >50% mortality at day 7, and 200 mg/liter treatments achieved >75% larval mortality within 24 h. The antimicrobial properties of silver nanoparticles were also examined, and culturable bacteria were recovered from larval-rearing media at 200 mg/liter but not at 400 mg/liter of silver nanoparticles. These data suggest that C. sonorensis larval mortality is primarily caused by silver nanoparticle toxicity and not by the reduction of bacteria (i.e., a larval food source). This work describes the first use of silver nanoparticles in C. sonorensis and shows the potential insecticide applications of these nanoparticles against this agricultural pest. The grain-polymer particles also successfully carried insecticidal silver nanoparticles, and their utility in loading diverse compounds could be a novel toxin delivery system for biting midges and similar pests.

Malaria was once endemic in the United States prior to its elimination in 1951. However, due to consistent introductions of travel-associated malaria cases and the presence of several native Anopheles species (Diptera: Culicidae) that are competent vectors of malaria, the potential for local (autochthonous) malaria transmission remains a persistent threat in the United States. While several intermittent cases of local malaria transmission have occurred in the United States in the decades since elimination, the emergence of autochthonous transmission in 4 states in 2023 demonstrates the continued risk for future outbreaks. Moreover, these recent examples also highlight significant gaps in current mosquito surveillance efforts that have predominantly focused on threats of arboviral disease, such that our understanding of Anopheles distributions relies only on historical records and offers limited insight into the ecological factors that influence their abundance. Herein, we summarize mosquito surveillance data collected over the last 20 years (2004-2023) across 59 Iowa counties to provide essential information into the spatial distribution, temporal abundance, and trap preferences of Anopheles species in the state. Further analyses of the 2 most abundant species, Anopheles punctipennis Say and Anopheles quadrimaculatus Say, reveal the additional influence of precipitation and forested habitats in defining An. punctipennis abundance. Together, we believe these results provide an increased understanding of previously neglected Anopheles species that have the potential for autochthonous malaria transmission in Iowa and that can be extended to other regions of the United States to enhance preparedness for future malaria outbreaks.

Aedes aegypti is fast spreading across California, with over 300 cities within 22 central and southern counties being infested since its introduction in 2013. Due to its cryptic breeding habitats, control efforts have not been successful so far. This calls for innovative tools such as sterile insect technique (SIT) to reinforce the existing integrated pest management (IPM). Here, we assessed fitness, survivorship, and dose response of X-ray irradiated male Ae. aegypti in California. Locally acquired Ae. aegypti eggs were hatched and reared in temperature-controlled laboratory setting at the West Valley Mosquito and Vector Control District in Ontario, California. Freshly emerged adult male mosquitoes were manually separated using motor-operated aspirators and treated with X-ray radiation at different dosage (42-60 Gy). Dose response of irradiated males was analyzed and induced sterility determined. Survivorship of males treated with different X-ray doses was compared. Fecundity of females that mated with irradiated males at different X-ray doses was generally comparable. Overall, induced sterility increased with higher X-ray doses. Nulliparous females that mated with male Ae. aegypti treated with 55-60 Gy laid eggs with over 99% sterility. Non-irradiated male mosquitoes had higher survivorship (mean = 0.78; P = 0.0331) than irradiated mosquitoes (mean range = 0.50-0.65). The competitiveness index of irradiated males decreased with increasing X-ray treatment doses, 1.14 at 55 Gy and 0.49 at 60 Gy, and this difference was significant (P < 0.01). Irradiated males showed high survivorship and competitiveness-key for the anticipated SIT application for the control of invasive Ae. aegypti in California.

Permethrin-treated clothing is often recommended as a first line of defense against tick-borne diseases. In 2012, the permethrin factory-treated Army Combat Uniform was first made available to active duty Soldiers, Army National Guard, Army Reserve Enlisted Soldiers, and the Senior/Junior Reserve Officers Training Corps. Subsequently, Air Force and Marine Corps personnel were also offered permethrin factory-treated uniforms. Here, we use the passive surveillance data collected through the Military Tick Identification/Infection Confirmation Kit (MilTICK) program to determine the effectiveness of permethrin-treated uniforms at protecting Department of Defense personnel from exposure to tick-borne pathogens in the United States. We analyzed whether submissions by self-reported users of the permethrin-treated uniforms had smaller proportions of engorged ticks, certain cohorts of MilTICK users were better protected than others, and specific tick species were better repelled than others. We found that permethrin use resulted in significantly lower proportions of engorged ticks submitted across MilTICK users. Army and Army National Guard personnel reported more permethrin-treated uniform use than other services. For submissions from active duty personnel serving in uniform, the proportion of tick engorgement in the presence of permethrin increased over time, possibly indicating that permethrin-treated uniforms suffer from reduced performance over the life of the garment. We also found that while permethrin reduced all tick species' ability to feed until engorgement or repletion, blacklegged tick adult females were better able to resist permethrin's lethal effects than lone star tick and American dog tick adult females. Permethrin-treated clothing plays an important role in keeping military personnel safe from tick-borne diseases.

As the range of Ixodes scapularis Say expands, host abundance and land use can play important roles in regions where ticks and their associated pathogens are emerging. Small mammal hosts serve as reservoirs of tick-borne pathogens, with Peromyscus leucopus Rafinesque often considered a primary reservoir. A sympatric species Peromyscus maniculatus Wagner is also a competent reservoir and is notoriously difficult to differentiate from P. leucopus. Anthropogenic land use can alter host and habitat availability, potentially changing tick exposure risk. We tested the hypotheses that tick infestation and pathogen prevalence differ between the two Peromyscus spp. and that host-seeking I. scapularis density and pathogen prevalence differ across land use and ecotone gradients. We live trapped small mammals and collected ticks across 3 land-use classifications and ecotones in Maine, an emergent area for tick-borne disease. We tested each small mammal and tick sample for Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti. While both Peromyscus spp. serve as hosts for immature ticks, P. leucopus exhibited a higher tick infestation frequency and intensity. We did not detect any significant difference in pathogen infection prevalence between the two species. The density of I. scapularis nymphs and the density of infected nymphs did not differ significantly between land-use types, though did differ across ecotones. We also noted a significant north/south gradient, with higher tick densities and pathogen prevalence at the southern end of the study area. Our study highlights the potential variability in tick density and pathogen prevalence across fine spatial scales within an emerging region for tick-borne disease.

Wildlife are hosts of ectoparasites, such as fleas and ticks that may transmit human and animal pathogens. Little is known about the ecology of many ectoparasite species native to southern Texas, or their role in pathogen maintenance and transmission. Much attention has been given to the role of nonnative nilgai antelope as cattle fever tick hosts and agents of dispersal, but little attention has been given to other ectoparasites that may utilize nilgai antelope as hosts. As southern Texas is a hot-spot for flea-borne (murine) typhus, it is important to examine flea species presence, abundance, and host use in this region. Fleas were opportunistically collected during wildlife depredation activities, from hunter-harvested animals, or during handling in the course of other research activities in several southern Texas counties. A total of 9 wildlife species were sampled, from which 3 flea species were identified. A total of 83 Pulex porcinus (Jordan and Rothschild) were collected from nilgai, coyotes, bobcats, javelina, feral swine, and a black-tailed jackrabbit. In total, 9 Euhoplopsyllus glacialis affinis (Baker) were collected from cottontail rabbits, and 1 Echidnophaga gallinacea (Westwood) was collected from a raccoon. To our knowledge, this represents the first report of fleas from nilgai antelope. Pulex porcinus, although often considered a specialist species, was collected from a wide range of hosts, including 2 (nilgai antelope and black-tailed jackrabbit) that represent new host records for this species. The role of P. porcinus as a pathogen vector is unknown, but its apparent abundance in this region warrants further investigation.

The ground-dwelling invertebrate fauna from an urban park in Belém, Amazonian Brazil, with particular reference to the subfamily Phlebotominae (Diptera: Psychodidae), were characterized. Sampling was performed from March 2022 to May 2023, with 10 emergence traps installed in 2 microhabitats, 5 in each 1: "M1," which included surrounding (up to 1.5 m) trees with tabular roots, and "M2," which included no trees with tabular roots. Invertebrates trapped in adhesive papers were assessed on 2 occasions/cycles (D21/D42). During 10 sampling cycles (10 traps/cycle = 100 samples), 6,490 invertebrates were captured (M1, n = 4,203; M2, n = 2,287) and classified into 5 classes and 21 orders, with Diptera (n = 2,309; 35.6%) being the most abundant. Twenty-nine specimens of the following phlebotomine species were captured: Nyssomyia antunesi (M1, n = 10; M2, n = 3), Trichophoromyia ubiquitalis (M1, n = 6; M2, n = 1), Th. brachipyga (M1, n = 0; M2, n = 2), Bichromomyia flaviscutellata (M1, n = 2; M2, n = 1) and 4 unidentified specimens (M1, n = 2; M2, n = 2). The male/female ratio was 1.08. Fractional vegetation cover was compared, and the physiochemical characteristics of the soil were compared between the microhabitats. Only temperature showed significant differences. A weak positive correlation was found between phlebotomines and other dipterans and between temperature and the amount of organic matter in the soil. Both sampled microhabitats were shown to be suitable for the development and maintenance of different invertebrates, mainly dipterans. The composition of ground-emerging phlebotomine species was similar to that previously surveyed with light traps, including species associated with the transmission of Leishmania spp.