Journal of medical entomology最新文献

In Diptera, reproductive strategies vary according to the stage of development of the newly deposited offspring and their abundance. The aim of our study is to establish connections between the reproductive strategies of flies (larviparous or oviparous) and the prevailing local conditions (sun or shade) as well as landscape attributes (low or high urbanization) in an urban setting. We collected flies using 2 baited traps (in the sun or shade) at each of the 13 study sites with varying levels of urbanization. We used generalized linear mixed models to examine the impact of landscape and local characteristics on the diversity (abundance and richness of larviparous and oviparous Diptera) of sarcosaprophagous flies. Our findings indicate that while the abundance and diversity of both larviparous and oviparous flies are affected by urbanization, larviparous flies would be less sensitive to more urbanized environments. Larviparous also exhibit a preference for resources under sun exposure, while the responses of oviparous seem more species-dependent. The observed patterns can be explained by the known biology of the studied groups.

Discarded vehicle tires serve as habitat for mosquito vectors. In New Orleans, Louisiana, discarded tires are an increasingly important public concern, especially considering that the city is home to many medically important mosquito species. Discarded tires are known to be associated with mosquito abundance, but how their presence interacts with other socioenvironmental gradients to influence mosquito ecology is poorly understood. Here, we ask whether discarded tire distribution could be explained by social factors, particularly median income, home vacancy and human population density, and whether these factors interact with urban heat islands (UHI) to drive mosquito vector assemblages. We surveyed tire piles across the city and adult mosquitoes in 12 sites, between May and October of 2020. We compared this data with the social indicators selected and UHI estimates. Our results show that median income and human population density were inversely related to tire abundance. Tire abundance was positively associated with Aedes albopictus abundance in places of low heat (LS) severity. Heat was the only predictor for the other monitored species, where high heat corresponded to higher abundance of Aedes aegypti, and LS to higher abundance of Culex quinquefasciatus. Our results suggest that low-income, sparsely populated neighborhoods of New Orleans may be hotspots for discarded vehicle tires, and are associated with higher abundances of at least one medically important mosquito (Ae. albopictus). These findings suggest potential locations for prioritizing source reduction efforts to control mosquito vectors and highlight discarded tires as a potential exposure pathway to unequal disease risk for low-income residents.

Haemaphysalis longicornis (Neumann) was first established in New Jersey and has rapidly spread across most of the eastern United States. This tick has the potential to infest a wide variety of hosts and can reproduce quickly via parthenogenesis, presenting a new threat to animal health. Here we report the first record of a single H. longicornis tick in Mecklenburg County, Virginia, from incidental field collections of ticks. In addition to H. longicornis, we collected 787 Amblyomma americanum, 25 Dermacentor variabilis, 6 Ixodes affinis, 1 Haemaphysalis leporispalustris, and 1 Amblyomma maculatum using standard dragging and flagging techniques. The expansion of H. longicornis will have economic consequences for livestock producers in south-central Virginia, who must now manage this species. Enhanced surveillance is needed to fully understand its growing geographic distribution in the United States and the subsequent consequences of its spread.

In the last 2 decades, there has been an increase in the geographic range and frequency of vector-borne diseases. Management of mosquito populations has become challenging due to increasing rates of resistance to existing insecticidal products and formulations. Several alternative tools have emerged to suppress or replace mosquito populations. One of these tools is the In2Care Mosquito Station (In2Care station). This dual-action station contains the insect growth regulator pyriproxyfen which disrupts the development of immatures and the entomopathogenic fungus Beauveria bassiana (B. bassiana) strain GHA which kills exposed adult mosquitoes. The In2Care stations have previously been shown to effectively control Aedes aegypti in field settings at a density of 6 stations/acre rather than the label-recommended 10 stations/acre. To further test the efficacy of low station density deployment, we deployed In2Care stations in the Pleasant Street Historic District of Gainesville, Florida, at a density of 3 stations/acre over a period of 2 years in the presence or absence of ground larvicidal applications. The deployment of stations resulted in no measurable impact on Ae. aegypti and Culex quinquefasciatus adult or immature abundance suggesting that the low-density deployment of In2Care stations is insufficient to reduce Ae. aegypti and Cu. quinquefasciatus abundance within treatment areas.

Blacklegged ticks (Ixodes scapularis) are the most medically and economically important vectors in North America. Each of their 3 life stages requires a blood meal from one of many potential host species, during which they can acquire or transmit pathogens. Host species, however, vary tremendously in their quality for ticks, as measured by differences in feeding and molting success. There should be clear fitness benefits for ticks that preferentially feed upon high-quality hosts (e.g., white-footed mice, Peromyscus leucopus), or at least avoid feeding on very low-quality hosts (e.g., Virginia opossums, Didelphis virginiana). Indeed, laboratory experiments have found some evidence of host preferences in I. scapularis; but these involve presenting ticks with hosts simultaneously and measuring movement towards hosts on a horizontal plane. In nature, however, host-seeking ticks encounter hosts sequentially and their movements are principally in a vertical plane. Here, we present the results of a study in which we measured the vertical movements of host-seeking juvenile blacklegged ticks before and after a host (P. leucopus, Tamias striatus, Sciurus carolinensis, or D. virginiana) was present, and whether the strength of their responses varies with host quality. We found ticks did not measurably alter the speed of their vertical movement in the presence of any hosts, regardless of host quality. Both larvae and nymphs quested slightly higher in the presence of hosts, but this did not vary by host species. These results call into question the existence of active host preferences, at least in this stage of the host-seeking process.

Propylene glycol (PG) demonstrates greater efficacy than other sugar polyols. However, the attributes it confers for toxicity and possible co-formulation with other ingredients are unknown. To evaluate this, α-glucosidase and glucose oxidase reactions were performed in Aedes aegypti (L.) (Diptera: Culicidae) to categorize if PG behaves similarly to prior studied sugar alcohols. A combination of no-choice and choice assays was used to determine effective ratios of PG and sucrose, competitiveness against a control of 10% sucrose, and whether mosquitoes recovered from PG consumption. The final trials included β-cyclodextrin encapsulated cinnamon leaf oil, clove stem oil, patchouli oil, garlic oil, cedarwood oil, and papaya seed oil formulated with 5% sucrose + 5% PG. PG functioned as a linear competitive inhibitor of α-glucosidase. The efficacy of PG was synergized by co-ingestion with equivalent ratios of sucrose. Unlike the high diuretic response to other sugar alcohols, PG resulted in diminished excretion regardless of being co-formulated with sucrose or terpenoids. PG is not especially competitive against unadulterated sugar meals but is likewise not clearly repellent. Although mosquitoes did not recover from ingestion of the glycol meals, there was no indication that mortality would continue to accumulate once the treatments were removed. Of the terpenoids tested, cinnamon and patchouli caused ~50% or less mortality; garlic, cedarwood, and clove caused 80-90% mortality; and papaya seed caused 100% mortality, exceeding all other test groups and the formulation blank. PG is a useful supporting ingredient in attractive toxic sugar bait formulations with flexibility in formulation.

Musca flies (Diptera: Muscidae) have been found culpable in the mechanical transmission of several infectious agents, including viruses, bacteria, protozoans, and helminths, particularly in low-income settings in tropical regions. In large numbers, these flies can negatively impact the health of communities and their livestock through the transmission of pathogens. In some parts of the world, Musca sorbens is of particular importance because it has been linked with the transmission of trachoma, a leading cause of preventable and irreversible blindness or visual impairment caused by Chlamydia trachomatis, but the contribution these flies make to trachoma transmission has not been quantified and even less is known for other pathogens. Current tools for control and monitoring of house flies remain fairly rudimentary and have focused on the use of environmental management, insecticides, traps, and sticky papers. Given that the behaviors of flies are triggered by chemical cues from their environment, monitoring approaches may be improved by focusing on those activities that are associated with nuisance behaviors or with potential pathogen transmission, and there are opportunities to improve fly control by exploiting behaviors toward semiochemicals that act as attractants or repellents. We review current knowledge on the odor and visual cues that affect the behavior of M. sorbens and Musca domestica, with the aim of better understanding how these can be exploited to support disease monitoring and guide the development of more effective control strategies.

Anopheles coluzzii (Coetzee & Wilkerson) and its sibling species Anopheles gambiae s.s. (Giles) are highly anthropophilic and among the major malaria vectors in sub-Saharan Africa. Mosquitoes use various senses to find hosts, but rely primarily on olfaction. Therefore, the mosquito olfactory system has been studied extensively, including a variety of studies comparing chemosensory gene expression between An. coluzzii and its zoophilic sibling species Anopheles quadriannulatus (Theobald). These studies revealed species-specific chemosensory gene expression in the antennae and maxillary palps, which raised the question of a potential role for the palps in determining species-specific host preferences. To answer this question, we mechanically ablated the antennae, maxillary palps, and labella, and ran both control and ablated mosquitoes through a dual-port olfactometer. While we aimed to identify the organs responsible for vertebrate host choice, the ablated mosquitoes exclusively responded to human odor, so we were unable to do so. However, we were able to refine our understanding of the roles of these organs in host-seeking activation (leaving the release cage) as well as odor response (entering an odor port). As expected, the antennae are the most important organs to both behaviors: activation was roughly halved and vertebrate odor response was abolished in antennae-ablated mosquitoes. Maxillary palp ablation had little impact on activation, but reduced odor response to a similar degree as the exclusion of CO2. Finally, while labellar ablation dramatically reduced activation (probably associated with the inability to feed), it had little impact on odor response, suggesting that any labellar role in host choice is likely not olfactory.