Journal of medical entomology最新文献

Ornithodoros turicata (Dugès) originating from Texas was reared under laboratory conditions by feeding each post-embryonic stage defibrinated swine blood through an artificial system using Parafilm M without the use of phagostimulants or blood treatments. Beginning with 300 larvae, adult ticks emerged following blood feeding of N5, N6, and N7 nymphs with a total yield of 15 males and 16 females. Membrane feeding success and molting at each feeding are described. Comparison is made of available published bionomic data for O. turicata fed on laboratory animals. Applications of artificial feeding for argasid tick species are discussed.

Larval application of insecticides (larviciding) is primarily conducted using a variety of biorational compounds as an essential function within integrated mosquito management. Larvicide-treated water has been sporadically investigated for deterring oviposition, but prior efforts have been primarily focused on Aedes aegypti (L.) with limited representation by other peridomestic or treehole species. A series of laboratory assays were conducted using 20 lb/acre (22.4 kg/ha) treatments of Lysinibacillus sphaericus (VectoLex FG), spinosad (Natular G30), and methoprene (Altosid XR-G Ultra) and compared to an untreated water option. These treatments were offered as a no-choice assay for Ae. aegypti in the laboratory and in an additional multi-choice test for Ae. aegypti, Aedes sierrensis (Ludlow), and Culex pipiens L. Significantly fewer Ae. aegypti eggs were collected from water treated with L. sphaericus in both the no-choice and arena tests. Significantly fewer Cx. pipiens eggs were deposited in water treated with methoprene, coinciding with elevated collections in water treated with spinosad. As a first report for the species, no significant trends were observed with Ae. sierrensis. Hatching eggs from spinosad and methoprene-treated water yielded lower success for both Aedes spp. We propose that gravid mosquitoes have some sensitivity towards certain larvicides and Aedes spp. eggs suffer ovicidal effects in treated water sources. Push effects may confound geotagged surveillance networks, such as for treehole and backyard mosquito species in peridomestic environments. However, we report that these preferences do not significantly impact ongoing control operations.

Methoprene has been employed to manage salt marsh mosquitoes, specifically Aedes taeniorhynchus, in the Indian River Mosquito Control District (IRMCD) since the mid-1970s. However, due to reduced effectiveness and significant increase in resistance among Ae. taeniorhynchus (Wiedemann) (Insecta: Diptera: Culicidae) to methoprene products, the use of methoprene for mosquito control in the IRMCD ceased in 2009. Given the current limited availability of safe, effective and affordable larvicide products, discussions have emerged about the potential reintroduction of methoprene-based products for Ae. taeniorhynchus control in the IRMCD. To determine the feasibility of methoprene product reintroduction in the field control operations, laboratory bioassays were conducted to assess the resistance status of Ae. taeniorhynchus populations from field collections directly. These bioassays involved exposing late 4th instar larvae of Ae. taeniorhynchus to technical grade methoprene. The results revealed varying levels of resistance to methoprene among 16 field Ae. taeniorhynchus populations for the last 2 yr. Our findings confirm that methoprene resistance persists in some of the local Ae. taeniorhynchus populations. The outcomes of this research will assist IRMCD in strategic decision-making regarding the utilization of methoprene products for future Ae. taeniorhynchus control measures.

The common bed bug, Cimex lectularius (L.) (Hemiptera: Cimicidae), is a pervasive indoor pest with prominent medical, veterinary, and economic impacts. Bed bug infestations are controlled by a wide range of insecticides, including pyrethroids, neonicotinoids, pyrroles, and phenylpyrazoles; however, bed bugs have evolved resistance mechanisms to most of these insecticides. Mutations in the Rdl (resistance to dieldrin) gene, located in a subunit of the γ-amino butyric acid (GABA)-gated chloride channel, have been identified in several pest insects, including the German cockroach. These have been found to confer resistance to fipronil, a phenylpyrazole insecticide commonly used in urban environments, in addition to cyclodienes (eg dieldrin), a class of insecticides banned in most countries since the 1990s. While resistance to dieldrin and fipronil has been reported in bed bugs, both C. lectularius and the tropical bed bug, C. hemipterus, the occurrence of mutations in the Rdl gene has yet to be thoroughly investigated. In this study, we sequence a fragment of the Rdl gene commonly found to harbor cyclodiene and phenylpyrazole conferring mutations from 134 unique populations collected across the United States and Canada spanning a 14-yr period. Homozygous genotypes for the A302S mutation were found in 2 geographically distinct populations. This finding represents the first record of a non-synonymous Rdl mutation in bed bugs and identifies another mechanism by which insecticide resistance may be conferred in this species.

The study of insect vector biological rhythms improves our understanding of their behavior, thereby helping to devise more efficient control strategies to reduce pathogen spread. In this study, the locomotor activity of Culex quinquefasciatus Say was evaluated for groups of virgin males, virgin nonfed females, inseminated nonfed females, virgin blood-fed females, and inseminated blood-fed females. Experiments were conducted using adults from an established laboratory colony using an activity monitor that tracked individual activity every 30 min. Our results showed that the locomotor activity of males and females of this species is nocturnal and bimodal, with the highest peak occurring during scotophase. After blood feeding, virgin and inseminated females showed less locomotor activity during scotophase than other experimental groups, with inseminated blood-fed females having the lowest activity. Inseminated and nonfed females showed a significantly greater increase in locomotor activity during scotophase than the other groups. This study provided the first comparative information on the locomotor activity of females in different physiological states and males of Cx. quinquefasciatus. These findings may improve our understanding of the behavior of Cx. quinquefasciatus and encourage new research in this field and in the development of control strategies.

Engineered gene drive (EGD) systems are probably the most high-tech approach considered for their potential role in the control of vector-borne diseases. Interestingly, the rhetoric around it often goes along with a negative presentation of the current "conventional" tools and exaggerated promises about EGD themselves, leading to a situation of hype.

Mosquito control operations have limited options available for adult mosquito reduction. Untapped alternatives exist in adjacent pest-management industries, but translation and validation for various technologies is still ongoing. The attractive targeted sugar bait (ATSB) strategy is a formulation platform that is amenable to toxicants not otherwise widely used for adult mosquito control techniques and equipment. To find fast-acting, effective toxicants for ATSB, choice assays were conducted using fipronil, spinosyn, dinotefuran, clothianidin, imidacloprid, bifenazate, indoxacarb, abamectin, and λ-cyhalothrin against Aedes aegypti (L.) (Diptera: Culcidae) as a model system. Active ingredients were emulsified in propylene glycol, a secondary toxicant and formulation aid in ATSB, and sucrose solution. Treatments were presented in tandem with unadulterated 10% sucrose in all assays. In both 24-h mortality and fecal droplet analysis, indoxacarb was ingested similarly as often as the sugar water-only control group and yielded the overall lowest mortality. Imidacloprid, λ-cyhalothrin, and abamectin were all readily ingested, and in some cases the fecal droplet analysis indicated bias towards consumption of the treated sugar solutions. Mortality in the first 24 h was over 95% for the aforementioned toxicants, supporting that they both kill in limited time and have a suitable palatability or repellency response profile with mosquitoes. But imidacloprid and λ-cyhalothrin (resistance) and imidacloprid (pollinators) have roadblocks for use in ATSB because of potential nontarget impact to pollinators and prevalent insecticide resistance issues. However, abamectin appears to be a promising ingredient for future ATSB formulations to establish quick vector interruption and improve insecticide class variety for resistance management.

Generally, the DNA barcode relying on a short fragment of the cytochrome c oxidase I (COI) gene is a powerful tool for facilitating species discovery and taxonomic resolution in Diptera, including black flies. However, the COI barcode lacks sufficient resolution to identify several species or infer phylogenetic relationships of black flies in the Simulium striatum species-group, whereas the fast-evolving nuclear big zinc finger (BZF) gene has been suggested as a key marker for identifying the species. In this study, a new species of black fly in the S. striatum species-group from Kamphaeng Phet province, central Thailand, was discovered and characterized through an integrated method combining morphological analysis and molecular data based on the BZF gene. The new species, Simulium (Simulium) concitatum sp. nov., was morphologically described for all life stages, excluding the egg. It shares many morphological similarities with other species of the S. striatum species-group, particularly S. thilorsuense Takaoka, Srisuka & Saeung, 2022 described from Tak province, western Thailand. Sequence analysis and phylogeny inferred from the BZF gene further confirmed that S. concitatum sp. nov. is a distinct species of the S. striatum species-group and revealed its close genetic relationship to S. wangkwaiense Takaoka, Srisuka & Saeung, 2020. The morphological differences between the new species and all known species of the S. striatum species-group documented in Thailand and other countries are provided to assist in species identification. Furthermore, this study underscores the BZF gene as an effective genetic marker to differentiate the species.

Precise identification of insect species and their developmental stages (instars) on human remains is crucial for estimating the postmortem interval (PMI) and detecting potential body tampering. However, larvae of many common species can only be reliably identified using molecular techniques, which are not always possible. Furthermore, determining the instar stage is even more challenging, as features necessary for precise identification are often poorly documented. Oiceoptoma thoracicum (Linnaeus, 1758) is a common necrophagous beetle in the Palearctic region from the Western Europe to Japan. The species is also frequently found on cadavers of large vertebrates, including human remains, making it a promising candidate for use as a bioindicator in forensic entomology. Adults can be easily distinguished from other species; however, larvae have never been thoroughly described. The identification of O. thoracicum based on immature stages, or the differentiation of instars of this species is therefore not yet possible. The aim of this study was to provide reliable morphological characters that would allow the identification of larvae and instar stages in O. thoracicum. Quantitative and qualitative morphological characters for instar and species identification are described and illustrated. A list of described immature stages of the genus Oiceoptoma is provided.

The evolution of pyrethroid insecticide resistance in Culex tarsalis Coquillett, a vector for West Nile and St. Louis encephalitis viruses, is a growing concern in Northern California. Common mechanisms of resistance include the target-site mutation, kdr, and increased levels of detoxification enzymes, such as mixed-function oxidases, GSTs, and esterases. The goal of this study was to compare the prevalence of kdr mutations (L1014F and L1014S) and detoxification enzymes between pyrethroid susceptible and resistant Cx. tarsalis individuals. Individual mosquitoes, categorized by resistance status from permethrin bottle bioassays, were prepared for both molecular and enzymatic testing by separating the legs of a mosquito from the remaining body. Legs were used to test for the presence of kdr mutations, while the bodies were used to test for the activity of detoxification enzymes. The number of phenylalanine (F) alleles present at the kdr target-site as well as levels of GST were increased in mosquitoes that survived the bottle bioassay compared to those that were knocked down. Individuals with 2 F alleles and an active GST level greater than or equal to 0.052 µg/ml showed a higher survival rate than either mechanism independently demonstrating resistance to pyrethroids in Cx. tarsalis is likely the result of multiple resistance mechanisms acting collectively. Further work is needed to determine the interplay of multiple resistance mechanisms to achieve phenotype resistance in this mosquito species.