Journal of medical entomology最新文献

This study investigated the response of tick movement to temperature and moisture stress, key factors influencing tick-borne disease risk. The blacklegged tick, Ixodes scapularis Say, a parasite found widely across the United States, transmits multiple pathogens and spends most of its life off-host, exposed to varying environmental conditions. We quantified the movement of adult female I. scapularis during experimental exposures to 5 temperatures (10 °C to 25 °C) crossed with 3 target relative humidities (75%, 84%, and 100%) using a Drosophila activity monitor (DAM). We then modeled the probability of tick movement as a function of temperature and vapor pressure deficit (VPD), a measure of moisture stress derived from the observed temperature and relative humidity, over 4 different trial durations (30, 45, 60, and 75 min). For all durations, the best-fitting model contained fixed effects of temperature, VPD, and their quadratic terms. The predicted probability of tick movement was concave-down with VPD, with movement increasing up to a certain threshold and then decreasing. Consistent with the cool-weather adult activity period, the predicted probability of tick movement was highest at 10 °C, decreasing as temperature increased and increasing slightly at the warmest temperatures. We conclude that adult female I. scapularis respond non-linearly to increases in both temperature and moisture stress; the DAM can be a useful tool for tracking I. scapularis movement over sub-daily time scales; and trial duration does not strongly impact the estimated response surface over the periods evaluated.

Culex tritaeniorhynchus is the primary vector of Japanese encephalitis virus (JEV) and is thought to exist as 2 forms: the continental type (Ct-C) and the Japanese type (Ct-J), distinguished by variations in the cytochrome oxidase subunit 1 (COI) region of mitochondrial DNA (mtDNA). However, the extent of genetic variation within and between the 2 types remains largely unexamined. To address this gap in the literature, we performed mitochondrial genome sequencing and additionally developed a rapid and cost-effective identification method that may facilitate efficient vector management and research. The method for type identification is based on a restriction fragment length polymorphism (RFLP) assay, targeting type-specific sequence variations in the COI region. Phylogenetic analysis using mtDNA confirmed that Ct-C and Ct-J represent genetically distinct taxa within the genus Culex. The proposed molecular identification method has been validated to effectively differentiate between the 2 types in the ROK. Early detection of cryptic invasions is critical for effective vector management. The results of this study confirm that the 2 types of Cx. tritaeniorhynchus, the primary vector of JEV, represent genetically distinct lineages. These findings may serve as a foundational reference for developing vector control strategies aimed at suppressing JEV in East Asia.

In Colombia, sand flies (Diptera: Psychodidae) are recognized as primary vectors of Leishmania spp. However, there are reports of infections caused by unidentified trypanosomatid parasites in sand flies circulating within leishmaniasis-endemic areas (2017 to 2018). This study aimed to identify trypanosomatid parasites other than Leishmania spp. infecting sand flies in a visceral leishmaniasis focus in northern Colombia. Between March 2017 and March 2018, sand flies were actively collected from tree bases and cavities and subsequently dissected for taxonomic identification and the detection of trypanosomatid parasites, which were identified by sequencing the V7V8 region of the small subunit ribosomal RNA (SSU rRNA) and the glycosomal glyceraldehyde-3-phosphate dehydrogenase gene (gGAPDH). A total of 1,615 sand flies were captured, and 1,385 females belonging to 5 species of this insect group were dissected. Micropygomyia cayennensis cayennensis (n = 75/974) and Micropygomyia micropyga (n = 6/320) were found to be infected with trypanosomatid parasites along the hindgut. Phylogenetic analyses showed that the sequences of parasites detected in Mi. c. cayennensis belong to the genus Trypanosoma. Within this genus, they formed a strongly supported monophyletic clade, showing a close relationship with a clade of parasites associated with lizards. This finding underscores the need for expanded ecological and molecular studies to assess the epidemiological role of these vectors and determine whether these parasites pose a risk to humans or other vertebrates.

Published studies and records of species of Anopheles that occur in Thailand are reviewed and lists in public databases are revised. ITS2 and COI sequences of specimens from Thailand available in GenBank were analyzed using a phylogenetic method and compared with sequences of species from other countries. Eighty-one species of Anopheles are currently known to occur in Thailand, including the informally recognized An. aconitus species B, An. annularis species A and B, An. jeyporiensis species B, An. tessellatus species A, C, and F, and An. subpictus species C and D. Three new species complexes, the Aconitus, Jeyporiensis, and Karwari Complexes, are recognized.

Forensic entomotoxicology studies require culture media that fulfill the nutritional needs of the relevant forensic species, enabling their proper growth and development from oviposition to maturity, while minimizing biases due to the presence of xenobiotics in tissues. This study aimed to optimize a culture medium for Megaselia scalaris (Diptera: Phoridae) (Loew, 1866) to enhance oviposition by this species. A bioinformatic approach was used to determine whether M. scalaris possesses homologs of the Ir76b receptor that is activated by putrescine and cadaverine and plays a role in food source identification in other species. Supplementing the media with these amines resulted in oviposition comparable to those observed in porcine tissue without adversely affecting the growth and development of other stages of the life cycle. The Ir76b receptor was also identified in Lucilia sericata (Diptera: Calliphoridae) (Meigen, 1826), another species of forensic relevance. Optimized media similarly supported oviposition in L. sericata, suggesting the formulation's broader applicability.

Since its invasion of the United States in the 1980s, Aedes albopictus (Skuse, 1894) has become a major pest and a significant public health threat in the Southeastern United States. Despite its importance, we know little about its population genetics at fine spatial scales that correspond to the level of management units. To remedy this lack of information, we analyzed Ae. albopictus spatial variation in mosquito abundance and genetic structure in an urban-rural landscape over 2 years (2016 and 2018) in Wake County, NC, United States. We used a reduced representation sequencing method to generate between 1,100 and 30,000 single-nucleotide polymorphisms for population genetic analyses. We found spatial variation in both the abundance and genetic diversity, and significant differences in genetic divergence among sites that varied between the 2 years. The year-to-year variation in the population genetic patterns at the within-county scale suggests a dynamic system that requires extensive geographic, temporal, and genomic sampling to resolve.

Mosquito-borne diseases are a major public health concern, and exploiting the mosquito's reliance on host odors is an effective way to prevent human exposure. We evaluated the attraction of non-blood-fed female Anopheles stephensi Liston, 1901 mosquitoes (Bandar Abbas strain, laboratory population) to four chemical components found in vertebrate host odors (at 5 dilutions) and their blends using an olfactometer in laboratory conditions. When each compound was combined with CO2, three of the four tested compounds showed significant attractancy (P < 0.05) at their optimal dilutions. Hexanoic acid was the most attractive, followed by 3-methyl-1-butanol and L-lactic acid. We created five blends using the most attractive dilutions, and two of these blends significantly attracted mosquitoes in the olfactometer (P < 0.05). The most promising blend contained 3-methyl-1-butanol and hexanoic acid. This blend has potential for use in odor-baited mosquito traps, but further field research is required to evaluate its effectiveness.

The increasing resistance to insecticides, the limited availability of new insecticides for mosquito control, and the emergence of new disease threats have created an urgent need for alternative tools to manage mosquito vector populations. Mosquito parasites may serve as potential sources for these alternatives. This study aimed to investigate the ectoparasites found on both larval and adult mosquitoes to identify natural biocontrol agents that could help reduce the mosquito population. Mosquitoes were collected in 2019 using dipping and mechanical aspiration methods, human-baited bed net trap, animal-baited bed net trap, and BG-Sentinel trap with CO2 gas. All mosquitoes and their ectoparasites were identified using morphological keys. A total of 1,756 adult mosquitoes and 9,789 mosquito larvae were collected from 3 genera: Anopheles, Culiseta, and Culex. Additionally, 125 water mite larvae were collected and identified as Arrenurus. It was found that 5.5% of adult mosquitoes were infested with this mite. There was a weak but statistically significant relationship between the Anophelinae and Culicinae subfamilies and parasitism by water mites at the P = 0.05 level. Additionally, infestation by Vorticella spp. was observed on the head, thorax, abdomen, and siphon of mosquito larvae. This study represents the first research on the parasitism of water mites and Vorticella spp. on mosquitoes in central Iran. Further detailed studies are needed to enhance our understanding of the biology and ecology of these aquatic organisms that parasitize mosquitoes in Iran, as well as to assess their potential role in mosquito control.

Leishmania infantum is one of the etiologic agents of leishmaniases in mammals. In the Americas, numerous sand fly species within the Lutzomyia genus drive Leishmania spp. transmission, such as the species complex Lutzomyia longipalpis sensu lato. It remains unknown if climatic changes could facilitate range expansion of Lu. longipalpis, creating conditions for local transmission in previously non-endemic regions. The objectives of this study were to identify the climatic and environmental variables of importance for Lu. longipalpis, current ecologically suitable area across the Americas, and determine future areas of ecological suitability under 30-year time periods. Occurrence records were obtained from GBIF, WRBU, and literature searches. Historic climate data (1981-2010) and projection data for Shared Socioeconomic Pathway 3-7.0 for time periods 2041-2070, and 2071-2100 were obtained from CHELSA, along with topographic data from EarthEnv. Using MaxEnt species distribution modelling algorithms, data were incorporated to identify areas which currently are or may become suitable for Lu. longipalpis. Ecological variables such as terrain ruggedness index, number of growing degree days at which mean daily air temperature is above >10 °C, Köppen-Geiger climate classification, and mean daily air temperature of the coldest quarter, were identified as drivers of suitability. Current regions of ecological suitability include areas from the southern United States to northern Argentina. Suitability may expand northward and increase within its current range, specifically in parts of Mexico and Brazil. Findings from this study identify climate and environmental variables impacting Lu. longipalpis distribution, and regions of potential range expansion.

Tick-borne diseases cause a high morbidity in the USA with Ixodes scapularis as the main vector, responsible for the majority of tick-borne diseases in the USA. Understanding disease dynamics requires not just human disease surveillance but also surveillance of the ticks themselves. This study collected 355 I. scapularis adults from 16 sites across Minnesota, Wisconsin and Iowa by drag cloths during 2017-2019. Ticks were tested using 16S sequencing and targeted PCR to identify human relevant tick-borne disease agents. We detected 168 Borrelia burgdorferi positive, 2 Borrelia mayonii positive, 33 Anaplasma phagocytophilum Human Active positive, 1 Anaplasma phagocytophilum Variant-1 positive, 14 Ehrlichia muris positive and 5 Borrelia miyamotoi positive ticks. These results add surveillance data on adult I. scapularis adults in the Upper Midwest.