Journal of the American Mosquito Control Association最新文献

Culicoides biting midges are a major nuisance in coastal residential areas of Australia, yet effective control strategies remain limited. This study evaluated the effectiveness of a residual insecticide treatment applied to a purpose-grown vegetation barrier in reducing biting midge nuisance in adjacent coastal residences, with secondary effects on mosquito abundance also monitored. Biting midge and mosquito populations were monitored continuously using automated smart traps (BG-Counter®) over 18 wk, including 11 wk of pretreatment and 7 wk posttreatment surveillance. During the pretreatment surveillance period, properties adjacent to the vegetation barrier (n = 4) recorded 71% fewer biting midges than nonadjacent properties (n = 2), although this effect was temporally variable (95% confidence interval [CI]: -95% to +55%) and not significant. No reduction in mosquito abundance was observed during the same period. Following treatment of the barrier with a residual insecticide (BiFlex AquaMax®, bifenthrin 100 g/liter), biting midge and mosquito populations declined by 86% (95% CI: 77-92%) and 79% (95% CI: 68-86%), respectively, across the study landscape, including in areas with and without the vegetation barrier. A significant barrier-insecticide interaction for both groups indicated that reductions were greatest in residences adjacent to the vegetation barrier. Decreases in mosquito abundance following application of the residual spray suggests that the vegetation barrier functioned as important harborage habitat, enabling targeted control within and beyond its immediate boundary. These findings support the integration of insecticide-treated vegetation barriers into pest management programs targeting nuisance biting midge and mosquito populations in coastal residential environments.

Mitigating the arboviral threat in Jamaica is predominantly dependent on vector control efforts which target the Aedes aegypti mosquito. This, however, is being hampered because of increased insecticide resistance to synthetic chemicals. Currently, environmentally friendly botanical agents are gaining interest globally as they possess promising mosquitocidal properties. In this study, the larvicidal activity of essential oils extracted from the leaves of Jamaican Hyptis verticillata and Pimenta dioica were evaluated at 24 h against Ae. aegypti, utilizing a modified World Health Organization bioassay. Subsequent gas chromatography-mass spectrometry analysis of the extracts revealed that the most abundant compounds of H. verticillata and P. dioica were cadina-4,10(15)-dien-3-one and eugenol, respectively. A dose-dependent response was noted, and LC50 values of 16.06 ppm and 56.23 ppm were obtained for H. verticillata and P. dioica respectively, against the Rockefeller laboratory strain of Ae. aegypti. Evaluation of H. verticillata against field strains showed that increased pigmentation was among the main phenotypical changes observed post treatment. The calculated resistance ratios varied across sites, with RR50 values ranging from 0.727 in Duhaney Park to 1.578 in Savanna La Mar, indicating overall low resistance across all strains. The current findings support the potential use of essential oils as alternative larvicidal agents in Jamaica.

Reliable determination of mosquito age and reproductive status is critical for understanding disease transmission dynamics and evaluating vector control strategies. In this study, we investigated the use of mid-infrared (MIR) spectroscopy combined with multivariate statistical models to predict the gonotrophic state (parity) and chronological age of Aedes triseriatus. Using a reflectance sampling geometry, we acquired IR spectra from the hind tibiae of Ae. triseriatus females to assess gonotrophic status. Spectral data in the 1800-650 cm-1 range were normalized and subjected to second-derivative transformation to minimize baseline variation. Partial least squares discriminant analysis (PLS-DA) was used to classify mosquitoes as parous or nulliparous based on their IR spectra, achieving clear separation between groups in the validation set. The model demonstrated 97% (95% CI: 92%-99%) classification accuracy, with a positive predictive value of 97% (95% CI: 88%-100%) and a negative predictive value of 97% (95% CI: 91%-99%), indicating robust statistical differentiation based on gonotrophic status. Using female Ae. triseriatus aged from 2 to 35 days old we assessed the ability of MIR to predict age. Partial least squares regression (PLS-R) yielded a strong correlation (R = 0.96) between spectral data and mosquito age. Statistical testing (ANOVA, Tukey's HSD) revealed that the model could not reliably distinguish between mosquitoes aged 2 and 7 days but could reliably distinguish Ae. triseriatus ≤ 7 days (1 week) old from those 2-5 weeks of age at the 95% confidence level. Collectively, these findings demonstrate that MIR spectroscopy, coupled with chemometric modeling (PLS analyses), provides a rapid and reproducible method for determining reproductive status and age in Ae. triseriatus. The methods reported here may improve La Crosse virus transmission risk assessments and better refine our understanding of enzootic maintenance and human spillover.

The Metropolitan Mosquito Control District, based in St. Paul, MN, has been protecting the residents of the Twin Cities metropolitan area of Minnesota from disease and annoyance from mosquitoes and other pests since 1958. Regarding mosquitoes, this mission is carried out by administering a wide-sweeping control program that is almost entirely larvicidal. For control of the Culex species, residual products containing the active ingredient S-methoprene have been heavily used for decades without product rotation in stormwater catch basins and ditches. In the fall of 2025, a preliminary investigation of S-methoprene and pyriproxyfen resistance was conducted using standardized laboratory bioassays. The preliminary data indicate that a field-collected population of Culex pipiens has developed high resistance to S-methoprene, with a resistance ratio at 50% mortality (RR50) value of 56.29 and were tolerant to pyriproxyfen with an RR50 of 4.35. Field-collected Cx. restuans remain susceptible to S-methoprene with an RR50 of 1.79. The preliminary data laid the groundwork needed to warrant further testing to determine where else this resistance is occurring and to what extent.

The Texas Panhandle (26 counties) and High Plains regions (41 counties) have one of the highest West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) human neuro-incidence rates in the USA, yet surveillance for these pathogens is predominately performed through passive measures (e.g., detecting human cases at hospitals and other health clinics). There is an overall lack of active pathogen surveillance (e.g., mosquito surveillance) systems in these regions, leading to knowledge gaps in our understanding of arboviral dynamics in enzootic cycles. To address this limitation, we implemented 2 surveillance projects in 2024: localized surveillance of WNV and SLEV in the city of Lubbock, TX, and regional surveillance throughout the Panhandle and High Plains regions of the state. We used BG sentinel traps and Centers for Disease Control and Prevention light traps baited with dry ice to collect Culex mosquitoes in a multitude of habitats for both projects. All mosquitoes were identified using a dichotomous key, and then female Cx. tarsalis and Cx. quinquefasciatus were tested for WNV and SLEV as super-pools (e.g., samples containing supernatant from up to 7 individual pools that contained between 1 and 50 mosquitoes) using a combination of commercial RNA extraction kits and real-time quantitative polymerase chain reaction. In the Lubbock study, we collected 21,066 Cx. tarsalis and 15,918 Cx. quinquefasciatus, which were tested as 308 and 238 super-pools, respectively. Sixty-three Cx. tarsalis and 36 Cx. quinquefasciatus super-pools tested positive for WNV, and 8 Cx. tarsalis and 4 Cx. quinquefasciatus super-pools tested positive for SLEV. Sixteen Panhandle counties were sampled by DSHS, which collected 1,060 Cx. tarsalis and 56 Cx. quinquefasciatus. A total of 23 super-pools of Cx. tarsalis and Cx. quinquefasciatus were tested, of which only 3 (13%) Cx. tarsalis samples were found to be positive for WNV. Overall we found an abundant number of Culex spp. mosquitoes that tested positive for both viruses, which supports the Texas Panhandle and High Plains regions as high-risk regions for WNV in the United States.

Ongoing surveillance of tick populations is critical for informing the health of humans, livestock, and companion animals. From 2004 to 2019 in the USA and its territories, the National Notifiable Disease Surveillance System data show a 2.1-fold increase in all reportable notifiable tick-borne diseases (TBDs) in humans. Eight tick-borne zoonotic pathogens and 1 syndrome were described for the first time in the USA between 2004 and 2024. In Missouri, 33 counties were surveyed over a 2-year period (2019 and 2021). More than 3,811 ticks were collected during the study: 89.0% Amblyomma americanum, 10.9% Dermacentor variabilis, <0.1% Amblyomma maculatum, <0.1% Haemaphysalis longicornus, and <0.1% Ixodes spp. Significantly greater tick density was found in metropolitan areas as compared to rural counties (P = 0.012). Of the 2 level I ecoregions in Missouri, the Eastern Temperate Forest (ETF) had a significantly greater tick density (P = 0.0045). Even so, D. variabilis had significantly higher density in the Great Plains ecoregion than in ETF (P = 0.031). Ozark Highlands had the highest tick density of the 5 level III ecoregions surveyed (5.12 ticks/100 m2). A moderate, positive correlation between a county's density of A. americanum nymphs and its quadrennial tick-borne disease rate was observed (r = 0.68, P = 0.002). Our study adds new data on established and reported tick populations for 13 counties and examines the relationships of tick density to TBDs and to area designation.

Mosquito sampling in both urban and rural areas leads to a better understanding of mosquito species diversity. Sampling is also essential to determine the presence of vectors able to transmit disease-causing pathogens. To study mosquito species richness in central Indiana (Hamilton County) and southern Indiana (Monroe County), we used ovitraps for the collection of larvae typically found in tree holes. We collected a total of 1,013 mosquitoes from 4 locations and 71 ovitraps. This study had a total of 1,493 ovitrap wk, calculated as the number of ovitraps multiplied by the number of wk each ovitrap was deployed. Ovitraps were deployed for 7 to 26 weeks with the first ovitraps being deployed on September 13, 2023, and the last ovitraps being removed on October 31, 2024. Aedes spp. accounted for 92.3% of the total larvae collected. We found the following species: Ae. albopictus, Ae. hendersoni, Ae. japonicus, Ae. triseriatus, Anopheles barberi, Culex pipiens, Orthopodomyia signifera, and Toxorhynchites rutilus. Aedes triseriatus was the most common species collected (n = 451, 45.7% of samples) and the least common species collected was An. barberi (n = 1). Analysis using species accumulation curves indicated comprehensive sampling of species. The Sørensen index of dissimilarity showed two clusters, one associated with forested environments and the other with urbanized and rural landscapes. We collected most mosquito species that have been reported in tree holes sampled across the US Midwest.

Recent research has demonstrated that larvicides can be an effective tool in integrated malaria vector control. However, the widespread adoption of this intervention has been limited by the need for frequent reapplication. To reduce operational efforts and costs, there is a growing need to explore long-lasting and environmentally friendly larvicides. In this study, an insect growth regulator, 0.5% pyriproxyfen (Surmilarv 0.5G), was evaluated both under laboratory conditions and at an experimental station for its efficacy against Anopheles coluzzii and An. arabiensis larvae, 2 major malaria vectors. In the laboratory, complete mortality was achieved at concentrations between 5 and 10 µg/liter for both species. In field trials with An. coluzzii, a concentration of 10 µg/liter resulted in almost complete inhibition of adult emergence during the monitoring period. The emergence inhibition rate (EIR) of 100% was achieved within 17 days, with pupal mortality exceeding 95%. Peak adult mortality was recorded on day 35 (32%), with 46% adult emergence still observed by day 81. At 0.1 µg/liter, 100% of EIR was achieved on day 8, with 48% adult emergence by day 81. For An. arabiensis, the 10 µg/liter concentration also resulted in full inhibition of adult emergence throughout the 35-day follow-up period. At 1 µg/liter, 100% of EIR was observed by day 9. Anopheles coluzzii and An. arabiensis are highly sensitive to Sumilarv 0.5G at low concentrations. The persistence of this granular formulation in treated habitats under standard field conditions highlights its potential as a valuable tool in malaria vector control.

Abstract: Culicoides insignis (Diptera: Ceratopogonidae) is an important vector of bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) that affect ruminants. This species is considered neotropical, and is distributed throughout much of South America, Central America, and the Caribbean. In the United States, C. insignis is mainly found in Florida; however, recent studies reported this species from Georgia, Alabama, Mississippi, and Louisiana, suggesting a northwestern range expansion of C. insignis in the southeastern USA. In Louisiana, C. insignis was reported from the northcentral region (Jackson-Bienville-Lincoln parishes) in 2018 based on a one trap-night collection of the species in August 2013, but was not found in the south. Here, we report multiple light-trap collections of C. insignis from East Feliciana parish in southeastern Louisiana from 2022 to 2023, providing new parish records for the species in Louisiana, demonstrating its likely establishment in the state, and confirming the northwestern range expansion of C. insignis in the southeastern USA. However, the role of C. insignis in the transmission of BTV/EHDV in Louisiana is currently unknown and should be examined in further studies.

Abstract: Aedes aegypti is the principal vector of dengue virus. Its vector ability is related to its capacity to adapt to different environments and to lay eggs in diverse sites to ensure the success of its progeny. The species abundance can be studied by estimating the infestation level using the Breteau Index (BI) and the House Index (HI). These indices indirectly reveal the practices and habits of house dwellers, who accumulate containers that contribute to the presence and abundance of Ae. aegypti and the potential transmission of dengue virus. The objective of this work was to analyze the relationship between these indices and environmental variables in drought years (2004-2005). The data analyzed were taken from entomological surveillance spreadsheets of the National Ministry of Health of Argentina, and included 156,288 houses and 658,656 artificial containers inspected by Ministry technicians. A correlation matrix was generated between the indices and the climatic variables to analyze cross correlations. When the relationships between climatic variables and the indices were significant, they were adjusted with General Linear Models (GLMs) taking into consideration the lowest value of the Akaike Information Criterion (AIC). The models were validated by testing the normal distribution of the residuals and the lack of autocorrelation. The results showed that 8,249 houses and 15,165 artificial containers were positive for Ae. aegypti. The BI and HI were positively correlated with precipitation, minimum temperature and maximum temperature at a zero-month time lag. The best GLM found between HI, minimum temperature and precipitation at a zero-month time lag was a gamma model. The increase of HI was related to the mean temperature at a 1-month time lag by using a gamma GLM. This increase in the HI may be potentially related to the accumulation of containers by humans under drought conditions, a behavior that favors the growth of immature forms of the main dengue vector.