Efficacy and Nontarget Effects of a Spinosad-Based Larvicide in Minnesota Vernal Pools and Cattail Marshes

ABSTRACT Larvicides that contain spinosad, a bacterial metabolite, are used to control mosquitoes in diverse aquatic habitats. These same habitats are home to other invertebrates, including Crustacea—fairy shrimp, isopods, and amphipods—and mollusks—fingernail clams and freshwater snails. A double-blind study evaluated the effects of Natular® G, a granular treatment containing spinosad, on spring Aedes spp. and nontarget invertebrates in vernal wetlands. Within 14 days after application, Natular G controlled larvae of spring Aedes by 53–84%, depending on species, but had no significant effects on numbers of fairy shrimp, fingernail clams, or freshwater snails. A second double-blind study evaluated effects on Coquillettidia perturbans and nontarget isopods and amphipods in cattail marshes. Treatment reduced emergence of Cq. perturbans by 25% but did not change numbers of isopods or amphipods. The 2 experiments indicate Natular G could be effective against spring Aedes in vernal wetlands, less so against Cq. perturbans in cattail marshes, and yet pose minimal risk to crustaceans and mollusks in either vernal wetlands or cattail marshes.

Diversity and community structure of mosquitoes (Diptera: Culicidae) in suburban, field, and forest habitats in Montréal, Québec, Canada

Understanding the medical and economic impacts of mosquitoes (Diptera: Culicidae) begins with knowing their natural history and distribution, including their association with habitat types, particularly those in which human activity is high. The effects of habitat on shaping the community structure of mosquitoes were studied across periurban habitats on the island of Montréal, Québec, Canada in 2014 and 2015. Mosquitoes were collected from 20 fixed sampling locations in suburban backyards, fields, and forests, using CO2-baited light-emitting diode encephalitis vector survey traps. A total of 184 607 mosquitoes were collected, representing eight genera and 35 species. Suburban, field, and forest sites had different communities of mosquitoes, but differences were not apparent among sites within similar habitat types in nonmetric multidimensional scaling ordinations and permutational multivariate analysis of variance. In both years, the greatest abundance of mosquitoes was collected from field habitat, and the highest species richness, from forests. Suburban sites consistently generated the lowest abundance and diversity. Nearly 75% of the total individuals collected were from three species: Aedes vexans (Meigen), 39%; Coquillettidia perturbans (Walker), 18%; and Aedes canadensis (Theobald), 16%. This research shows that diverse communities of mosquitoes can be found in forests, fields, and backyards, yet the communities between forests differ from more open habitats. Our community analysis reveals that medically important species (e.g., Culex sp.) are more commonly encountered in suburban backyards, yet overall mosquito nuisance potential is greater in forest and field habitats. This information highlights important patterns of mosquito abundance and species occurrence, vital for the development of management programmes.

Mapping the Vector Abundance of Endemic Mosquito-Borne Diseases in Southern Quebec

Background: Climate change is increasing the dispersion of mosquitoes and the spread of viruses of which some mosquitoes are the main vectors. This increases the risk of humans coming into contact with infected mosquitoes and developing diseases with sometimes fatal consequences. In Quebec, the surveillance and management of endemic mosquito-borne diseases, such as West Nile virus or Eastern equine encephalitis, could be improved by mapping the areas of risk supporting vector populations. However, there is currently no active tool tailored to Quebec that can predict annual mosquito population abundances. Methods: Our modelling approach is designed to meet this need. Four species of mosquitos were studied in this project for the period from 2003 to 2014 for the southern part of the province: Aedes vexans (VEX), Coquillettidia perturbans (CQP), Culex pipiens-restuans group (CPRg) and Ochlerotatus stimulans group (STMg) species. We used a mixed linear regression approach to model the abundances of each species or species groups as a function of meteorological and land cover variables. Results: The best models incorporate, for CPRg, the agricultural land, grassland and woodland classes and the average minimum temperature in September of the previous year; for STMg, the urban and woodland classes and the mean precipitation in June; for CQP, urban areas and the mean precipitation in January and August; and finally, for VEX, the agricultural land class and the mean precipitation in January, February and September. Conclusions: The models proved to be robust and precise over almost the entire study area, and the presence of significant climate variables for each of the species or species groups makes it possible to consider their use in predicting long-term spatial variations, based on climate and landscape change, in the abundance of mosquitoes potentially harmful to public health in southern Quebec.

Mapping the Vector Abundance of Endemic Mosquito-Borne Diseases in Southern Quebec

Background: Climate change is increasing the dispersion of mosquitoes and the spread of viruses of which some mosquitoes are the main vectors. This increases the risk of humans coming into contact with infected mosquitoes and developing diseases with sometimes fatal consequences. In Quebec, the surveillance and management of endemic mosquito-borne diseases, such as West Nile virus or Eastern equine encephalitis, could be improved by mapping the areas of risk supporting vector populations. However, there is currently no active tool tailored to Quebec that can predict annual mosquito population abundances.Methods: Our modelling approach is designed to meet this need. Four species of mosquitos were studied in this project for the period from 2003 to 2014 for the southern part of the province: Aedes vexans (VEX), Coquillettidia perturbans (CQP), Culex pipiens-restuans group (CPRg) and Ochlerotatus stimulans group (STMg) species. We used a mixed linear regression approach to model the abundances of each species or species groups as a function of meteorological and land cover variables.Results: The best models incorporate, for CPRg, the agricultural land, grassland and woodland classes and the average minimum temperature in September of the previous year; for STMg, the urban and woodland classes and the mean precipitation in June; for CQP, urban areas and the mean precipitation in January and August; and finally, for VEX, the agricultural land class and the mean precipitation in January, February and September.Conclusions: The models proved to be robust and precise over almost the entire study area, and the presence of significant climate variables for each of the species or species groups makes it possible to consider their use in predicting long-term spatial variations, based on climate and landscape change, in the abundance of mosquitoes potentially harmful to public health in southern Quebec.Manuscript intended for publication in International J. of Health Geographics

New distribution records and range extensions of mosquitoes in British Columbia and the Yukon Territory

We report the first records of Aedes euedes Howard, Dyar, and Knab, and Coquillettidia perturbans (Walker) from Canada’s Yukon Territory, and the first record of Ae. decticus Howard, Dyar, and Knab from British Columbia. We also report range extensions in northern BC for the western treehole mosquito, Aedes sierrensis (Ludlow), the common house mosquito, Culex pipiens L., and the cool weather mosquito Culiseta incidens (Thomson).

Cases of Eastern equine encephalitis in humans associated with Aedes canadensis, Coquillettidia perturbans and Culiseta melanura mosquitoes with the virus in New York State from 1971 to 2012 by analysis of aggregated published data

From 1971 to 2012, in New York State, years with human Eastern equine encephalitis (EEE) were more strongly associated with the presence of Aedes canadensis, Coquillettidia perturbans and Culiseta melanura mosquitoes infected with the EEE virus (Fisher's exact test, one-sided P = 0.005, 0.03, 0.03) than with Culiseta morsitans, Aedes vexans, Culex pipiens-restuans, Anopheles quadrimaculatus or Anopheles punctipennis (P = 0.05, 0.40, 0.33, 1.00, 1.00). The estimated relative risk of a case in a year in which the virus was detected vs. not detected was 14.67 for Ae. canadensis, 6.38 for Cq. perturbans and 5.50 for Cs. morsitans. In all 5 years with a case, Cs. melanura with the virus was detected. In no year was there a case in the absence of Cs. melanura with the virus. There were 18 years with no case in the presence of Cs. melanura with the virus. Such observations may identify the time of increased risk, and when the methods may be used to prevent or reduce exposure to vector mosquito species in this geographic region.

Seasonal Distribution, Blood-Feeding Habits, and Viruses of Mosquitoes in an Open-Faced Quarry in Connecticut, 2010 and 2011

ABSTRACT Seasonal abundance of mosquitoes, their viruses, and blood–feeding habits were determined at an open-faced quarry in North Branford, CT, in 2010 and 2011. This unique habitat had not previously been sampled for mosquitoes and mosquito-borne viruses. Thirty species of mosquitoes were identified from 41,719 specimens collected. Coquillettidia perturbans, Aedes trivittatus, and Ae. vexans were the most abundant species and represented 34.5%, 17.7%, and 14.8% of the totals, respectively. Jamestown Canyon virus was isolated from 6 species of mosquitoes collected from mid-June through July: Cq. perturbans (3 pools), Ae. cantator (3), Ae. trivittatus (2), Ae. aurifer (1), Ae. excrucians (1), and Culex pipiens (1). West Nile virus was cultured from 8 pools of Cx. pipiens and from 1 pool of Culiseta melanura collected from mid-August through late September. Cache Valley virus was isolated from 4 species of mosquitoes in 3 genera from about mid-August through late September 2011: Cq. perturbans (5 pools), Ae. trivittatus (2), Anopheles punctipennis (1), and An. quadrimaculatus (1). Nine different mammalian hosts were identified as sources of blood for 13 species of mosquitoes. White-tailed deer, Odocoileus virginianus, were the most common mammalian hosts (90.8%), followed by raccoon, Procyon lotor (3.1%), coyote, Canis latrans (2.4%), and human, Homo sapiens (1.2%). Exclusive mammalian blood-feeding mosquitoes included: Ae. canadensis, Ae. cantator, Ae. excrucians, Ae. japonicus, Ae. vexans, An. punctipennis, and Cx. salinarius. Fourteen species of birds, mostly Passeriformes, were identified as sources of blood from 6 mosquito species. Five species that fed on mammals (Ae. thibaulti, Ae. trivittatus, Ae. cinereus, Cq. perturbans, and Cx. pipiens) also fed on birds.