Lawrence J. Hribar

Potential for North American mosquitoes to transmit Rift Valley fever virus.

ABSTRACT The rapid spread of West Nile viral activity across North America since its discovery in 1999 illustrates the potential for an exotic arbovirus to be introduced and widely established across North America. Rift Valley fever virus (RVFV) has been responsible for large outbreaks in Africa that have resulted in hundreds of thousands of human infections and major economic disruption due to loss of livestock and to trade restrictions. However, little is known about the potential for North American mosquitoes to transmit this virus should it be introduced into North America. Therefore, we evaluated selected mosquito species from the southeastern United States for their ability to serve as potential vectors for RVFV. Mosquitoes were fed on adult hamsters inoculated 1 day previously with RVFV. These mosquitoes were tested for infection and ability to transmit RVFV after incubation at 26°C for 7–21 days. None of the species tested (Aedes taeniorhynchus, Ae. vexans, Culex erraticus, Cx. nigripalpus, Cx. quinquefasciatus, and Cx. salinarius) were efficient vectors after they fed on hamsters with viremias ranging from 104.1 to 106.9 plaque-forming units (PFU)/ml. However, Ae. taeniorhynchus, Ae. vexans, and Cx. erraticus all developed disseminated infections after they fed on hamsters with viremias between 108.5 and 1010.2 PFU/ml, and both Ae. vexans and Cx. erraticus transmitted RVFV by bite. These studies illustrate the need to identify the ability of individual mosquito species to transmit RVFV so that appropriate decisions can be made concerning the application of control measures during an outbreak.

Mosquitoes infected with West Nile virus in the Florida Keys, Monroe County, Florida, USA.

Abstract More than 30,000 mosquitoes in 22 species or species groups were collected from the Florida Keys, Monroe County, FL, USA, in dry ice-baited light and gravid traps. Dry ice-baited traps collected more mosquitoes than did gravid traps. West Nile virus was detected in pools of Anopheles atropos Dyar & Knab, Deinocerites cancer Theobald, and Ochlerotatus taeniorhynchus (Wiedemann).

MOSQUITO LARVAE (CULICIDAE) AND OTHER DIPTERA ASSOCIATED WITH CONTAINERS, STORM DRAINS, AND SEWAGE TREATMENT PLANTS IN THE FLORIDA KEYS, MONROE COUNTY, FLORIDA

Abstract We investigated the larval dipteran fauna of artificial and natural containers, sewage treatment plants, and storm drains in the Florida Keys. Mosquitoes collected were Aedes aegypti, Ae. albopictus, Anopheles crucians, Culex atratus, Cx. nigripalpus, Cx. peccator, Cx. quinquefasciatus, Deinocerites cancer, Ochlerotatus taeniorhynchus, and Wyeomyia vanduzeei, as well as an unidentified Culex (Melanoconion) species and an unidentified Anopheles species. Other Diptera collected included a chironomid species in the Chironomus decorus Johannsen group; the filter fly, Clogmia albipunctata; an undescribed psychodid in the genus Austropericoma; a ceratopogonid midge, Dasyhelea pseudoincisurata; and a phorid fly, Megaselia scalaris.

A Large Scale Biorational Approach Using Bacillus thuringiensis israeliensis (Strain AM65-52) for Managing Aedes aegypti Populations to Prevent Dengue, Chikungunya and Zika Transmission

Background Aedes aegypti is a container-inhabiting mosquito and a vector of dengue, chikungunya, and Zika viruses. In 2009 several cases of autochthonous dengue transmission were reported in Key West, Florida, USA prompting a comprehensive response to control A. aegypti. In Key West, larvae of this mosquito develop in containers around human habitations which can be numerous and labor intensive to find and treat. Aerial applications of larvicide covering large areas in a short time can be an efficient and economical method to control A. aegypti. Bacillus thuringiensis israelensis (Bti) is a bacterial larvicide which is highly target specific and appropriate for wide area spraying over urban areas, but to date, there are no studies that evaluate aerial spraying of Bti to control container mosquitoes like A. aegypti. Methodology This paper examines the effectiveness of aerial larvicide applications using VectoBac® WG, a commercially available Bti formulation, for A. aegypti control in an urban setting in the USA. Droplet characteristics and spray drop deposition were evaluated in Key West, Florida, USA. The mortality of A. aegypti in containers placed under canopy in an urban environment was also evaluated. Efficacy of multiple larvicide applications on adult female A. aegypti population reduction was compared between an untreated control and treatment site. Conclusions Droplet characteristics showed that small droplets can penetrate through dense canopy to reach small containers. VectoBac WG droplets reached small containers under heavy canopy in sufficient amounts to cause > 55% mortality on all application days and >90% mortality on 3 of 5 application days while controls had <5% mortality. Aerial applications of VectoBac WG caused significant decrease in adult female populations throughout the summer and during the 38th week (last application) the difference in adult female numbers between untreated and treated sites was >50%. Aerial larvicide applications using VectoBac WG can cover wide areas in a short period of time and can be effective in controlling A. aegypti and reducing A. aegypti-borne transmission in urban areas similar to Key West, Florida, USA.

The association between meteorological variables and the abundance of Aedes taeniorhynchus in the Florida Keys

ABSTRACT: The black salt marsh mosquito, Aedes taeniorhynchus, is a serious nuisance pest and a potential vector of a number of arboviruses. This study examined the effect of wind direction, wind speed, temperature, and time of year on the abundance of Ae. taeniorhynchus collected in CO2-baited light traps at 12 sites in the Florida Keys during 2004. The dependent variable analyzed was the natural log of weekly mosquito abundance. The previous weeks wind speed and wind direction, and the current weeks temperature were used as independent variables. Simple and multiple linear regression models were used to assess the significance and nature of association between the meteorological variables and the natural log of mosquito abundance, and to determine whether the meteorological variables had significant associations with mosquito abundance after also controlling for time of year. Week of year was treated as a circular independent variable in the regression models, using the sine and cosine of week in radians to model the periodic seasonal fluctuation in mosquito abundance. Mosquito abundance was significantly associated with all meteorological variables and with week of year. Individually, previous weeks wind speed and wind direction, and current weeks temperature were able to explain respectively 24.5%, 24.5%, and 52.1% of the variation in mosquito abundance observed over the year. Week of year had the strongest individual association with mosquito abundance, explaining 65.7% of the variation in mosquito abundance. The meteorological variables were still significantly associated with mosquito abundance, after controlling for week of year. Week and the meteorological variables together explained 79.2% of the variation in mosquito abundance. The regression models fit to the data from this study suggest a strong periodic seasonal variation in mosquito abundance, with meteorological conditions explaining a significant portion of the variation beyond the seasonal trend.

MOSQUITO FAUNA OF WILDERNESS ISLANDS WITHIN THE NATIONAL KEY DEER REFUGE AND THE GREAT WHITE HERON NATIONAL WILDLIFE REFUGE, MONROE COUNTY, FLORIDA

Abstract Dry ice–baited light traps, counts of mosquitoes biting and landing on technicians, and larval surveillance were used to determine mosquito species abundance on Annette Key, Little Knockemdown Key, Little Pine Key, Raccoon Key, and the Water Keys, all of which are located offshore, within the National Key Deer Refuge and Great White Heron National Wildlife Refuge in Monroe County, FL. Due to the close proximity of these wilderness islands to the inhabited islands of the Florida Keys, it is important to understand the abundance and composition of the mosquitoes and the effects they may have on populations on inhabited islands. Thirty different species were collected during 2004–2008. Aedes taeniorhynchus, the black salt-marsh mosquito, was the most abundant mosquito species collected at all locations. Other mosquitoes collected in large numbers at all locations were Anopheles atropos, Culex bahamensis, Cx. nigripalpus, and Deinocerites cancer. Because these wilderness islands are difficult to traverse due to vegetative growth, the placement of mosquito traps close to the perimeter of the islands may influence assessment of the abundance and diversity of mosquito species collected on each island.

MOSQUITO FAUNA OF KEY LARGO, FLORIDA

ABSTRACT A total of 28 species of mosquitoes was collected in dry-ice–baited light traps on Key Largo, Florida during 2002–2004. Total number of mosquitoes increased each year during the study.

The Old World biting midge, Forcipomyia (Lepidohelea) pulcherrima SANTOS ABREU, new to the fauna of the United States (Diptera: Ceratopogonidae)

ABSTRACT We provide the first United States records of the Old World biting midge, Forcipomyia (Lepidohelea) pulcherrima SANTOS ABREU (Diptera: Ceratopogonidae), from California, Florida and Hawaii. The fourth instar larva of F. pulcherrima is also described and illustrated for the first time.

Larviciding Offshore Islands Reduces Adulticidal Treatment of Populated Areas Adjacent To National Wildlife Refuges

Abstract The Florida Keys Mosquito Control District has conducted larvicide missions on uninhabited offshore islands of the Great White Heron National Wildlife Refuge and the National Key Deer Refuge since 2003. The objective of these missions is to reduce the need to apply adulticides on nearby populated islands where private lands are interspersed with refuge lands that support a diverse assemblage of native butterflies and insect-pollinated plants on Big Pine Key, No Name Key, Little Torch Key, Middle Torch Key, and Big Torch Key (the Torch Keys). More than 800 visits were made to refuge islands by Florida Keys Mosquito Control District personnel; 334 aerial larvicide missions were flown. From 2003 to 2010, a marked reduction in adult mosquito numbers was seen on Big Pine Key, and to a lesser extent on No Name Key. Seasonal distribution of mosquitoes was not different, however. Number of aerial adulticide missions flown on Big Pine Key, No Name Key, and the Torch Keys was 2, 1, and 2 in 2003; 9, 10, and 7 in 2004; 4, 4, and 2 in 2005; 6, 6, and 7 in 2006; 1, 0, and 0 in 2007; 3, 2, and 4 in 2008; 4, 3, and 4 in 2009; and 1, 1, and 3 in 2010, respectively. This is a dramatic reduction from prior years; from 1998 to 2002, 57 aerial adulticide missions were flown on Big Pine Key, 45 missions were flown on No Name Key, and 38 on the Torch Keys. Larviciding is an important component of an integrated approach to mosquito management that seeks to reduce environmental impacts on the national wildlife refuges.

Empicoris subparallelus (Hemiptera: Heteroptera: Reduviidae), a Predatory Bug New to the Fauna of Florida

Abstract The predatory hemipteran Empicoris subparallelus McAtee and Malloch, belonging to the family Reduviidae, subfamily Emesinae, is reported from Grassy Key, Key Largo, Long Point Key, and No Name Key in the Florida Keys, Monroe County, Florida. This is a new species record for the Florida fauna, and only the second state record for the United States. A diagnosis, description, and digital images of the adult are provided to help distinguish this species from other species of Empicoris in Florida.