Evaluation of a Novel User-Friendly Arthropod Repellent Gel, Verdegen.

Hand sanitizers are developed as alcohol-based liquid gel formulations, generally used to decrease the amount of infectious agents on human hands. Verdegen, LLC proposed to prepare an arthropod repellent gel for public use when the recent outbreaks of Zika infection vectored through Aedes mosquitoes in the American continents prompted multi-faceted emergency measures. Four different gel formulations were developed, comprising two of the most efficacious commercial arthropod repellent active ingredients, N,N-diethyl-3-methyl benzamide (deet) and 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester (picaridin), each at different concentrations (20 and 33% deet, or 20 and 33% picaridin). Compliance with the use of topical arthropod repellents remains an issue among military personnel. One of the most common complaints by Soldiers is that they do not like how the repellents applied on their skin leave behind an oily or greasy residue. These new gel formulations offer a user-friendly alternative for commonly used arthropod repellents formulations for the military and civilian personnel. We tested the efficacy and protection time of these new gel formulations in comparison with the commercially available cream formulations of deet and picaridin at similar concentrations. Our data show that gel formulations have better topical attributes, and offer equal or better biting protection for up to 48 h against host-seeking Aedes aegypti (L.) (Diptera: Culicidae) female mosquitoes.

Host-Feeding Patterns of Culex stigmatosoma (Diptera: Culicidae) in Southern California.

Knowledge of the blood-feeding patterns exhibited by arthropod vectors is essential for understanding the complex dynamics of vector-borne disease transmission. Some species of mosquitoes belonging to the genus Culex have been implicated as having major roles in the transmission of arboviruses such as West Nile virus, Saint Louis encephalitis virus, and Western equine encephalitis virus. Although the host-feeding patterns for many of these Culex species are well studied, the host-feeding patterns of Culex stigmatosoma Dyar are relatively poorly studied, even though this species is suspected to be an important maintenance vector for West Nile virus and other arboviruses. In the current study, bloodmeals from 976 blood-engorged Cx. stigmatosoma, collected from 30 sites in southern California from 2009-2012, were processed for vertebrate host identification by nucleotide sequencing following polymerase chain reaction to amplify portions of the cytochrome oxidase I and cytochrome b genes of vertebrate animals. Vertebrate DNA was amplified, sequenced, and identified from a total of 647 Cx. stigmatosoma bloodmeals, revealing that 98.6% of bloodmeals were from birds, 1.2% from three mammal species, and a single bloodmeal was from a reptile species. In total, 40 different host species were identified. The greatest number of bloodmeals identified was from domestic chicken (Gallus gallus domesticus L.) (38% of bloodmeals), house sparrow (Passer domesticus L.) (23%), house finch (Haemorhous mexicanus Müller) (17%), American crow (Corvus brachyrhynchos L.) (4%), and mourning dove (Zenaida macroura L.) (3%). However, chicken bloodmeals were identified almost entirely from a single site where mosquito collection devices were placed in the near vicinity of confined domestic chickens. The strongly ornithophilic feeding behavior shown in this study for Cx. stigmatosoma supports the hypothesis that this mosquito species may be an important maintenance (or endemic) vector for arboviruses that circulate among susceptible birds.

Laboratory and semi-field evaluations of two (transfluthrin) spatial repellent devices against Aedes aegypti (L.) (Diptera: Culicidae).

Two transfluthrin-based spatial repellent products (Raid Dual Action Insect Repellent and Home Freshener and Raid Shield (currently not commercially available), SC Johnson, Racine WI) were evaluated for spatial repellent effects against female Aedes aegypti (L.) mosquitoes under laboratory (wind tunnel) and semi-field (outdoor enclosure) conditions. The placement of either product in the wind tunnel significantly reduced host-seeking behaviors. The mean baseline (control) landing counts for the Raid Dual Action and Raid Shield were reduced by 95% and 74% respectively. Mean probing counts for the Raid Dual Action were reduced by 95%, while the probing counts for the Raid Shield were decreased by 69%. Baseline blood-feeding success was significantly reduced for both treatments: Raid Dual Action (100%) and Raid Shield (96%). Semi-field evaluations were conducted in outdoor enclosures at the Navy Entomology Center of Excellence, Jacksonville, Florida. A moderate reduction in mosquito entry into military style tents resulted when either product was placed near the tent opening. The Raid Shield reduced mosquito entry into tents by 88%, while the Dual Action decreased entry by 66%.

Effect of CO2 concentration on mosquito collection rate using odor-baited suction traps.

Carbon dioxide (CO2 ) has been used for decades to enhance capture of host-seeking mosquitoes when released in association with traps commonly used by mosquito and vector control agencies. However, there is little published work evaluating the effect of altering CO2 release rates relative to the number of mosquitoes captured in these traps. This study investigated how varying CO2 concentration altered the mosquito collection rate at a freshwater wetlands in southern California. Host-seeking mosquitoes were captured in CDC-style traps baited with one of six CO2 release rates ranging from 0-1,495 ml/min from gas cylinders. Species captured were Aedes vexans, Anopheles franciscanus, An. hermsi, Culex erythrothorax, and Cx. tarsalis. A biting midge, Culicoides sonorensis, was also captured. For all species, increasing CO2 release rates resulted in increasing numbers of individual females captured, with the relative magnitude of this increase associated to some extent with known feeding preferences of these species. We found that variation in CO2 release rate can significantly alter mosquito capture rates, potentially leading to imprecise estimates of vector activity if the relationship of CO2 release rate to mosquito capture rate is not considered.

Vector surveillance to determine species composition and occurrence of trypanosoma cruzi at three military installations in San Antonio, Texas.

Chagas disease, also known as American trypanosomiasis, is caused by the hemoflagellate protozoan Trypanosoma cruzi which is transmitted by blood-sucking triatomine bugs (Hemiptera: Reduviidae; Triatominae). The disease is endemic to south Texas, but exists almost exclusively as a zoonosis. Chagas disease has proven to be a serious public health threat to military working dogs. In 2007, seroprevalence of Chagas disease in military working dogs in San Antonio, Texas, reached 8%. A faunal survey was conducted at 3 San Antonio area military installations (Camp Bullis, Fort Sam Houston, and Lackland Air Force Base). A total of 140 triatomines representing 4 species (Triatoma gerstaeckeri, T. sanguisuga, T. lectularia, and T. indictiva) were collected. Trypanosoma cruzi infected bugs were only collected at Lackland Air Force Base, where the overall infection rate was 16%. The wood excavation technique developed during this study collected all life stages. Only 2 life stages (adult and 5th instar) were positive for T. cruzi.

Survey of mosquito fauna in San Antonio, Texas.

A faunal survey of mosquitoes was conducted in 2008, 2009, and 2010 at various trapping locations throughout the city of San Antonio, TX. A total of 22,739 mosquitoes representing 41 species in 8 genera were collected during this study. The most prevalent mosquito species collected were Aedes vexans (25%), Ae. sollicitans (14%), Culex tarsalis (13.5%), and Cx. erraticus (11%). Four mosquito species (Ae. bimaculatus, Anopheles freeborni, Cx. declarator, and Psorophora horrida) not previously recorded in this area were collected, whereas several species historically occurring in San Antonio were not collected during this survey.

Attractiveness of botanical infusions to ovipositing Culex quinquefasciatus, Cx. nigripalpus, and Cx. erraticus in San Antonio, Texas.

Field experiments were conducted on the Fort Sam Houston Military Reservation, San Antonio, TX, in fall 2008 to observe the attractiveness of selected botanical infusions to ovipositing female mosquitoes. The following infusions were tested in Centers for Disease Control and Prevention gravid traps: Bermuda grass (Cynodon dactylon), oak leaf (Quercus virginiana), acacia leaf (Acacia schaffneri), rabbit chow (alfalfa pellets), and algae (Spirogyra sp.). Four (Bermuda, acacia, oak, and algae) of the 5 infusions were effective in collecting Culex quinquefasciatus, Cx. nigripalpus, and Cx. erraticus. Of the 4 infusions, Bermuda collected the greatest number of the mosquitoes sampled. Female Aedes albopictus mosquitoes were collected in moderate numbers during this study.

Comparison of the attractiveness of organic infusions to the standard CDC gravid mosquito trap.

Field experiments were conducted in southeastern Texas in 2008 to compare the attractiveness of selected gravid-trap infusions to ovipositing female mosquitoes. Comparisons were made among the following infusions: Bermuda grass, oak leaves, acacia leaves, rabbit chow (alfalfa pellets) and green algae. Experiments were conducted at 6 trap locations in Fort Sam Houston military reservation in San Antonio, Texas. Four (Bermuda grass, acacia leaves, oak leaves, and algae) of the 5 infusions were effective in collecting Culex quinquefasciatus, Cx nigripalpus, and Cx erraticus. However, Bermuda grass attracted the greatest numbers of the mosquito species. Aedes albopictus female mosquitoes were collected in moderate numbers during this study; however the infusions were not determined to be significantly different from one another in their attractiveness for this species.