Evaluation of bifenthrin and permethrin as barrier treatments for military tents against mosquitoes in Queensland, Australia

Spatial Repellents Protect Small Perimeters from Riceland Mosquitoes in a Warm-Humid Environment

Recent experiments suggest spatial repellents may significantly reduce biting pressure from host-seeking riceland mosquitoes, such as Anopheles quadrimaculatus, in a warm-humid open-field habitat. However, little is known regarding efficacy of these formulations in partially enclosed spaces where US military personnel may be sheltered or concealed in an operational environment. In this study we investigated the capability of 3 spatial repellents-metofluthrin, linalool, and d-cis/trans allethrin-to reduce mosquito incursion into small open-top enclosures of US military camouflage netting. We found that metofluthrin was more effective in partially enclosed spaces compared with the open field, whereas both linalool and d-cis/trans allethrin provided superior protection in the open. These findings support strategic selection of spatial repellents depending on the environment immediately surrounding the host.

Transfluthrin Spatial Repellent on US Military Materials Reduces Culex tarsalis Incursion in a Desert Environment

Standard residual pesticides applied to US military materials such as camouflage netting can reduce mosquito biting pressure in the field but may contribute to the evolution of resistance. However, residual applications of a spatial repellent such as transfluthrin could allow mosquitoes the opportunity to escape, only inducing mortality if insects linger, for example after becoming trapped in a treated tent. In this study we investigated the capability of transfluthrin on 2 types of US military material to reduce natural populations of disease vector mosquitoes in a cool-arid desert field environment in southern California. We found that transfluthrin could reduce Culex tarsalis incursion into protected areas by up to 100% upon initial treatment and up to 45% for at least 16 days posttreatment, showing that this compound could be an effective element in the US Department of Defense integrated vector management system appropriate for further study.

Residual Pesticide On Hesco® Blast Protection Wall In Temperate Florida Habitat Effective Against Mosquitoes, Stable Flies, and Sand Flies

United States military troops in the field are exposed to the environment and are thus at high risk for transmission of arboviruses, and degradation of mission from continual harassment from insects. Passive vector control, such as application of residual insecticides to US military materials common in the field such as tents and camouflage netting, has been shown to be effective and can contribute to a successful integrated vector management (IVM) plan in the field to reduce this risk. However, other common US military field materials have not been evaluated with residual pesticides. In this study we conducted the first known investigation of the efficacy and longevity of a residual pesticide containing λ-cyhalothrin applied to HESCO^® blast protection wall geotextile. We exposed treated material to a temperate Florida environment and found that this treatment can be effective against sand flies, filth-breeding flies, and mosquitoes for at least 6 wk. This study provides evidence that residual treatment of this US military material may be leveraged as an IVM component to enhance the US Department of Defense pest management system.

Efficacy of residual insecticide Biflex AquaMax applied as barrier treatments for managing mosquito populations in suburban residential properties in southeast Queensland

The pyrethroid insecticide Biflex AquaMax (bifenthrin) was evaluated for its ability to suppress coastal mosquito populations in a controlled suburban backyard study in Mango Hill, Queensland, Australia. The insecticide was applied to perimeter vegetation, fencing in selected backyards, or both, and mosquito populations were monitored weekly from 3 wk before to 8 wk after treatment (11 wk total) by using CDC miniature light traps and human bait landing rates. In addition, bioassays were conducted on vegetation and wood surfaces to monitor residual activity. The two most common species in light trap collections were the Ross River Virus vectors Aedes vigilax (Skuse) and Culex annulirostris Skuse. After treatment, Ae. vigilax populations in treated properties were significantly lower (75-90%) compared with untreated properties. In contrast, Cx. annulirotris, Coquillettidia xanthogaster (Edwards) and Mansonia uniformis (Theobald) populations were not impacted by the treatment. Bioassays revealed that the product gave better residual mortality when applied to vegetation (94.6 +/- 11.8%) than wooden surfaces (75.9 +/- 29.1%) during the 8-wk posttreatment period.

The past and present threat of vector-borne diseases in deployed troops

From time immemorial, vector-borne diseases have severely reduced the fighting capacity of armies and caused suspension or cancellation of military operations. Since World War I, infectious diseases have no longer been the main causes of morbidity and mortality among soldiers. However, most recent conflicts involving Western armies have occurred overseas, increasing the risk of vector-borne disease for the soldiers and for the displaced populations. The threat of vector-borne disease has changed with the progress in hygiene and disease control within the military: some diseases have lost their military significance (e.g. plague, yellow fever, and epidemic typhus); others remain of concern (e.g. malaria and dengue fever); and new potential threats have appeared (e.g. West Nile encephalitis and chikungunya fever). For this reason, vector control and personal protection strategies are always major requirements in ensuring the operational readiness of armed forces. Scientific progress has allowed a reduction in the impact of arthropod-borne diseases on military forces, but the threat is always present, and a failure in the context of vector control or in the application of personal protection measures could allow these diseases to have the same devastating impact on human health and military readiness as they did in the past.

Evaluation of barrier treatments on native vegetation in a southern California desert habitat

Treating perimeters with residual insecticides for protection from mosquito vectors has shown promise. These barrier treatments are typically evaluated in temperate or tropical areas using abundant vegetation as a substrate. However, there is an emerging interest to develop this technology to protect deployed US troops in extreme desert environments with sparse vegetation. We used a remote desert area in the Coachella Valley, California, to 1) evaluate bifenthrin barrier treatments on native xeric vegetation and 2) compare treatments applied with electrostatic and conventional spray technologies. Through a combination of laboratory bioassays on treated and control vegetation sampled at specific intervals over 63 days, synchronized with field surveillance of mosquitoes, we measured the temporal pattern of bioactivity of bifenthrin barriers under natural hot, dry, and dusty desert conditions. Regardless of spray technology, mosquito catch in treated plots was about 80% lower than the catch in control plots 1 day after treatment. This reduction in mosquito numbers in treated plots declined each week after treatment but remained at about 40% lower than control plots after 28 days. Field data were corroborated by results from bioassays that showed significantly higher mosquito mortality on treated vegetation over controls out to 28 days postspray. We concluded that barrier treatments in desert environments, when implemented as part of a suite of integrated control measures, may offer a significant level of protection from mosquitoes for deployed troops. Given the comparable performance of the tested spray technologies, we discuss considerations for choosing a barrier treatment sprayer for military scenarios.

Evaluation of the inhibition of egg laying, larvicidal effects, and bloodfeeding success of Aedes aegypti exposed to permethrin- and bifenthrin-treated military tent fabric

Laboratory studies were conducted to evaluate the effects of treating military canvas tent fabric with bifenthrin and permethrin on the survival of the eggs and larvae of Aedes aegypti. Gravid female Ae. aegypti were able to oviposit on tent canvas treated with either bifenthrin or permethrin. However, none of the eggs laid on treated canvas hatched, and no larvae added to water in treated trays survived. Low residual concentrations of bifenthrin and permethrin on treated canvas prevented the development of eggs and larvae of Ae. aegypti. Inhibition of bloodfeeding was shown when Ae. aegypti adults were exposed to lower concentrations (10-50% of operational concentrations) of bifenthrin- and permethrin-treated canvas tent fabric. These experiments have shown that military tent canvas treated with either bifenthrin or permethrin can reduce the development of Ae. aegypti eggs and larvae and reduce bloodfeeding success of adults.

Evaluation of Bistar 80SC (bifenthrin) as a tent treatment for protection against mosquitoes in Northern Territory, Australia

A field trial to assess the efficacy of Bistar 80 SC as a barrier treatment of Australian military tents was conducted over 10 d at Mount Bundey Military Training Area, Northern Territory, Australia, in March 2003. Four pairs of standard eight-person tents were erected, with a single tent in each pair treated with 0.1% Bistar 80 SC as a course spray, and the remainder left as untreated control tents. Carbon dioxide-baited traps were operated in each tent nightly, and biting collections conducted over 8 nights. There was a mean increase in protection of 81% for mosquitoes entering treated tents and 90.4% increase in protection against biting of predominantly Culex annulirostris Skuse. In addition, bifenthrin applied to the military tents enhances the protection of occupants against bites from this important arbovirus vector.