Exploring new thermal fog and ultra-low volume technologies to improve indoor control of the dengue vector, Aedes aegypti (Diptera: Culicidae).

Control of the mosquito vector, Aedes aegypti (L.), inside human habitations must be performed quickly and efficiently to reduce the risk of transmission during dengue outbreaks. As part of abroad study to assess the efficacy of dengue vector control tools for the U.S. Military, two pesticide delivery systems (ultra-low volume [ULV] and thermal fog) were evaluated for their ability to provide immediate control of Ae. aegypti mosquitoes with a contact insecticide inside simulated urban structures. An insect growth regulator was also applied to determine how well each sprayer delivered lethal doses of active ingredient to indoor water containers for pupal control. Mortality of caged Ae. aegypti, pesticide droplet size, and droplet deposition were recorded after applications. In addition, larval and pupal mortality was measured from treated water samples for 4 wk after the applications. The ULV and the thermal fogger performed equally well in delivering lethal doses of adulticide throughout the structures. The ULV resulted in greater larval mortality and adult emergence inhibition in the water containers for a longer period than the thermal fogger. Therefore, the ULV technology is expected to be a better tool for sustained vector suppression when combined with an effective insect growth regulator. However, during a dengue outbreak, either delivery system should provide an immediate knockdown of vector populations that may lower the risk of infection and allow other suppression strategies to be implemented.

Impact of phlebotomine sand flies on United States military operations at Tallil Air Base, Iraq: 5. Impact of weather on sand fly activity.

In this study, we examined the effect of weather and moon illumination on sand fly activity, as measured by light trap collections made between 2 May 2003 and 25 October 2004 at Tallil Air Base, Iraq. Wind speed, temperature, dew point, percentage of sky cover, and moon illumination were entered into principal components analysis. The resulting principal components were entered into stepwise regression to develop a model of the impact of the weather on sand fly collections. Wind speed, percentage of sky cover, and moon illumination each had a strong inverse relationship with the number of sand flies collected, whereas temperature displayed a direct relationship to sand fly collections. Our data indicate that sand fly light trap catches at Tallil Air Base are highest on warm, clear nights with low wind speed and minimal illumination from the moon.

Impact of phlebotomine sand flies on United State military operations at Tallil Air Base, Iraq: 6. Evaluation of insecticides for the control of sand flies.

We conducted a series of field experiments in 2003 and 2004 to evaluate the efficacy of a variety of insecticides and insecticide application technologies for the control of phlebotomine sand flies at Tallil Airbase, Iraq. During the experiments, 53,263 sand flies were collected. The experiments evaluated the following: (1) routine sand fly control operations using a variety of residual and area-wide insecticides; (2) a combination of five different insecticide application methods in and around tents; (3) residual application of lambda-cyhalothrin and ultra-low volume application of pyrethrins in houses; (4) carbaryl and lambda-cyhalothrin applied as barrier sprays; (5) a deltamethrin-impregnated fence; (6) lambda-cyhalothrin applied as a residual spray in concrete manholes; (7) deltamethrin-treated flooring in tents; and 8) ultra-low volume-applied malathion. Although some of the experiments resulted in limited reductions in the number of sand flies collected in light traps, in no instance did we completely eliminate sand flies or reduce populations for a sustained period. The implications of these findings are discussed.

Use of vector diagnostics during military deployments: recent experience in Iraq and Afghanistan.

Vector-borne diseases such as malaria, dengue, and leishmaniasis are a threat to military forces deployed outside of the United States. The availability of specific information on the vector-borne disease threat (e.g., presence or absence of a specific disease agent, temporal and geographic distribution of competent vectors, and vector infection rates) allows for effective implementation of appropriate measures to protect our deployed military forces. Vector diagnostics can provide critical, real-time information crucial to establishing effective vector prevention/control programs. In this article we provide an overview of current vector diagnostic capabilities, evaluate the use of vector diagnostics in Operation Enduring Freedom and Operation Iraqi Freedom, and discuss the concept of operations under which vector diagnostics are employed.

Impact of phlebotomine sand flies on U.S. military operations at Tallil Air Base, Iraq: 4. Detection and identification of leishmania parasites in sand flies.

Sand flies collected between April 2003 and November 2004 at Tallil Air Base, Iraq, were evaluated for the presence of Leishmania parasites using a combination of a real-time Leishmania-generic polymerase chain reaction (PCR) assay and sequencing of a 360-bp fragment of the glucose-6-phosphate-isomerase (GPI) gene. A total of 2,505 pools containing 26,574 sand flies were tested using the real-time PCR assay. Leishmania DNA was initially detected in 536 pools; however, after extensive retesting with the real-time PCR assay, a total of 456 pools were considered positive and 80 were considered indeterminate. A total of 532 samples were evaluated for Leishmania GPI by sequencing, to include 439 PCR-positive samples, 80 PCR-indeterminate samples, and 13 PCR-negative samples. Leishmania GPI was detected in 284 samples that were sequenced, to include 281 (64%) of the PCR-positive samples and 3 (4%) of the PCR-indeterminate samples. Of the 284 sequences identified as Leishmania, 261 (91.9%) were L. tarentolae, 18 (6.3%) were L. donovani-complex parasites, 3 (1.1%) were L. tropica, and 2 were similar to both L. major and L. tropica. Minimum field infection rates were 0.09% for L. donovani-complex parasites, 0.02% for L. tropica, and 0.01% for the L. major/tropica-like parasite. Subsequent sequencing of a 600-bp region of the "Hyper" gene of 12 of the L. donovani-complex parasites showed that all 12 parasites were L. infantum. These data suggest that L. infantum was the primary leishmanial threat to U.S. military personnel deployed to Tallil Air Base. The implications of these findings are discussed.

Deployable, field-sustainable, reverse transcription-polymerase chain reaction assays for rapid screening and serotype identification of dengue virus in mosquitoes.

Dengue virus universal and serotype 1 to 4 fluorogenic probe hydrolysis, reverse transcription (RT)-polymerase chain reaction (PCR) assays and positive-control RNA template were freeze-dried in a thermally stable, hydrolytic enzyme-resistant format and deployed for testing in a dengue fever-endemic region of Thailand. The study site presented austere testing conditions. Field-collected Aedes aegypti mosquitoes spiked with inoculated A. aegypti mosquitoes and individual and pooled, field-collected, A. aegypti, A. albopictus, and Culex tritaeniorhynchus mosquitoes were used for RT-PCR assay evaluations. For dengue virus-inoculated A. aegypti mosquitoes and spiked samples, in vitro sensitivity and specificity results for all five assays were concordant with indirect fluorescent antibody assay results. A single pool of field-collected, female, A. aegypti mosquitoes was identified as dengue virus positive. Cross-reactivity was not observed across heterologous serotypes, mosquito vectors, or human DNA. The limit of detection was >7 to < or =70 genomic equivalents. Sample processing and analysis required <2 hours. These results show promise of field-formatted RT-PCR reagents for rapid, sensitive, specific dengue virus screening and serotype identification in mosquitoes under field-deployed conditions.

Impact of phlebotomine sand flies on U.S. Military operations at Tallil Air Base, Iraq: 2. Temporal and geographic distribution of sand flies.

CDC miniature light traps were used to evaluate the general biology of phlebotomine sand flies from April 2003 to November 2004 at Tallil Air Base, Iraq. Factors evaluated include species diversity and temporal (daily and seasonal) and geographic distribution of the sand flies. In addition, the abundance of sand flies inside and outside tents and buildings was observed. In total, 61,630 sand flies were collected during 1,174 trap nights (mean 52 per trap, range 0-1,161), with 90% of traps containing sand flies. Sand fly numbers were low in April, rose through May, were highest from mid-June to early September, and dropped rapidly in late September and October. More than 70% of the sand flies were female, and of these sand flies, 8% contained visible blood. Phlebotomus alexandri Sinton, Phlebotomus papatasi Scopoli, Phlebotomus sergenti Parrot, and Sergentomyia spp. accounted for 30, 24, 1, and 45% of the sand flies that were identified, respectively. P. alexandri was more abundant earlier in the season (April and May) than P. papatasi, whereas P. papatasi predominated later in the season (August and September). Studies on the nocturnal activity of sand flies indicated that they were most active early in the evening during the cooler months, whereas they were more active in the middle of the night during the hotter months. Light traps placed inside tents with and without air conditioners collected 83 and 70% fewer sand flies, respectively, than did light traps placed outside the tents. The implications of these findings to Leishmania transmission in the vicinity of Tallil Air Base are discussed.

Impact of phlebotomine sand flies on U.S. Military operations at Tallil Air Base, Iraq: 1. background, military situation, and development of a "Leishmaniasis Control Program".

One of the most significant modern day efforts to prevent and control an arthropod-borne disease during a military deployment occurred when a team of U.S. military entomologists led efforts to characterize, prevent, and control leishmaniasis at Tallil Air Base (TAB), Iraq, during Operation Iraqi Freedom. Soon after arriving at TAB on 22 March 2003, military entomologists determined that 1) high numbers of sand flies were present at TAB, 2) individual soldiers were receiving many sand fly bites in a single night, and 3) Leishmania parasites were present in 1.5% of the female sand flies as determined using a real-time (fluorogenic) Leishmania-generic polymerase chain reaction assay. The rapid determination that leishmaniasis was a specific threat in this area allowed for the establishment of a comprehensive Leishmaniasis Control Program (LCP) over 5 mo before the first case of leishmaniasis was confirmed in a U.S. soldier deployed to Iraq. The LCP had four components: 1) risk assessment, 2) enhancement of use of personal protective measures by all personnel at TAB, 3) vector and reservoir control, and 4) education of military personnel about sand flies and leishmaniasis. The establishment of the LCP at TAB before the onset of any human disease conclusively demonstrated that entomologists can play a critical role during military deployments.