Evaluation of surveillance devices for monitoring Aedes aegypti in an urban area of northeastern Peru

In this study, we assessed the efficacy of the American Biophysics Corporation Standard Professional (ABC-PRO) light trap, the Omni-Directional Fay-Prince trap (with and without CO2), and the Centers for Disease Control and Prevention Wilton trap as a means of evaluating populations of adult Aedes aegypti in an urban area of northeastern Peru. Efficacies of collections from each of the trap types were compared to backpack-aspirator collections and human-landing collections. Collections were conducted twice daily, 3 days per week, for 27 wk from July 2001 to July 2002. Backpack-aspirator collections yielded significantly more mosquitoes (1,764) than any of the other collecting methods with a mean of 21.80 mosquitoes collected per sampling period. This method was less specific for Ae. aegypti than were human-landing collections because only 28.3% of mosquitoes collected with backpack aspirators were Ae. aegypti. Human-landing collections yielded only 23% (554/2,411) of the total mosquitoes collected. However, more than 80% (445/554) of the mosquitoes collected by this method were Ae. aegypti. None of the trapping devices evaluated collected mosquitoes, specifically Ae. aegypti, as effectively as backpack-aspirator or human-landing collections. The ABC-PRO trap, which was the most effective device in collecting mosquitoes, particularly Ae. aegypti, collected less than 2% of the total mosquitoes (mean of 0.12 mosquitoes/sampling period), and less than 3% of total Ae. aegypti (mean of 0.11 Ae. aegypti/sampling period). We conclude that none of the trap devices evaluated in this study is an acceptable alternative to backpack-aspirator or human-landing collections for monitoring populations of adult Ae. aegypti in Peru.     

Genetic relationships among populations of Aedes aegypti in Taiwan by using phenotypic and random amplified DNA-polymerase chain reaction markers

An analysis of gene flow was conducted among collections of Aedes aegypti from 7 localities along the southwestern and southeastern coasts in Taiwan. Markers include 7 types of scaling patterns and 23 random amplified polymorphic DNA (RAPD) loci amplified by the polymerase chain reaction. Differences in scaling pattern and in the frequencies of RAPD markers were detected among populations and cluster analyses revealed 2 main groups on each side of the Central Mountain Range. Regression analysis of geographic distances and pairwise F(ST) values estimated from RAPD markers showed that southwestern populations are isolated by distance and that populations within 15 km are panmictic. This is a shorter distance than detected among collections of Ae. aegypti in similar published studies from Mexico and Argentina.     

Field efficacy of the BG-Sentinel compared with CDC Backpack Aspirators and CO2-baited EVS traps for collection of adult Aedes aegypti in Cairns, Queensland, Australia

In this study, we compared the efficacy of the newly available BG-Sentinel with an established "gold standard,", the CDC Backpack Aspirator, and a CO2-baited EVS trap for the collection of Aedes aegypti (L.) in Cairns, Australia. BG-Sentinels collected significantly more (P = 0.017) female Ae. aegypti (mean per collection, 1.92 +/- 0.39) than both the CDC Backpack Aspirator (1.00 +/- 0.35) and the EVS trap (0.71 +/- 0.27). Male-only and combined male-female Ae. aegypti collections for th BG-Sentinel and the CDC Backpack Aspirator were also greater than EVS trap collections. The CDC Backpack Aspirator and the BG-Sentinel captured proportionally fewer females compared with the EVS trap. The BG-Sentinel was the most Ae. aegypti specific collection method. The CDC Backpack Aspirator collected proportionally more bloodfed Ae. aegypti than the other methods, which collected a greater proportion of nullipars. The data presented here will aid researchers in deciding what Ae. aegypti sampling device best suits their needs. BG-Sentinels and CDC Backpack Aspirators should be considered as alternatives to human-bait collections for Ae. aegypti sampling.     

Optimizing ovitrap use for Aedes aegypti in Cairns, Queensland, Australia: effects of some abiotic factors on field efficacy

Insecticide-treated lethal ovitraps are used for control of the dengue vector Aedes aegypti in north Queensland, Australia. In an effort to optimize their use, the influence of deployment height, premise shading, and protection from wind on trap efficacy was assessed in field experiments. Sticky ovitraps were used as a proxy for lethal ovitraps because they provide a direct measure of adult visitation rates. Sticky ovitraps deployed at ground level for 1 wk captured significantly more female Ae. aegypti (mean +/- SE, 1.7 +/- 0.4) than those set at 1.75-m elevation (1.0 +/- 0.3). Setting traps on the leeward side of houses significantly improved collections during a dry season experiment but not in the wet season. Traps set at lightly or heavily shaded premises performed equally well. To determine the optimum number of ovitraps to set per premise, five treatments making up different numbers of traps (1, 2, 4, 6, or 8) were trialled in a Latin square experimental design. Female Ae. aegypti collections increased as more traps were deployed, although mean collections by using 4 (2.6 +/- 0.6), 6 (2.4 +/- 0.5), or 8 traps (4.8 +/- 1.3) could not be separated statistically, suggesting that 4 traps was the optimum number for routine deployment.     

Laboratory and field assessment of some kairomone blends for host-seeking Aedes aegypti

Using laboratory Y-tube olfactometers, the attractiveness of lactic acid and 2 kairomone blends from the United States Department of Agriculture (USDA) and BioGents GmbH (BG) was assessed for attractiveness to Aedes aegypti. Four geographically disparate populations were assessed: North Queensland Australia (NQA), Florida USA, Minas Gerais Brazil (MGB), and Singapore. In descending order, populations were attracted to USDA, BG blends, and lactic acid. MGB was poorly attracted to lactic acid alone. The blends were less attractive than human odor. Proprietary blends were modified, and their attractiveness was assessed to find the optimum attractive mixture for NQA. Adding acetone to BG, and ammonia and caproic acid to USDA, improved attractiveness in the laboratory. Field attractiveness was assessed by coupling the blends with a newly developed BG-Sentinel Ae. aegypti trap. Trials were carried out using the BG blend, BG blend plus acetone, USDA blend, USDA blend plus ammonia and caproic acid, and a control trap with no kairomones. The traps were highly effective, with mean 24-h collections up to 11.15 Ae. aegypti per trap, and this species made up 91.7% of collections. However, the effectiveness of the unbaited control trap indicated that the BG-Sentinel has visual attractive properties for Ae. aegypti and that the kairomone lures added little to trap performance in NQA.     

Genetic differentiation of Aedes aegypti mainland and island populations from southern Thailand

Isozymes of 5 wild-caught collections of Aedes aegypti were compared by using starch gel electrophoresis. All collections were collected from Surat-Thanee Province, southern Thailand, an area considered to be a hyperendemic zone for dengue virus. One collection was from Donsak Harbor, whereas the other 4 collections were from 4 districts of Samui Island. The percent polymorphic loci (24.2-33%) in the 4 island collections was lower than in the mainland collection (36.4%). This study revealed a large effective migration rate among all 5 collections. No fixed differences were detected. No significant differentiation was found among the 5 collections from Surat-Thanee Province.     

The association of Aedes aegypti and Ae. albopictus in Allende, Nuevo León, Mexico

The recent appearance of Aedes Stegomyia albopictus (Skuse) in Nuevo León (NL) worries health officials. It is a vector of dengue fever in Asia and is more resistant to lower temperatures than Ae. aegypti. The objective of this study was to learn about some ecological parameters of Ae. albopictus and their association with Ae. aegypti, and other culicids in Allende, NL, Mexico, during 1999. Allende is a small town close to metropolitan Monterrey, which has 4 million inhabitants. The design was random with monthly sampling of 175 ovitraps. Chi-square analyses were performed with data of presence, absence, frequency, and relative abundances. During the study, the species Culex tarsalis (Coquillet), Cx. thriambus (Dyar), Cx. pipiens (Linnaeus), Cx. coronator (Dyar and Knab), Ae. albopictus, Ae. aegypti, Toxorhynchites rutilus (Coquillet), and Ae. triseriatus (Say) were found. April is the month for large numbers of mosquito species. September had the highest populations in positive ovitraps (66.67%), followed by July (63.27% of traps). Aedes aegypti was the most abundant (65.13%), followed by Ae. albopictus (19.71%). Both Ae. albopictus and Ae. aegypti were found from April until December. Aedes aegypti was more abundant than Ae. albopictus, except in August, when they were similar (chi2 = 0.197, P < 0.05). We found significant association between the presence of both species for every study month (chi2 = 9.837, P < 0.05), with a contingency coefficient of 0.247. September and November were the months having the most mosquitoes in this association. Only considering Ae. albopictus, more were found in ovitraps in July (34.6%), followed by September (33.3%). However, its presence was not significant throughout the year. Of 2 zones, in town and at the river, prevalence indicated that Ae. albopictus preferred the river. This mosquito is in its establishment phase in this area and requires further studies.     

A comparison of seven traps used for collection of Aedes albopictus and Aedes aegypti originating from a large tire repository in Harris County (Houston), Texas

Among 7 traps tested, significantly higher (P < 0.01) mean numbers of Aedes albopictus (269) and Aedes aegypti (55) females were collected within the Mosquito Magnet Liberty trap compared with the remaining traps. The second highest mean captures for both species were obtained from omnidirectional Fay-Prince (77 Ae. albopictus) and Dragonfly (13 Ae. aegypti) traps, which were not significantly different (P > 0.01) from an experimental moving-target trap that produced mean captures of 40 Ae. albopictus and 6 Ae. aegypti (alpha = 0.01). In terms of Ae. albopictus capture, no significant differences (P > 0.01) existed between Dragonfly, CDC without light (CDC -), and CDC with light (CDC +) captures, which were significantly different (P < 0.01) from Mosquito Deleto. No statistical significance existed between moving-target, omnidirectional, CDC +, CDC -, and Mosquito Deleto traps in terms of Ae. aegypti capture (P > 0.01), individual trap positions, or number of Ae. albopictus and Ae. aegypti females collected throughout the 21-day test (P > 0.05). Mosquito Magnet Liberty collected 7,208 Ae. albopictus, 1467 Ae. aegypti, and 13 other species representing 5 genera, which comprised the largest total (9662) and percentage (62.5%) of mosquitoes collected by all traps combined. Omnidirectional and moving-target traps captured 1941 and 1050 Ae. albopictus, 138 and 220 Ae. aegypti, and 2171 (14.0%) and 1397 (9.0%) of the total mosquitoes captured by all traps, with 8 and 10 species representing 5 genera, respectively, included in these collections. The Dragonfly captured 476 Ae. albopictus, 376 Ae. aegypti, and 1008 total specimens (6.5%) representing 8 species and 4 genera in these collections. CDC + and CDC - traps collected nearly identical numbers of Ae. albopictus (431, 450) and Ae. aegypti (71, 71) with 537 (3.4%) and 551 (3.5%) total specimens, respectively. Eight species representing 5 genera were captured from CDC +, whereas CDC - captured 6 species representing 4 genera. Mosquito Deleto captured 118 mosquitoes, including 19 Ae. albopictus and 62 Ae. aegypti females (0.7%), with 6 species representing 4 genera. Battery-powered traps with contrasting color schemes and movement worked considerably better than stationary CDC miniatures without color or movement. Omnidirectional Fay-Prince and moving-target traps without octenol captured Ae. albopictus and Ae. aegypti females as frequently as some commercial traps. Additionally, costs incurred per mosquito trapped, future trap design, and important consumer-centered issues are briefly discussed.     

Space treatments of insecticide for control of dengue virus vector Aedes aegypti in southern Mexico. I. Baseline penetration trials in open field and houses

We studied the efficacy of space ultra-low volume treatments of 3 insecticides for the control of the dengue virus vector Aedes aegypti in southern Mexico. Insecticides tested were permethrin (Aqua-Reslin Super), d-phenothrin (Anvil), and cyfluthrin (Solfac), applied at rates of 10.87, 7.68, and 2 g/ha, respectively, by using London Fog, HP910-PHXL, or Micro-Gen pumps mounted on vehicles. Studies included 1) open field penetration tests and 2) house penetration tests. Open field tests indicated that Anvil and Solfac were more effective than Aqua-Reslin Super. In house tests, Anvil yielded the highest mosquito mortalities (>/=88%) of the three insecticides in the front porch, living room, bedroom, and backyard. Therefore, Anvil proved to be better than other insecticides evaluated to control Ae. aegypti in Chiapas, Mexico.     

Detection of dengue viruses in field-caught Aedes aegypti (Diptera: Culicidae) in Maracay, Aragua state, Venezuela by type-specific polymerase chain reaction.

Virological surveillance of dengue viruses in Aedes aegypti populations constitutes a powerful tool for early prediction of dengue outbreaks. We have standardized a protocol for viral RNA extraction from individual and pools of mosquitoes that permits a sensitive detection of dengue virus without RNA degradation or PCR inhibition when we apply a semi-nested RT-PCR. The limit of detection for each dengue serotype was 0.1 PFU. In a prospective field study conducted from November 2000 to December 2001, adult female A. aegypti mosquitoes from several municipalities with high dengue transmission in Maracay, Aragua State, Venezuela were collected and screened for dengue viruses using RT-PCR. We analyzed a total of 296 A. aegypti pools (1,632 mosquitoes); of these, 154 pools (469 mosquitoes) were collected from houses with persons with clinical diagnosis of dengue (dengue houses), and 142 pools (1,163 mosquitoes) from adjacent residences (neighbour houses). From the dengue houses, eight mosquito pools (5.2%) were positive for DENV-1 (0.7%), DENV-3 (3.2%) and DENV-4 (1.3%) viruses. From the neighbour houses, 18 mosquito pools (12.7%) were positive for DENV-3 (12%) and DENV-4 (0.7%) viruses. From these 26 RT-PCR positive mosquito pools (containing 1-25 mosquitoes each), 22 pools (84.6%) were positive for DENV-3. The most prevalent serotype in the 2001 dengue outbreak was also DENV-3. The minimum infection rate in both A. aegypti collections, from dengue houses and neighbour houses was 17 and 15 per 1,000, respectively. The relevance of these results for dengue surveillance is discussed.     

Evaluation of the efficacy of lambda-cyhalothrin applied by three spray application methods for emergency control of Aedes aegypti in Costa Rica

An extended duration formulation of lambda-cyhalothrin (Icon CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new hand-held sprayer (Twin-Fog) or as a low-volume spray (LV) from a backpack mist blower against Aedes aegypti was evaluated in Costa Rica. Spray applications were made at the front door for 1 min or to each room for 15 sec for the ULV and LV, and thermal fog applications were made to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and mosquito collections from within houses using hand-held, battery-powered aspirators. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for the ULV and thermal fog spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 3 wk of significant control (P < 0.05) based on adult Ae. aegypti house collections.     

Comparison of ground and aerial ultra-low volume applications of malathion against Aedes aegypti in Santo Domingo, Dominican Republic

Efficacy of ground and aerial ultra-low volume (ULV) applications of 91% malathion at 438 ml/ha against Aedes aegypti in the Dominican Republic was evaluated using indoor collections, oviposition trapping and adult sentinel mortality rates. Ground compared to aerial ULV applications in this study were found to have a greater effect on Ae. aegypti when measured by the described sampling techniques. Neither application method provided the level of Ae. aegypti suppression believed necessary for control in the event of a dengue virus epidemic.     

Detection of CYP1A1 gene polymorphism using designed RFLP and distributions of CYP1A1 genotypes in Japanese

Isoleucine (Ile)-valine (Val) polymorphism, which is caused by a point mutation from A to G in exon 7, is reported to be associated with an elevated risk of lung cancer among Japanese. Because CYP1A1 catalyzes bioactivation of environmental procarcinogens, such as benzo[a]pyrene, it is very important to study the clinical meaning of Ile-Val polymorphism using an epidemiological study. In an epidemiological study, easy, economical, rapid and reliable identification of the CYP1A1 genotype is necessary. The present study shows that the new method, designed restriction fragment length polymorphism (designed RFLP), can detect Ile-Val polymorphism of CYP1A1 The Ile-Val polymorphism detected using this new method was consistent with that found by the allele-specific PCR amplifications (ASA) method in six cases tested. This new method detected Ile-Va1 polymorphism of CYP1A1 using 240 healthy Japanese who lived in the northern Kyusyu region. The frequency of the genotypes was as follows: Ile/Ile, 159 (66.2%); Ile/Val, 65 (27.1%); Val/Val, 16 (6.7%). The frequency of the Ile gene was 0.798 and that of the Val gene, 0.202. There was no difference in Ile-Val polymorphism based on sex or age. Racial differences influenced the distribution of this polymorphism, but Japanese regional differences did not. Since this new method, designed RFLP, is rapid, reliable and suitable for large-scale screening of polymorphisms, it may be used routinely to detect Ile-Val polymorphism of CYP1A1 Furthermore, it will help to evaluate the relationship between CYP1A1 polymorphism and individual sensitivity to xenobiotics that may affect the incidence of lung cancer.     

Laboratory evaluation of susceptibility of natural subpopulations of Aedes aegypti larvae to temephos

Aedes aegypti showed the ability to develop resistance to different insecticides, including temephos, the most widely used larvicide. The objectives of this work were to 1) determine the resistance value of 4 natural subpopulations of Ae. aegypti, identified by their different haplotypes, to the insecticide temephos "Abate 1G (1%)"; 2) determine the lethal concentration (LC)50 and LC90 values by using the Rockefeller strain as control; and 3) estimate the resistance ratios. Mosquito samples were collected in Catamarca, Córdoba, and Posadas (Argentina) and in Yacuiba (Bolivia). Six insecticide concentrations were tested. The Rockefeller strain and the Posadas sample showed susceptibility to the diagnostic concentration (0.012 mg/liter), whereas the mortality in Catamarca was 87%. In the Yacuiba and Córdoba collections, mortality was 74% and 75%, respectively, indicating resistance. These results were coincident with those of the Probit analysis from which the highest resistance ratios were estimated for the last 2 subpopulations (5.2 and 4.9, respectively). Before this study, no information was available about the existence of resistance in natural populations of Ae. aegypti in the studied area.     

育龄期21-羟化酶缺乏症误诊为多囊卵巢综合征二例并文献复习

21-羟化酶缺乏症（21-hydroxylase deficiency,21-OHD）是先天性肾上腺皮质增生症最常见的一种,部分21-OHD患者的临床症状不典型,容易漏诊、误诊。报道2例因月经紊乱、不孕及高雄激素血症就诊而误诊为多囊卵巢综合征（polycystic ovary syndrome,PCOS）的21-OHD患者的临床资料,基因测序显示1例携带c.374G>A(p.Arg125His)和c.518T>A(p.Ile173Asn)杂合错义突变,明确了突变基因来自患者父母;另1例携带c.518T>A(p.Ile173Asn)纯合错义突变,因亲属未检测故未明确突变来源。给予地塞米松口服治疗,2例患者均恢复规律月经,高雄激素血症临床症状得到改善,其中1例成功妊娠并分娩。育龄期女性如以不孕、高雄激素血症表现就诊,诊断为PCOS而治疗效果不佳时,应考虑21-OHD,进一步行17-羟孕酮测定、促肾上腺皮质激素兴奋试验和基因突变检测可明确诊断。     

Baseline data on Aedes aegypti populations in Santo Domingo, Dominican Republic

Baseline field studies were conducted from April 1987 to July 1988 on Aedes aegypti in Santo Domingo, an endemic area for dengue fever. Premise, container and Breteau indices were measured in one treated area and 2 nearby control areas. These indices averaged 69.6, 46.3 and 142.1, respectively. The principal larval habitats of Ae. aegypti were 208-liter (55-gal) concrete-lined drums. The estimated daily adult production was approximately 60 per house. Adult mosquito populations were monitored using oviposition traps and by sweep net collections. There was no correlation between adult abundance and the larval indices. Monitoring the natural adult densities was more efficient for evaluating the impact of ULV malathion application than the use of standard bioassay procedures.     

Evaluation of the efficacy of lambda-cyhalothrin applied as ultra-low volume and thermal fog for emergency control of Aedes aegypti in Honduras.

An extended-duration formulation of lambda-cyhalothrin (Demand CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new handheld sprayer (Terrier) against Aedes aegypti was evaluated in Honduras. Spray applications were made at the front door for 1 min or to each room for 15 sec, both for the ULV and thermal fog applications to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and collection of mosquitoes within houses with a backpack power aspirator. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for all spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 4 wk of significant control (P < 0.01) based on adult Ae. aegypti house collections.     

Invasion of cemeteries in Florida by Aedes albopictus.

Aedes albopictus has been found in 53 of the 67 Florida counties. The initial discoveries in 11 of these counties were made in cemeteries. At several locations, Ae. albopictus became well-established in cemeteries before appearing in nearby accumulations of waste tires. The recycling of plastic floral baskets may be aiding the spread of Ae. albopictus. Mosquitoes were commonly found in all types of flower-holding containers in cemeteries, except bronze vases. In the laboratory, most Aedes aegypti eggs laid in bronze vases hatched, but larvae subsequently died. The spread of Ae. albopictus in cemeteries seems to occur at the expense of Ae. aegypti populations. At one cemetery immature Ae. albopictus and Ae. aegypti were found in about 70% of the Aedes-positive containers at the start of a monitoring program. In subsequent collections from this site, Ae. albopictus was found in nearly all Aedes-positive containers, whereas there was a progressive decrease in containers with Ae. aegypti. This trend did not appear to be the result of any seasonal pattern because in a nearby cemetery where Ae. albopictus was absent, Ae. aegypti did not show a similar decline. Limiting flower-holding containers to those with drain holes or to bronze vases would greatly limit mosquito production.     

New tools for surveillance of adult yellow fever mosquitoes: comparison of trap catches with human landing rates in an urban environment

A novel mosquito trapping system, the BG-Sentinel trap, was evaluated as a monitoring tool for adult Aedes aegypti in field tests in the city of Belo Horizonte, Brazil. Human landing/biting collections, a gas-powered CO2 trap, and a Fay-Prince trap with only visual cues serving as references to evaluate the efficacy of the new trap. The BG-Sentinel is a simple suction trap that uses upward-directed air currents as well as visual cues to attract mosquitoes. The trap was tested with a new dispenser system (BG-Lure) that releases artificial human skin odors and needs no CO2. In comparison with the two other traps, the BG-Sentinel caught significantly more Ae. aegypti. Although human landing rates were the highest, there was no significant difference between human landing rates and the capture rates of the BG-Sentinel trap. The finding indicates that the trap can be considered as an acceptable alternative to human landing/biting collections in the surveillance of adult host-seeking dengue vectors. The addition of BG-Lure to the gas-powered CO2 trap greatly increased its efficacy. This combination, however, was not significantly more effective than the BG-Sentinel without CO2. In a 6-month comparison between the BG-Sentinel and a sticky ovitrap for gravid females, the BG-Sentinel proved to be a far more efficient and sensitive tool to measure the density of Ae. aegypti populations.     

Introduction of different lineages of Aedes aegypti in Argentina

Based on sequence analysis of the mitochondrial gene ND4, we determined the presence in Argentina of 3 haplotypes representing different Aedes (Stegomyia) aegypti lineages previously identified in other countries of the Americas, Africa, and Asia. Haplotype 17, the most frequent in Argentina, was previously detected in Brazil. Haplotype 7, restricted in our study to the northwest of Argentina and Bolivia, was formerly found in low frequency in the USA, Brazil, Mexico, and Senegal. Also haplotype 11, belonging to a different haplogroup than the other two, was observed in the present study; it had been reported before in Africa and Asia, but not in the Americas. The coexistence of haplotypes belonging to divergent haplogroups supports the hypothesis of multiple introductions of the species in Argentina.