Jorge R. Arias

FIELD COMPARISON OF NOVEL AND GOLD STANDARD TRAPS FOR COLLECTING AEDES ALBOPICTUS IN NORTHERN VIRGINIA

ABSTRACT Aedes albopictus is a potential West Nile virus bridge vector in Northern Virginia; however, information regarding its virus transmission dynamics is limited, as this species is not readily collected in existing traps. This study used 5 replicates of a 5 × 5 Latin square to evaluate the efficiency and effectiveness of 2 novel host-seeking mosquito traps (the BG-SentinelTM and the Collapsible Mosquito Trap (CMT-20TM) in collecting Ae. albopictus, relative to a carbon dioxide (CO2)–baited Centers for Disease Control and Prevention (CDC) miniature light trap. When used with CO2, the BG-Sentinel (with BG-Lure) collected 33 times more female Ae. albopictus per 24-h trapping period than did the CO2-baited CDC light trap. Without CO2, the BG-Sentinel (with BG-Lure) still collected over 6 times as many female Ae. albopictus as the CO2-baited CDC trap. Both configurations of the BG-Sentinel were significantly more effective than the other traps. The BG-Sentinel was also significantly more efficient in collecting Ae. albopictus and collected a high proportion of this species, both with CO2 and without CO2. The CMT-20 (with SkinLureTM) collected significantly more Ae. albopictus when used with CO2 than without CO2, but did not collect significantly more Ae. albopictus than the CO2-baited CDC light trap. The proportion of Ae. albopictus collected in the CMT-20 with CO2 and without CO2 did not differ significantly from the proportion of Ae. albopictus collected in the CDC trap.

Interspecific Larval Competition Between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in Northern Virginia

Abstract Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus.

The Zumba™ Mosquito Trap and Bg-Sentinel™ Trap: Novel Surveillance Tools for Host-Seeking Mosquitoes

Abstract In a periurban habitat located in Northern Virginia, this study used 13 replicates of a 4 × 4 Latin square to evaluate the efficacy of 2 novel mosquito traps, the Zumba™ mosquito trap and the BG-Sentinel™ trap, against 2 existing host-seeking mosquito traps [Centers for Disease Control and Prevention (CDC) miniature light and CDC Fay-Prince]. All traps were baited with the BG-Lure® and CO2. The Zumba trap, baited with the BG-Lure and CO2 (Zumba trap combination) was the most productive and diverse trap, averaging 35.51 mosquitoes and 4.16 species per trapping period. It collected 19 times as many Culex pipiens/restuans, which will be referred to as Cx. pip/res, as the other traps and was the only trap to collect West Nile virus (WNV)-infected host-seeking Cx. pip/res in the study area. The BG-Sentinel trap, baited with the BG-Lure and CO2 (BG-Sentinel trap combination) collected 7 times as many female Aedes albopictus as the CDC miniature light or Fay-Prince traps. The Zumba trap combination collected 4 times as many female Ae. albopictus as the CDC miniature light or Fay-Prince traps. The WNV infection rate of Cx. pip/res and Ae. albopictus collected by the Zumba trap combination was consistently greater than the infection rates for these species collected in the Fairfax County programs routine CDC miniature light traps and comparable to the infection rate found in the Cx. pip/res collected in the programs routine gravid traps. Both the Zumba and BG-Sentinel trap combinations collected WNV-infected Ae. albopictus in the study area.

Distinct variation in vector competence among nine field populations of Aedes aegypti from a Brazilian dengue-endemic risk city

BackgroundIn Brazil, dengue epidemics erupt sporadically throughout the country and it is unclear if outbreaks may initiate a sustainable transmission cycle. There are few studies evaluating the ability of Brazilian Aedes aegypti populations to transmit dengue virus (DENV). The aim of this study was to compare DENV susceptibility of field-captured Ae. aegypti populations from nine distinct geographic areas of the city of Belo Horizonte in 2009 and 2011. Infection Rate (IR), Vector Competence (VC) and Disseminated Infection Rate (DIR) were determined.MethodsAedes aegypti eggs from each region were collected and reared separately in an insectary. Adult females were experimentally infected with DENV-2 and the virus was detected by qPCR in body and head samples. Data were analyzed with the Statistical Package for the Social Sciences version 17.ResultsIR varied from 40.0% to 82.5% in 2009 and 60.0% to 100.0% in 2011. VC ranged from 25.0% to 77.5% in 2009 and 25.0% to 80.0% in 2011. DIR oscillated from 68.7% to 100.0% in 2009 and 38.4% to 86.8 in 2011. When the results were evaluated by a logistic model using IR as covariate, North, Barreiro, South-Central and Venda Nova showed the strongest association in 2009. In 2011, a similar association was observed for South-Central, Venda Nova, West and Northeast regions. Using VC as covariate, South-Central and Venda Nova showed the most relevant association in 2009. In 2011, South-Central, Venda Nova and Barreiro presented the greatest revelation associations. When DIR data were analyzed by logistic regression models, Pampulha, South-Central, Venda Nova, West, Northeast and East (2009) as well as South-Central, Venda Nova and West (2011) were the districts showing the strongest associations.ConclusionsWe conclude that Ae. aegypti populations from Belo Horizonte exhibit wide variation in vector competence to transmit dengue. Therefore, vector control strategies should be adapted to the available data for each region. Further analysis should be conducted to better understand the reasons for this large variability in vector competence and how these parameters correlate with epidemiological findings in subsequent years.

Community ecology of container mosquitoes (Diptera: Culicidae) in Virginia following invasion by Aedes japonicus.

ABSTRACT The success of an invasive species in a new region depends on its interactions with ecologically similar resident species. Invasions by disease vector mosquitoes are important as they may have ecological and epidemiological consequences. Potential interactions of a recent invasive mosquito, Aedes japonicus Theobald, with resident species in Virginia were evaluated by sampling larvae from containers and trapping adults. Distinct species compositions were observed for artificial containers and rock pools, with Ae. albopictus most abundant in the former and Ae. japonicus in the latter. However, these two species were found to co-occur in 21.2% of containers sampled. Among the six mosquito species most common in containers from May through September, 2006, only interspecific associations of Ae. japonicus with Aedes albopictus (Skuse) and Aedes triseriatus (Say) were significant, and both were negative. In addition to differences in habitat preference, mean crowding estimates suggest that interspecific repulsion may contribute to the significant negative associations observed between these species. High relative abundances of late instars and pupae of Ae. japonicus seem to provide this species with a mechanism of evading competition with Ae. albopictus, facilitating their coexistence in artificial containers. Although annual fluctuations were observed, trends in adult populations over a 6-yr period provide no evidence of declines. In summary, this survey of diverse container types and all life stages provided only limited evidence for competitive displacements or reductions of resident container species by Ae. japonicus, as observed elsewhere in its invasive range.

Spotted Fever Group Rickettsiae in Multiple Hard Tick Species from Fairfax County, Virginia

Spotted fever group rickettsiosis (SFGR) is a potentially fatal disease that has displayed increasing incidence in the United States in recent years. The most well-known and severe type of this disease is Rocky Mountain spotted fever, but there are other mild forms that occur. Recently, human infection with Rickettsia parkeri has been reported and linked with the tick Amblyomma maculatum. In 2010, a population of R. parkeri-infected A. maculatum was discovered in Fairfax County, Virginia, leading to increased surveillance of tick species. In this study, we report the presence of R. parkeri in Rhipicephalus sanguineus, Haemaphysalis leporispalustris, and Dermacentor variabilis in Fairfax County. R. parkeri was discovered in two Rh. sanguineus, one H. leporispalustris, and 17 D. variabilis. These findings suggest that spillover infections of R. parkeri may be occurring in tick species not typically associated with this pathogen; however, vector competence studies need to be conducted to determine if these tick species can serve as potential vectors for human SFGR.

Detection of Rickettsia massiliae in Rhipicephalus sanguineus from the Eastern United States

We report the first evidence of Rickettsia massiliae in the brown dog tick, Rhipicephalus sanguineus, from the East Coast of the United States. As part of routine pathogen surveillance, DNA samples from ixodid ticks were tested for spotted fever group rickettsiae by nested PCR. A R. massiliae-positive tick was collected off a beagle mix recently rescued from North Carolina. Infection was confirmed by partial sequence analysis of the htrA, gltA, ompB, ompA, and sca4 genes, which had 100% identity to a R. massiliae isolate from Arizona.

The Efficacy of the BG-Sentinel™ CO2 Nozzle in Collecting Host-Seeking Mosquitoes in Fairfax County, Virginia

Abstract This study determined whether the addition of a CO2 nozzle made specifically for the BG-Sentinel™ trap increased the efficacy of collecting host-seeking mosquitoes, particularly Aedes albopictus and Culex spp., which includes Cx. pipiens, Cx. restuans, and occasionally Cx. salinarius in Fairfax County, VA. Twenty BG-Sentinel traps were incorporated into the Fairfax County West Nile virus (WNV) surveillance program: 10 traps were randomly selected each week to have the nozzle attached, and the remaining 10 traps were without the nozzle. The BG-Sentinel traps collected 20 mosquito species with the nozzle and 19 mosquito species without the nozzle. The traps with the nozzle collected 46.58 (SE 3.236) mosquitoes per 24-h trap-period and the traps without the nozzle collected 46.73 (SE 2.942) mosquitoes per 24-h trap-period, and no significant difference (P > 0.05) was found. There was no significant difference (P > 0.05) in the collection of Aedes albopictus, Culex spp., Anopheles punctipennis, Ae. vexans, and Aedes triseriatus between the traps with or without the nozzle. Other mosquito species were collected in low numbers and statistical analysis was not performed. Both the traps with and without the nozzle collected WNV-infected Aedes albopictus and Culex spp.

Diel and seasonal activity and trapping of ticks (Acari: Ixodidae) in Northern Virginia, U.S.A.

Abstract The effectiveness of various trap intervals (two, four, six, eight, sixteen and twenty-four hours) for collecting ticks was compared for different times of the day throughout a one-year period. A total of 9,508 ticks [Amblyomma americanum (L.), Amblyomma maculatum Koch, Dermacentor variabilis (Say), Ixodes scapularisSay; (Acari: Ixodidae)] were collected on carbon dioxide baited traps. The eight-hour (8:00–16:00 h) trapping interval caught the most ticks. Amblyomma americanum nymphs and adults as well as I. scapularis nymphs were most common in May, while I. scapularis adults were collected most often during the winter months. PeakA. americanum activity shifted from midday to morning during the warmest months of the year.