Harry M. Savage

Host Feeding Patterns of Established and Potential Mosquito Vectors of West Nile Virus in the Eastern United States

An important variable in determining the vectorial capacity of mosquito species for arthropod-borne infections is the degree of contact of the vector and the vertebrate reservoir. This parameter can be estimated by examining the host-feeding habits of vectors. Serological and polymerase chain reaction based methods have been used to study the host-feedings patterns of 21 mosquito species from New York, New Jersey, and Tennessee, 19 of which previously have been found infected with West Nile virus. Mammalophilic mosquito species in New Jersey and New York fed primarily upon white-tailed deer, while those from Memphis, Tennessee, fed mainly upon domestic dogs. A total of 24 different avian host species were detected among the avian-derived blood meals. American Robin, Northern Cardinal, Northern Mockingbird, Tufted Titmouse, and Brown-headed Cowbird were common avian hosts, while blood meals derived from the American Crow were relatively rare. Although the majority of common host species were potentially among the most abundant birds at each location, the proportion of blood meals from the most commonly fed upon avian species was greater than was predicted based upon the likely abundance of these species alone. These findings suggest that vector species for West Nile virus may preferentially feed upon certain avian hosts.

Host-Feeding Habits of Culex and Other Mosquitoes (Diptera: Culicidae) in the Borough of Queens in New York City, with Characters and Techniques for Identification of Culex Mosquitoes

Abstract The host-feeding patterns of mosquitoes (n = 247) collected in the Borough of Queens in New York City in July and August 2000 were investigated using an indirect ELISA and a polymerase chain reaction (PCR)-heteroduplex assay. Culex pipiens L. and Cx. restuans Theobald fed primarily on birds, and their feeding habits support their implication as enzootic vectors of West Nile virus. Culex salinarius Coquillett and Coquillettidia perturbans (Walker) fed mainly on mammals, with fewer blood meals taken from birds, and these two species are potential bridge vectors of West Nile virus. Culex mosquitoes took blood meals (n = 54) from 11 different avian species. Only the northern cardinal (Cardinalis cardinalis), American robin (Turdus migratorius), and Brown-headed cow bird (MolIothrus ater) were fed upon by all three Culex species. Multiple blood feedings on avian hosts were detected in Cx. pipiens and Cx. restuans. Species identifications of Culex mosquitoes made using morphological characteristics were confirmed with a PCR assay that employed species-specific primers. All Cx. pipiens (n = 20) and Cx. salinarius (n = 10) specimens were correctly identified, but three (20%) of 15 Cx. restuans were misidentified as Cx. pipiens.

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 October 2009–30 November 2009

This article documents the addition of 411 microsatellite marker loci and 15 pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Acanthopagrus schlegeli, Anopheles lesteri, Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus oryzae, Aspergillus terreus, Branchiostoma japonicum, Branchiostoma belcheri, Colias behrii, Coryphopterus personatus, Cynogolssus semilaevis, Cynoglossus semilaevis, Dendrobium officinale, Dendrobium officinale, Dysoxylum malabaricum, Metrioptera roeselii, Myrmeciza exsul, Ochotona thibetana, Neosartorya fischeri, Nothofagus pumilio, Onychodactylus fischeri, Phoenicopterus roseus, Salvia officinalis L., Scylla paramamosain, Silene latifo, Sula sula, and Vulpes vulpes. These loci were cross‐tested on the following species: Aspergillus giganteus, Colias pelidne, Colias interior, Colias meadii, Colias eurytheme, Coryphopterus lipernes, Coryphopterus glaucofrenum, Coryphopterus eidolon, Gnatholepis thompsoni, Elacatinus evelynae, Dendrobium loddigesii Dendrobium devonianum, Dysoxylum binectariferum, Nothofagus antarctica, Nothofagus dombeyii, Nothofagus nervosa, Nothofagus obliqua, Sula nebouxii, and Sula variegata. This article also documents the addition of 39 sequencing primer pairs and 15 allele specific primers or probes for Paralithodes camtschaticus.

Isolation and Genetic Characterization of Rift Valley fever virus from Aedes vexans arabiensis, Kingdom of Saudi Arabia

An outbreak of Rift Valley fever in the Kingdom of Saudi Arabia and Yemen in 2000 was the first recognized occurrence of the illness outside of Africa and Madagascar. An assessment of potential mosquito vectors in the region yielded an isolate from Aedes vexans arabiensis, most closely related to strains from Madagascar (1991) and Kenya (1997).

Evaluation of Potential West Nile Virus Vectors in Volgograd Region, Russia, 2003 (Diptera: Culicidae): Species Composition, Bloodmeal Host Utilization, and Virus Infection Rates of Mosquitoes

Abstract Potential West Nile virus (family Flaviviridae, genus Flavivirus, WNV) vectors were assessed during 2003 at indoor and outdoor collection sites in urban Volgograd, Russia, and in three nearby towns and surrounding rural areas. In total, 9,182 female mosquitoes comprising 13 species in six genera were collected. Relative abundance and bloodmeal host utilization differed temporarily and spatially. During June and July in Volgograd, Aedes vexans (Meigen) (85.4%) and Culex p. pipiens L. (7.6%) were the two most abundant species collected indoors, whereas during August, Cx. p. pipiens was the dominant species, accounting for 87.9% of specimens collected. Two WNV-positive mosquito pools were detected in August: one pool was composed of Cx. p. pipiens and the other pool of Culex modestus Ficalbi. Anopheles messeae Falleroni, Aedes caspius (Pallas), Ae. vexans, Cx. modestus, and Cx. p. pipiens used both humans and birds as bloodmeal sources. In urban areas, 20.4% of the Cx. p. pipiens fed on humans, 58.1% fed on chickens, and six specimens were positive for both chicken and human blood. Culex p. pipiens collected from flooded basements were predominantly autogenous (91.7%), whereas adult females resting in buildings with dry basements were composed of 67.5% anautogenous and 32.5% autogenous specimens. Our data suggest that the primary WNV vectors in the Volgograd region were Cx. p. pipiens and Cx. modestus and that intense transmission of WNV to humans in urban areas during the epidemic of 1999 may have been facilitated by the abundance and concentration of anautogenous Cx. p. pipiens in multistory buildings. The role of autogenous Cx. p. pipiens in urban transmission remains unresolved.

Detection of West Nile virus antigen in mosquitoes and avian tissues by a monoclonal antibody-based capture enzyme immunoassay.

ABSTRACT An antigen capture immunoassay to detect West Nile (WN) virus antigen in infected mosquitoes and avian tissues has been developed. With this assay purified WN virus was detected at a concentration of 32 pg/0.1 ml, and antigen in infected suckling mouse brain and laboratory-infected mosquito pools could be detected when the WN virus titer was 102.1 to 103.7 PFU/0.1 ml. In a blindly coded set of field-collected mosquito pools (n = 100), this assay detected WN virus antigen in 12 of 18 (66.7%) TaqMan-positive pools, whereas traditional reverse transcriptase PCR detected 10 of 18 (55.5%) positive pools. A sample set of 73 organ homogenates from naturally infected American crows was also examined by WN virus antigen capture immunoassay and TaqMan for the presence of WN virus. The antigen capture assay detected antigen in 30 of 34 (88.2%) TaqMan-positive tissues. Based upon a TaqMan-generated standard curve of infectious WN virus, the limit of detection in the antigen capture assay for avian tissue homogenates was approximately 103 PFU/0.1 ml. The recommended WN virus antigen capture protocol, which includes a capture assay followed by a confirmatory inhibition assay used to retest presumptive positive samples, could distinguish between the closely related WN and St. Louis encephalitis viruses in virus-infected mosquito pools and avian tissues. Therefore, this immunoassay demonstrates adequate sensitivity and specificity for surveillance of WN virus activity in mosquito vectors and avian hosts, and, in addition, it is easy to perform and relatively inexpensive compared with the TaqMan assay.

Microsatellite Characterization of Subspecies and Their Hybrids in Culex pipiens Complex (Diptera: Culicidae) Mosquitoes Along a North-South Transect in the Central United States

ABSTRACT Mosquitoes in the Culex pipiens complex, Cx. p. pipiens L. and Cx. p. quinquefasciatus Say are morphologically similar and important vectors of West Nile and St. Louis Encephalitis viruses in the United States. The subspecies differ with respect to overwintering strategies, with Cx. p. pipiens entering diapause in response to winter conditions and Cx. p. quinquefasciatus lacking this ability, yet they hybridize when found in sympatry. Specimens (n = 646) were collected using gravid traps set along a transect from New Orleans, LA, to Chicago, IL. Microsatellite markers were used to: genetically characterize subspecies and hybrids, determine the degree and extent of hybridization to better define the hybrid zone, and examine the efficacy of hybrid detection between microsatellites and a singlegene assay based on the acetylcholinesterase.2 gene (HotAce.2). The results support the presence of two distinct genetic entities, with abroad, stable hybrid zone in between. Admixture analyses classified >40% of individuals as hybrids. Allelic richness was markedly different at the northern and southern ends of the transect, and there was a significant isolation by distance effect. The hybrid zone seems to be wider and extends further to the south than previous work indicated, and as a result, we propose new boundaries compared with those indicated by a previous study. Microsatellites detected more hybrids than the HotAce.2 assay, although the latter assay remains useful as a screening tool. We suggest that the parental subspecies and the hybrid zone are maintained by heterosis combined with selection for diapause at northern latitudes.

West Nile virus-infected mosquitoes, Louisiana, 2002.

Culex quinquefasciatus was identified as probable vector.

A comparison of aboveground and belowground populations of Culex pipiens (Diptera: Culicidae) mosquitoes in Chicago, Illinois, and New York City, New York, using microsatellites.

ABSTRACT Aboveground and belowground populations of the mosquito Culex pipiens L. are traditionally classified as form pipiens and form molestus, respectively, and gene flow between forms is thought to be limited. Relatively few f. molestus populations have been found in the United States, which has hindered their study in North America. In this study, we used microsatellites to characterize a newly discovered population of f. molestus in Chicago, IL, and compared levels of genetic diversity and differentiation in aboveground and belowground populations from Chicago and New York City, NY. Levels of genetic diversity, as measured by expected heterozygosity and allelic richness, were markedly lower in both f. molestus populations. Allele frequencies were distinctly different between the two f. molestus populations, and some alleles were present in one belowground population and not the other. Pairwise FST values between populations indicated that f. molestus populations were highly divergent from each other, as well as from their associated aboveground populations. Cluster analysis suggested the most likely number of groups was three, with the four f. pipiens populations in one cluster, and each of the f. molestus populations in its own cluster. Admixture analysis detected a low number of hybrids, 8%, between forms. We also tested the efficacy of two assays purported to distinguish between the forms, the CQ11 assay and a restriction fragment-length polymorphism assay of the COI gene, and found neither assay reliable in this regard. Our findings support the hypothesis that f. molestus populations in Chicago and New York City arose from local aboveground populations.

INTRODUCTION AND ESTABLISHMENT OF AEDES (FINLAYA) JAPONICUS JAPONICUS (THEOBALD) ON THE ISLAND OF HAWAII: IMPLICATIONS FOR ARBOVIRUS TRANSMISSION

ABSTRACT On November 24, 2003, 1 female adult specimen of Aedes (Finlaya) japonicus japonicus (Theobald) was collected in a New Jersey (NJ) light trap on the island of Hawaii. From June through October, 2004, female and male adults were collected by NJ light traps and gravid traps placed at multiple sites on the island of Hawaii. Larvae were collected in artificial containers and reared to adults for identification. Aedes (Fin.) j. japonicus is the 8th mosquito species to be introduced and established in the State of Hawaii. Currently, this species is known only from the island of Hawaii. Aedes (Fin.) j. japonicus is a competent laboratory vector for a number of arboviruses. Increased quarantine inspections, inspection and treatment of imported used tires and plants, disinsection of airline cargo holds, enhanced vector surveillance, and the development of sanitary corridors around airports and port facilities are necessary to reduce the introduction of vectors and pathogens.