West Nile virus-infected mosquitoes, Louisiana, 2002.Human cases of West Nile virus West Nile virus, microorganism and the infection resulting from it, which typically produces no symptoms or a flulike condition. The virus is a flavivirus and is related to a number of viruses that cause encephalitis. (WNV WNV West Nile Virus
WNV World Net Visions ) disease appeared in St. Tammany and Tangipahoa Parishes in southeastern Louisiana in June 2002. Cases peaked during July, then rapidly declined. We conducted mosquito mosquito (məskē`tō), small, long-legged insect of the order Diptera, the true flies. The females of most species have piercing and sucking mouth parts and apparently they must feed at least once upon mammalian blood before their eggs can collections from August 3 to August 15 at residences of patients with confirmed and suspected WNV disease to estimate species composition, relative abundance, and WNV infection rates. A total of 31,215 mosquitoes representing 25 species were collected by using primarily gravid gravid /grav·id/ (grav´id) pregnant.
Carrying eggs or developing young.
gra·vid traps and C[O.sub.2]-baited light traps. Mosquitoes containing WNV RNA RNA: see nucleic acid.
in full ribonucleic acid
One of the two main types of nucleic acid (the other being DNA), which functions in cellular protein synthesis in all living cells and replaces DNA as the carrier of genetic were obtained from 5 of 11 confirmed case sites and from 1 of 3 sites with non-WNV disease. WNV RNA was detected in 9 mosquito pools, including 7 Culex Culex /Cu·lex/ (ku´leks) a genus of mosquitoes found throughout the world, many species of which are vectors of disease-producing organisms.
n. quinquefasciatus, 1 Cx. salinarius, and 1 Coquillettidia perturbans. Mosquito infection rates among sites ranged from 0.8/1,000 to 10.9/1,000. Results suggest that Cx. quinquefasciatus was the primary epizootic/epidemic vector, with other species possibly playing in a secondary role.
Since the first appearance of West Nile virus (WNV) (family Flaviviridae: genus Flavivirus) in the Western Hemisphere Western Hemisphere
Part of Earth comprising North and South America and the surrounding waters. Longitudes 20° W and 160° E are often considered its boundaries. in 1999 (1), the virus has spread rapidly south and west from its initial focus in the New York City New York City: see New York, city.
New York City
City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. metropolitan area. By the end of 2001, WNV-infected mosquitoes, birds, horses, or humans had been reported from 27 states, and human cases of WNV disease occurred as far south as southern Florida and as far west as Arkansas and Louisiana (2,3).
In the northeastern United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , the primary epizootic/epidemic vector of WNV is Culex pipiens, a species that feeds primarily on birds (4-6). Other potentially important vector species, based on frequency of isolations of WNV or laboratory vector competence studies, include Cx. restuans and Cx. salinarius (7,8). WNV has been isolated from an additional 57 species, but their status as vectors is unknown (Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. [CDC See Control Data, century date change and Back Orifice.
CDC - Control Data Corporation ], http://www.cdc.gov/ncidod/dvbid/westnile/MosquitoSpecies.htm). In the southern United States The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive region in the southeastern and south-central United States. , WNV was isolated from Cx. quinquefasciatus, Cx. salinarius, and Cx. nigripalpus in Florida and Georgia (9), Cx. nigripalpus in northern Florida (10), and from Anopheles Anopheles: see mosquito. atropos, Deinocerites cancer, and Aedes taeniorhynchus in the Florida Keys Florida Keys, chain of coral and limestone islands and reefs, c.150 mi (240 km) long, extending from Virginia Key, S of Miami Beach, to Key West, and forming the southern extremity of Florida. (11). However, the role these species play in epidemics of WNV disease in the southern states Southern States
government of 11 Southern states that left the Union in 1860. [Am. Hist.: EB, III: 73]
popular name for Southern states in U.S. and for song. [Am. Hist. has not been determined. Ae. albopictus is common in urban, suburban, and rural residential settings throughout the southern states and is a competent laboratory vector of WNV (12,13). Although the virus has been isolated from Ae. albopictus in the Northeast (14), this species' importance in transmission of WNV to humans is unknown.
During May and June 2002, WNV infection was identified in chickens, horses, dead wild birds, and in pools of Cx. quinquefasciatus mosquitoes from St. Tammany Parish, on the north shore of Lake Pontchartrain Lake Pontchartrain (local English pronunciation [leɪk ˈpʰɑntʃətʰɹeɪn]) (French: Lac Pontchartrain, pronounced in southeastern Louisiana (15). Human cases of WNV neuroinvasive disease began to appear in late June, and 27 cases were reported by the end of July. Intense local WNV transmission was indicated by the St. Tammany Parish Mosquito Abatement A reduction, a decrease, or a diminution. The suspension or cessation, in whole or in part, of a continuing charge, such as rent.
With respect to estates, an abatement is a proportional diminution or reduction of the monetary legacies, a disposition of property by will, when District's surveillance program, which detected WNV immunoglobulin immunoglobulin: see antibody; immunity; immunology.
Any of the glycoproteins in the blood serum that are induced in response to invasion by foreign antigens and that protect the host by eradicating pathogens. (Ig)M antibody in 17% of their sentinel sentinel /sen·ti·nel/ (sen´ti-n'l) one who gives a warning or indicates danger.
a recording mechanism, such as an animal, a farm or a veterinarian, posted explicitly to record a possible occurrence or series of chickens and WNV antigen from 11 mosquito pools by the end of July (15). The human cases tended to cluster in 2 areas of St. Tammany Parish, Slidell and the Covington-Mandeville area. In neighboring neigh·bor
1. One who lives near or next to another.
2. A person, place, or thing adjacent to or located near another.
3. A fellow human.
4. Used as a form of familiar address.
v. Tangipahoa Parish, human cases were also being reported, with most clustering in the Hammond-Pontchatula area (Louisiana Department of Health and Hospitals, unpub, data).
The recognition of a growing outbreak of WNV disease in humans provided an opportunity to describe the transmission dynamics of WNV in locally occurring mosquitoes during epidemic transmission and to compare these dynamics to patterns seen in the northeastern states (4-6). Accordingly, we conducted an entomologic en·to·mol·o·gy
The scientific study of insects.
ento·mo·log survey in St. Tammany and Tangipahoa Parishes during August 2002. The specific aims of the survey were to document species composition, relative abundance, and WNV infection rates in mosquitoes at residences of patients with confirmed cases and at residences of patients with suspected cases of WNV fever, the most likely locations where transmission to humans occurred. We were particularly interested in attempting to ascertain the importance of Cx. quinquefasciatus and Ae. albopictus as vectors of WNV in this epidemic.
Materials and Methods
Study Sites and Specimen Collection
Mosquitoes were collected in St. Tammany and Tangipahoa Parishes from August 3 to August 15, 2002. Two study sites were selected in each parish (denoted as St. Tammany A and B, and Tangipahoa A and B). These sites were located at or near residences of patients with confirmed cases of WNV neuroinvasive disease. As suspected cases of WNV fever (persons reporting as outpatients with undifferentiated undifferentiated /un·dif·fer·en·ti·at·ed/ (un-dif?er-en´she-at-ed) anaplastic.
Having no special structure or function; primitive; embryonic. febrile febrile /feb·rile/ (feb´ril) pertaining to or characterized by fever.
Of, relating to, or characterized by fever; feverish. illness with headache) were identified, collections were made at the residences of these patients.
Mosquitoes were collected primarily by using CDC miniature light traps baited with dry ice to collect host-seeking females, Reiter gravid traps (16) to collect females seeking a location to deposit eggs, and ovitraps to collect eggs from container-breeding mosquitoes. Both light and gravid traps at the 4 initial study sites were operated for 24 h/day in an attempt to maximize the collection of Ae. albopictus, a daytime feeder. Some additional collections were made by using Fay-Prince traps and duplex cone traps and by aspirating resting adult mosquitoes from the outside of residences or other structures. Collections were transferred to 2.0-mL cryovials and frozen on dry ice until returned to the CDC laboratory in Fort Collins, Colorado The City of Fort Collins, a home rule municipality situated on the Cache la Poudre River along the Colorado Front Range, is the county seat and most populous city in Larimer County, Colorado. , where they were stored at -80[degrees]C. Mosquito eggs collected in ovitraps were hatched in the insectary in·sec·tar·y or in·sec·tar·i·um
n. pl. in·sec·tar·ies or in·sec·tar·i·a
A place for keeping, breeding, or observing living insects. , reared to adulthood, held for 48 h at 27[degrees]C and 80% relative humidity relative humidity
The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. , then identified and processed for virus testing as described below.
Mosquito Processing and Testing
Mosquitoes were identified to species on a refrigerated re·frig·er·ate
tr.v. re·frig·er·at·ed, re·frig·er·at·ing, re·frig·er·ates
1. To cool or chill (a substance).
2. To preserve (food) by chilling. chill table. Pools of [less than or equal to] 50 specimens sorted by species and collection site and date were triturated in 1.75 mL of diluent diluent /dil·u·ent/ (dil´oo-int)
1. causing dilution.
2. an agent that dilutes or renders less potent or irritant.
Serving to dilute.
n. by using a Mixer Mill apparatus (Qiagen Inc., Valencia, CA, USA) and centrifuged (17). Supernatants from the mosquito suspensions were tested for the presence of WNV RNA by TaqMan reverse transcription--polymerase chain reaction (RT-PCR RT-PCR
reverse transcriptase-polymerase chain reaction. See PCR1. ), and positive pools were retested by using a different primer set to confirm the presence of WNV RNA (18). Mosquito infection rates were determined by calculating the maximum likelihood estimate (MLE MLE Maximum Likelihood Estimation
MLE Managed Learning Environment
MLE Maximum Likelihood Estimate
MLE Medical Laboratory Evaluation (Medical Laboratory Proficiency Testing Program, Washington, DC) ) with 95% confidence intervals confidence interval,
n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. (19).
Collections were made at 14 sites, 12 in St. Tammany Parish and 2 in Tangipahoa Parish. Residences of WNV neuroinvasive disease or fever case-patients are denoted by upper case letters. Non-case-patient residences are denoted by italicized lower case letters. Eight St. Tammany sites (A, C, D, E, F, g, I, J) were in or near the city of Slidell in the southeast corner of the parish, St. Tammany site B was located in Abita Springs, east of Covington, and 3 sites (K, l, m) were in Pearl River Pearl River, uninc. village (1990 pop. 15,314), Rockland co., SE N.Y., near the N.J. line. It is a residential suburb of New York City, and a computer and telecommunications research and development center.
River, central Mississippi, U. in the east-central region of the parish. The 2 Tangipahoa parish sites (A, B) were on the northwest and northern outskirts of Ponchatoula.
Trapping trapping, most broadly, the use of mechanical or deceptive devices to capture, kill, or injure animals. It may be applied to the practice of using birdlime to capture birds, lobster pots to trap lobsters, and seines to catch fish. effort at each site and elapsed time e·lapsed time
The measured duration of an event.
Noun 1. elapsed time - the time that elapses while some event is occurring between onset of illness and mosquito collection are shown in Table 1. Although traps were run for 24 h/day at some sites, only mosquitoes collected overnight are used to calculate mosquitoes per trap night. The earliest date of onset was June 21, and the latest date of onset was August 4. Mosquito collection dates ranged from 8 to 50 days after onset of illness. Trapping effort per site ranged from 2 to 60 trap nights for light trap collections, and from 2 to 59 trap nights for gravid trap collections. No notable changes in the weather occurred during the collection period that might bias comparisons of mosquito abundance.
A total of 31,215 mosquitoes were collected during the trapping period of August 3 to August 15 (Table 2). Cx. erraticus was the most commonly collected species, accounting for 28% of the total collected. Cx. quinquefasciatus, Ae. albopictus, Coquillettidia perturbans, and Cx. salinarius were other commonly collected species. Ovitraps yielded 335 Ae. albopictus and 778 Ae. triseriatus/hendersoni reared to adults. Aspirator as·pi·ra·tor
An apparatus for removing fluid from a body cavity, consisting usually of a hollow needle and a cannula, connected by tubing to a container in which a vacuum is created by a syringe or a suction pump. collections yielded 658 mosquitoes of 16 species, of which 474 were Ae. albopictus. Cone traps collected 33 mosquitoes (9 species) and Fay-Prince traps yielded 214 mosquitoes (15 species). Mosquitoes were sorted into 2,471 pools for processing and virus testing.
Relative population densities (light trap or gravid trap counts per trap night) of the species in which we detected WNV RNA, and of Ae. albopictus, were calculated for case and non-case sites (Table 3). For most species, light trap counts per night greatly exceeded gravid trap counts. For Cx. quinquefasciatus, however, gravid trap counts were 7-58 times greater than were light trap collection counts. Neither gravid traps nor light traps collected large numbers of Ae. albopictus. Light trap counts per trap night for Ae. albopictus were approximately the same as gravid trap counts except at site 1 where 35.5 mosquitoes were collected per gravid trap night compared to 4.5 per light trap night.
No relationship was shown between the population densities of the species examined and whether the site was a case-patient or non-case-patient residence, except for Cx. quinquefasciatus, for which much higher densities were found at sites of non-case-patients. Cx. quinquefasciatus gravid trap counts per trap night ranged from 0.4 to 44.1 for confirmed WNV disease case-patient residence sites, and 59.6 to 142.8 for non-case-patient sites (p<0.001, Wilcoxon rank sum test).
WNV RNA was detected in 9 mosquito pools by TaqMan RT-PCR (Table 4). Five viral RNA positive pools were from St. Tammany Parish and 4 were from Tangipahoa. Seven of the positive pools contained Cx. quinquefasciatus; 4 of these were from St. Tammany Parish, and 3 were from Tangipahoa. The other 2 positive pools consisted of a pool of Cx. salinarius from St. Tammany and a pool of Cq. perturbans from Tangipahoa. All of the WNV-positive Cx. quinquefasciatus were collected in gravid traps, while the positive Cx. salinarius and Cq. perturbans were collected in light traps. No virus was detected in mosquitoes collected by the other methods. WNV infection rates ranged from 0.81/1,000 to 10.91/1,000 by MLE (Table 4). The highest infection rate was seen in Cx. salinarius and the lowest in Cq. perturbans. Infection rates in Cx. quinquefasciatus were similar among sites (2.31/1,000-5.64/1,000).
No relationship was found between the relative densities of mosquitoes collected and the finding of WNV-infected mosquitoes (Tables 3 and 4). Three infected pools of Cx. quinquefasciatus were collected from Tangipahoa site B, with 15.1 mosquitoes per gravid trap night, whereas no infected pools were collected from St. Tammany site m, which had the highest Cx. quinquefasciatus count per gravid trap night (142.8). Likewise, the only WNV-infected Cx. salinarius pool was from St. Tammany site B, which had 1.6 mosquitoes per light trap night, 1 of the lower density sites for that species. Eight other sites had higher light trap counts but no WNV-positive mosquitoes were detected. Cq. perturbans was found in high densities at only Tangipahoa sites A and B, and the densities at these sites were similar at 17.7 and 16.2 per light trap night, respectively. Infected Cq. perturbans were found only at Tangipahoa site A.
Detection of WNV-infected mosquitoes was not influenced by elapsed time between dates of onset of illness (a surrogate surrogate n. 1) a person acting on behalf of another or a substitute, including a woman who gives birth to a baby of a mother who is unable to carry the child. 2) a judge in some states (notably New York) responsible only for probates, estates, and adoptions. for date of infection) and mosquito collection dates. We obtained 3 isolates from Tangipahoa site B, where the date of onset was 47-50 days before mosquito collection (Tables 1 and 4).
The results of our survey indicate that the natural history of WNV in the southern United States is similar to that seen in the northern states, where Cx. mosquitoes, especially Cx. pipiens, Cx. restuans, and Cx. salinarius, are thought to be the species primarily involved in enzootic en·zo·ot·ic
Prevalent among or restricted to animals of a specific geographic area. Used of a disease.
An enzootic disease.
peculiar to or present constantly in a location. See also endemic. , epizootic ep·i·zo·ot·ic
Affecting a large number of animals at the same time within a particular region or geographic area. Used of a disease.
ep , and epidemic transmission (3-6). Seven of 9 (78%) WNV-infected mosquito pools were Cx. quinquefasciatus. Both Cx. pipiens and Cx. quinquefasciatus are primarily ornithophilic, although some studies indicate that Cx. quinquefasciatus feeds more readily on mammals The class Mammalia (the Mammals) is divided into two subclasses based on reproductive techniques: egg laying mammals (the Monotremes); and mammals which give live birth. The latter subclass is divided into two infraclasses: pouched mammals (the marsupials); and the placental mammals. (20-22). One of the 2 other positive pools was of Cx. salinarius, which feeds primarily on mammals (20-22). WNV has been isolated frequently from this species (5,6,23), and laboratory studies indicate that it is a competent vector (8). Cx. salinarius has been associated with an outbreak of human WNV illness in New York City (6) and appears likely to be important in transmitting WNV to humans and domestic mammals in the southern United States as well. The other positive pool was of Cq. perturbans. WNV isolates previously have been obtained from this species, but it is an inefficient vector in the laboratory (8).
Eight mosquito pools containing WNV RNA were collected at 5 (45%) of 11 confirmed WNV case-patient residences, while the remaining pool was from 1 (33%) of 3 non-case-patient sites. This finding suggests that many, perhaps most, human infections are acquired near their residences.
Although substantial numbers of Ae. albopictus were tested, no virus was detected in this competent laboratory vector of WNV. This finding was perhaps due to the blood-feeding habits of this species. Two studies of engorged en·gorge
v. en·gorged, en·gorg·ing, en·gorg·es
1. To devour greedily.
2. To gorge; glut.
3. To fill to excess, as with blood or other fluid.
v.intr. specimens wild caught in the continental United States United States territory, including the adjacent territorial waters, located within North America between Canada and Mexico. Also called CONUS. found that 1% and 17% of blood meals were taken from birds (24,25). The remaining meals were from a variety of mammals, including humans. In our study area, relatively few blood meals may have been taken from birds, thus reducing the exposure of host-seeking Ae. albopictus to the high-titered levels of WNV viremia viremia /vi·re·mia/ (vi-re´me-ah) the presence of viruses in the blood.
The presence of viruses in the bloodstream. seen in many species of birds. Little data have been published on WNV viremia levels in mammals, but in horses, dogs, and cats, viremia levels are transient, of low titers, or both (12,26). If this condition is also the case for other mammalian mammalian
emanating from or pertaining to mammals. species, then most blood meals taken by Ae. albopictus from WNV-infected hosts would be below the threshold titer titer /ti·ter/ (ti´ter) the quantity of a substance required to react with or to correspond to a given amount of another substance. necessary to initiate infection.
In our study, gravid traps were clearly preferable to light traps as an effective surveillance tool for detecting WNV RNA in mosquitoes. All the positive Cx. quinquefasciatus pools and 91% of total Cx. quinquefasciatus were from gravid traps. The other 2 WNV-positive pools were from mosquitoes collected in light traps. Gravid traps were a more effective means of collecting Ae. albopictus than were light traps. Unlike Cx. quinquefasciatus, most female Ae. albopictus collected in gravid traps were not gravid, and numerous males were also collected. Ae. albopictus were also readily collected by aspiration and ovitrapping.
Although active transmission of WNV was still occurring at the time of our collection efforts during the first half of August, most human patients had dates of onset between late June and late July. Thus, the relative numbers and species composition we observed may not have been representative of the situation when most human infections were occurring. Mosquito control activities intensified in St. Tammany Parish in response to the high level of WNV activity (15). Mosquito surveillance by the parish showed large reductions in total mosquito counts and in Cx. quinquefasciatus counts in CDC light traps and in New Jersey light traps from May to August. Eleven WNV antigen-positive mosquito pools were detected, all in June and July. Ten of these positive pools were of Cx. quinquefasciatus, and 1 was of Cx. salinarius, similar to our findings in August. Notably, the number of sentinel chickens developing WNV IgM antibody peaked during the third week of July, declined during early August, then rose again during late August (15). This finding suggests that exposure of sentinel chickens to infected mosquitoes was ongoing, and perhaps increasing, during the period of our study. Serologic se·rol·o·gy
n. pl. se·rol·o·gies
1. The science that deals with the properties and reactions of serums, especially blood serum.
2. conversions in sentinel chickens continued to be detected into November. Serologic studies of wild birds caught in mist nets Mist nets are used by ornithologists to capture wild birds for banding or other research projects. Bat biologists use them for the same purposes. The mesh net is typically made of nylon and resembles an oversized volleyball net. in St. Tammany Parish were conducted in August, and again in October (27). These data indicated that enzootic WNV transmission continued to occur in the parish, although likely at a reduced level, after human cases were no longer being reported. Long-term studies are needed to monitor the transmission dynamics of WNV in mosquito populations during epidemic and nonepidemic years.
We thank the staff of the St. Tammany Parish Mosquito Abatement District, Slidell, Louisiana Slidell is a city in St. Tammany Parish in Louisiana, situated on the northeast shore of Lake Pontchartrain.   As of the 2000 census, the city had a population of 25,695. Slidell is a suburb of New Orleans. , for logistical support and the anonymous reviewers for helpful suggestions.
The Louisiana Department of Health and Hospitals, New Orleans New Orleans (ôr`lēənz –lənz, ôrlēnz`), city (2006 pop. 187,525), coextensive with Orleans parish, SE La., between the Mississippi River and Lake Pontchartrain, 107 mi (172 km) by water from the river mouth; founded , supported this study.
Mr Godsey is a microbiologist microbiologist
a specialist in microbiology. in the Entomology entomology, study of insects, an arthropod class that comprises about 900,000 known species, representing about three fourths of all the classified animal species. and Ecology Activity, Arbovirus arbovirus
Any of a large group of viruses that develop in arthropods (chiefly mosquitoes and ticks). The name derives from “arthropod-borne virus.” The spheroidal virus particle is encased in a fatty membrane and contains RNA; it causes no apparent harm to the Diseases Branch, Division of Vector-Borne Infectious Diseases infectious diseases: see communicable diseases. , CDC, in Fort Collins, Colorado. His research interests are in arbovirus ecology.
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Any member of the largest phylum, Arthropoda, in the animal kingdom. Arthropoda consists of more than one million known invertebrate species in four subphyla: Uniramia (five classes, including insects), Chelicerata (three classes, including arachnids and horseshoe vectors. Monath TP, editor. St. Louis encephalitis St. Louis encephalitis
see St. Louis encephalitis. . Washington: American Public Health Association The American Public Health Association (APHA) is Washington, D.C.-based professional organization for public health professionals in the United States. Founded in 1872 by Dr. Stephen Smith, APHA has more than 30,000 members worldwide. ; 1980. p.313-80.
(23.) Andreadis TG, Anderson JF, Vossbrinck CR. Mosquito surveillance for West Nile virus in Connecticut, 2000: isolation from Culex pipiens, Cx. restuans, Cx. salinarius, and Culiseta melanura. Emerg Infect Dis. 2001;7:670-4.
(24.) Savage HM, Niebylski ML, Smith GC, Mitchell C J, Craig GB. Host-feeding patterns ofAedes albopictus (Diptera: Culicidae) at a temperate temperate /tem·per·ate/ (tem´per-at) restrained; characterized by moderation; as a temperate bacteriophage, which infects but does not lyse its host.
adj. North American site. J Med Entomol. 1993;30:27-34.
(25.) Niebylski ML, Savage HM, Nasci RS, Craig GB. Blood hosts of Aedes albopictus in the United States. J Am Mosq Control Assoc. 1994; 10:447-50.
(26.) Austgen LE, Bowen RA, Bunning ML, Davis BS, Mitchell CJ, Chang G-JJ. Experimental infection of cats and dogs Cats and Dogs
A slang term referring to speculative stocks that have short or suspicious histories for sales, earnings, dividends, etc.
In a bull market analysts will often mention that everything is going up, even the cats and dogs. with West Nile virus. Emerg Infect Dis. 2004;10:82-6.
(27.) Komar N, Panella NA, Langevin SA, Brault AC, Amador M, Edwards E, et al. Avian hosts for West Nile virus in St. Tammany Parish, Louisiana St. Tammany Parish (French: Paroisse de Saint-Tammany) is a parish located in the U.S. state of Louisiana, in the New Orleans metropolitan area. The parish seat is Covington, and as of 2000, the population was 191,268. , 2002. Am J Trop Med Hyg. 2005;73: In press.
Marvin S. Godsey Jr, * Roger Nasci, * Harry M. Savage, * Stephen Aspen, * Raymond King, * Ann M. Powers, * Kristen Burkhalter, * Leah Colton, * Dawn Charnetzky, * Sarah Lasater, * Viki Taylor, ([dagger]) and Charles T. Palmisano ([dagger])
* Centers for Disease Control and Prevention, Fort Collins, Colorado, USA; and ([dagger]) St. Tammany Parish Mosquito Abatement District, Slidell, Louisiana, USA
Address for correspondence: Marvin S. Godsey Jr, Division of Vector-Borne Infectious Diseases, CDC, P.O. Box 2087 (Foothills Campus), Fort Collins, CO 80522, USA; fax: 970-221-6476; email: email@example.com
Table 1. Trapping effort at West Nile virus (WNV) case-patient and non-case-patient residences, August 3-15, 2002 Parish Site * Case onset date Collection dates St. Tammany A Jul 11 Aug 3-6 B Jul 13 Aug 3-6 C Jul 24 Aug 12-15 D Jul 29 Aug 12-15 E Aug 2 Aug 12-15 F Aug 4 Aug 12-15 I Jul 28 Aug 12-15 J Aug 4 Aug 12-15 K Jul 29 Aug 13-15 9 Not given Aug 13-15 1 Not given Aug 14-15 m Not given Aug 14-15 Tangipahoa A Jul 11 Aug 7-10 B Jun 21 Aug 7-10 No. trap nights ([dagger]) Other methods Parish Light Gravid ([double dagger]) St. Tammany 55 59 59 51 12 12 A 8 8 A 11 16 4 F, 4 D, A 19 21 12 12 A 3 3 6 6 9 15 3 F 2 2 4 4 Tangipahoa 54 59 60 48 * Capital letters denote confirmed WNV neuroinvasive disease and WNV fever case sites; italicized lower case letters denote non-WNV case sites. ([dagger]) Only night collections used for trap night calculations. ([double dagger]) A, aspiration outside buildings; F, Fay-Prince trap; D, duplex cone. Numbers denote trap nights; aspiration times not recorded. Table 2. Mosquito species collected in St. Tammany and Tangipahoa Parishes, Louisiana, August 3-15, 2002 No. of mosquitoes Species No. of pools Light traps Culex erraticus 310 8,319 Cx. quinquefasciatus 311 539 Aedes albopictus 321 1,007 Coquillettidia perturbans 107 2,159 Cx. salinarius 144 1,809 Culex species 171 389 Ae. triseriatus/hendersoni ([dagger]) 159 198 Psorophora ferox 117 909 Ps. howardii 112 680 Uranotaenia sapphirina 59 631 Ae. vexans 83 500 Ae. infirmatus 90 465 Ae. atlanticus/tormentor ([dagger]) 78 371 Ae. taeniorhynchus 41 231 Aedes species 59 198 Ps. columbiae 54 188 Anopheles crucians complex 66 184 10 other species 193 317 Total 2,471 19,094 No. of mosquitoes Species Gravid traps Other methods * Culex erraticus 411 3 Cx. quinquefasciatus 6,326 98 Aedes albopictus 1,457 860 Coquillettidia perturbans 114 0 Cx. salinarius 155 49 Culex species 1,318 37 Ae. triseriatus/hendersoni ([dagger]) 86 782 Psorophora ferox 27 37 Ps. howardii 2 4 Uranotaenia sapphirina 48 0 Ae. vexans 18 24 Ae. infirmatus 7 17 Ae. atlanticus/tormentor ([dagger]) 28 37 Ae. taeniorhynchus 12 46 Aedes species 15 17 Ps. columbiae 4 4 Anopheles crucians complex 4 3 10 other species 65 6 Total 10,097 2,024 No. of mosquitoes Species Total (%) Culex erraticus 8,733 (27) Cx. quinquefasciatus 6,963 (22) Aedes albopictus 3,324 (11) Coquillettidia perturbans 2,273 (7) Cx. salinarius 2,013 (7) Culex species 1,744 (6) Ae. triseriatus/hendersoni ([dagger]) 1,066 (3) Psorophora ferox 973 (3) Ps. howardii 686 (2) Uranotaenia sapphirina 679 (2) Ae. vexans 542 (2) Ae. infirmatus 489 (2) Ae. atlanticus/tormentor ([dagger]) 436 (1) Ae. taeniorhynchus 289 (<1) Aedes species 230 (<1) Ps. columbiae 196 (<1) Anopheles crucians complex 191 (<1) 10 other species 388 (1) Total 31,215 (100) * Other methods: mechanical aspirator, duplex cone trap, Fay-Prince trap oviposition trap. ([dagger]) Not identified to species. Table 3. Population densities of selected mosquito species at West Nile virus (WNV) case-patient and non-case-patient residences * No. of mosquitoes collected per trap night (LT/GT) ([dagger]) Culex quinquefasciatus Cx. Salinarius St. Tammany A 1.7/21.7 1.6/0.05 B 0.5/3.7 1.5/0.1 C 0.3/17.4 2.6/0 D 0.6/18.1 1.0/0 E 3.7/44.1 5.4/0.06 F 1.0/19.4 5.0/0 I 1.3/15.7 3.2/0 J 2.3/39.3 6.7/0.3 K 1.5/12.2 1.0/0 g 4.4/59.6 6.7/0.07 l 6.5/105.0 0.5/0 m 7.0/142.8 0/0 Tangipahoa A 0.02/0.4 6.4/1.0 B 3.2/15.1 8.0/1.2 No. of mosquitoes collected per trap night (LT/GT) ([dagger]) Aedes albopictus Coquillettidia perturbans St. Tammany A 1.8/1.2 0.2/0 B 0.9/1.7 0/0 C 1.5/1.0 0/0 D 1.6/2.8 0/0 E 2.2/3.0 0/0 F 2.8/2.1 0/0 I 2.4/2.9 0/0 J 2.3/0.3 0/0 K 9.8/11.2 0.2/0 g 4.1/3.6 0/0 l 4.5/35.5 0.5/0 m 0.8/0.3 0/0 Tangipahoa A 0.7/1.9 17.7/1.6 B 5.2/8.5 16.2/0.3 * Capital letters denote confirmed WNV neuroinvasive disease and WNV fever case sites; italicized lower case letters denote non-WNV case sites. ([dagger]) LT, light trap; GT, gravid trap; only night collections used for trap night calculations. Table 4. Estimated mosquito pool West Nile virus (WNV) infection rates per 1,000 mosquitoes and 95% confidence intervals (CIs) * Site Sampling Trap type WNV+ Parish ([dagger]) period ([double dagger]) pools St. Tammany B Aug 3-6 Light 1 E Aug 12-15 Gravid 2 F Aug 12-15 Gravid 1 1 Aug 14-15 Gravid 1 Tangipahoa A Aug 7-10 Light 1 B Aug 7-10 Gravid 3 No. mosquitoes Infection rate: Parish Species tested MLE (95% CI) St. Tammany Cx. salinarius 92 10.91 (5.46-21.83) Cx. quinquefasciatus 829 2.61 (1.31-5.22) Cx. quinquefasciatus 427 2.31 (1.16-4.62) Cx. quinquefasciatus 223 5.64 (2.82-11.28) Tangipahoa Cq. perturbans 1,223 0.81 (0.41-1.62) Cx. quinquefasciatus 922 3.41 (1.71-6.82) * Calculated by using a bias-corrected maximum likelihood estimate (MLE). ([dagger]) Capital letters denote confirmed WNV neuroinvasive disease and WNV fever case sites; italicized lower case letters denote non-WNV case sites. ([double dagger]) Light denotes C[O.sub.2]-baited CDC miniature light trap; gravid denotes Reiter gravid trap.