RESUMEN
La Crosse (LAC) virus, a California serogroup bunyavirus, is the leading cause of pediatric arboviral encephalitis in the United States and an emerging disease in Tennessee, West Virginia, and North Carolina. Human cases of LAC encephalitis in Tennessee and North Carolina have increased above endemic levels during 1997 to 1999 and may represent an expansion of a new southeastern endemic focus. This report describes the isolation of LAC virus from the exotic mosquito Aedes albopictus. The discovery of LAC virus in wild populations of Ae. albopictus coupled with its expanding distribution in the southeastern United States, suggests that this mosquito may become an important accessory vector, potentially increasing the number of human cases in endemic foci or expanding the range of the disease.
Asunto(s)
Aedes/virología , Encefalitis de California/virología , Virus La Crosse/clasificación , Virus La Crosse/aislamiento & purificación , Aedes/fisiología , Animales , ADN Viral/análisis , Humanos , Insectos Vectores/virología , Virus La Crosse/genética , North Carolina , Reacción en Cadena de la Polimerasa , Vigilancia de la Población , TennesseeRESUMEN
Widespread deaths of American Crows (Corvus brachyrhynchos)were associated with the 1999 outbreak of West Nile (WN) virus in the New York City region. We compared six organs from 20 crow carcasses as targets for WN virus detection. Half the carcasses had at least one positive test result for WN virus infection. The brain was the most sensitive test organ; it was the only positive organ for three of the positive crows. The sensitivity of crow organs as targets for WN virus detection makes crow death useful for WN virus surveillance.
Asunto(s)
Enfermedades de las Aves/virología , Brotes de Enfermedades , Pájaros Cantores/virología , Fiebre del Nilo Occidental/veterinaria , Virus del Nilo Occidental/aislamiento & purificación , Enfermedades de las Aves/patología , New Jersey/epidemiología , ARN Viral/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Fiebre del Nilo Occidental/patología , Fiebre del Nilo Occidental/virología , Virus del Nilo Occidental/genéticaRESUMEN
As part of an investigation of an encephalitis outbreak in New York City, we sampled 430 birds, representing 18 species in four orders, during September 13-23, 1999, in Queens and surrounding counties. Overall, 33% were positive for West Nile (WN) virus-neutralizing antibodies, and 0.5% were positive for St. Louis encephalitis virus-neutralizing antibodies. By county, Queens had the most seropositive birds for WN virus (50%); species with the greatest seropositivity for WN virus (sample sizes were at least six) were Domestic Goose, Domestic Chicken, House Sparrow, Canada Goose, and Rock Dove. One sampled bird, a captive adult Domestic Goose, showed signs of illness; WN virus infection was confirmed. Our results support the concept that chickens and House Sparrows are good arbovirus sentinels. This study also implicates the House Sparrow as an important vertebrate reservoir host.
Asunto(s)
Enfermedades de las Aves/epidemiología , Aves/virología , Brotes de Enfermedades , Reservorios de Enfermedades/veterinaria , Pájaros Cantores/virología , Fiebre del Nilo Occidental/veterinaria , Virus del Nilo Occidental/aislamiento & purificación , Animales , Anticuerpos Antivirales/sangre , Enfermedades de las Aves/sangre , Enfermedades de las Aves/inmunología , Enfermedades de las Aves/virología , Aves/sangre , Aves/inmunología , Reacciones Cruzadas , Virus de la Encefalitis de San Luis/inmunología , Gansos/virología , Masculino , Pruebas de Neutralización , Ciudad de Nueva York/epidemiología , Estudios Seroepidemiológicos , Pájaros Cantores/sangre , Pájaros Cantores/inmunología , Fiebre del Nilo Occidental/sangre , Fiebre del Nilo Occidental/epidemiología , Fiebre del Nilo Occidental/virología , Virus del Nilo Occidental/inmunologíaRESUMEN
We evaluated West Nile (WN) virus seroprevalence in healthy horses, dogs, and cats in New York City after an outbreak of human WN virus encephalitis in 1999. Two (3%) of 73 horses, 10 (5%) of 189 dogs, and none of 12 cats tested positive for WN virus-neutralizing antibodies. Domestic mammals should be evaluated as sentinels for local WN virus activity and predictors of the infection in humans.
Asunto(s)
Brotes de Enfermedades , Enfermedades de los Perros/epidemiología , Enfermedades de los Caballos/epidemiología , Fiebre del Nilo Occidental/veterinaria , Virus del Nilo Occidental/aislamiento & purificación , Animales , Animales Domésticos , Anticuerpos Antivirales/sangre , Gatos , Enfermedades de los Perros/inmunología , Enfermedades de los Perros/virología , Perros , Enfermedades de los Caballos/inmunología , Enfermedades de los Caballos/virología , Caballos , Humanos , Mamíferos , Pruebas de Neutralización , Ciudad de Nueva York/epidemiología , Estudios Seroepidemiológicos , Fiebre del Nilo Occidental/epidemiología , Fiebre del Nilo Occidental/inmunología , Fiebre del Nilo Occidental/virología , Virus del Nilo Occidental/inmunologíaRESUMEN
Buggy Creek (BCR) virus is an arthropod-borne alphavirus that is naturally transmitted to its vertebrate host the cliff swallow (Petrochelidon pyrrhonota) by an invertebrate vector, namely the cimicid swallow bug (Oeciacus vicarius). We examined how the prevalence of the virus varied with the group size of both its vector and host. The study was conducted in southwestern Nebraska where cliff swallows breed in colonies ranging from one to 3700 nests and the bug populations at a site vary directly with the cliff swallow colony size. The percentage of cliff swallow nests containing bugs infected with BCR virus increased significantly with colony size at a site in the current year and at the site in the previous year. This result could not be explained by differences in the bug sampling methods, date of sampling, sample size of the bugs, age structure of the bugs or the presence of an alternate host, the house sparrow (Passer domesticus). Colony sites that were reused by cliff swallows showed a positive autocorrelation in the percentage of nests with infected bugs between year t and year t+1, but the spatial autocorrelation broke down for year t+2. The increased prevalence of BCR virus at larger cliff swallow colonies probably reflects the larger bug populations there, which are less likely to decline in size and lead to virus extinction. To the authors' knowledge this is the first demonstration of arbovirus infection increasing with group size and one of the few known predictive ecological relationships between an arbovirus and its vectors/hosts. The results have implications for both understanding the fitness consequences of coloniality for cliff swallows and understanding the temporal and spatial variation in arboviral epidemics.
Asunto(s)
Infecciones por Alphavirus/veterinaria , Infecciones por Arbovirus/veterinaria , Enfermedades de las Aves/epidemiología , Reservorios de Enfermedades/veterinaria , Hemípteros/virología , Insectos Vectores/virología , Pájaros Cantores/virología , Factores de Edad , Alphavirus/fisiología , Infecciones por Alphavirus/epidemiología , Animales , Infecciones por Arbovirus/epidemiología , Enfermedades de las Aves/virología , Densidad de Población , Prevalencia , Factores de TiempoRESUMEN
After an outbreak of West Nile virus (WNV) infections in people, horses, and wildlife in Staten Island, NY, during the summer of 2000, we surveyed the bird population of the island for evidence of infection. Neutralizing antibodies were detected in 59 of 257 (23.0%) resident birds and none of 96 transient (migrating) birds sampled in early October. Species with the greatest seroprevalence were northern cardinal (Cardinalis cardinalis) (69.2%) and rock dove (Columba livia) (54.5%). House sparrows (Passer domesticus) and chickens (Gallus gallus) had lower than expected seroprevalences, 8.6% and 5.5%, respectively. The geographic distribution of seropositivity suggested focal transmission at several locations on the island. The concentration of seropositive birds among resident bird populations on Staten Island supports the concept that many birds survive WNV infection and that some of these play an important role in the WNV-bird-mosquito transmission cycle.
Asunto(s)
Enfermedades de las Aves/epidemiología , Brotes de Enfermedades/veterinaria , Pájaros Cantores , Fiebre del Nilo Occidental/veterinaria , Virus del Nilo Occidental/inmunología , Animales , Anticuerpos Antivirales/sangre , Enfermedades de las Aves/sangre , Enfermedades de las Aves/inmunología , Aves , Reservorios de Enfermedades/veterinaria , Humanos , Pruebas de Neutralización/veterinaria , Ciudad de Nueva York/epidemiología , Estudios Seroepidemiológicos , Fiebre del Nilo Occidental/sangre , Fiebre del Nilo Occidental/epidemiología , Fiebre del Nilo Occidental/inmunología , Virus del Nilo Occidental/aislamiento & purificaciónRESUMEN
The authors report on the development and application of a rapid TaqMan assay for the detection of West Nile (WN) virus in a variety of human clinical specimens and field-collected specimens. Oligonucleotide primers and FAM- and TAMRA-labeled WN virus-specific probes were designed by using the nucleotide sequence of the New York 1999 WN virus isolate. The TaqMan assay was compared to a traditional reverse transcriptase (RT)-PCR assay and to virus isolation in Vero cells with a large number ( approximately 500) of specimens obtained from humans (serum, cerebrospinal fluid, and brain tissue), field-collected mosquitoes, and avian tissue samples. The TaqMan assay was specific for WN virus and demonstrated a greater sensitivity than the traditional RT-PCR method and correctly identified WN virus in 100% of the culture-positive mosquito pools and 98% of the culture-positive avian tissue samples. The assay should be of utility in the diagnostic laboratory to complement existing human diagnostic testing and as a tool to conduct WN virus surveillance in the United States.
Asunto(s)
Enfermedades de las Aves/diagnóstico , Culicidae/virología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Polimerasa Taq/metabolismo , Fiebre del Nilo Occidental/diagnóstico , Virus del Nilo Occidental/aislamiento & purificación , Animales , Enfermedades de las Aves/virología , Aves/virología , Encéfalo/virología , Chlorocebus aethiops , Humanos , ARN Viral/sangre , ARN Viral/líquido cefalorraquídeo , Sensibilidad y Especificidad , Células Vero , Cultivo de Virus , Fiebre del Nilo Occidental/veterinaria , Fiebre del Nilo Occidental/virología , Virus del Nilo Occidental/genéticaRESUMEN
Aedes triseriatus (Say) population density patterns and La Crosse encephalitis virus infection rates were evaluated in relation to a variety of habitat parameters over a 14-wk period. Ovitraps and landing collections were used in a La Crosse virus-enzootic area in Nicholas County, WV. Study sites were divided into categories by habitat type and by proximity to the residences of known La Crosse encephalitis cases. Results demonstrated that Ae. triseriatus population densities were higher in sugar maple/red maple habitats than in hemlock/mixed hardwood habitats or in a site characterized by a large number of small red maple trees. Sites containing artificial containers had higher population densities than those without. La Crosse virus minimum infection rates in mosquitoes collected as eggs ranged from 0.4/1,000 to 7.5/1,000 in the 12 study sites, but did not differ significantly among sites regardless of habitat type or proximity to human case residences. La Crosse virus infection rates in landing Ae. triseriatus mosquitoes ranged from 0.0/1,000 to 27.0/1,000. La Crosse virus was also isolated from host-seeking Ae. canadensis (Theobald) in two study sites, at rates similar to those found in the Ae. triseriatus populations. The Ae. triseriatus oviposition patterns and La Crosse virus infection rates suggest that this mosquito species disperses readily in the large woodlands of central West Virginia. The La Crosse enzootic habitats in Nicholas County, WV, are contrasted with those studied in other geographic regions where La Crosse virus is found.
Asunto(s)
Aedes/virología , Insectos Vectores/virología , Virus La Crosse/aislamiento & purificación , Animales , Conducta Animal , Femenino , Humanos , Tiempo (Meteorología) , West VirginiaRESUMEN
West Nile fever caused fatal disease in humans, horses, and birds in the northeastern United States during 1999. We studied birds from two wildlife facilities in New York City, New York, that died or were euthanatized and were suspected to have West Nile virus infections. Using standard histologic and ultrastructural methods, virus isolation, immunohistochemistry, in situ hybridization and reverse-transcriptase polymerase chain reaction, we identified West Nile virus as the cause of clinical disease, severe pathologic changes, and death in 27 birds representing eight orders and 14 species. Virus was detected in 23/26 brains (88%), 24/ 25 hearts (96%), 15/18 spleens (83%), 14/20 livers (70%), 20/20 kidneys (100%), 10/13 adrenals (77%), 13/ 14 intestines (93%), 10/12 pancreata (83%), 5/12 lungs (42%), and 4/8 ovaries (50%) by one or more methods. Cellular targets included neurons and glial cells in the brain, spinal cord, and peripheral ganglia; myocardial fibers; macrophages and blood monocytes; renal tubular epithelium; adrenal cortical cells; pancreatic acinar cells and islet cells; intestinal crypt epithelium; oocytes; and fibroblasts and smooth muscle cells. Purkinje cells were especially targeted, except in crows and magpies. Gross hemorrhage of the brain, splenomegaly, meningoencephalitis, and myocarditis were the most prominent lesions. Immunohistochemistry was an efficient and reliable method for identifying infected cases, but the polyclonal antibody cross-reacted with St. Louis encephalitis virus and other flaviviruses. In contrast, the in situ hybridization probe pWNV-E (WN-USAMRIID99) reacted only with West Nile virus. These methods should aid diagnosticians faced with the emergence of West Nile virus in the United States.
Asunto(s)
Enfermedades de las Aves/patología , Brotes de Enfermedades/veterinaria , Fiebre del Nilo Occidental/veterinaria , Animales , Aves , Inmunohistoquímica , Hibridación in Situ/veterinaria , Microscopía Electrónica/veterinaria , Ciudad de Nueva York , Fiebre del Nilo Occidental/patología , Virus del Nilo OccidentalRESUMEN
Plant-derived acaricides, extracted from various botanical species, and commercially available phytochemicals were evaluated for biological activity against immature Ixodes scapularis (Say) using the disposable pipet method. In addition, residual activity of the plant extracts was determined. Of the 13 plant extracts tested, 9 exhibited biological activity with Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., being the most effective against the nymphal ticks (LC50 = 0.151% wt:vol) and eastern red cedar, Juniperus virginiana L., showing the greatest activity against larval ticks (LC50 = .001% wt:vol). The commercially available products were significantly less active than the plant extracts we prepared, but some commercial compounds did exhibit limited activity. Only the Alaska yellow cedar exhibited any residual activity that lasted 21 d after treatment.
Asunto(s)
Insecticidas , Ixodes , Control Biológico de Vectores , Plantas , Control de Ácaros y Garrapatas , AnimalesRESUMEN
This report describes the vector competence of 3 ixodid tick species, Ixodes scapularis (Say), I. spinipalpis (Nuttall), and Dermacentor andersoni (Stiles), for Borrelia burgdorferi in Colorado. The study was based on preliminary field work performed in 6 Colorado counties, where rodents and ticks were collected and assayed for the presence of B. burgdorferi. Four of the 6 counties produced 52 rodent and 39 I. spinipalpis isolates of B. burgdorferi. Two B. burgdorferi isolates were tested under laboratory conditions and found to be infective to Imperial Cancer Research Fund (ICRF) outbred mice. The 1st, a low-passage strain originating from New York (B-31, passage 6) was used as a control, and the 2nd was isolated from ear tissue of a Neotoma mexicana (Baird) (Mexican wood rat) that was trapped in Colorado. Larvae of I. scapularis, I. spinipalpis. and D. andersoni were fed on infected mice and cultured in Barbour-Stoner-Kelly media to assay for infection at 1, 2, 3, and 4 wk after repletion. The infection rates in replete larvae. were 75, 69, and 8.5%, respectively, whereas transstadial nymphal infection rates were 80, 75, and 0%, respectively. Both I. scapularis and I. spinipalpis were shown to be competent vectors that acquired the infection from the host reservoir mice and subsequently transmitted it to naive mice. Given that I. scapularis are not found in Colorado, I. spinipalpis are restricted to the nests and burrows of rodents, and because of the semiarid environment in Colorado, the risk of human contact with B. burgdorferi appears to be low.
Asunto(s)
Vectores Arácnidos/microbiología , Grupo Borrelia Burgdorferi/aislamiento & purificación , Dermacentor/microbiología , Ixodes/microbiología , Enfermedad de Lyme/veterinaria , Infestaciones por Garrapatas/veterinaria , Animales , Enfermedad de Lyme/parasitología , Enfermedad de Lyme/transmisión , Ratones , Roedores/microbiología , Infestaciones por Garrapatas/parasitologíaRESUMEN
The efficacy of a liquid permethrin-treated bait tube controlling fleas and ticks on Mexican wood rats, Neotoma mexicana Baird, was evaluated during a 1-yr study in north-central Colorado. Results indicated that the bait tubes were effective for reducing flea and tick infestations on wood rats. The effects of treatment persisted throughout the study, despite the fact that bait tubes were replenished with bait and permethrin only during the first 4 mo (4 replenishments). Our results suggest that these bait tubes provide an effective, economical, and environmentally acceptable means of controlling vectors of flea or tick-borne diseases, although slight modifications of the basic bait tube design might be required to maintain the effectiveness of the tube under different ecological conditions.