Effects Of West Nile Virus Research Articles

Uncovering the neurological effects of West Nile virus during a record-breaking southern Spain outbreak in 2020–2021

The 2020–21 West Nile Virus (WNV) outbreak in Andalusia, Spain, was the largest reported in the country, with eight cases of West Nile Neuroinvasive Disease (WNND) diagnosed in a tertiary hospital. Diagnosis of WNND is based on detecting WNV RNA, viral isolation, or demonstrating a specific immune response against the virus, with additional tests used to support the diagnosis. Treatment remains supportive, with variable outcomes. The potential efficacy of plasma exchange (PLEX) in select cases raises the possibility of an autoimmune component secondary to infectious pathology of the central nervous system. The influence of climate change on the expansion of WNV into new regions is a significant concern. It is crucial for physicians practicing in high-risk areas to be knowledgeable about the disease for early prevention and effective control measures.

West Nile Virus and Eastern Equine Encephalitis Virus High Probability Habitat Identification for the Selection of Sentinel Chicken Surveillance Sites in Florida.

To mitigate the effects of West Nile virus (WNV) and eastern equine encephalitis virus (EEEV), the state of Florida conducts a serosurveillance program that uses sentinel chickens operated by mosquito control programs at numerous locations throughout the state. Coop locations were initially established to detect St. Louis encephalitis virus (SLEV), and coop placement was determined based on the location of human SLEV infections that occurred between 1959 and 1977. Since the introduction of WNV into Florida in 2001, WNV has surpassed SLEV as the primary arbovirus in Florida. Identifying high probability locations for WNV and EEEV transmission and relocating coops to areas of higher arbovirus activity would improve the sensitivity of the sentinel chicken surveillance program. Using 2 existing models, this study conducted an overlay analysis to identify areas with high probability habitats for both WNV and EEEV activity. This analysis identified approximately 7,800 km2 (about 4.5% of the state) as high probability habitat for supporting both WNV and EEEV transmission. Mosquito control programs can use the map resulting from this analysis to improve their sentinel chicken surveillance programs, increase the probability of virus detection, reduce operational costs, and allow for a faster, targeted response to virus detection.

West Nile Virus: Veterinary Health and Vaccine Development.

West Nile virus (WNV) (Flaviviridae: Flavivirus) was discovered in Africa more than 80 yr ago and became recognized as an avian pathogen and a cause of neurologic disease in horses largely during periodic incursions into Europe. Introduction of WNV into North America stimulated great anxiety, particularly in the equine industry, but also for pet owners and livestock producers concerned about the effect of WNV on other domestic animals. Numerous subsequent studies of naturally occurring and experimentally induced disease greatly expanded our understanding of the host range and clinical consequences of WNV infection in diverse species and led to rapid development and deployment of efficacious vaccines for horses. In addition to humans, horses are clearly the animals most frequently affected by serious, sometimes lethal disease following infection with WNV, but are dead-end hosts due to the low-magnitude viremia they develop. Dogs, cats, and livestock species including chickens are readily infected with WNV, but only occasionally develop clinical disease and are considered dead-end hosts for the virus.

Studying the effects of emerging infections on the fetus: Experience with West Nile and Zika viruses.

Emerging infections have the potential to produce adverse effects on the pregnant woman or her fetus; however, studying these effects is often challenging. We review our experiences with investigating the prenatal effects of two mosquito‐borne infections that emerged in the past 2 decades, West Nile virus (WNV) and Zika virus. Concerns regarding teratogenicity were raised about both viruses; Zika virus has been confirmed to be teratogenic, while WNV appears not to increase the risk for adverse outcomes, although teratogenicity has not been excluded. Study designs used to examine the effects of both viruses include case reports and series, pregnancy registries, and cohort studies. Case–control studies and birth defects surveillance systems are being used to study the effects during pregnancy of Zika virus, but not the effects of WNV, because a specific phenotype was observed among infants with congenital Zika infection, but not among infants with congenital WNV infection. Experimental data that demonstrated that Zika virus was neurotropic have also been useful because they provided biologic plausibility for Zika virus's teratogenic effects: these findings were consistent with observations in congenitally infected infants. Challenges encountered with studies to evaluate the effects of these infections include the broad range of possible adverse outcomes, the inability to include all infected pregnant women in studies because many infections are asymptomatic, and the difficulty with interpretation of diagnostic testing of infants (WNV and Zika) and pregnant women (Zika). This review might be helpful to guide future studies of the effects of emerging infections during pregnancy. Birth Defects Research 109:363–371, 2017. © 2017 Wiley Periodicals, Inc.

Outbreaks of West Nile virus in captive waterfowl in Ontario, Canada

The detrimental effects of West Nile virus (WNV) have been well characterized in several taxonomic groups of North American birds, such as corvids and raptors. Relatively less is known about the virus' effects in waterfowl species, many of which are abundant in North America and occupy habitats, for example wetlands and marshes, likely to harbour dense mosquito populations. In two successive years, outbreaks of WNV-associated disease were observed in waterfowl at a rehabilitation centre. In the present report, clinical and pathological findings are provided for seven mallards (Anas platyrhynchos) and one Canada goose (Branta canadensis) that developed acute disease and either died or were killed humanely. The most severe and consistent microscopic lesion in mallards was myocardial degeneration and coagulative necrosis consistent with acute heart failure. The Canada goose had necrotizing myocarditis. Other lesions included pulmonary perivascular oedema, lymphoplasmacytic hepatitis, and splenic and bursal lymphoid depletion. WNV infection was confirmed using reverse transcriptase-polymerase chain reaction and immunohistochemical staining. Myofibres within all cardiac muscle layers had positive immunohistochemical staining, as did blood vessel walls in the heart and spleen. These results suggest that juvenile mallards are highly susceptible to fatal WNV-associated cardiac failure, and confirm that adult Canada geese are susceptible to fatal WNV-associated disease. The synchronous timing of clinical disease and death in these waterfowl are consistent with WNV mosquito-borne infections within a WNV transmission focus during the summer (July and August) of 2012 and 2013.

Survival of West Nile virus-challenged Southern house mosquitoes, Culex pipiens quinquefasciatus, in relation to environmental temperatures.

We investigated the effect of West Nile virus (WNV) infection on survival in two colonies of Culex pipiens quinquefasciatus Say (Diptera: Culicidae) originating from Vero Beach and Gainesville, FL. Mosquitoes were fed West Nile virus-infected blood and checked daily for survival. Exposure to WNV decreased survival among Cx. p. quinquefasciatus from Gainesville relative to unexposed individuals at 31° C. In contrast, exposure to WNV enhanced survival among Cx. p. quinquefasciatus from Vero Beach relative to unexposed individuals at 27° C. These results may suggest that exposure to WNV and associated infection could increase or decrease components of fitness, dependent on environmental temperature and intraspecific variation in Cx. p. quinquefasciatus. The relationship between lifespan (time of death in days) and WNV titer differed in the colonies at 31° C and 27° C, suggesting that intraspecific species variation in response to temperature impacts interactions with WNV. While further work is needed to determine if similar effects occur under field conditions, this suggests intraspecific variation in vector competence for WNV and adult survival of Cx. p. quinquefasciatus, both aspects of vectorial capacity.

Reprint of: Core protein-mediated 5′–3′ annealing of the West Nile virus genomic RNA in vitro

Genome cyclization through conserved RNA sequences located in the 5′ and 3′ terminal regions of flavivirus genomic RNA is essential for virus replication. Although the role of various cis-acting RNA elements in panhandle formation is well characterized, almost nothing is known about the potential contribution of protein cofactors to viral RNA cyclization. Proteins with nucleic acid chaperone activities are encoded by many viruses (e.g., retroviruses, coronaviruses) to facilitate RNA structural rearrangements and RNA–RNA interactions during the viral replicative cycle. Since the core protein of flaviviruses is also endowed with potent RNA chaperone activities, we decided to examine the effect of West Nile virus (WNV) core on 5′–3′ genomic RNA annealing in vitro. Core protein binding resulted in a dramatic, dose-dependent increase in 5′–3′ complex formation. Mutations introduced in either the UAR (upstream AUG region) or CS (conserved sequence) elements of the viral RNA diminished core protein-dependent annealing, while compensatory mutations restored the 5′–3′ RNA interaction. The activity responsible for stimulating RNA annealing was mapped to the C-terminal RNA-binding region of WNV core protein. These results indicate that core protein – besides its function in viral particle formation – might be involved in the regulation of flavivirus genomic RNA cyclization, and thus virus replication.

Core protein-mediated 5′–3′ annealing of the West Nile virus genomic RNA in vitro

Genome cyclization through conserved RNA sequences located in the 5′ and 3′ terminal regions of flavivirus genomic RNA is essential for virus replication. Although the role of various cis-acting RNA elements in panhandle formation is well characterized, almost nothing is known about the potential contribution of protein cofactors to viral RNA cyclization. Proteins with nucleic acid chaperone activities are encoded by many viruses (e.g., retroviruses, coronaviruses) to facilitate RNA structural rearrangements and RNA–RNA interactions during the viral replicative cycle. Since the core protein of flaviviruses is also endowed with potent RNA chaperone activities, we decided to examine the effect of West Nile virus (WNV) core on 5′–3′ genomic RNA annealing in vitro. Core protein binding resulted in a dramatic, dose-dependent increase in 5′–3′ complex formation. Mutations introduced in either the UAR (upstream AUG region) or CS (conserved sequence) elements of the viral RNA diminished core protein-dependent annealing, while compensatory mutations restored the 5′–3′ RNA interaction. The activity responsible for stimulating RNA annealing was mapped to the C-terminal RNA-binding region of WNV core protein. These results indicate that core protein – besides its function in viral particle formation – might be involved in the regulation of flavivirus genomic RNA cyclization, and thus virus replication.

Experimental West Nile Virus Infection in Gyr-Saker Hybrid Falcons

West Nile disease (WND) has become a major public and veterinary health concern since the appearance of West Nile virus (WNV) in New York in 1999. The following panzootic spread in the U.S. and the recent WNV outbreaks in Europe and the Mediterranean Basin have increased interest in WND. Despite considerable investigation of WNV infection in birds, the effects of WNV on avian populations are still largely unknown. In Europe, raptors have been found to be particularly susceptible to WNV infection, but studies in birds of prey are lacking. To our knowledge, the present study is the first to report an experimental infection with WNV in Gyr-Saker hybrid falcons. We show that 10-week-old captive-reared Gyr-Saker (Falco rusticolus × Falco cherrug) hybrid falcons are susceptible to WNV infection. Neither morbidity nor mortality was observed after subcutaneous WNV inoculation with mixed extracts of non-infected mosquito salivary glands. Both the macroscopic and microscopic lesions observed were similar to those previously reported in naturally and experimentally infected North American raptors. The results obtained in the present study demonstrate that although Gyr-Saker hybrid falcons do not seem to be a good reservoir for WNV transmission via mosquito, they can become infected with WNV, develop viremia and antibodies, and are able to shed the virus.

Efficacy of Three Vaccines in Protecting Western Scrub-Jays (Aphelocoma californica) from Experimental Infection with West Nile Virus: Implications for Vaccination of Island Scrub-Jays (Aphelocoma insularis)

The devastating effect of West Nile virus (WNV) on the avifauna of North America has led zoo managers and conservationists to attempt to protect vulnerable species through vaccination. The Island Scrub-Jay (Aphelocoma insularis) is one such species, being a corvid with a highly restricted insular range. Herein, we used congeneric Western Scrub-Jays (Aphelocoma californica) to test the efficacy of three WNV vaccines in protecting jays from an experimental challenge with WNV: (1) the Fort Dodge West Nile-Innovator(®) DNA equine vaccine, (2) an experimental DNA plasmid vaccine, pCBWN, and (3) the Merial Recombitek(®) equine vaccine. Vaccine efficacy after challenge was compared with naïve and nonvaccinated positive controls and a group of naturally immune jays. Overall, vaccination lowered peak viremia compared with nonvaccinated positive controls, but some WNV-related pathology persisted and the viremia was sufficient to possibly infect susceptible vector mosquitoes. The Fort Dodge West Nile-Innovator DNA equine vaccine and the pCBWN vaccine provided humoral immune priming and limited side effects. Five of the six birds vaccinated with the Merial Recombitek vaccine, including a vaccinated, non-WNV challenged control, developed extensive necrotic lesions in the pectoral muscle at the vaccine inoculation sites, which were attributed to the Merial vaccine. In light of the well-documented devastating effects of high morbidity and mortality associated with WNV infection in corvids, vaccination of Island Scrub-Jays with either the Fort Dodge West Nile-Innovator DNA vaccine or the pCBWN vaccine may increase the numbers of birds that would survive an epizootic should WNV become established on Santa Cruz Island.

In Vitro and In Vivo Effects of West Nile Virus Propagated in Cells of Different Passage

Tissue cultures are used to propagate viruses for use in mosquito infection studies and to detect live virus in field-collected specimens. Microscopic evaluation of cytopathic effects is used to visualize virus presence. In this study, both low-passage (LP; n = 35) and high-passage (HP; n = 218) lines of African green monkey kidney (Vero) cells were infected with West Nile virus, and virus growth kinetics were quantitated over different incubation periods (IPs) (2, 6, 10, 24, 48, 72, and 96 h postinfection). Virus titers were significantly (P < 0.05) higher in the HP compared with LP line 24, 48, and 96 h postinfection. No differences were observed in plaque morphology between the LP and HP lines. Culex pipiens quinquefasciatus were fed infectious blood meals created using supernatant from the 2 lines and maintained at 28 degrees C for a 12-day IP. Although the virus dose was higher (P < 0.05) in the HP compared with the LP line, there were no significant differences in mosquito infection or dissemination rates at the end of the IP. The significance of these observations for assessing virus presence and pathogenicity is discussed.

The Effects of West Nile Virus on the Reproductive Success and Overwinter Survival of Eastern Bluebirds in Alabama

We tested for negative effects of West Nile virus (WNV) on a breeding population of eastern bluebirds in Alabama by comparing fecundity and reproductive success in years before and after the arrival of WNV and by comparing fecundity, reproductive success, and overwinter survival of seropositive and seronegative individuals within the same population in the same years. We found that female bluebirds were more likely to be seropositive than male bluebirds. Age and individual condition did not affect likelihood of being seropositive. Being seropositive for WNV was not associated with any negative effects on reproduction or survival. However, female fecundity was higher in years after WNV compared to years before the arrival of WNV. The reproductive success of males who tested positive for WNV exposure was higher than that of males that were seronegative. Overall, we found no negative effects on reproduction or survival after exposure to WNV.

Impacts of the West Nile Virus Epizootic on the Yellow-Billed Magpie, American Crow, and Other Birds in the Sacramento Valley, California

Abstract. After spreading across North America, West Nile virus (WNV) arrived in the Sacramento Valley of California in 2004 and began killing many corvids. To estimate the regional effect of WNV on corvids and other birds, we reinitiated a road survey along six routes totaling 203 km in the Sacramento Valley. We surveyed these transects 30 times in fall and winter from 1990 to 1995 and repeated the surveys each fall and winter from 2005 to 2008. By 2007–08, annual maximum counts of the Yellow-billed Magpie, American Crow, and Loggerhead Shrike had declined 83%, 63%, and 63%, respectively, from those of the 1990s. These species declined in riparian and rice-cultivation areas, most substantially outside Yolo County. The magpie declined 90% along our routes north of Yolo County, causing us concern for the viability of the species. After a lag, the crow began declining quickly in 2007. We recommend the Yellow-billed Magpie be given special status. Also, searches for Yellow-billed Magpies should be extended a...

DIFFERENTIAL IMPACT OF WEST NILE VIRUS ON CALIFORNIA BIRDS.

The strain of West Nile virus (WNV) currently epidemic in North America contains a genetic mutation elevating its virulence in birds, especially species in the family Corvidae. Although dead American Crows (Corvus brachyrhynchos) have been the hallmark of the epidemic, the overall impact of WNV on North America's avifauna remains poorly understood and has not been addressed thoroughly in California. Here, we evaluate variation by species in the effect of WNV on California birds from 2004 to 2007 by using (1) seroprevalence in free-ranging birds, (2) percentage of carcasses of each species reported by the public that tested positive for WNV, (3) mortality determined from experimental infections, and (4) population declines detected by trend analysis of Breeding Bird Survey (BBS) data. Using Bayesian linear models, we extrapolate trends in BBS data from 1980-2003 (pre-WNV) to 2004-2007 (post-WNV). We attribute significant declines from expected abundance trends in areas supporting epiornitics to WNV transmission. We combine risk assessed from each of the four data sets to generate an overall score describing WNV risk by species. The susceptibility of California avifauna to WNV varies widely, with overall risk scores ranging from low for the refractory Rock Pigeon (Columba livia) through high for the susceptible American Crow. Other species at high risk include, in descending order, the House Finch (Carpodacus mexicanus), Black-crowned Night-Heron (Nycticorax nycticorax), Western Scrub-Jay (Aphelocoma californica), and Yellow-billed Magpie (Pica nuttalli). Our analyses emphasize the importance of multiple data sources in assessing the effect of an invading pathogen.

West Nile Virus in The Americas

West Nile virus causes sporadic disease in the Eastern hemisphere that is often asymptomatic or mild, whereas in the Western hemisphere, West Nile virus has been associated with illness and profound mortality in many avian species. West Nile virus might have been transported to North America by an infected mosquito or the virus could have entered within a vertebrate host like a bird. Although the most important method of West Nile virus transmission is by Culex species mosquitoes, additional modes of transmission have been identified. West Nile virus has been isolated from almost 300 species of Western birds. The long-term effects on common species such as corvids, sparrows, grackles, finches, hawks, and robins are still being debated. However the potential effect of West Nile virus on small populations or species with limited geographic distribution, such as Hawaiian avifauna, could be much more catastrophic.

The Seasonal Effect of West Nile Virus in a Semi-arid Zone, Nigeria

The Seasonal Effect of West Nile Virus in a Semi-arid Zone, Nigeria

West Nile virus and high death rate in American crows.

We document effects of West Nile virus (WNV) on American Crows. More than two thirds of our crows died of WNV infection, peaking when the proportion of infected mosquitoes at roosts was greatest. WNV antibody prevalence in crows was low. Local ecologic effects can be dramatic as WNV inhabits new areas.

The effects of West Nile virus on major histocompatibility complex class I and II molecule expression by Lewis rat Schwann cells in vitro

The expression of major histocompatibility complex (MHC) class I and II molecules by Lewis rat Schwann cells after infection with West Nile virus (WNV) in vitro was examined by fluorescence microscopy and flow cytometry. WNV enhanced the expression of MHC class I molecules and induced the expression of MHC class II molecules by Schwann cells. Irradiated medium from WNV-infected Schwann cell cultures upregulated class I molecule expression on dissociated Schwann cell cultures but did not induce the expression of class II molecules. This finding has implications for virally triggered autoimmune diseases of nervous tissue.

The effects of West Nile virus on MHC class I and II molecule expression by Lewis rat schawnn cells in vitro

The effects of West Nile virus on MHC class I and II molecule expression by Lewis rat schawnn cells in vitro

The effects of west Nile virus on MHC class I and II molecule expression by Lewis rat Schwann cells in vitro

The effects of west Nile virus on MHC class I and II molecule expression by Lewis rat Schwann cells in vitro