Indigenous human disease caused by West Nile virus (WNV) was first identified in the United States in August 1999 in the greater New York City area. By the end of 2004, human WNV disease had been reported in all states except Washington, Hawaii, and Alaska, and WNV transmission to humans had been documented by five routes: mosquito bites (principally from Culex spp.), blood transfusions, organ transplantation, transplacental transfer, and breastfeeding. During 1999-2005, a total of 19,525 cases of WNV disease in humans and 771 deaths were reported in the United States. In 2000, CDC first published guidelines for WNV surveillance, prevention, and control and created ArboNET, an electronic surveillance and reporting system. Beginning in 1999, WNV surveillance and prevention activities had been initiated in selected states and large cities through the CDC Epidemiology and Laboratory Capacity (ELC) cooperative agreements for emerging infectious diseases and subsequently expanded to all 50 states, six large cities/counties, and Puerto Rico. In 2005, to assess the capacity of state and large-city/county health departments to conduct WNV surveillance, prevention, and control activities, the Council of State and Territorial Epidemiologists (CSTE), with assistance from the Association of Public Health Laboratories (APHL) and CDC, surveyed WNV programs in the 50 states and six large-city/county health departments. This report describes the results of that assessment, which indicated that all participating states and cities had well-developed surveillance and control programs for human, avian, equine, or mosquito WNV.
Division of Paediatric Medicine, The Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8. michael.weinstein@sickkids.ca
Between August 25 and September 25, 2003 seven patients with West Nile virus neurological manifestations were identified through the hospital neurology consultation services in Calgary, Alberta, Canada. Three of the seven patients were treated with interferon alpha-2b (IFN alpha-2b). In this report we document the clinical characteristics of these seven cases.
Clinical and laboratory information was obtained from a retrospective review of patient hospital and clinic charts. Patients were included if they had serological evidence of West Nile virus infection and had clinical evidence of aseptic meningitis, encephalomyelitis, cerebellar syndrome or motor neuronopathy. Three patients received a treatment course of three million units IFN alpha-2b, administered by subcutaneous injection once per day for 14 days.
Four patients had cerebellar signs without change in consciousness, two had both encephalitis and neuromuscular weakness, and one patient had focal lower motor neuron arm weakness. The mean age was 52 (range 24 - 73). All patients had flu-like illness and fever as presenting symptoms and six had severe headaches. Two patients were immunocompromised prior to infection. Two patients with cerebellar signs (one with opsoclonus-myoclonus) improved spontaneously and exhibited only mild residual deficits on discharge. The other two patients with cerebellar findings developed brainstem involvement, one coinciding with and one subsequent to the cerebellar symptoms. Within one week of treatment with IFN alpha-2b these latter two patients showed marked improvement. One patient with encephalitis and neuromuscular weakness, was treated with IFN alpha-2b and subsequently recovered.
In this case review of seven patients, multiple neurological symptoms occurred in each patient and the neurological presentation was varied. Four patients had predominant cerebellar findings and one patient had opsoclonus-myoclonus, not previously reported. The marked improvement in three patients who received IFN alpha-2b raises preliminary optimism towards this potential treatment.
Notes
Comment In: Can J Neurol Sci. 2004 May;31(2):131-415198433
Comment In: Can J Neurol Sci. 2004 May;31(2):135-715198434
[Circulation of West Nile virus (Flaviviridae, Flavivirus) and some other arboviruses in the ecosystems of Volga delta, Volga-Akhtuba flood-lands and adjoining arid regions (2000-2002)].
Comprehensive virological, serological as well as genetic studies of the ecology of West Nile Virus (WNV) as well as of some other arboviruses were undertaken in different ecosystems in the territories of the Astrakhan Region and of the Kalmyk Republic. The main carriers (mosquitoes, ticks, birds and mammals) were defined as involved in the circulation of viruses within the natural and anthropogenic biocenosis. Phylogenetic examinations of isolated strains and samples, which were positive in RT-PCR, showed an absolute predominance of genotype I virus that was most closely related to American and Israeli strains. At the same time, epidemic strains had up to 6% of nucleotide differences versus the historic strains isolated in the same region 20-30 years ago. Besides, the circulation of genotype IV was discovered; it was characterized by a lower pathogenicity, which, possibly, ensures the shaping of a pronounced immune interlayer bearing no epidemic consequences. An analysis of the study results on the WNV ecology denotes the epicenter of the endemic territory located in the middle part of the Volga delta.
In 1999, there was the large outbreak of West Nile fever (WNF) in Southern Russia (>500 cases in the Volgograd Province). In 2000-2004, the WNF incidence rate decreased steadily to zero, but a new outbreak occurred in 2007 (64 cases). The analysis of historical climate data for Volgograd from 1900 to present showed that the years 1999 and 2007 were the hottest ones due to a very mild "winter" (Dec.-Mar.) and a hot "summer" (June-Sep.). There are up to 15 potential WNF vectors in Volgograd, but only Culex pipiens and Culex modestus are abundant in late summer, both in urban and rural settings. Only these species are naturally attracted to and feed on both humans and birds. The RNA of pathogenic WN virus genovariant was found by reverse transcriptase polymerase chain reaction only in Culex mosquitoes at the infection rate of about 0.04%. So these species may be considered as potential WNF "bridge vectors" between birds and humans as well as main vectors in sylvatic avain cycle. Their abundance in an epidemic season was higher in the years with a mild winter and a hot summer, so this phenomenon may serve as a connecting link between a climate and WNF epidemiology. These findings give some hints on the predisposing factors for WNF epidemic as well as the possibility to predict WNF outbreaks in the temperate climate zones.
Laboratory of Public Health, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Kita-18, Nishi-9, Kita-Ku, Sapporo 060-0818, Japan. kariwa@vetmed.hokudai.ac.jp.
Source
Int J Environ Res Public Health. 2013 Dec;10(12):7144-64
In this review, we discuss the possibility that the glycosylation of West Nile (WN) virus E-protein may be associated with enhanced pathogenicity and higher replication of WN virus. The results indicate that E-protein glycosylation allows the virus to multiply in a heat-stable manner and therefore, has a critical role in enhanced viremic levels and virulence of WN virus in young-chick infection model. The effect of the glycosylation of the E protein on the pathogenicity of WN virus in young chicks was further investigated. The results indicate that glycosylation of the WN virus E protein is important for viral multiplication in peripheral organs and that it is associated with the strong pathogenicity of WN virus in birds. The micro-focus reduction neutralization test (FRNT) in which a large number of serum samples can be handled at once with a small volume (15 ?L) of serum was useful for differential diagnosis between Japanese encephalitis and WN virus infections in infected chicks. Serological investigation was performed among wild birds in the Far Eastern region of Russia using the FRNT. Antibodies specific to WN virus were detected in 21 samples of resident and migratory birds out of 145 wild bird samples in the region.
Since the outbreak of vector-borne West Nile virus in New York City in 1999, the disease has spread across United States and Canada, resulting in the use of larvicides such as methoprene at catch basins for widespread urban mosquito control. Although the manufacturer has recommended a methoprene dosage for catch basin application, the effect of rainfall on this dosage is not known. A field study on the fate of methoprene pellets and ingots was conducted during the summer of 2004 at three catch basins in the City of Toronto, Canada. Water samples from each catch basin were collected daily and during rain storms and analyzed for methoprene concentration using gas chromatography mass spectrometry. It was found that: (1) the methoprene concentration at the catch basin sump fell below the minimum lethal concentration most of the time; (2) rainfall events greater than 25 mm flushed methoprene pellets out of the catch basin; (3) the higher the sump water depth, the higher the residual methoprene concentration at the catch basin sump; and (4) rainfall flushed methoprene from the catch basins into the storm sewer outfall at concentrations much lower than the detrimental level which might cause ecosystem damage.
Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada. rebecca.corrigan@usask.ca
In 2003, an outbreak of West Nile virus (WNV) occurred in Saskatchewan, Canada from July to September. One-hundred thirty-three horse cases and 947 human cases were recorded and data were analyzed retrospectively for evidence of clustering to determine if clinical infection in the horse population could be used to estimate human risk of infection with WNV. Kulldorff's scan statistic was used to identify spatial-temporal clusters in both the human and horse cases. In most areas, human clusters were not preceded by horse clusters. In one area, a significant cluster of horse cases preceded human cases by 1 week; however, 1 week does not provide sufficient time for human-health authorities to act and provide advance warning for the public.
