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West Nile Virus - |
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| West Nile Virus (WVN) is categorized as a flavivirus. |
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| Flavivirus: |
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May cause serological illnesses
Most of these infections are arthropod-borne
Transmission to vertebrates is by chronically infected mosquitoes and ticks (also bats and rodents have been identified as vectors
Clinical symptoms of flaviviral infection may include: fever, encephalitis, hemorrhagic fever.
Spherical, 40-60nm; Capsid: Symmetry indistinct, 2 proteins: nucleocapsid ('C') and matrix ('M'); Envelope: 1 glycoprotein ('E').
Single-stranded, (+)sense RNA, ~10.5kb. 5' cap but not polyadenylated. Genetic organization differs from Toga's - structural proteins at 5' end of genome, N.S. at 3' end.
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| West Nile Virus: |
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| Vector: mosquitoes/ticks - Mosquitoes, largely bird-feeding species, are the principal vectors of West Nile virus. The virus has been isolated from 43 mosquito species, predominantly of the genus Culex (Table 1). In Africa and the Middle East, the main vector is Cx. univittatus (although Cx. poicilipes, Cx. neavei, Cx. decens, Aedes albocephalus, or Mimomyia spp. play an important role in certain areas). In Europe, the principal vectors are Cx. pipiens, Cx. modestus, and Coquillettidia richiardii, and in Asia, Cx. quinquefasciatus, Cx. tritaeniorhynchus, and Cx. vishnui predominate. Successful experimental transmission of the virus has been described in Culiseta longiareolata, Cx. bitaeniorhynchus, and Ae. albopictus. Transovarial transmission of the virus has been demonstrated in Cx. tritaeniorhynchus, Ae. aegypti, and Ae. albopictus, though at low rates |
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Vertebrate Host: Birds
Geographic Distribution of Disease: Africa, Europe, Asia and has been seen increasingly in the United States.
Mainly causes disease in Birds, but also able to cause severe infections to horses and Humans |
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| West Nile Virus is part of a group flaviviruses, which include Kinjin, MVE,SLE and JE viruses. All are considered antigenic complex. Kinjin is closely related to WVN |
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| Incubation Period: 1-6 days |
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| Symptoms: |
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| Fever |
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| Headache |
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| Backache |
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| Generalized myalgia |
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| Anorexia |
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Rash may occur (if it does either during fibrile phase or at the end of the febrile phase)
Rash is roseolar or maculopapular (non irritant and mainly involves back, chest and upper extremities) |
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| Nausea, vomitting, diarrhea and abdominal pain |
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| sore throat |
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| arthralgia |
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| fatigue |
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| conjunctivitis |
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| retrobulbar pain |
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| Clinical Features: |
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| Lymphadenopathy |
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| Pharyngitis/gastrointestinal symptoms |
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| May result in aseptic meningitis or meningioencephalitis |
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| Neurological presentations, which include anterior myelitis and encephalopolyradiculitis |
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| Rarely complication occur, that cause myocarditis or pancreatitis |
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| In Africa WVN can be responsible for Yellow Fever and Hepatitis |
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| WVN when grown, produces CPE or plaques in a wide range of tissues. |
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| Diagnosis: |
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| WVN can be isolated in 38% of the patients (77% when isolated after 1st day) |
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| Viremia detectable after 5 days |
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| Titers are generally low |
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Serologic diagnoses possible:
Indirect IF
ELISA
Radial Hemolysis in-in -gel used to detect IgG antibodies |
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| Treatment: |
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As of now no vaccine available, but recently a vaccine for horses has been approved. However the effectiveness of the vaccine is unknown
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