The West Nile Virus: Ocular and Systemic Manifestations

Summer is back and there is a resurgence of the West Nile Virus in Southern California.  This virus can affect eye sight may cause  serious even lethal complications.  Here we review the origin of the virus, systemic manifestations, ocular manifestations and how to prevent infection and spread of the disease.

Virus Origin and Spread

The West Nile Virus (WNV) was first reported in 1937 in a febrile woman living in the West Nile District of Uganda.  The virus caused encephalitis which is inflammation of the brain and spinal cord.   The virus spreads via mosquito bite and can infect horses, birds and humans. We now know the WNV is a flavivirus. Other viruses from this same genius are responsible for similarly severe diseases including yellow fever and dengue. 

Systemic Manifestations

The majority of those infected (80%) are asymptomatic.  Those that develop symptoms usually present with West Nile Fever with a constellation of signs and symptoms including fever, headache, fatigue, skin rash on the trunk of the body (occasionally), swollen lymph glands (occasionally), and eye pain.  Severe cases end with meningitis, encephalitis and death.

Ocular Manifestations

The most commonly reported ocular features of WNV infection are multifocal, bilateral chorioretinitis with chorioretinal lesions characteristically found in either a scattered or linear pattern. Other features include anterior uveitis, retinal vasculitis, optic neuritis and vitritis; less commonly, nystagmus, abducens nerve palsy, optic disc edema and absence of corneal reflex have been reported. Patients were also reported to present with blurred vision, floaters, redness, visual field defects and diplopia. Ocular symptoms of WNV are generally self limited although vision loss may develop.   Late onset wet macular degeneration with CNV, for example, may occur and is responsive to intravitreal treatment with anti-VEGF medication, namely Avastin.

Diagnosis and Treatment

The WNV is diagnosed from serum tests for the IgM antibody made against the virus.  This is elevated in the 2 weeks following infection.  PCR tests are available but less reliable.  There is no specific treatment for West Nile virus infection. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.  It is now known that the virus blocks the immune signaling by the interferon alpha/beta receptor or IFNAR, thereby evading the immune system and leading to damage of the body.  Development of a vaccine based on the receptor is underway.  For ocular disease, treatment of the secondary inflammation with topical steroids is effective and may restore vision in aggressive cases.

Prevention

Exposure to WNV can be limited by personal protection, mosquito control programs, and screening of blood and organs for transplantation. Personal protection during the months of August and September includes staying indoors between dusk and dawn when mosquitoes are most active, wearing protective clothing when outdoors (i.e., long sleeves and pants with socks and shoes), and using mosquito repellants. The most effective mosquito repellant for use on skin is N, N-diethyl-m-toluamide (DEET). Removal of standing water in barrels, buckets, gutters and flowerpots, which can be used as breeding sites, helps to reduce the mosquito population.

In summary, the West Nile Virus remains a worrisome cause of potentially fatal systemic disease and can affect the eyes as well.  Choroiretinitis is the most common findings with ocular involvement and is usually self limiting.  When associated with significant uveitis, topical steroids may help preserve vision.  When a patient presents with encephalitis or meningitis put this disorder at the top of your list.  While it may not be the diagnosis it is one you don’t want to miss it. 

Ron P. Gallemore, M.D, Ph.D.

Founder and Director

Retina Macula Institute and the

Retina Macula Research Center

South Bay 310-944-9393

Los Angeles 323-466-9393