West Nile Virus in Birds

By Rick Axelson, DVM

This virus is commonly found in Africa, West Asia, Eastern Europe and in the Middle East. It is believed to have arrived in eastern U.S.A. in the summer of 1999.

How is West Nile Virus spread?west_nile_virus_in_birds-1

The West Nile Virus (WNV) is transmitted by the bite of a mosquito (primarily Culex species) that is infected with the virus. The mosquitoes become infected after biting birds carrying the West Nile Virus. The virus circulates in the blood of infected birds for several days prior to the bird dying. The WNV incubates in the mosquito for 10-14 days before it can be transmitted to another host. Birds, humans and animals are exposed when the mosquito bites to obtain a blood meal. Birds participate in spreading the virus, as they are both susceptible to the virus and act as the host.

Do they all get sick?

"Not every healthy person, animal or bird bitten by an infected mosquito will come down with WNV."

Not every healthy person, animal or bird bitten by an infected mosquito will come down with WNV. It is rare for humans and animals to develop severe or fatal illness. Some birds such as raptors (owls, falcons, eagles, hawks, kestrels, etc.), crows and jays are extremely susceptible to WNV and have been hit hard by this virus in several areas around North America. Avian pathologists agree that our pet birds are definitely susceptible. Any exposure has risk. Apparently, most infected wild birds do survive.

What should I look for?

A parrot with a severe WNV infection may become sick very quickly and will be found on the bottom of the cage, or will be suddenly found dead with few or no warning clinical signs. There are few documented cases of pet birds with WNV so there is an incomplete picture of what to expect. Speculation leads us to believe the chances are very good that an infected susceptible parrot may not show signs of illness at all, as seems to occur in many species of indigenous birds.

WNV can cause encephalitis (inflammation of the brain). The signs include fever, neck stiffness (at least in other species), stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis and death.

How can I prevent my bird from getting sick?

"Keep your bird indoors during the mosquito season if possible especially dawn, dusk and early evening."

There is NO treatment once infected with WNV. It is easier to prevent the problem than to deal with it once it has happened. The most effective means of preventing contraction of WNV is to eliminate exposure to mosquitoes. Keep your bird indoors during the mosquito season if possible especially dawn, dusk and early evening. Have properly sealed screen windows and keep the doors closed. Mosquitoes can sneak indoors as you come and go. Be diligent about reducing standing or stagnant water in your immediate surroundings. Old tires, buckets, clogged eaves troughs, puddles, ponds, poorly drained land, ditches, etc., can be ideal breeding grounds for mosquitoes. If it is not possible to eliminate the water then treat it with a mosquito larvicide. There are various products (such as SonicWebä) that will attract and kill biting insects. Mosquito repellents have not been sufficiently tests for safety on birds and are NOT recommended at this time.

Is there any vaccine against West Nile Virus?

A vaccine is available for use in horses. Research has shown that while the vaccine seems to cause no harm in avian or bird species, it appears that the vaccine may not stimulate the immune system enough to produce a protective titer (the antibodies produced against the virus). This means that the vaccine may not effectively protect a bird from the WNV. There may be special cases where it might be in the bird's best interest to vaccinate it with the equine vaccine. These cases include high risk species such as raptors, or birds in high exposure areas.

"Vaccine may not effectively protect a bird from the WNV."

This is a topic of much concern and ongoing research. Even the information presented in this summary may be quickly outdated. Please contact a veterinarian familiar with birds for the most recent information about this important disease.

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