West Nile Virus is in a group of viruses called flaviviruses. Scientists believe that the virus has been in the eastern U.S. since the early summer of 1999, or perhaps longer. This virus is commonly found in Africa, West Asia, Eastern Europe and the Middle East. With the ease of international travel, it is very easy to spread viruses to other parts of the world. In the case of the West Nile Virus (WNV), the virus was able to establish itself in the eastern U.S. The virus is transmitted by the bite of a mosquito (primarily one of the Culex species) that is infected with the virus.
So, how is this virus spread? Mosquitoes become infected when they bite infected birds. Infected birds may circulate the virus in their blood for a few days before they die. After the virus incubates in the mosquito for 10-14 days, infected mosquitoes can then transmit the WNV to humans and animals when they bite to obtain a blood meal. The virus is harbored in the salivary glands of the mosquito, and when it feeds, it can inject the virus into its victim, where it may multiply, possibly causing illness. Not every person or animal bitten by an infected mosquito will come down with WNV. People and animals with strong immune systems may be able to effectively eliminate the virus from their bodies. Most people who become infected with WNV will have either no symptoms or only mild ones. WNV can result in severe or fatal illness in rare cases.
Some animals, such as the crow and jay, appear to be extremely susceptible to this virus, as anyone living in the area where the virus is prevalent knows! According to Dr. Randall Crom, staff veterinarian with U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS), avian veterinarians should reassure clients that "the risk is low" for their bird or horse contracting the virus, and that there are measures they can take to prevent an attack, such are reduction in stagnant water, where mosquitoes breed. WNV can infect people, horses, many types of birds and some other animals. At this time, over 110 species of birds are known to have been infected with WNV. Although birds, especially crows and jays, infected with WNV can die or become ill, most infected birds do survive.
You cannot catch the virus directly from another person. It is only transmitted from the bite of an infected mosquito. Recently, however, there is the suspicion that a human contracted the virus from a blood transfusion from a person harboring the WNV. That person (seriously injured in a car accident) died after receiving multiple transfusions, and then her organs were used for transplantation. Now, it appears that the recipients of the transplants may have contracted the virus from the transplanted organs.
In Asia and Africa, ticks have been found to harbor the virus, but so far, there is no information to suggest that ticks played any role in the most recent outbreak in the U.S.
There is also no evidence that a person can catch WNV from handling live or dead infected birds. If you live in an area in the United States known to have WNV, and you are finding dead crows or other birds in your yard, to be safe, you should probably not handle dead birds with your bare hands. Wear disposable gloves, or use double plastic bags to pick up a carcass for disposal. It is best to call your local health department to report dead birds so that you may receive specific instructions on what to do with any dead birds in your yard.
From recent discussions that I have had with avian pathologists and virologists, our psittacine and passerine birds are definitely susceptible to WNV. There are currently several different tests available for testing parrots for WNV. Antech Diagnostic Laboratories, where I am an avian/exotic veterinary consultant, is currently offering three tests for West Nile Virus. These are being run through state-of-the-art veterinary laboratories around the country. A blood test, called serum neutralization, is a titer that can show if a parrot has been exposed to WVN. A positive titer indicates past or present infection (or vaccination). A second titer may be necessary to confirm an active infection. (Note: a vaccination against WNV is now available for horses, but no vaccine is approved for use in birds. More on that later.) A very specific test, called a DNA PCR, can be run on a bird that might have died from WNV. A swab of the bird's brain, spinal cord or kidney can be tested for the presence of the virus. Spinal fluid or blood can also be tested for the presence of the virus in a living bird, using the DNA PCR test. Also, another test, called virus isolation can be performed on brain, spinal cord or kidney of a deceased bird, or from a renal biopsy in a live bird.
A parrot seriously infected with WNV is likely to become ill very quickly, and will either be found down on the floor of the cage, or it might be discovered dead with few or no clinical signs before death. Theoretically, a bird ill with WNV would have a low white blood cell count (WBC) which is typical with many viral infections. There have only been a few documented cases in psittacine birds that I know of that have died of WNV in the United States (including a cockatiel and a cockatoo). At this time, we do not have a complete picture of what to expect if pet birds become ill from WNV. We can extrapolate what we've seen in other species of birds and what we know about the virus in general, but until researchers and veterinarians report cases in parrots, we can only speculate. However, the chances are very good that a susceptible parrot that has become infected may show no signs of illness at all, as occurs in many species of indigenous birds.
If a pet bird is suspected of having WNV, there is no specific treatment for the virus itself. While we have some drugs for treating certain viruses, unfortunately this isn't one of those viruses. Technically, an avian veterinarian can provide support care, such as intravenous fluids, heat, oxygen, good nursing care and medications to prevent secondary infections if a bird is caught in time and has signs of a viral infection (low WBC, encephalitis, etc.) This virus can cause encephalitis, which is actually an inflammation in the brain. The signs may be fever, neck stiffness (at least in other species), stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis and death.
So, what can you do if you live in an area that has WNV? The best thing that you can do is be diligent in preventing mosquitoes from entering your home. Make sure your window screens are in good shape, and properly seal windows. Enter and exit your home quickly, to prevent mosquitoes from sneaking into your home (that means no door dialogues that many families are famous for!) Some perfumes and fragrances seem to attract mosquitoes. Wear long-sleeved shirts, long pants, socks and a hat when outside during the times mosquitoes are most active. If possible, stay indoors during peak mosquito times (dawn, dusk and early-evening). Apply insect-repellent containing DEET. Clothes can be treated with DEET or permethrin, since mosquitoes may bite through thin clothing. Do not apply permethrins directly to the skin. Make sure there is no standing water in your yard. Encourage your neighbors to do the same. You can purchase disks that can be placed in water outside that will kill mosquito larvae (check at your local hardware store). Keep your pet birds inside during mosquito season if possible.
For birds living outdoors in aviaries and for outside pets, I recommend a product called SonicWebTM. This device can cover approximately one acre and will attract mosquitoes and other biting insects (including no-see-ums, biting flies and midges) to the unit where they will be trapped and killed. The SonicWeb has four genetic lures, including a heartbeat lure to attract mosquitoes. It also draws insects using octenol, a natural fragrance that mimics breath. The unit combines ultraviolet reflection and contrasting stripes to visually attract insects. The unit also uses heat, to mimic the body temperature of living animals (110 degrees F). Once attracted, the insects are captured with a sophisticated adhesive paper with a glue that works in all weather conditions. SonicWeb can also be used to help control/remove mosquitoes from around the home. This will help prevent mosquitoes from entering homes, patios and porches. The SonicWeb is the only mosquito control unit that this author recommends.
Minimizing exposure to mosquitoes is the best and safest way to prevent exposure to WNV. People with outdoor pets would be well-advised to purchase an effective mosquito unit that is safe and non-toxic to pets. Foggers produce a spray that is meant to kill mosquitoes, but they have not been found to be very effective. If possible, cages and aviaries can be covered with mosquito netting.
The good news is that mosquitoes don't have an easy time biting most parrots and passerine birds, because the skin on the feet and legs is covered with scales, and feathers often a good layer of protection against bites. Birds with bare skin on the face may be bitten there (macaws, for example), but all birds are susceptible to bites on the bare skin around the eyes. I would not recommend using mosquito repellant on birds, since no testing has been performed to determine the safety of these chemicals on birds.
So, the main thing that you can do to protect your pet birds is to minimize the chance of exposure to mosquitoes. Be especially diligent about keeping doors closed at dawn, dusk and early evening, when mosquitoes are most active. Perhaps it would be a good idea to cover your birds' cages at night with mosquito netting. Please note that, according to the CDC (Centers for Disease Control and Prevention), vitamin B and "ultrasonic" devices are not effective in preventing mosquito bites.
Raptors (owls, falcons, eagles, hawks, kestrels, etc.) are being hard hit by this virus in several areas around the country, according to reports from avian vets in practice. A vaccine is now available for horses. Preliminary tests being performed by avian specialists who have vaccinated birds with the equine vaccine are not especially promising. Their research has shown that while the vaccine seems to cause no harm in avian species, it also does not appear to stimulate the immune system enough to produce a protective titer (a measure of the antibodies produced against the virus). This means that the vaccine will probably not adequately protect a bird from the virus. There may be special cases where it might be in the bird's best interest to vaccinate it with the equine vaccine (rare raptors, ratites, including emus, rheas, cassowaries, and ostriches, and birds with other immune-compromising diseases). Another equine vaccine for Eastern Equine Encephalitis (EEE) has been successfully used in ratites to protect against EEE and WEE. Much more work needs to be performed before recommending vaccinating pet birds against WNV.
Some of this information was taken from the CDC website. For further information, you can contact the CDC. For information on the effects of WNV on humans, please contact your physician or local health department.
Copyright © 2006 Margaret A. Wissman, D.V.M., D.A.B.V.P.
All Rights Reserved
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