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West Nile Virus

also see Granulometous meningioencephalitis (GME)
also see Hepatic Encephalopathy

 

West Nile Virus

 

Question: DR Mike

Please help me with any information you can on west nile virus in dogs. We live in the Texas Panhandle and have just found out that our dog has been tested positive. After extensive tests since her initial onset of illness Dec 7, 2002 and our continual bugging them have this bit of information, but no know treatment, cure, or where to go from here. My dog, Molly, a 6 yr old Schnauzer became ill in the night, awakening me with her left front paw partially paralyzed, with in 15 minutes the entire left side was paralyzed, and with in 30-45 minutes she was paralyzed from the neck down. We rushed her to the emergency animal clinic which monitored her a little more that 24 hours before sending us to Oklahoma State University Vet School for further testing and assistance. From the very beginning we asked if this could be related to West Nile Virus, partially due to the fact that we live on a lake with the possibility of her getting into alot of germs, everytime being told no. A barrage of test were performed, cat scan, mylogram, spinal tap, x-rays, and supposedly many blood tests. Some of these tests were also sent to Michigan State for testing. None of these came back to show us anything after weeks of waiting and her suffering. She did manage to regain some motion and took her first step on Christmas Day by her self. We called her our little "tiny tim" on Christmas. She still has severe damage to the left side. Our veterinarian here has tried every treatment that all the so called experts have given, including 4 days of injections of some "cancer tx agent" not sure what was in it. She seemed to improve to a small degree, but not much. She still has great problems with urinary control and has to wear diapers. About 10 days ago our vet ran another blood test directly after the last injections to check for white blood cell count and to specifically ask for testing of west nile virus, AGAIN. This test was sent to the Texas A & M University. The results revealed that she is positive west nile virus. We are now trying everywhere to get all the information possible to help her, protect our other pet who is much older that we rescued from an animal shelter 3 years ago, she is blind in one eye and probably doesn't have the strength to fight this disease as Molly has fought. We also want to do what we can to inform and protect our neighbors and protect ourselves with correct and documented information. Is this contagious to our other pet that eat and drink together, and can it be transmitted to one of us by either blood or saliva, especially through a dog bite? Any and all information will be appreciated. We love our pets as children and would do what it takes to help and protect them.

I thank you for your assistance in advance and will be anxiously awaiting a response.
Debbie 

Answer: Debbie-

West Nile Virus (WNV) infection in dogs is still a rare event. There isn't a lot of information on how to treat dogs that are affected or what the long term prognosis for recovery is in dogs who have been affected by the condition. There is more information on horses, since they get the disease more frequently and information on people, who have been affected more frequently than dogs even though it is still pretty uncommon in people, too.

Based on the experiences with other mammals, it is unlikely that the virus can be spread from Molly to any other other animal. At the present time (and this could change as more information is developed), WNV is not thought to be contagious from a mammal, even when a mosquito bites an infected individual. Mammals are considered to be "dead end" hosts. This doesn't rule out exposure of other pets, or people, in the household by mosquito bites from infected mosquitoes, since Molly's exposure indicates that the virus does exist in your area.

I can't tell if the test that was run was a titer test, or not. Titers indicate exposure but do not definitely confirm that WNV is actually causing the clinical signs that are seen. Obviously, it seems reasonable to assume that it is a high probability when neurologic signs and a positive titer are found in the same individual. The signs of WNV are supposed to be variable, but may include fever, ataxia (incoordination), paresis (weakness) or paralysis and immune compromise.

I know of no treatment considered to be effective at killing the virus. Supportive treatment for the patients, such as fluid therapy, medications to control fever, assisted feeding, physical therapy, etc. can all be beneficial in helping the patient survive and recover. Horses who do not die from the infection are reported to improve over the course of several months in some cases and to have residual damage in other cases.

I wish that I had more information specifically relating to dogs.

This is information from the USDA:

APHIS West Nile Virus Factsheet


Provided by United States Department of Agriculture, Animal and Plant Health Inspection Service (APHIS)

Veterinary Services
January 2002

West Nile is a mosquito-borne virus that was first detected in the United States in 1999 The virus, which causes encephalitis, or inflammation of the brain, has been found in Africa, western Asia, the Middle East, the Mediterranean region of Europe, and most recently in various parts of the eastern United States.

Mosquitoes acquire the West Nile virus from birds and pass it on to other birds, animals, and people. While humans and horses may be infected by the virus, there is no documentation that infected horses can spread the virus to uninfected horses or other animals. Migrating birds may play a role in spreading the disease.

History of West Nile Virus in the United States

On September 14, 1999, the National Veterinary Services Laboratories (NVSL) of the U.S. Department of Agricultures (USDA) Animal and Plant Health Inspection Service (APHIS) isolated a virus from neurological and other tissues of flamingos and tragopans (pheasants) from the Bronx Zoo and crows from the New York City area.

Samples of the isolated virus were sent to the U.S. Department of Health and Human Services Centers for Disease Control and Prevention (CDC) for identification. On September 27, CDC officials announced that the isolated virus was very similar to that of the West Nile virus, previously unseen in the Western Hemisphere. CDC later confirmed the virus as West Nile and connected it to an encephalitis outbreak that killed 7 people and infected at least 55 others in the New York City area in 1999. The virus has since been identified in horses, mosquitoes, and wild birds in more than 20 States in the eastern United States and the District of Columbia.

Because this virus is transmitted by mosquitoes, it has the potential to affect livestock and poultry. In 1999 and 2000, a total of 85 horses were diagnosed with encephalitis caused by West Nile virus. The horses were located in numerous States along the eastern coast.

Clinical signs of West Nile virus infection in the New York horses included ataxia (stumbling and incoordination), depression or apprehension, weakness of limbs, partial paralysis, muscle twitching, or death. Fever was not generally observed.

Although the role of commercial poultry in maintaining or transmitting the virus is not thoroughly understood, no clinical signs have been reported in U.S. poultry. According to scientific literature, chickens can develop a short-lived infection, but clinical signs are not seen.

Federal Actions to Protect Agriculture

Any horses showing clinical signs of encephalitis in an area without previous equine cases that year, where other common causes such as rabies can be ruled out, will be investigated by APHIS Veterinary Services (VS) program as having a potential foreign animal disease. VS has developed reliable diagnostic tests for West Nile virus and is on the lookout for virus activity along the Atlantic seaboard. APHIS' Wildlife Services (WS) program collects wild birds to test for West Nile virus. WS initially focused on east coast States from Connecticut to Florida but has now expanded its efforts to the Midwest.

USDAs Agricultural Research Service has conducted inoculation studies with turkeys. NVSL did the same with chickens and NVSLs Foreign Animal Disease Diagnostic Laboratories conducted studies with horses. Only chickens showed the likely potential to produce enough virus in their blood to infect mosquitoes. Each species developed antibodies after being inoculated, and encephalitis was not observed in any of the animals.

VS continues to treat all situations where birds show neurological signs as having the potential for hosting a foreign animal disease. This will allow NVSL to rule out exotic poultry diseases, such as Newcastle disease and highly pathogenic avian influenza, before testing for West Nile.

The CDC, the U.S. Geological Surveys National Wildlife Health Center, and USDA are cooperating to survey for the virus in a wide range of wild birds. This Federal working group, in conjunction with relevant State agencies, gathers and analyzes surveillance data to define the extent to which the virus may be distributed in mosquito and bird populations in the United States.

How You Can Protect Your Animals

You can decrease the chances of your animals being exposed to the virus by decreasing their exposure to adult mosquitos. The best way to do this is by removing any potential sources of water in which mosquitoes can breed. Dispose of any water-holding containers, including discarded tires. Drill holes in the bottom of containers that are left outside. Clean clogged roof gutters on an annual basis. Turn over plastic wading pools or wheelbarrows when not in use, and do not allow water to stagnate in birdbaths. Aerate ornamental pools or stock them with fish. Clean and chlorinate swimming pools that are not in use and be aware that mosquitoes can breed in the water that collects on swimming pool covers. Use landscaping to eliminate standing water that collects on your property; mosquitoes can breed in any puddle that lasts more than 4 days. Thoroughly clean livestock-watering troughs on a monthly basis. Local mosquito-control authorities can help in assessing the mosquito breeding risks associated with your property.

Birds can also be protected by limiting their exposure to mosquitoes. In areas reporting large numbers of bird deaths, investigations are conducted and samples collected to determine the cause of the deaths. People finding dead birds should notify local health officials.

No treatment is currently available for the West Nile virus; however, VS is working to assist all companies interested in producing a vaccine. On August 1, 2001, USDA issued a conditional license for one year to Fort Dodge laboratories, Inc. of Fort Dodge, IA, a division of American Home Products, Inc., for a vaccine intended to aid in the prevention of disease in horses caused by West Nile. The product is restricted to use by a veterinarian in those States where use of the product has been approved by the State's regulatory authorities.

Additional Information

For more information about West Nile virus, contact:
USDA, APHIS, Veterinary Services
4700 River Road, Unit 41
Riverdale, MD 20737-1231
Phone: (301) 734-8073
Fax: (301) 734-7817

For more information about human health issues related to West Nile virus, check the CDC Website.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD).
To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.
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I hope that you find some of this helpful.

Mike Richards, DVM
2/1/2003

also see Canine Distemper Virus

also see Meningitis in Dogs

also see Infectious Disease - Herpes Virus