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New Ross Veterinary Services Treatment with Care and Compassion |
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horses and west nile virus
Horse Owners: Take Precautions Against West Nile Virus All horses that are older than four months of age should be vaccinated for the West Nile Virus. The vaccine is relatively new, but appears to be safe, with thousands of horses vaccinated nationally. The vaccine is a killed virus, so there is no threat of contracting the disease from the vaccine. Horses do not spread the disease from one horse to another, nor can they spread it to humans. WNV is spread by mosquitoes, after biting an infected bird (mainly crows). Mosquito control is also highly recommended, and will help prevent the further spread of WNV. Most fly sprays will also repel mosquitoes, as well. We carry fly spray which does repel mosquitoes, and we also carry a spot-on product, Freedom, which keeps flies & mosquitoes off for 14 days." As in humans, elderly and young horses are particularly susceptible to the virus and to its most severe symptoms. Signs of West Nile disease may include: ataxia, muscle tremors in trunk and lips, weakness in the hind limbs, inability to get up, and sudden death. Severely affected horses develop swelling in the brain and central nervous system, and often die of the disease. In most cases, early treatment has been the key to survival. Infected horses should be treated symptomatically, and may be able to be treated on the farm, since there is no cure for the disease itself. Severely affected horses would probably need to be referred to an equine hospital for intensive treatment. The closest such referral center would be the Purdue Large Animal Hospital. Click on this link to read about West Nile Virus on the CDC website: http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm Q: Where did West Nile virus come from? A: West Nile virus was first identified in the West Nile district of Uganda in 1937, and has since been found in other parts of Africa, Eastern Europe, West Asia, the Middle East, and the United States. The strain of virus found in the United States most closely resembles that found in the Mediterranean and Middle East. Q: How is West Nile virus transmitted? A: Mosquitoes draw the virus from infected birds and transmit it to other animals, including humans, through bites. West Nile viral encephalitis develops when the virus multiplies and crosses the blood-brain barrier. West Nile virus is not transmitted directly from animal to person, person to animal, animal to animal or person to person; however, rare instances of transmission via organ transplantation or blood transfusion have been reported. Ticks infected with the virus have been found in Asia and Africa but there are no verified reports of ticks spreading the virus and their role in transmission has not been determined. Q: What is the risk of a person contracting West Nile virus? A: The risk of becoming ill from a single mosquito bite is extremely low. In areas where mosquitoes carry the virus, less than 1% are actually infected. Even if mosquitoes are infected, less than 1% of people bitten and infected by those mosquitoes become severely ill. Q: What clinical signs are associated with West Nile virus infection? A: Humans—Most humans infected with the virus are not aware that they have contracted it. If a person does become ill, clinical signs are usually mild and include fever, headache, body aches and, in some cases, skin rash and swollen lymph glands. Signs of more severe infection include high fever, neck stiffness, muscle weakness, convulsions and paralysis. Death rates associated with severe infection range from 3% to 15% and are highest among the elderly. Horses—The most common sign is weakness, usually in the hindquarters. Weakness may be indicated by a widened stance, stumbling, leaning to one side, and toe dragging. In extreme cases, paralysis may follow. Fever is sometimes evident, as are depression and fearfulness. Approximately 33% of cases of West Nile viral encephalitis in horses proved fatal during the 2001 outbreak in the United States. Other animals—Wild birds infected with West Nile virus in the United States are most often found dead; therefore, descriptions of clinical signs in wild birds are not readily available. Nor have clinical signs associated with West Nile virus infection in dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, and domestic birds been well described. It appears that, although they may be infected, many members of these latter species rarely develop clinical signs of disease. Q: How is West Nile viral encephalitis diagnosed and treated? A: Diagnosis of West Nile viral encephalitis is based on a history of exposure, clinical signs, and results of diagnostic tests. As for all viral diseases, treatment consists of providing support (e.g., hospitalization, intravenous fluids, respiratory support, prevention of secondary infections, and good nursing care) while the affected individual's immune system responds to the infection. Q: Can West Nile viral encephalitis be prevented? A: A vaccine is now available for horses. For other species, including humans, limiting exposure to mosquitoes is considered effective prevention. The following actions may reduce the risk of mosquito bites and possible exposure to West Nile virus:
West Nile viral encephalitis is an emerging disease and new information continues to become available. Visit the AVMA home page, www.avma.org for more information on this and other animal and public health issues. Another important vaccination for horses that is often neglected is rabies. Several bats in Montgomery county have tested positive for rabies. Horses, just like dogs, cats, and humans, are susceptible to rabies. Horses should be vaccinated against rabies yearly. © 2006 New Ross Veterinary Services |
