West Nile Virus Infection Threatens Horses Jonathan Palmer, VMD, DACVIM Associate Professor of Medicine New Bolton Center, School of Veterinary Medicine University of Pennsylvania West Nile Virus (WNV) pri marily causes disease in birds and is usually spread by a mos quitoes, but it occasionally causes disease in horses. Horses become infected with WNV by the bit of a mosquito which previously (at least six to 10 days earlier) fed on a bird in fected with WNV. Infection does not always cause clinical disease in horses. In the recent outbreak of WNV on Long Island, N.Y., as many as a third of the horses on the outbreak farms may have been infected but only 14 per cent developed disease. When horses have clinical signs, the disease can be very se rious. Half of the clinically af fected horses on Long Island died or were euthanized. This is the only outbreak of WNF in horses ever reported in North America, but the disease in horses has been frequently re ported in Europe and Africa with similar results. Horses with West Nile Fever can have a variety of clinical signs. They may have a mild flu like syndrome with fever, de pression, listlessness, and occasionally somnolence. When fever occurs, it may be biphasic, with the early fever associated with mild flu-like signs and a second fever a week later associ ated with the onset of more se rious neurologic signs. Some cases will develop muscle fasciculations and an un usual muzzle twitching. They may show more serious neurolo gic signs including incoordina tion and ataxia (stumbling), circling, aimless wandering, head pressing, and hyperexcita bility followed by convulsions, coma, and death. In some outbreaks a progres sive hind limb paresis (incoordi nation, ataxia, stumbling) progressing to complete hind limb paralysis (inability to rise behind) and finally front leg in volvement is reported as typical. POURED SOLID CONCRETE RSS 17 Years Experience In Pouring Concrete Manure Pits! .^eJ!K * * "•% Far Left: 1-Million Gallon Circular Manure Storage Tank Far Right: 2 Silage Pits In-Barn Manure Receiving Pit f*“l • »-W-'-i . - ■■ ■ .■■■- —— " -*■*- » ■■^V^.t':' **, ***-—». >« ** 300' Long Manure Pit For Hog Confinement All sizes available round or rectangular Simultaneously, brain signs will be progressive (depression, som nolence or hyperexcitability, convulsions, coma). Death may occur within five to 10 days of development of serious signs in half of the cases. The other half will recover with the most dra matic improvement within three weeks. West Nile virus is primarily transmitted between birds by mosquitoes. Occasionally virus carrying mosquitoes will bit mammals exposing them. The Veterinary Services sec tion of Animal and Plant Health Inspection Service (APHIS)/ USDA has concluded, based on experimental inoculations car ried out on horses, that horses are not involved in the transmis sion cycle on WNV. That is, horses are terminal hosts be cause they do not maintain a sufficient viremia to infect mos quitoes or other mammals (see the USDA Website at http://www.aphis.usda.gov/vs/ epAVNV/). Previous studies in horses support this conclusion. This means, as stated by the Centers for Disease Control and Preven tion, (see the CDC Website at http://www.cdc.gov/ncidod/ dvbid/arbor/W est —N ile —Q A. htm) that infected horses will not transmit WNV to other horses or to people. So an in fected horse is not a threat to other horses in contact with it and people cannot contract West Nile Fever by caring for an infected horse. However, special care should be taken when han dling blood, spinal fluid, or ner vous tissue from suspect animals, since these may contain virus. The virus has not yet been identified in Pennsylvania or Delaware; however it has been found in birds in New York, Connecticut, New Jersey, and in one bird in Maryland (see USDA Website for a map). The virus is introduced into an area through infected birds. In the outbreak last fall, some infected birds developed neuro logic signs such as ataxia (loss of coordination), tremors, abnor mal head posture, circling, and -I Take the questions out of your new construction. Cali Balmer Bros, for quality engineered walls. Invest in Quality - Balmer Bros, CONCRETE WORK. INC. Liquid Manure Tank - 400,000 Gallons 425,000 Gallons It will last a lifetime. convulsions followed by death. The appearance of dead birds in an area may be an early warning that the virus is present. When handling dead birds that may have died from WNV infection, care should be taken. There is no evidence that people can catch this disease from dead birds, but the Center for Disease Control and Preven tion recommends that no one should ever touch any dead animal barehanded. Call your local health department for proper procedures for handling of dead birds. How can horses be protected from WNV infection if the virus enters the area? The key is mos quito control to stop the bird mosquito infection cycle. The primary mosquito vector is Culex spp. This mosquito spends its entire life within a range of about 1,000 yards. Thus local control can be very effec tive in stopping WNV transmis sion. The most effective method of mosquito control is to destroy the mosquito larval habitat. Culex mosquitoes can breed in any puddle that lasts more than four days. So it is important to reduce the amount of standing water available for breeding such as water troughs (should be cleaned at least once or twice a week), water buckets not in use, plastic wading pools, bird baths, wheelbarrows, clogged roof gutters, discarded tires, tin cans, plastic containers, ceramic pots, or any water-holding container. Although less effective than preventing mosquito breeding, efforts to limit the horse’s expo sure to adult mosquitoes can also be attempted. Horses should be stabled inside during peak mosquito feeding times which are dusk and dawn. Also, insect repellent approved for horses can be used (always follow label instructions). CONCRETE PUMPING SERVICE AVAILABLE l iTT ,r ..Jurfi CASHS Team Participates In Pa. Envirothon CHAMBERSBURG (Frank lin Co.) Penncrest High School, Delaware County, has won the 17th Annual Envi rothon and will represent Penn sylvania at the National Envirothon in Nova Scotia, Canada, July 31-Aug. 6. The 13th National Canon En virothon will be at Acadia Uni versity in Wolfville, Nova Scotia, Canada. Pennsylvania has won the national event in 1988,1989,1994, and 1997. “The Pennsylvania Envi rothon program is an essential part of our students’ environ mental education,” Department of Environmental Protection Secretary James Seif said. “Pennsylvania students learn about the environment, ways to care for it, what to do to protect it, and, ultimately, gain respect for nature.” More than 300 high school students from 62 counties par ticipated in this year’s Envi rothon, representing more than 500 school districts, 61 conserva tion districts, and Philadelphia County. The annual event was May 25 at Shawnee State Park, Bedford County. Placing 17th overall in the competition from Franklin County, the team members from LANCASTER (Lancaster Co.) The Tobacco Board of Trade was founded in 1905 to promote equitable principles and foster trade and commerce for the tobacco industry in Lan caster County. The board is trying a new en deavor this year by offering scholarships for students furth ering their education in an agri cultural field. This is to Mixer And Boom Trucks 243 Miller Road Akron, PA 17501 (717) 733-0353 6.30 AM - 3.30 PM (717) 859-2074 After 6:00 PM Lancaster Farming, Saturday, July 1, 2000-C3 Tobacco Board Awards Scholarships Chambersburg Area Senior High School (CASHS) include Tyler Black, Greg Hershey, Sea sons Suders, Matt Booher, and Tom Harwood. The team’s fac ulty adviser is Eddie Parsons. This team won first place at the local Envirothon competi tion at Cowans Gap State Park on April 26 sponsored by the Franklin County Conservation District. The District’s Environ mental Education Coordinator Donna Hays plans the event locally with Fulton County Con servation District’s Coordinator Karen Kelly. The Envirothon tests stu dents’ knowledge of environ mental resources and their relation to each other and human activities. Students in grades nine through 12 complete exercises in aquatics, forestry, soils, wildlife, and a current en vironmental issue. The 2000 cur rent issue was wetlands management. Technical expertise for the Envirothon is provided by the Department of Environmental Protection, the Department of Conservation and Natural Re sources, the Pennsylvania Game Commission, the Pennsylvania Fish and Boat Commission, and the USDA’s Natural Resources Conservation Service. encourage a new generation to preserve our agricultural heri tage. The board has awarded three scholarships for the year 2000. The winners are Audrey Nissly of Penn Manor High School, $2,000; Russell Howard of Lam peter-Strasburg High School, $1,500; and Melinda Morrison, runner-up of Ephrata High School, $l,OOO.
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