ArizonaRealCountry.com 5 January 2019 There do not seem to be as many West Nile cases now as there were several years ago. Do I still need to vaccinate? YES! While it is true that the incidence of West Nile Virus in horses has decreased, it is still a very prevalent and deadly disease. West Nile Virus (WNV) first entered the United States in 1999. 2002 was the peak year for horses with 15,257 cases nationwide. The number of equine cases has continued to go down each year to 109 US equine cases in 2010. The decrease in the number of cases has been attributed to vaccination and to natural immunity from exposure. 70 to 90% of non-vaccinated control horses become viremic and 90 to 100% develop serious signs of encephalomyelitis. There is no vaccine available for humans, and while the incidence has decreased in humans, it has not decreased at nearly the rate of horses where we have a very effective vaccine. The case fatality rate for horses exhibiting clinical signs of WNV infection is approximately 33%. Data have supported that 40% of horses that survive the acute illness caused by WNV still exhibit residual effects, such as gait and behavioral abnormalities, 6 months post-diagnosis. Thus vaccination for West Nile virus is recommended as a core vaccine and is an essential standard of care for all horses in North America. Should I vaccinate for tetanus? Tetanus (lockjaw) is caused by a toxin-producing bacteria called Clostridium tetani that is ubiquitous in the soil. It gains entry to the body through wounds, especially puncture wounds. Horses are much more sensitive to the toxin than humans, which results in extreme muscle tension and spasms. It is a terrible, painful disease that is nearly impossible to treat and has a fatality rate close to 100%. We vaccinate horses frequently for this disease because we cannot prove what titer (level of circulating antibodies to Clostridium tetani) will protect the horse should it become exposed. These levels are fairly well established in humans and less frequent booster shots have been proven to protect against the disease. The high frequency of contaminated puncture wound events in horses means that most are exposed several times during their lives. The tetanus toxoid vaccine is a very safe, reliable, and inexpensive vaccine compared to the terrible consequences of infection, so we tend to err on the side of caution and recommend yearly vaccination as well as a booster vaccination in the presence of a wound to prevent serious illness. To tailor your horse’s vaccination program to his situation, consider: Location: The horse should be vaccinated against diseases he’s likely to encounter where he lives or may be shipped. Some risks are widespread, some regional and some local. Lifestyle: Horses that go to shows or other venues where they encounter horses from other barns need protection against diseases that spread horse to horse. Where other horses could bring infection onto the farm, even horses that stay home need protection. Horses can carry some diseases without showing symptoms, shedding bacteria and viruses, and infecting others. Use: Broodmares may need protection against diseases that can cause abortion. Revaccinating mares four to six weeks before foaling helps ensure high levels of antibodies in colostrum (first milk), which help protect foals in the first months of life. Age: Young horses (under age 5) are more susceptible to some diseases, such as equine herpesvirus and West Nile virus. Ask the Vet VACCINATIONS Arizona REAL COUNTRY the magazine Mike Barna Publisher ArizonaRealCountryMagazine@gmail.com (602) 622-3695 Erika Smith Royal Editor erika963realcountry@gmail.com Misty Voitovski Creative Director Contributing Writers Lee Anderson, Desiree’Byrne, Kimmie Dillon, Charlie LeSueur, Jim Olson, Robert Piekow, Bill Roberts, Alan Rockman, Bob Roloff, Hank Sheffer, Buddy Uldrikson, Michele Wilson Arizona Real Country is owned and published by Barna Broadcasting LLC. No person, organization or party can copy or reproduce the content on our website and/or magazine or any part of this publication without a written consent from the editor’s panel and the author of the content, as applicable. The publisher, authors and contributors reserve their rights with regards to copyright of their work. Follow Arizona Real Country for news, events, giveaways and more! 801 W. Wickenburg Way Wickenburg, AZ 85390 (602) 622-3695 ArizonaRealCountry.com Thus vaccination for West Nile virus is recommended as a core vaccine and is an essential standard of care for all horses in North America.