For those horse owners who have been given conflicting reports on West Nile Virus and the safety and efficacy of the vaccination currently in use (produced by Fort Dodge Laboratories), I feel compelled to share our recent experience.
A few weeks ago, our aged stallion stopped eating and drinking and showed symptoms of dehydration and neurological dysfunction. We gave him 10 milliliters of Banamine and called our veterinarian. He asked us to take a blood sample and bring it to his office to test for West Nile.
The virus is believed to have infected many horses that showed only mild symptoms or none at all and so they were not tested or reported.
A local horse had been euthanized a few weeks ago by another vet who reported the case to Los Angeles County where it was stabled. Unfortunately, some local horse owners may have overreacted to the news and rushed to inoculate their animals, though there is no known horse-to-horse transmission. A mosquito transfers the virus from an infected wild bird to a horse. Of three horses at one stable that received the shot, one died the next day, one got sick but recovered and the other showed no symptoms. This seems to be in keeping with a reported 30 percent fatality rate from the vaccine.
Our vet told us to keep giving Banamine twice a day for pain and to reduce inflammation, Electroplex paste to encourage drinking and to put Vedalyte (electrolyte) powder in his water. He said that the disease runs its course in three days with just supportive treatment and that antibiotics are definitely not indicated (as with any virus). Though this regimen has been successful in most cases, because of our stallion’s age (30), we were afraid he might not recover.
On the second day, he was losing control of his hind legs and had difficulty getting up, but managed to do so and continued to eat and drink. After four days, he was back to his normal behavior, though he had lost weight and his coat looked dry and dull. His blood test, performed at UC Davis, was positive for IgM antibodies to West Nile Virus, indicating recent exposure or infection.
Of two Bakersfield vets we often consult, there is total disagreement on the safety of the vaccine. One refuses to admit that there has been any fatality “proven” to have been caused by the vaccine. The other says the fatality rate among vaccinated horses is at least 30 percent, while the inoculation provides only 50 percent immunity. He also said that while he’s had dozens of horses recover from the disease, he hasn’t been able to save any who developed symptoms from the vaccination. He also said pregnant mares should not be vaccinated because there have been many cases of spontaneous abortion the day after inoculation. Mares vaccinated earlier have also delivered severely deformed foals. Even the Fort Dodge Web site reports complications with pregnant mares.
Only two horses on our ranch had been vaccinated; one because it was being shipped to Montana. That mare had a serious reaction to the shot and developed hives and indications of a compromised immune system that persisted for six months. She did recover. The other horse, a young gelding, had no noticeable reaction to the vaccine.
Only 20 percent of humans infected with the virus show symptoms, usually fever and aches. But in some cases it affects the nervous system and can develop into encephalitis or meningitis. These were the neurological symptoms we observed in our horse.
A recent Weekly Confirmed Equine Case Report issued by the California Department of Food & Agriculture lists two cases in L.A. County with one fatality. Kern County has reported 20 cases for the year to date (two for the past week) with five fatalities. However, only cases testing positive for the virus and submitted by a veterinarian are listed, so many deaths are not reported or attributed to the vaccine.
On its Web site, UC Davis reports that resistance (immunity) following recovery from natural infection with the virus is still unknown.
The USDA has issued a license for a new DNA vaccine for horses to Fort Dodge Laboratories (a division of Wyeth). That vaccine contains genes for two WNV proteins, and therefore does not contain any whole WNV, live or killed. The DNA version may prove to be safer, but studies on length of immunity are ongoing. Also, vaccinated horses may not be eligible for export as current commercially used tests may not be able to differentiate between this vaccine, conventional vaccines and horses that have been exposed to the actual virus.
For those interested in a more natural approach, a holistic veterinarian in Florida has developed a protocol to weaken the virus and boost the immune system using nutrition, homeopathy, therapeutic-grade essential oils and flower essences. I’ve used homeopathics and acupuncture on my horses for decades and found them most useful particularly when conventional treatments failed.
The season for WNV and other mosquito-borne infections is tapering off with the coming of cool weather. By mid-October it should be about over until next year. Then we hope to know more, but only if people whose horses have had adverse reactions will inform the USDA www.aphis.usda.gov, Fort Dodge Laboratories 800.685.5656 and the Center for Veterinary Biologics 800.752.6255.