West
Nile Virus Update 2011
West
Nile is still active in Arizona. We have been fortunate to have fewer cases in
horses due to preventative vaccinations. But, it is still out there. In 2011,
there have been 96 positive mosquito pools in Maricopa County. So far in 2011,
19 humans and 2 horses have been infected with the disease. Most horses we now
see that become affected by this virus were not vaccinated. We are recommending
to our clients to vaccinate their horses with the West Nile Virus vaccine. The
cost is $30 for the annual vaccine. We recommend vaccinating your horses
against West Nile annually in the spring prior to mosquito season. We have had
minimal reactions to the vaccination after thousands of shots. Foals must be at
least 3 months old. Pregnant mares must be at least 45 days in foal.
As
most of you are aware from recent news, West Nile Virus (WNV) has been very
active in the U.S. since 1999. The mortality rate is about 30-40%. The reason
for the decrease in cases in horses and increase in cases in humans is
attributed to the extensive vaccination program of horses in the
The
horses most susceptible are the young and old, especially horses over 25 years
old. WNV is a mosquito- borne virus. It is maintained in nature by a
bird-mosquito cycle. Thousands of birds nation-wide have died from this disease.
Horses and humans can contract the disease from infected mosquitoes only. The
disease is not transmissible from horse to human, or vice versa. Moreover,
horses are not contagious to each other. Given that mosquitoes are associated
with WNV transmission, the key to preventing or controlling outbreaks of WNV is
to control mosquito populations and prevent exposure to mosquitoes. This can
include dumping stagnate water, using mosquito repellants, and the use of barn
fans may help.
The
disease affects the nervous system. The most common signs of WNV infection in
horses have been incoordination, depression, weakness of the limbs, muscle
tremors or twitching in the muzzle, hypersensitivity to touch & sound, and
a horse down and unable to stand. Fever is only detected in 25% of positive
cases. Diagnosis is based on clinical signs and a positive blood test. If a
horse is positive with clinical signs, they are treated with supportive care
and anti-inflammatories. There is now an anti-serum and hyper-immune plasma
available for treatment as well. 70% of
horses will fully recover; although some may take several months to completely
recover.
The
WNV vaccine is licensed. There are two companies who now produce the vaccine.
We use Fort Dodge’s vaccine. Study results have indicated approximately 90%
protection. Please be sure to vaccinate
your horse as this virus is still prevalent in our area and we see fatalities
from this preventable disease.
Rabies Update 2011
As of Sept 1, 2011, there have been 37 positive rabies cases in wildlife in Arizona with 36 domestic animals that have been exposed. In 2010, there were 114 rabid wild animals. In 2009, there were 273 positive cases of rabies with 3 horses fatally affected. The Arizona State Health Laboratory confirmed rabies infection in a bobcat and coyote from Rainbow Valley in South Buckeye in 2007.
If an animal (horse, dog, cat, livestock) is bitten or otherwise exposed to a rabid animal, it must undergo an extended quarantine. For dogs or cats that are not currently vaccinated for rabies which are exposed to a rabid animal, according to state regulations, must either undergo a 6 month quarantine at an animal control center or veterinary clinic (at the owner’s expense) or be euthanized. If they are currently vaccinated and are exposed to a rabid animal, an immediate rabies vaccine must be administered and a 45-day home quarantine is required.
Rabies is a virus which affects the nervous system. The disease is usually contracted from a bite or saliva contaminating an open wound. In Arizona, skunks, bats and foxes are the most common carriers of this virus. In both of these cases, the viruses were the gray fox variant of rabies. Wild animals which could carry the disease in Arizona include foxes, skunks, bats, coyotes, javelina, coati, and raccoons. The incubation time can vary from weeks to months before clinical signs appear. Since rabies affects the nervous system, the most common sign is behavioral changes. In horses, signs can include fever, depression, lameness, wobbly gait, muscle fasciculations, or anorexia. These symptoms will quickly progress over the next 5-7 days until death. There is no treatment, only prevention. Once an animal shows clinical signs of the disease, it is almost always fatal.
We are recommending to all Buckeye residents to be sure that all your dogs, cats and horses are vaccinated for rabies. You can call our clinic to set up an appointment to have your horses vaccinated. Foals can be vaccinated if they are older than 3 months. Boosters are recommended annually for horses. The AAEP (American Association of Equine Practitioners) now recommends rabies vaccine as one of the “core vaccines”. Even if you don’t live in Buckeye, if you camp, travel, or would like to have your horse vaccinated, please call for an appointment. If you need your dog or cat vaccinated, please call your local small animal veterinarian.
If you see a wild animal acting unusual, neurologic, or aggressive, please call the Arizona Dept of Health at 602-364-4562. Do not approach any wildlife acting unusual or aggressive. Humans are also susceptible to this fatal disease if bitten.
EHV-1 2011 Information
We understand that there was a high level of concern regarding reports of an outbreak of EHV-1 (neurologic herpes) in May 2011 and how it may affect horses in Arizona. This outbreak is reported to have started at a NCHA cutting show in Ogden, Utah which was attended by horses from many western states. There were several confirmed cases of EHV-1 in most of the Western States including Arizona. Every affected horse was at the cutting horse show in Ogden, Utah, or horses directly exposed to those horses at that show.
At that time, we were
recommending that anyone who suspects that their horse may have been exposed to
the virus take their horses temperature twice daily and notify our clinic at
623-386-2928 if their horse has a fever of over 102. We also ask that you call
if your horse shows respiratory signs (cough, nasal discharge) or any
neurological sign. We were recommending limiting travel to necessary travel
only and minimizing your horses exposure to other horses as much as possible.
At that time, we were taking temperatures on horses coming to the clinic as a
precaution. Below is a statement that was issued by the American Association of
Equine Practitioners (AAEP) regarding the previous EHV-1 situation. Further information can be
obtained by visiting the AAEP website at aaep.org
There were reports of
equine herpes virus myeloencephalopathy (EHM) affecting an unconfirmed number
of horses in the U.S. and Canada. This outbreak appears related to initial
cases at a cutting horse show in Ogden, Utah, which was held from April 29 -
May 8. Horses at that event may have been exposed to this virus and
subsequently spread the infection to other horses. While the true extent of
this disease outbreak is uncertain, there is clearly a very significant
elevated risk of EHM cases at this time. At this time control of the outbreak
is critically dependent on biosecurity. Laboratory
submission of nasal swabs and whole blood samples collected from the exposed
horse can be utilized for virus detection and isolation. Please consider
testing any suspected cases.
The EHV-1 organism spreads quickly from horse to horse but typically only
causes neurological disease sporadically. However, in an outbreak of EHV-1
neurologic such as we are experiencing now, the disease can reach high
morbidity and case fatality rates. The incubation period of EHV-1 infection is
typically 1-2-days, with clinical signs of fever then occurring, often in a
biphasic fever, over the following 10 days. When neurological disease occurs it
is typically 8-12 days after the primary infection, starting often after the
second fever spike. In horses infected with the neurologic strain of EHV-1,
clinical signs may include: nasal discharge, incoordination, hind end weakness,
recumbency, lethargy, urine dribbling and diminished tail tone. Prognosis
depends on severity of signs and the period of recumbency. There is no specific
treatment for EHV-1, although antiviral drugs (i.e. valacyclovire) may have
some value before neurological signs occur. Non-specific treatment may include
intravenous fluids, and other appropriate supportive therapy; the use of
anti-inflammatory drugs (NSAIDs) is strongly recommended. Currently, there is
no equine vaccine that has a label claim for protection against the
neurological strain of the virus.
Horse-to-horse contact, aerosol transmission, and contaminated hands,
equipment, tack, and feed all play a role in disease spread. However, horses
with severe clinical signs of neurological EHV-1 infection are thought to have
large viral loads in their blood and nasal secretions and therefore, present
the greatest danger for spreading the disease. Immediate separation and
isolation of identified suspect cases and implementation of appropriate
biosecurity measures are key elements for disease control.
At this time, there have been no new cases of EHV-1 since May 2011 and the
outbreak has been contained. Travel restrictions have been removed and there is
no longer a high risk in this state.
© Durango Equine copyright all rights reserve.