Guidelines released by AAEP 1-24-08
January 24, 2008—The Infectious
Disease Committee of the American Association of Equine
Practitioners has issued revised guidelines for the administration
of vaccinations to horses. The Committee, chaired by Mary Scollay,
DVM, has made recommendations for the use of vaccines based on the
age of the horse and its previous vaccination history. The
guidelines are intended to serve as a reference for veterinarians as
they employ vaccines in their respective practices.
Highlights of “Guidelines for the Vaccination of Horses” include:
The identification of tetanus, Eastern/Western Equine
Encephalomyelitis, West Nile virus and rabies as “core” vaccines.
Core vaccines have clearly demonstrated efficacy and safety, and
exhibit a high enough level of patient benefit and low enough level
of risk to justify their use in the majority of patients.
The addition of a vaccination protocol for anthrax.
Recommendations for the storage and handling of vaccines, as well as
information on vaccine labeling and adverse reactions.
Inclusion of the AAEP’s Infectious Disease Control Guidelines, which
provide an action plan for the containment of infectious disease
during an outbreak.
The Committee stresses that veterinarians, through an appropriate
veterinarian-client-patient relationship, should use the vaccination
guidelines coupled with available products to determine the best
professional care for their patients. Horse owners should consult
with a licensed veterinarian before initiating a vaccination
“The goal of the guidelines is to provide current information that
will enable veterinarians and clients to make thoughtful and
educated decisions on vaccinating horses in their care,” explained
Dr. Scollay. “The vaccination schedules are complemented by
supporting information on topics including vaccine technology and
disease risk-assessment, allowing veterinarians to customize
vaccination programs specific to the needs of an individual horse or
group of horses. The impact of infectious disease has been felt
across the equine industry in recent years, and the Committee hopes
that these guidelines will be a useful tool in preventing or
mitigating the effects of equine infectious disease.”
The Committee, comprised of researchers, vaccine manufacturers and
private practitioners, updated guidelines that were established by
the AAEP in 2001.
The complete document, along with easy reference charts, is
available on the AAEP Web site at
The American Association of Equine Practitioners, headquartered in
Lexington, Kentucky, was founded in 1954 as a non-profit
organization dedicated to the health and welfare of the horse.
Currently, the AAEP reaches more than 5 million horse owners through
its 9,000 members worldwide and is actively involved in ethics
issues, practice management, research and continuing education in
the equine veterinary profession and horse industry.
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Colic: Updates & Prevention
(From: AAEP News, Dr Nancy Loving)
one of those emergency crises that horse owners seek to avoid. The
National Animal Health Monitoring System (NAHMS) survey says that
for every 100 horses, there will be 4.2 colic events every year. 1.2
percent of these events will be surgical, and 11 percent will be
fatal. The objective of a conscientious horse owner is to find ways
to prevent colic so your horse doesn’t become one of these
statistics, while also understanding how to appropriately manage
colic if it does occur.
horse might appear depressed or “zoned-out,” or he may display
anxious behavior like pawing, looking at his sides, lying down,
getting up, rolling, and a general state of distress. A thorough
veterinary examination helps determine the cause of these behaviors,
and also rules out other medical conditions like tying-up,
laminitis, pneumonia or foaling difficulties. When you
call your veterinarian to attend your
horse, it is greatly helpful to have information about your sick
horse’s vital signs so a
determination can be made about the seriousness of the horse’s
condition, and how quickly the horse needs medical attention.
Learn how to take your horse’s vital
signs -- heart rate, temperature, capillary refill time, and
whether or not there are audible gut sounds. Normal heart rate is
about 32 to 40 beats per minute (bpm). A heart rate over 64 bpm
signifies pain and possibly a more serious problem. A stethoscope is
the easiest means of obtaining a horse’s heart rate, but if you
don’t have one, you can take a pulse from the big vessels behind the
fetlock or along the jaw. The digital pulses on a limb are often
difficult to feel on a healthy horse that isn’t experiencing any
problems, so practice in advance.
Normal rectal temperature in an adult horse is 97 to 101 degrees
Fahrenheit, while a foal may normally run up to 102 degrees
Fahrenheit. A horse may feel sick, depressed and off his feed for
many reasons, including a fever, but a fever may also be a sign of
some serious intestinal problem related to colic, like a necrotic,
leaking or ruptured bowel.
The gums should be healthy and pink and should return to that color
within two seconds of pressing with your finger on the gum line
above the teeth and then releasing. This is referred to as capillary
refill time. A longer time to return color to the gums indicates
that the circulatory system is in distress. Gums that are pale with
a purple flush around the edges of the teeth, called injection or
margination, denotes endotoxin in the circulation as a result of
bacterial overgrowth from gut stagnation.
What Not to Do
Historically, horse owners have walked a colicky horse while
awaiting arrival of the vet. This as an overrated and old myth; a
horse should be kept walking only if he persists in trying to roll
or thrash and is a danger to himself or humans. If the horse will
lie quietly, you can let him be. When you first discover your horse
has colic, it is valuable to try trotting him vigorously on the
longe line for about 15 minutes to see if that will ease pain from a
gas or spasmodic colic. A trailer ride also jiggles the bowel to
achieve similar relief for a simple colic. Under no circumstances
should non-steroidal anti-inflammatory medications (NSAIDs), like
phenylbutazone or BanamineR, be given without first discussing your
case with your veterinarian. These drugs are capable of masking the
pain of a surgical condition and thereby may delay appropriate
treatment. In addition, a horse with intestinal stasis and poor
motility may not absorb oral medications sufficiently to provide a
therapeutic advantage when intravenous administration would work
vet arrives, your horse will be evaluated with a thorough physical
exam. Additionally, your vet may conduct a rectal examination to
determine if there is an impaction or a displaced bowel. A
nasogastric tube passed into the nostril, down the esophagus and
into the stomach is helpful to check for reflux and to administer
fluids, electrolytes, and laxatives when indicated. Depending on the
horse’s condition, it might be appropriate for your horse to receive
pain-relieving drugs and intravenous fluids to improve his comfort
and to improve gut motility. The administration of ample IV fluids
is highly effective in increasing fluid volume in the bowel;
over-hydration of the intestinal tract and its circulation improves
blood flow and motility that might relieve an impaction or return a
mild displacement to normal.
In the event that a horse does not respond well to medical therapy
in a reasonable time, the horse should be shipped to a referral
hospital for further diagnostic workup and possible surgery.
Abdominal ultrasound, abdominal fluid analysis, and blood analysis
are helpful to perform on site at a referral hospital to gain as
much information as possible about your horse’s condition. In
addition, precautionary steps will be taken to protect against
laminitis, which is a possible side effect of severe colic due to
circulatory disturbances created by the release of endotoxins
associated with gut stagnation.
Preventive Steps -- Updates
steps a horse owner can take to minimize the risk of colic.
Many practical measures rely on altering feeding practices, as for
example, limiting the amount of grain fed – too much grain is known
to disturb intestinal health. A pound or two a day is not
necessarily problematic provided a horse also has access to 15 to 20
pounds of hay per day (for the average 1000 lb. horse), but in
general, grain or concentrates should not be the first choice in
nutritional options. Optimal digestion occurs in the large
intestine, but grain is processed mostly in the small intestine yet
is incompletely digested there. This results in passage of a lot of
starch into the large intestine where it is not digested
effectively. Subsequently, the large intestinal pH is altered to a
more acid environment, which then causes the die-off of resident
bacterial flora that are essential for efficient processing of
fiber. Other bacteria also die in the altered environment, with the
potential to release endotoxin into the circulation.
Grain also amplifies acid production in the stomach. Gastric ulcers
are known to be more prevalent in grain-fed horses, especially when
fasted for long periods between feedings. A horse with ulcers might
suffer intermittent bouts of colic, be reluctant to work or is
lack-luster in performance, and often has a poor appetite in spite
of weight loss. Ulcers occur in as many as 93 percent of
high-stressed horses (racehorses, high-level show horses) and 60
percent in the average riding horse or less intense show horse. Risk
factors for ulcers include stress of any kind, such as transport,
illness or injury, dehydration, confinement or social competition in
a herd. NSAIDs (phenylbutazone or BanamineR) are notorious in their
propensity to induce gastric ulcers. Not all risk factors can be
controlled, but offering free-choice hay and substituting other
feeds, like soaked beet pulp or high-fat rice bran or vegetable oil,
for grains helps to reduce the risk of developing gastric ulcers.
Gastric ulcers are confirmed and visualized with a gastroscope,
which is a three meter long, fiberoptic tube with an attached camera
that allows a view of the inside of the stomach. A horse must first
be fasted for about 12 hours prior to passing the tube and scooping
his stomach. Anti-ulcer medications are currently available as a
safe means of treating a horse with gastric ulcers.
Feeding practices influence digestive efficiency in other ways:
Grain ingestion reduces the fluid content of the bowel by 15
percent, and to compound the problem, in an effort for a horse owner
to control a horse’s daily caloric intake, a grain-fed horse is
typically offered less hay. Yet, fiber is an essential component of
intestinal health, and it also serves as a fluid reservoir in the
bowel. The common practices of keeping horses in stalls for a large
portion of the day and feeding them large meals only twice a day
wreak havoc with their digestive health. Stall confinement increases
the risk of colic by at least 50 percent. Intestinal motility is
reduced by confinement and by fasting between large meals. With
reduced intestinal motility comes the risk of impaction colic or gas
distention. The best strategy for minimizing colic is to offer
free-choice grass hay so a horse can “graze” intermittently through
the day. Also, limit grain fed, while providing daily turnout and
Other causes of colic include sand ingestion, often related to
restricted access to hay. Ample fiber in the diet is instrumental in
moving dirt and sand through the digestive tract. If fiber is
restricted and/or if a bored horse nibbles at remaining particles of
hay on the ground, sand may accumulate in the bowel. The best
prevention for sand colic is to feed ample hay, and, when possible,
use feeders (like large tractor tires) to confine the hay and keep
it from being strewn across the ground. Since many horses persist in
throwing hay out of many forms of commercial feeders, sand ingestion
cannot be prevented entirely – it is recommended to feed psyllium
for a week each month to help move through any sand that has
Obesity and parasites also are risk factors for colic, but a
conscientious owner can prevent and manage these concerns. Your
horse should be fed by weight, not volume since the density of hay
varies from bale to bale. Pasture your horses on non-irrigated,
dryland pasture when possible. If your only pasture option is a
rich, irrigated field, then many problems, including obesity, can be
avoided by fitting your horse with a grazing muzzle or by limiting
turnout time. This prevents intake of highly fermentable, rich grass
that can contribute to gas or spasmodic colic episodes.
Tapeworms have been identified to cause as many as 22 percent of
spasmodic colic cases. Parasite control is managed with regular
deworming schedules of the appropriate anthelmintics. It also is
important to clean up manure at least twice a week to limit the
development of other infective parasite larvae in areas where the
horse might eat. It also helps to rotate your pastures to prevent
overgrazing and to facilitate ultraviolet kill of remaining
management that prevents colic includes the following
Feed at least 60 percent of the daily ration as forage (hay or
When possible, pasture in non-irrigated fields and/or use a grazing
muzzle to control weight and intake of rich forage
Limit grain to as little as possible – none is preferable
Substitute high-fat feeds and high-fiber feed for grain supplements
when more calories are needed
Provide feeding systems that limit the intake of sand and dirt
Provide plenty of turnout and exercise each day
Provide clean, ice-free drinking water
Implement regular and frequent deworming programs for the herd
Implement a herd health program of preventive care
Minimize stress (transport, herd dynamics, housing, illness, injury)
as much as possible
Not every one of these suggestions is feasible for every horse
owner, but many practical steps can be taken to improve digestive
health. Even the smallest details can make a large difference. In
the overall picture, a healthy horse is a happy horse and able to
perform to his best ability.
For more in-depth information, please refer
to Dr. Loving’s book, All Horse Systems Go:The Horse Owner’s
Full-Color Veterinary Care and Conditioning Resource for Modern
Performance, Sport and Pleasure Horses.
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Strangles: Dispelling the Myths
Posted March 27 2007
The infection caused by the bacteria Streptococcus equi,,
commonly known as strangles, has been described in horses for almost
800 years. The name strangles describes the condition in which an
affected horse is suffocated as lymph nodes in the throat region
become enlarged and obstruct the airway. Many misunderstandings
exist regarding strangles, most likely due to horse people passing
on tales regarding the infection.
Strangles is characterized by a sudden onset of
fever with formation of abscesses under the jaw and within the
throat approximately 7-21 days following exposure. These abscesses
can open and produce a thick yellow discharge, which might also be
seen as a nasal discharge. The symptoms of the disease can vary from
severe lymph node enlargement with difficulty breathing to no
outward signs with only a slight nasal discharge.
Misunderstandings regarding the transmission of
the bacteria causing strangles, Streptococcus equi, exist. It
is often said that once a farm has had an outbreak of strangles, the
problem will always be on the farm and can show up at anytime. A
fact that needs to be understood is that the source of infection
from year to year and farm to farm is the horse, not any part of a
barn, pasture, farm, or other animals besides horses.
With two to three weeks after outward clinical
signs of strangles have ceased, the majority of horses clear the
bacteria and no longer pose a threat for infecting others.
However, following an outbreak a number of horses
(can be as high as 10%) cannot clear the bacteria and become
persistently infected. The bacteria can survive in the guttural
pouches, which are located in the pharyngeal region, for years. A
carrier horse that undergoes some form of stress such as foaling,
weaning, competing at a show, or a simple change in routine, can
begin to shed the bacteria and serve as a source of infection for
Transmission of Strep. equi occurs by
either direct or indirect contact. Direct transmission occurs during
horse-to-horse contact through everyday social behavior.
The indirect transmission can be more difficult to
control and occurs through the sharing of contaminated stalls, water
buckets and troughs, feed tubs, and bits. Water sources, either in
shared stalls or in field settings with a common water supply, are
the most common culprit when it comes to infecting a herd during an
outbreak. When a horse is shedding the bacteria and dips their nose
into a water source, the water serves as a reservoir for the
bacteria to be passed to every horse that comes in contact with the
There is a misunderstanding regarding the
persistence of Strep. equi in the environment. Besides in a
water source, the bacteria will not survive for prolonged periods in
the environment. This means horses do not become infected with the
bacteria from the soil, grass, or fences unless a horse currently
shedding bacteria is present.
Strangles is often diagnosed by clinical signs,
but it takes a positive culture with or without a positive PCR test
to confirm the presence of Strep. equi. Both tests utilize a
sample from a nasal wash or guttural pouch sample or direct swab
from an enlarged lymph node. Each test has its limitations, but when
used in conjunction can be very effective in detecting the bacteria
in a horse showing clinical signs and a carrier horse that might
Once a horse is confirmed to have strangles, they
should be isolated from other horses and provided with supportive
care to control fevers and ensure an open airway. The best
management during an outbreak is to segregate the horses showing
clinical signs, and monitoring the temperatures of the healthy
horses for two to three weeks after the last horse with clinical
signs was removed. Once the affected group of horses is no longer
showing signs, they should be tested to confirm they have not become
carriers of the bacteria. This is a critical step in preventing
Steps can be taken to prevent the exposure of your
horse to strangles. It is important to remember that a horse does
not have to be showing active clinical signs of strangles to be
capable of infecting others. Care should be taken to minimize
exposure to other horses, particularly at shows and farms with a
changing population. When traveling to shows, water buckets should
be brought and not shared with other horses. Do not permit direct or
indirect contact with other horses while at the show. This includes
nose-to-nose contact as well as sharing such things as stalls, water
buckets, feed tubs, grooming tools, tack, and trailers.
In a stable or herd situation, a few simple
prevention methods can be used to decrease the likelihood of
exposure to strangles. Isolation of all horses for two to three
weeks before they come in contact with others can decrease the
potential exposure. Testing incoming horses for Strep. equi
can be an effective tool in limiting the introduction of strangles
into a herd or stable. Strangles is a preventable disease and with
the proper steps, the risk of exposure can be minimized.
Ask your veterinarian how they can help you
protect your horse and farm from this preventable disease.
Article courtesy of The Kentucky Equine
Education Project (KEEP),
UC Davis experts: Sources on West Nile virus, mosquito-borne
UC Davis has the largest West Nile research and
public-testing programs in the state of California.
Read new and important
information on biology of West Nile, mosquito control, and West Nile in
people and animals.
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What is EVA?
Equine viral arteritis (EVA) is an infectious viral disease of horses that
causes a variety of clinical symptoms, most significantly abortions. The
disease is transmitted through both the respiratory and reproductive
systems. Many horses are either asymptomatic or exhibit flu-like symptoms
for a short period of time. An abortion in pregnant mares is often the
first, and in some cases, the only sign of the disease. EVA has been
confirmed in a variety of horse breeds, with the highest infection rate
found in adult Standardbreds.
Breeders, racehorse owners, and show horse owners all have strong economic
reasons to prevent and control this disease. While it does not kill mature
horses, EVA can eliminate an entire breeding season by causing numerous
mares to abort. In addition, U.S. horses that test positive for EVA
antibodies and horse semen from EVA-infected horses can be barred from
entering foreign countries. As the horse industry becomes increasingly
internationalized, nearly all major horse-breeding countries are including
in their import policies measures to reduce the risk of EVA. The U.S.
Department of Agriculture's (USDA) Animal and Plant Health Inspection
Service's (APHIS) Veterinary Services (VS) program provides the equine
industry with EVA diagnostic and surveillance support.
In the past 15 years, few equine diseases have stimulated more interest or
gained greater international notoriety than EVA The disease was thrust into
the limelight of industry attention following a 1984 epidemic on a large
number of Thoroughbred breeding farms in Kentucky. No outbreaks of EVA had
previously been reported in Thoroughbreds in North America. Few equine
diseases have been the subject of more misinformation or misperception than
EVA. It is an acute, contagious viral disease known to affect horses and
other members of the equid family only. EVA is not transmissible to humans
or other domestic species. Like influenza and rhinopneumonitis, it is
considered primarily a viral infection of the equine respiratory tract.
More than a century ago, a disease fitting the
clinical description of what we now call EVA was reported in European
veterinary literature. However, the virus was not isolated from horses in
this country until 1953 during an epidemic of abortions and respiratory
The most recent EVA epidemic occurred in 1984 when this disease affected 41
thoroughbred breeding farms in Kentucky. This outbreak brought to light two
very important findings about EVA: the efficiency with which an acutely
infected stallion could venereally transmit the virus and the high carrier
rate that immediately occurred in stallions following natural infection with
EVA is primarily a respiratory disease. Particles from acutely infected
horses' nasal discharges are inhaled, often during the movement of horses at
sales, shows, and racetracks. Horses are herd animals that tend to
commingle, and this close contact facilitates the spread of the virus.
However, unlike other respiratory diseases, EVA can also be transmitted
venereally during breeding, either naturally or by artificial insemination.
When a mare, gelding, or sexually immature colt contracts the disease, the
animal will naturally eliminate the virus and develop a strong immunity to
reinfection. On the contrary, infected stallions are very likely to become
virus carriers for a long time. Once stallions are in the carrier state,
they transmit the virus to mares during breeding.
While the mare will shed the virus easily, a
pregnant mare infected with EVA may pass the virus to her unborn fetus.
Depending on the stage of pregnancy, the fetus can become infected, die, and
be aborted. If the infected foal is born, it will only live for a few days.
Many horses infected with EVA are asymptomatic. When symptoms do occur in
the acute stage of the disease, they can include any or all of the
following: fever, nasal discharge, loss of appetite, respiratory distress,
skin rash, muscle soreness, conjunctivitis, and depression. Other clinical
signs in infected animals are swelling around the eyes and ocular discharge,
swollen limbs, swollen genitals in stallions, and swollen mammary glands in
Abortion in pregnant mares is also a symptom of EVA. Abortion rates in
EVA-infected mares can be as low as 10 percent or as high as 70 percent.
Horse owners should suspect EVA when respiratory symptoms accompany an
abortion in a mare. Since the clinical signs of EVA are similar to those of
other respiratory disease, and no characteristic lesions are in EVA-aborted
fetuses, only diagnostic tests can confirm the disease. Virus isolation can
be attempted from swabs of the nose, throat, or eyes; semen, placentas, or
fetal tissue; and blood samples. However, the most common method of
diagnosis is testing blood for the virus' neutralizing antibodies that cause
EVA. While the presence of these antibodies alone does not indicate active
infection, it does indicate EVA exposure has occurred. Very high levels of
antibodies on a single sample or a rising antibody titer from paired blood
samples collected 14 to 28 days apart indicate active infection.
While there is no specific treatment for EVA, treatment should include rest
and in selected cases, antibiotics, which may decrease the risk of secondary
bacterial infection. Adult horses recover completely from the clinical
disease. However, the virus commonly persists in the accessory glands of
recovered stallions, so these carrier stallions continue to shed the virus
for years and remain a significant source of infection.
Prevention and Control
Fortunately, there is a way the industry can work to prevent and control
EVA. A safe, effective, and low-cost avirulent live virus is now available.
Combining this vaccine with isolation of the vaccinated animal from
noninfected horses can prevent the spread of EVA.
Since properly vaccinated EVA-negative stallions do not become carriers, all
EVA-negative colts less than 270 days old should be vaccinated. The vaccine
is not approved for use in pregnant mares.
Blood samples for EVA testing should be collected from all horses before
breeding, and virus isolation should be performed on imported semen before
use. Strict hygiene and disinfection of instruments and equipment are
essential to minimize spread of the virus. EVA-negative mares should be bred
only to EVA-negative, noncarrier stallions.
If blood test results are positive in a
stallion, but there is no official documentation of negative EVA status
prior to vaccination, the stallion must be tested for the presence of a
carrier state. Virus isolation can be attempted on the semen from two
separate ejaculations, or by mating two EVA-negative mares with the
stallion. Twenty-eight days after breeding, mares' blood should be tested
for the development of the neutralizing antibodies to the EVA virus.
Carrier stallions should be bred only to EVA-positive mares or mares that
are properly vaccinated. When breeding an EVA-positive or carrier stallion
to an EVA-negative, vaccinated mare, isolate both horses for 24 hours after
breeding to prevent mechanical spread of EVA from voided semen. If this is
the first time the mare has been bred to a carrier stallion, she should be
isolated from other horses for an additional 21 days due to potential virus
All vaccinated horses should receive yearly boosters to protect against
infection and, for the stallions, to prevent the development of a carrier
state. In a generation or two, these practices could all but eliminate the
population of carrier stallions.
Current information on animal diseases is also available on the Internet at
www.aphis.usda.gov. All information
contained in this article is from:
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