Strangles Fact Sheet

Potomac Horse Fever Facts

Potomac Horse Fever Facts

Summertime, and the living is easy…for the carriers of Potomac Horse Fever (PHF). Our wet spring and recent hot weather provide favorable environments for the aquatic insects and snails that carry the bacteria and infect horses. Here are some key pieces of information about PHF that can help protect your horses:

What to look for: Common signs of horses with PHF include fever (up to 107° F), colic, diarrhea, poor appetite, laminitis (founder), depression/lethargy, swelling of the limbs and/or ventral abdomen, and pregnancy loss. A horse with PHF may show any, all, or a combination of these signs. Because prompt treatment increases the chance of successful treatment, call your veterinarian if you think your horse may have PHF.

Infection: Infection with PHF comes from contact with caddisflies, mayflies, dragonflies, damselflies, and some snails. Because horses become infected with PHF due to insects in the environment, multiple horses on a property may become infected. Although it is an infection, it is not contagious from one horse to another. However, because some contagious diseases show the same signs (fever, colic, diarrhea), it is prudent to keep any horse with these signs isolated from others until the cause of the illness can be determined. Also, some horses with PHF can have other intestinal diseases at the same time.

Treatment: Tetracycline antibiotics are used to kill the organism, and supportive care is often also needed to treat the colitis (intestinal inflammation) that results from infection. Colitis can be very serious, even fatal in horses, and treatment may be complicated and expensive. Laminitis may further complicate treatment and outcome.

Prevention: Horses most at risk are those housed within 5 miles of a stream or pond. Risk of infection can be decreased by vaccinating horses against PHF, and through some environmental management. The vaccine is not always successful at preventing infection, but horses that have been vaccinated generally experience a milder form of the disease if they do become ill. In some circumstances, it may be beneficial to booster the vaccine in late summer; a discussion with your veterinarian can help determine if this would be helpful. Because many of the insects that carry PHF are attracted to light, turning off the barn lights at night can help protect horses from becoming sick.

We have seen multiple cases of PHF in our hospital already this year, and if the hot, rainy weather continues, we are likely to have more cases. Please give our office a call if you have any questions about PHF.


A Good Biosecurity Program

 A good biosecurity program is important to protect your horse from disease. The following are some protocols you can implement to keep your horse safe. Talk to your veterinarian about biosecurity on the farm, and ensure you have a plan set up for emergencies.
When Traveling:
– Ensure your horse is up to date on vaccinations and Coggins.
– Do not use any common water buckets, feed troughs
– Do not share any of your horse’s equipment including halters, lead ropes, lip chains, and grooming tools
– Do not allow any nose to nose contact between your horse and other horses. Select a stall where your horse will not be in contact with other strange horses, choose a tack-stall strategically to isolate your horse!
– Monitor your horse closely for changes in attitude, manure consistency, temperature, or any other change.
At Home:
– Ensure all horses on the property are up to date on vaccinations and Coggins.
– Isolate any incoming horses for 2-3 weeks (i.e. no nose-to-nose contact). This will prevent them from spreading disease to others before they show any clinical signs.
– Ensure each horse has its own buckets, grooming tools and feed buckets. No sharing!
– Take steps to eliminate mosquitoes and flies (i.e. remove stagnant water, fly spray, fly predators etc.)
– Keep the end of the hose out of buckets when filling so it does not become contaminated with dirty water.
Sick Horses:
– Have materials ready and work with your veterinarian to have a (written) quarantine plan in place! Be ready the moment you suspect your horse may have an infectious disease!
– Quarantine the sick horse immediately.
– Clean and disinfect all equipment and tools which have been in contact with the horse (including muck tub and muck fork). Ensure the sick horse has its own tools and equipment. After the horse has recovered, clean and disinfect all tools again!
– Have hand sanitizer and a shallow basin to disinfect shoes available to use after touching the sick horse before coming into contact with the healthy horses.
– Call and work with your veterinarian to set up a plan specific for your horse’s disease. Some diseases are more contagious than others and will require more intensive biosecurity protocols.

What Is Equine Piroplasmosis?

Recently, 17 racing Quarter Horses in Tennessee tested positive for Equine Piroplasmosis (EP), and the investigation into this outbreak is ongoing. Piroplasmosis is considered a Foreign Animal Disease in the United States, and is thus a reportable disease in horses. Although officially considered a disease foreign to the USA, EP outbreaks occasionally occur. Read on to learn more, including how to keep your horses safe.

Equine Piroplasmosis is caused by 2 species of blood parasites in horses and occurs naturally in many parts of the world, including Central and South America, southern Europe, Asia, and Africa. The parasites cause breakdown of the red blood cells, causing anemia. Clinical signs of the disease include dark/discolored urine, fever, colic, lethargy, pale membranes, and weakness. Infected horses may appear completely healthy, or may become fatally ill. Once infected, horses become carriers of the parasites unless treated to clear the infection. Most horses with the parasites are outwardly healthy.

Transmission of EP requires blood transfer from an infected individual. In nature, this occurs through the feeding of ticks on multiple hosts. Only specific tick species are capable of transmitting the disease; so far, only 2 such tick species in the USA have been identified; these are ticks that favor tropical and sub-tropical climates. By far, the most common mode of transmission between horses in the United States has been by people. Unsanitary practices, such as re-using a needle in more than one horse, sticking a used needle into a vial of injectable medication, using tattoo equipment on multiple horses without cleaning it in between, or using blood products from one horse on another put horses at risk for transmitting blood borne diseases from one horse to the next.

In general, horses in the general population in the USA are at very low risk for becoming infected with EP. Simple, common sense adherence to good medical hygiene is all that is needed for most horses to be protected from EP. Never re-use a needle or syringe after it has been used on a horse; always follow the one horse/one needle/one time rule. Never use blood contaminated equipment on multiple horses; always make sure that veterinary equipment is cleaned between patients. Never perform any transfusion procedures without a veterinarian, and in high risk regions (such as south Texas, where an outbreak due to natural transmission occurred) always test blood donors for EP before using their blood. In high risk regions (south Texas, endemic countries), the risk of infection can also be lowered by regularly checking the horses for ticks and using fly sprays that repel ticks. Again, the vast majority of horses in the United States live in regions where natural spread of the disease has NEVER occurred, and where ticks that can spread EP do not live, so the risk of transmission is limited to the exposure of blood contaminated medical equipment.

Tired Of Watching Your Horse Struggle To Breathe?



If you know a horse with one of these diseases (which you may know as equine COPD or heaves) – you’ve seen how they can suffer. Inflammation of the airways causes breathlessness, wheezing, and coughing that no horse should experience


If your horse is over age four and has been diagnosed with Recurrent Airway Obstruction (RAO) or Summer Pasture Associated Obstructive Pulmonary Disease (SPAOPD), your horse may be eligible to participate in this FDA-regulated clinical study of an investigational medication that will help bring much-needed quality research to the equine community.

Afflicted horses are now being recruited for this study to carefully evaluate an investigational drug with the potential to treat RAO and SPAOPD.

Our hope is that the research will result in an approved treatment – because today there are far too few FDA-approved drugs for horses afflicted with these diseases.

You can get full information on the study here, including which horses qualify, what’s involved, benefits to you, and how you can help.

SPAOPD (Summer Pasture Associated Obstructive Pulmonary Disease) season is here, is your horse suffering?

Horses over age four and diagnosed with RAO (Recurrent Airway Obstruction) or SPAOPD are being sought to participate in a free FDA-regulated study of a new investigational drug. Please call our practice if you own or know a horse with one of these debilitating diseases.

Visit to see if your horse may qualify.


Horses are born to run…

But with asthma-like RAO or SPAOPD, every breath can be a struggle.

If your horse is over age four and has been diagnosed with one of these conditions – contact us today about participating in a free research study.

Call us today, or visit to see if your horse may qualify.


People get asthma – do you know what horses get?

Many horses have trouble breathing because of RAO or SPAOPD, both asthma-like diseases.

Horses over age four and diagnosed with one or both of these diseases are being sought to participate in a two-phase, FDA-regulated, placebo-controlled study of an investigational drug that could open the door to treatment.

See if your horse may qualify at


Calling all horses with RAO or SPAOPD (and their owners).

Our practice is part of a new research study seeking a treatment for these terrible asthma-like conditions. Horses over age four and diagnosed with one or both of these diseases are being sought to participate.

Participation is free, it’s an FDA-regulated study, and you could help stop the suffering.

Call us to see if your horse may qualify or find out more at


Three ways you can stop horses from suffering.

RAO and SPAOPD are asthma-like horses that affect horses. By helping us recruit horses for an important research study, you may help us find a new treatment!

1.     If you own a diagnosed horse, call us immediately.

2.     If you know someone who owns a horse with RAO or SPAOPD, forward this post!

3.     Share with your horse-loving network

Thank you for spreading the word!

For details and to see if your horse may qualify, visit



Did you know some horses are smart enough to do research?

Horses over age four and diagnosed with RAO or SPAOPD are being sought to participate in a new, high-quality research study.

Participation is free, including all diagnostic tests and evaluations required for the study. During Phase 1, we’ll even travel to your location to evaluate your horse.

Call us today or visit to see if your horse may qualify.


Horses with RAO and SPAOPD can still be champions.

Champions for science, that is! Our practice is taking part in an FDA-regulated clinical trial to potentially provide a new FDA-approved alternative for safely treating RAO and SPAOPD.

If your horse meets these criteria, please call us right away!

·         Diagnosed by your equine veterinarian as having RAO or SPAOPD

·         ≥ 4 years of age

·         Has had two or more RAO/SPAOPD episodes since age four.

·         ≥ 200 kg (441 lbs.)

·         Not pregnant or lactating

·         Not intended for breeding during the study period


Get more details at




Did you know we’re an investigator site for an important new study?


Here’s why. RAO and SPAOPD cause considerable suffering and diminished quality of life for affected horses, and today there are very few FDA-approved drugs for animals afflicted with these diseases.


Our research may result in an important new FDA-approved option for treatment, providing relief for horses all across the U.S. If you know a horse with one of these diseases, please contact us right away! Visit for more information and to see if your horse may qualify.




The weather is beautiful, but your horse can’t breathe.


RAO and SPAOPD can make life hard for your horse. That’s why we’re part of a research team studying a new investigational drug. We’re also seeking horses over age four who have been diagnosed with one of these diseases to participate. The study is free, and it’s important. Call us today, or visit for more info and to see if your horse may qualify




You know we’re veterinarians, but did you know we’re also researchers?


That’s why we’re seeking owners of horses over age four and diagnosed with RAO or SPAOPD. You are one of the few people who can help with an important research and possibly open the door to a new treatment. Call us today! Or visit to see if your horse may qualify for this free study.




RAO or SPAOPD? Call us!

Afflicted horses over age four are now being recruited for a study to carefully evaluate an investigational drug with the potential to treat RAO and SPAOPD.

Our hope is that the research will result in an approved treatment – because today there are far too few FDA-approved drugs for horses afflicted with these diseases. Call us now or visit to see if your horse may qualify.



New Equine Leptospirosis Vaccine Available

Leptospirosis is a bacterial disease of worldwide distribution that can cause illness in many species of mammals, including people. In horses, leptospiral infection has been associated with kidney failure, pregnancy loss, and equine recurrent uveitis, which can lead to blindness. Horses become infected with leptospirosis through contact of mucus membranes or broken skin with infected water.  The kidney is the target organ of the bacteria, and the horse can spread the disease through infected urine. Disease may be asymptomatic, limited to mild fever and malaise, or may cause acute renal failure, uterine infections leading to abortion in mares, or recurrent bouts of uveitis that may affect one or both eyes.

Until recently, control measures for leptospirosis in horses were limited to providing access to clean drinking water, vaccinating other susceptible in-contact animals such as cattle and dogs, and using ruminant vaccines off label. Recently, an equine specific vaccine was introduced (LEPTO EQ EQ INNOVATOR ®) to protect horses against Leptospira pomona, which is reported to be the species of leptospirosis most commonly associated with clinical disease in horses. This vaccine may be especially helpful broodmares, horses with access to ponds or other natural water sources, and horses with equine recurrent uveitis. Please contact your veterinarian to learn more about whether your horse would benefit from this vaccine.

Should I Vaccinate My Horse Against Potomac Horse Fever?

As is true every year, we are starting to see horses that have Potomac Horse Fever in our practice. In some cases, the horses had received the vaccine this spring. Some commonly asked questions are: Why is the vaccine not 100% protective? Should I revaccinate my horse even if he got a vaccine in the spring?

Potomac Horse Fever causes signs of fever, mild to severe diarrhea, inappetance, colic and laminitis. Any combination of these signs may be present. Abortion may occur in pregnant mares if infected. It has a wide geographical distribution, occurring in most of the United States, Canada, South America and some European countries. It is most prevalent in the late spring through early fall. Most cases occur in July, August and September. The organism is an ehrlicia, Neorickettsia risticii. Horses become infected when they ingest infected aquatic insects such as mayflies, damselflies or caddie flies.  The disease has been associated with rivers and streams where these insects are in abundance. However, dead insects in the water buckets or hay may also be a source. The disease can be endemic on a farm in which case disease may be expected in future years.  But it is also known to occur sporadically.

A vaccine for Potomac Horse Fever exists. It is made from the killed organism.  Many horses that are vaccinated still develop the disease. It is a widely held view among veterinarians that the disease seen in vaccinated horses is less severe than in unvaccinated horses. However, there is no scientific evidence to support this view at this time.

Why is the vaccine not 100% effective? 1) There are several strains of Neorickettsia risticii. The vaccines on the market are based on one isolated strain. The vaccine may offer some cross protection against different strains.  2) The immunity is short lived with the vaccine. The immune response to this particular vaccine is poor compared to other vaccines. It peaks at 3-4 weeks post vaccination but may continue to provide immunity for 3-4 months.

Should I have my horse revaccinated even if he got a vaccine in the spring? There is not much scientific evidence to suggest that revaccinating horses a few months later offers them more protection against the clinical disease. But we do know that the antibody titers are low in response to the vaccine and do not last long. Owners that might want to consider revaccinating are those that have pregnant mares, especially those 90-120 days in foal and owners that have horses that live in an area in close proximity to water or on a farm where Potomac Horse Fever has been diagnosed in the past. In cases where revaccination is appropriate, we recommend revaccinating no sooner than 3 months after the first vaccine.  One of the Blue Ridge Equine veterinarians can talk to you about your horse’s risk and whether revaccination is in his or her best interest.

Keeping the barn lights off at night will prevent the attraction of flying insects that may carry Potomac Horse Fever. In barns that have had previous cases, we recommend taking all horses temperatures twice a day and calling the veterinarian when any horse has a temperature over 101.6o.

Heat Stroke In Horses

Summer is here and it can be a difficult season for our four legged friends. Horses have natural methods for regulating their body temperature, such as sweating and an increased respiratory rate, which allows heat to be expelled during the breathing process. Usually horses can handle the outside temperature and humidity, but remember that summer is the time that we put an increased demand on our horses physically.

Exercise increases the amount of heat that your horse produces and makes it more difficult for your horse to cool itself down. Heat stroke can also be seen in horses stalled in a poorly ventilated area. The signs of heat stroke  in horses can be a high temperature (up to 106), rapid breathing, a rapid pulse, weakness, depression, and an unwillingness to eat or move. Severe heat stroke can lead to collapse, convulsions and even death.

The clinical signs of heat stroke may be either mild or severe, but either way, treatment is indicated. If you are concerned your horse is having a heat stroke, place your horse in the shade and begin hosing him down with cold water. Placing a fan on your horse may also help to cool him down. Your horse should be offered frequent, small amounts of water in order to rehydrate him. Electrolyte paste, and in severe cases, IV fluids may also be indicated.

While it is important to be able to recognize the signs of heat stroke, prevention is even better! The most important thing to consider when riding your horse on these hot summer days is that your horse is adequately hydrated. The average adult horse drinks 8-10 gallons of water each day. If your horse is engaging in exercise, then he can easily require more than that. An electrolyte supplement is also helpful. Use one without sugar, dextrose or sucrose. Put the electrolytes in their feed. If you put it in their water, make sure they have an alternate plain source of water as well.

If you have an older horse that has trouble shedding out his winter coat, body clipping him can also help prevent heat stroke. It is also important to make sure that your horse is adequately in shape for the physical tasks that you ask of him. Take the time to work your horse up slowly. While even a fit horse can have problems on a hot, humid day, having a horse that is in shape will decrease his risk of heat stroke, as well as making for a more enjoyable ride. Enjoy the fun days of summer and stay cool!


Equine 911: When Do I Really Need To Call The Vet?

When horses are sick or injured, it can be difficult to know what problems need a veterinarian’s care on an emergency basis, and which can wait until morning or later. Some situations, such as major bleeding, thrashing colic, or a horse that is down and can’t get up, clearly require veterinary intervention, but others are more subtle. In the less dramatic cases, there can be hesitation to call, both because of a reluctance to “bother” the veterinarian, and to avoid the expense of an emergency visit if one isn’t really needed. It is worth remembering that putting a call into the veterinarian isn’t a commitment to having someone come out, and a conversation with the veterinarian can often be very helpful in determining if one is needed. Below are 10 conditions that warrant calling for help.

1.       Signs of abdominal pain/discomfort: A horse that is stretching out as if to urinate every few moments, doesn’t want to eat, sulks in the back of the stall, is away from the herd, looks, bites, or kicks at his sides, spends too much time lying down, curls up his upper lip, or gets up and down frequently with or without rolling has colic. “Colic” is a generic term that means abdominal pain. There are many causes for colic, which may be anything from harmless to life threatening. A veterinarian can help to sort out how serious the situation is, and even in mild colic, early intervention is key to help prevent dangerous and costly complications.

2.       Severe lameness: Limping noticeably at the walk or refusing to bear weight on one leg may be as simple as a foot abscess or as serious as a broken bone or infected joint. Prompt evaluation and treatment of all of these conditions helps to provide the best care as soon as possible.

3.       Eye problems: Squinting, tearing, or cloudiness of the eye allsignal an eye problem. Problems with the eye can progress rapidly, so prompt treatment is key in successful treatment. Delay can lead to scarring of the eye, loss of vision, or even loss of the eye.

4.       Bleeding: Not all bleeding is an emergency, but it is best to consult a veterinarian if there is blood coming from a cut or out of the nose or other body orifice, as it may signal a serious condition.

5.       A wound near or over a joint: Any wound that is near or overlying a joint should be evaluated by a veterinarian as soon as reasonably possible. Especially on the legs, there is not much tissue between the skin surface and the joint capsules, so even relatively superficial appearing wounds can penetrate into a joint. The joint is the cartilage covered union between two bones that is filled with synovial fluid, which acts as a joint lubricant. Once bacteria gain entrance to a joint (or tendon sheath, which is a synovial fluid space surrounding tendons), the resulting infection causes damage quickly, leading to a very painful and difficult to treat condition. Once a horse has an infection in a joint or tendon sheath, which is characterized by severe lameness, the chances of curing the infection and returning the horse to soundness are dramatically reduced. This is definitely a case of, “an ounce of prevention is worth a pound of cure.”

6.       Choke: Horse “choke” isn’t really choking at all, it is blockage of the esophagus. Signs include retching, feed material coming out of the nose, excess salivation, coughing, and signs of colic. A horse with choke should be seen by a veterinarian to relive the blockage, and should not be allowed to attempt to eat anything while choked. In some cases, choke can lead to the horse aspirating feed material, leading to severe pneumonia.

7.       A mare having trouble foaling: If a mare is in labor and hasn’t made rapid progress (unlike cows, mares deliver in about 20 minutes), or if there is a red membrane covering the exiting foal, call the vet IMMEDIATELY. In the case of the red membrane (red bag delivery, caused by premature separation of the placenta associated with fescue consumption by the mare), cut or tear open the red bag first, allowing the foal to breathe.

8.       Reluctance to move: A horse that is planted in place and does not want to walk may have laminitis or myopathy (“tied up”), both of which can be very serious. Prompt attention of these conditions gives the best chance for a good outcome.

9.       Red or brown urine: Although normal horse urine turns red when it mixes with snow, horse urine should be yellow when it comes out of the horse. Bloody or brown urine can signal a serious condition.

10.   Sudden incoordination or other neurologic signs: Neurologic problems in horses can progress rapidly and are best addressed early in the course of the problem. Horses that are dizzy or suddenly incoordinated can be dangerous to themselves or their handlers. Early determination of the problem and aggressive treatment are usually key to resolving the problem.

A New Reason To Hate Ticks On Horses: Equine Anaplasmosis

Equine anaplasmosis (also known as Equine Granulocytic Erlichiosis) is a tick-borne disease caused by the bacterium Anaplasma phagocytophila (formerly known as Erlichia equi), also the cause of human granulocytic erlichiosis (HGE). It was first described in horses in California in the 1960’s, but has since been reported in multiple states of the USA and in Europe. Several cases have been diagnosed in the Shenandoah Valley so far this fall.

Anaplasma phagocytophila is a bacterium that lives within blood cells and is carried by deer ticks, the same ticks that carry Lyme disease. Possible natural reservoirs of the disease include deer, rodents and birds. Horses seem to only suffer transient infection, so that they do not harbor latent disease. The disease is not contagious from one horse to another, but multiple horses on a property may be infected, depending on the local tick population.

Horses most commonly get sick with anaplasmosis in the fall to late winter. They commonly show signs of fever, loss of appetite, reluctance to move (people with the disease complain of headache and muscle pain), leg swelling, petechiation (red spots on the gums and whites of the eyes), jaundice, and lethargy. Occasionally, horses may show neurologic signs, or have trouble rising. The clinical signs are in part due to the fact that the bacteria invades some white blood cells (neutrophils and eosinophils), leading to the destruction of red blood cells, white blood cells, and platelets. Bloodwork shows low platelets, which are important for clotting the blood, and anemia.

Diagnosis can be made in several ways. The most definitive way to diagnose the disease is to look at the blood cells under a microscope to look for the presence of the bacteria inside the neutrophils. In some infections, though, only a small number of neutrophils may be affected, and therefore they may not be detected this way. Because horses mount a strong immune response to the bacteria, titer levels can be tested to confirm recent exposure.

The treatment for anaplasmosis is the administration of tetracycline, usually oxytetracycline, minocycline, or doxycycline. Some horses with mild disease may recover without treatment. Most horses recover fully, although some may relapse in 3-4 weeks. Fatality from the disease is rare. There is currently no vaccine available, so prevention is limited to tick control.