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Health Topics

Probiotics & Prebiotics:

Please follow this link to learn more about how these supplements may, or may not, benefit your horse.

Equine Emergency Care:

Please follow this link to learn more about making a first aid kit and what you can do in case of an equine emergency.

Recurrent Airway Obstruction (Heaves):

Please follow this link to learn more about this respiratory condition in horses.

Potomac Horse Fever:

Potomac Horse Fever (PHF) is a diarrheal disease of horses caused by the bacterium Neorickettsia risticii. The disease is typically seen from late spring to late summer, but horses can be infected from May through November. Transmission of the disease is not very well understood, but it is likely caused by ingestion of organisms that harbor the bacteria. These may include snails, aquatic insects such as Caddisflies, and trematode parasites present in aquatic habitats. It is no surprise that the disease is more common to horses that live near freshwater sources such as streams, rivers, marshes or other standing water.

Signs of the disease may vary, but horses initially show mild depression and poor appetite. This is followed by a fever ranging from 102-107°F. Remember that a horse’s normal body temperature typically ranges from 98-101.5° F. At this point, most horses have decreased gastrointestinal sounds. Within 24-48 hours, the disease may progress to diarrhea that varies from “cow pie” to a watery or “pipestream” consistency. Other signs can include abdominal discomfort with mild to severe colic, dehydration, and edema along the lower belly. Laminitis is a common and severe complication of the disease and may progress despite improvement of other signs. Pregnant mares that develop PHF may suffer spontaneous abortion. A horse with PHF can have all or any combination of these clinical signs. Fatality depends mostly on the strain involved, ranging from 5-30%, and is usually associated with toxins from the bacteria and severe laminitis.

Diagnosis of PHF is usually made based on the clinical signs described, but can be detected in the blood or feces using tests provided by a specialized laboratory. Diarrhea develops because of damage to the lining of the large intestine by the bacteria. Horses with PHF can be treated by intravenous (IV) therapy with the antibiotic oxytetracycline and, if necessary, fluid replacement to correct dehydration. If treatment is started early, the clinical signs frequently resolve within 3-5 days. Prevention of laminitis with anti-inflammatories, stall confinement, and foot support such as cold therapy, deep bedding and pads is critical for a successful outcome.
Potomac Horse Fever can often be prevented with a commercial vaccine. Protection is not 100% and the immunity provided is much shorter than for other vaccines. This is because the organism is a bacteria and there are several variant strains that cause the disease. Vaccination should be two injections given 4 weeks apart for a horse that has not been immunized against PHF. After an initial series, horses should be vaccinated every 4-6 months. Limiting access to freshwater streams, ponds and irrigated pastures during peak times of the year may also reduce a horse’s chances of becoming infected with PHF.
You can improve your horse’s chances of survival from this disease by keeping him up-to-date on vaccinations and learning to recognize subtle signs. The earlier you are able to identify Potomac Horse Fever and have your horse seen by a veterinarian, the better. Please contact Thornwood Equine if you have any questions about this article or Potomac Horse Fever.

Fecal Testing:

Please consider having your horse(s) manure tested for the presence of internal parasite eggs, or worm eggs. Even though paste de-wormers are used at regular intervals, your horse could still be currently infected. It is wise to periodically assess the effectiveness of your de-worming program with a fecal examination to identify problems before they become clinical. After all, at one point in history, worms were the number one cause for causing colic in the horse. We simply need 1-2 fresh manure balls in labeled, zip-loc bag and the results will be available in 2-3 days. Also click here for a link to our recommended de-worming schedule.

Vaccine Reactions:    

It is not uncommon for horses to experience local reactions shortly after receiving spring immunizations. Symptoms such as local muscle pain or swelling, mild fever, decreased energy, or poor appetite can be observed but typically resolve on their own within 24 hours. We always ask that you call and alert us to any side effects; this allows us to track frequency of problems with a given product and see trends which may affect what products we purchase in subsequent seasons. Other more serious side effects can happen and are fortunately quite rare. These include hives, difficulty or rapid breathing, colic, and anaphylactic shock. These reactions typically occur within the first 12 hours and can be life-threatening, so contact your veterinarian immediately if you suspect these complications.