Written by: Nicole Kitchener

Find out which gross and potentially fatal diseases you can get from your horse, and how to avoid them.

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Pam MacKenzie Photo

There are indeed some diseases that can be transmitted from horses to humans. Diseases that are communicable between animals and humans are called zoonotic. Luckily, most of those we can catch from horses are avoidable with good sanitation and biosecurity, although some can be quite dangerous.

ZOONOTIC DISEASES

People who work with or spend time around horses should be aware of the zoonotic diseases that exist and be ready to deal with them if necessary.

Leptospirosis

What is it?
A bacterial infection linked to abortion in pregnant mares and the chronic eye condition equine recurrent uveitis (ERU or moon blindness). The spiral-shaped bacteria, Leptospira, are highly capable of movement, allowing them to spread through the bloodstream and affect various organs.

Symptoms

  • Mild illness: fever, lethargy, loss of appetite
  • Rarely kidney and/or liver failure
  • Respiratory distress
  • Mid- to late-term abortion
  • Birth of weak foals
  • Eye swelling, light sensitivity, excessive tearing, discharge, cloudiness, redness, muscle spasms, blindness

Transmission
Shed in urine, blood and other discharges of infected animals, leptospirosis is transmitted by direct contact with mucous membranes and broken skin, but most often by eating or drinking food or water contaminated by wild animals. Foals can be infected in-utero.

Carrier Status
Infected animals may shed bacteria for at least a year.

Diagnosis
Blood or urine tests.

Treatment

  • Antibiotics
  • Eye symptoms: topical steroids to reduce inflammation, atropine to dilate the iris and relieve muscle spasms, photosensitivity and other symptoms

Incubation
One to three weeks.

Illness Duration
Ranging from mild illness lasting a few days, to chronic effects.

Disease-specific Prevention

  • Control wildlife population around barns and pastures, especially at feed and water sources.
  • Eliminate standing water.
  • Vaccine: Lepto EQ Innovator, released late 2015.

Effects on Humans

  • Flu-like symptoms, vomiting, diarrhea
  • More seriously: jaundice, kidney or liver failure, meningitis and rarely death

Most Common Route of Contagion
Direct contact with urine from infected animal via open skin or mucous membranes.

Treatment for Humans

  • Antibiotics

Salmonellosis

What is it?
An intestinal infection caused mainly by the bacteria strain Salmonella typhimurium in horses.

Symptoms

  • Moderate to severe watery diarrhea; may be foul-smelling or contain blood
  • Loss of appetite
  • Lethargy
  • Dehydration
  • Weakness
  • Colic
  • Organ failure and death, particularly in foals

Transmission
Excreted through feces, salmonella is usually transmitted orally when horses consume contaminated water or food, but it’s also spread indirectly via contaminated items such as grooming and stable supplies, tack and clothing. The bacteria can live for months to years in warm, moist environments.

Carrier Status
Many horses shed salmonella for many months post-illness. Others carry it without falling ill. Sickness and stress can fuel shedding.

Diagnosis
Fecal sample cultures

Treatment

  • Fluid, electrolyte therapy
  • Anti-inflammatories to reduce shock, prevent laminitis
  • Antibiotics (although controversial as some experts believe they aren’t effective, may reduce helpful intestinal microflora and promote drug resistance)

Incubation
About seven to 10 days.

Illness Duration
Five to seven days.

Disease-specific Prevention

  • Minimize stress and illness; institute day-to-day biosecurity protocols
  • Vaccine: Aren’t widely commercially available

Effects on Humans

  • Diarrhea
  • Vomiting
  • Stomach cramps
  • Fever

Most Common Route of Contagion
Oral transmission of fecal matter from affected horse or contaminated objects (mainly due to poor hand washing practices).

Treatment for Humans

  • Re-hydration

Ringworm

What is it?
A skin infection, scientifically known as dermatophytosis, that’s caused by Trichophyton and Microsporum fungi that feed on keratin, the primary protein that makes up hair and skin. Young horses are particularly susceptible, as they have yet to develop immunity, while adults generally are affected to a lesser degree and see quicker resolution.

Symptoms

  • Small, circular tufts of hair, which then fall out, leaving scaly skin patches.
  • Rarely itchy or bothersome, ringworm can appear anywhere on the body, but usually affects areas in contact with tack or other items such a rider’s boots.

Transmission
Horses pick up the fungal spores by direct contact with other infected animals, contaminated tack, equipment, grooming tools and blankets. Ringworm can also survive dormant for many years on surfaces such as stall walls or fences.

Carrier Status
Horses can carry ringworm without showing symptoms.

Diagnosis
Fungal culture of hair or skin.

Treatment
Clip hair away from lesions, gently removing scabs. Spot treat with an anti-fungal medication or bathe horse with an anti-fungal shampoo, then treat with medication. Stop treatment when no new lesions appear and the skin looks healthy.

Incubation
Between one and six weeks.

Illness Duration
With treatment, usually about three weeks.

Disease-specific Prevention

  • Isolate and treat horses new to a premises with anti-fungal.
  • During treatment, carefully dispose of loose hair and skin, which will still contain spores.

Effects on Humans
Itchy, circular red skin lesions, with hair loss if on scalp.

Most Common Route of Contagion
Skin contact with infected horse or items containing spores.

Treatment for Humans
Topical antifungals

RARE BUT DEADLY ZOONOTIC DISEASES

Following are zoonotic diseases that are extremely fatal to both humans and horses but are, thankfully, uncommon in both. All cases must be reported to the Canadian Food Inspection Agency under Canada’s Health of Animals Act.

Rabies

What is it?
A central nervous system disease caused by Lyssavirus.

Symptoms
Highly variable, rabies can mimic many other diseases as the virus travels from nerves at the infection site to the brain. Subtle signs can include colic and lameness. More extreme symptoms include aggression and neurologic issues.

Transmission
Horses usually contract rabies from the saliva of infected raccoons, skunk and foxes via bites or less often, open cuts or mucous membranes.

Diagnosis
Post-mortem brain examination.

Treatment
None

Incubation
Usually two to six weeks.

Illness Duration
Death within a week.

Disease-specific Prevention
Rabies vaccine is highly effective. Also vaccinate farm cats and dogs.

Effects on Humans
Without prompt post-exposure vaccinations, 100 per cent fatal.

Most Common Route of Contagion
Saliva of infected animal enters open skin or mucous membranes.

Treatment for Humans
Fourteen-day post-exposure course of rabies vaccine and/or rabies immunoglobulin (blood antibodies). If symptoms are present, supportive care until death.

Anthrax

What is it?
An infection caused by the bacterium Bacillus anthracis.

Symptoms

  • Difficulty breathing
  • Loss of appetite
  • Chills
  • Fever
  • Depression
  • Severe colic
  • Bloody diarrhea
  • Shock
  • Swellings in the neck, sternum, abdomen

Transmission
Extremely hardy, anthrax spores can live in soil for many years. Horses are usually infected by ingesting spores from contaminated pasture. It can also be contracted through inhalation, a break in the skin or mucous membranes when dead animals shed the disease. Insect bites can also transmit anthrax.

Diagnosis
Blood samples

Treatment

  • Antibiotics
  • Anti-inflammatories
  • Fluid therapy

Incubation
Three to seven days.

Illness Duration
Called “the quick killer,” without treatment, death occurs within three days.

Disease-specific Prevention
Horses in endemic areas can be given a livestock vaccine.

Effects on Humans
Humans rarely contract the disease, but symptoms can include skin infections, gastrointestinal issues and potentially deadly respiratory problems.

Most Common Route of Contagion
Spores enter the body through open skin or by inhalation.

Treatment for Humans

  • Two months antibiotic treatment
  • Antitoxins in some cases

Brucellosis

What is it?
An infection caused by the bacterium Brucella abortus.

Symptoms

  • Painful inflammation and pus-filled wounds of the bursa (fluid sacs) along the spine (also called fistulous withers and poll evil)
  • Abortion

Transmission
Usually contracted from infected cattle by ingesting contaminated pasture or via direct contact through open skin or mucous membranes. Also shed in equine manure and tissues from aborted fetuses.

Diagnosis
Blood tests

Treatment

  • Antibiotics
  • Anti-inflammatories
  • Surgical drainage and removal of diseased tissue

Incubation
Up to two years.

Illness Duration
Can take many months to heal post-treatment, with a high re-occurrence rate.

Disease-specific Prevention

  • Avoid horse-cattle contact in endemic areas. (Although Canada eradicated brucellosis in livestock with the last confirmed case reported in 1989.)
  • Vaccine isn’t available.

Effects on Humans
Rarely humans contract brucellosis via direct contact with discharges and aerosol exposure. The disease, called undulant fever, is quite serious.

Most Common Route of Contagion
Direct contact with infected tissues or fluids of an infected animal.

Treatment for Humans
Antibiotic

BIOSECURITY: WHAT IS IT?

Biosecurity is “a set of principles and practices that are used to reduce the risks posed by pathogens.” This definition is from the National Farm and Facility Level Biosecurity Standard for the Equine Sector, released June 2016, a joint project of the Canadian Food Inspection Agency, Agri-Food Canada, Equestrian Canada and horse industry groups.

Long-time horse industry player and current chairman of the Horse Welfare Alliance of Canada, Bill desBarres, is a member of the advisory committee that helped create the standards. “We need to be more aware of the increasing and significant impact that these creeping diseases have on our horse society,” said desBarres. “We need to get used to managing our disease control protocols and that’s called biosecurity.”

A guide based on the standards is currently being developed that will help lay horse people better understand why biosecurity is critical and how they can implement measures to prevent disease transmission.

Preventing Contagion: Everyday Biosecurity Practices
Incorporating biosecurity protocols into everyday barn life can help prevent and minimize the risk of transferring diseases. Your veterinarian can help develop a plan that’s appropriate for you. In the meantime, here are some basics to consider.

At Home

  • Vaccinate to increase resistance to many contagious diseases.
  • Each horse should have its own bucket, feed tubs, grooming tools and equipment.
  • Routinely clean and disinfect stalls, stable equipment, grooming tools.
  • Ask visitors to wash hands or use a liquid hand disinfectant before handling horses.
  • Minimize rodent, wildlife, bird and insect populations and keep them away from feeding areas and water sources.
  • Maintain pastures, manage manure and avoid overcrowding.
  • Group like-used horses (i.e. separate broodmares from competition animals).
  • Isolate new horses, those returning from off-farm events or hospital for a minimum of two weeks to monitor for disease.
  • Disinfect your shoes, equipment after shows, visiting other barns.

Off-property

  • Don’t allow horses to co-mingle with other animals.
  • Only use your own equipment cleaning tools, buckets and equipment during that time.
  • Don’t let horses eat off the ground or use community water troughs, buckets.
  • Wash your hands after touching other horses.
  • Clean and disinfect your trailer after every trip.

Help! My Horse May Be Contagious
If any of the contagious diseases mentioned here are suspected, execute the following sick horse biosecurity protocols.

  • Quarantine sick horse(s).
  • Call veterinarian immediately.
  • Post signs warning of illness and quarantine.
  • Assign care of sick horses to specific individuals.
  • Wear protective clothing when dealing with infected animals. Remove immediately and dispose or launder.
  • Install footbaths and alcohol-based hand sanitizers at the quarantine area exit.
  • Wash hands thoroughly with pump-dispensed soap.
  • Handle healthy horses and muck out their stalls first.
  • Use separate stable equipment to muck out infected horses.Contain stall waste to a separate bin and don’t spread or put it on manure piles.
  • Don’t allow dogs, cats or other farm animals near isolated horses.
  • Clean and disinfect stalls regularly, especially after a sick horse has used the space.

Busy Barn Biosecurity
Riverlands Equestrian in Pemberton, B.C., is primarily a centre where coaches bring students to train between shows, but the facility also hosts clinics, event stabling and layovers, while maintaining their own and boarders’ horses.

With so much equine traffic, trainer Wes Schild said the well-being of all the animals is a priority. “Before anyone brings their horse, we have an information form they complete telling us about their horse’s health, said Schild. “One of the main items we require is that their vaccinations are up to date. We request that all horses have a five-way vaccine [East and West Nile virus, equine herpesvirus, equine influenza, tetanus] along with strangles a minimum of two weeks prior to arrival.” Mares also require a Coggins test for equine infectious anemia.

Guest horses are housed on the far side of the barn separate from Riverlands’ sales and training horses. Before visitors arrive, stalls are completely disinfected and bedded with fresh shavings. They’re also turned out in separate, dedicated paddocks. “They don’t go near our horses, as there are no shared fence lines. There’s actually a walkway between the fence lines so they can’t go nose to nose with our horses,” said Schild. “Another reason for the separate paddocks is for better parasite management.”

Riverlands also has an Agriculture Canada-approved quarantine barn for imported horses located at the far end of the facility’s property.