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Indiana State Board of Animal Health

BOAH > Species Information > Cattle, Sheep & Ruminants > EHD Suspected > Biosecurity Information > Species Specific Biosecurity Tips > Equine/Horses Equine/Horses

Equine Infectious Anemia (EIA)
Equine Infectious Anemia (EIA) is also known as Swamp Fever. Acute, chronic and inapparent are three forms of EIA to which horses are susceptible. EIA can be detected through a Coggins or EIA blood test processed at a laboratory. However, no cure or vaccine exists for this disease. Acute cases generally occur within 7 days to 30 days after initial exposure. Horses may exhibit fever, go off feed or suddenly die. Test results may indicate negative for 16 days to 42 days after exposure. Chronic cases produce positive tests. Signs of chronic cases include weight loss, weakness, anemia, swelling of lower legs, chest and abdomen. Symptoms will subside, but may reoccur. Acute episodes can emerge after stress from hard work, hot weather, pregnancy or other disease. Inapparent cases exhibit no outward signs, but test positive for the disease. If a horse becomes stressed, symptoms can appear. Infected animals may not be able to fight off other diseases and they pose the greatest risk of spreading EIA to other horses because they may not show clinical signs. Clinical signs of EIA may include fever, depression, decreased appetite, fatigue, sweating, rapid weight loss, swelling of the legs, lower chest and abdomen, weakness, pale or yellowish mucous membranes, abortion in mares and colic.

Exposure: Exposure can occur through blood-to-blood contact by biting flies, contaminated needles and medical instruments or blood transfusion.

Examples: Excessive fly population, failure to use clean/disinfected equipment on each animal, contaminated needles.

Biosecurity Control Points:

  • Control fly population.
  • Use insect repellant.
  • Keep horses inside at dusk and dawn.
  • Keep Coggins test current.
  • Allow your veterinarian to treat any/all medical problems.

Equine Protozoal Myeloencephalitis (EPM)
Equine Protozoal Myeloencephalitis (EPM) is a disease affecting the central nervous system. EPM is spread by a parasite in feces of opossums. Symptoms vary, depending on where the parasite localizes in the nervous system. Horse owners may notice lameness, stumbling, incoordination and weakness, usually in the rear limbs. Other signs include stiff walking, leaning or standing splay-footed, loss of condition, facial nerve paralysis, head tilt, difficulty chewing and swallowing, snoring, drooped eyelid or lip, abnormal eye movements, back soreness, attitude change, circling, suddenly lying down or falling asleep, seizures, collapse and death. EPM can be detected by a blood test. About 60 percent of EPM-positive horses respond to treatment within the first month.

Exposure: Feed, hay, bedding and water that have been contaminated by the parasite.

Examples: Uncovered grain, storing hay in an unmanageable area, dirty water, dead animals in the area, large bird population.

Biosecurity Control Points:

  • Keep opossums out of barns and away from feed and hay.
  • Tightly cover grain, feed supplies.
  • Feed processed grain; steam-crimped and pelleted to kill parasites
  • Install mesh wore fencing with a "hot wire" around the outside to deter opossums.
  • Dispose of dead animals, including birds, small rodents and opossums, to prevent the spread of parasitic eggs.
  • Limit bird populations in the barn.

Equine Influenza Virus
Equine Influenza Virus is an acute, highly contagious infection caused by different strains of the influenza virus. Clinical signs may not be apparent for several days even though the horse in infected and contagious. Vaccinated horses may show mild clinical signs, which can be missed easily. Influenza is transmitted via aerosol, through inhalation of droplets containing the virus. The incubation period is usually one to three days, but can range from 18 hours to 5 days. Clinical signs include fever, dry, harsh cough for several weeks if secondary infection is involved, nasal discharge that becomes yellow with a secondary bacterial infection, depression, loss of appetite, weakness, watery eyes, enlarged lymph nodes, edema and leg stiffness, difficulty breathing.

Exposure: Via aerosol, inhalation of droplets containing the virus.

Examples: Bad ventilation, excessive dust, and poor supportive care. Horse owners should seek medical treatment in timely fashion for any cold symptoms, such as fever and cough.

Biosecurity Control Points

  • Vaccination, beginning at an early age with adequate boostering will provide protection and reduce the severity of signs.
  • Good management.
  • Early recognition of symptoms and signs.
  • Quarantine new horses up to six week.

Streptococcus equi (Strangles)
The strangles usually affects equine younger than two years of age, but any horse is susceptible. Foals younger than four months are protected by passive immunity through colostrum. The strangles, caused by bacterium Streptococcus equi, is highly contagious. The organism can live in a moist, cool environment for several months, but is also sensitive to drying. This bacteria can remain viable in frozen discharges and survive weeks in water, but dies quickly in soil and pasture. Twenty percent of horses will shed bacteria for a month after clinical signs are gone. Crowded conditions, inadequate housing, poor sanitation, inadequate nutrition, stress from lengthy transportation and new animal additions can contribute to the development of strangles. Incubation period depends on climate conditions and the overcrowding of animals, but usually ranges from 4 to 14 days. Clinical signs include lethargy, depression, slight cough, fever, nasal discharge that quickly changes to thick and yellow, difficulty swallowing, loss of appetite and enlarged lymph nodes in lower jaw. A horse may stand with its neck extended due to the pain in the throat area. As swelling progresses, infection will abscess and drain, then recovery will begin. Occasionally the abscesses spread to other parts of the body (lungs, liver or brain) commonly known as "bastard strangles."

Exposure: Nasal secretions (sneezing, coughing, nose-to-nose contact) and draining abscesses, flies and contaminated equipment (water buckets or troughs, feed, stalls, fences, tack pitchforks, etc.). People can also carry the organism on clothing, boots or un-washed hands.

Examples: Introducing new horses, traveling to shows with several other equine, poor management, poor nutrition, over-crowding, inadequate housing, poor sanitation and long trips on the trailer.

Biosecurity Control Points:

  • Practical biosecurity procedures.
  • Quarantine new horses.
  • Avoid mingling with other horses at shows and other events.
  • Avoid sharing water buckets and equipment.
  • Vaccinate to reduce severity and spread of disease. However, vaccination will not prevent the disease and is not recommended for equine incubating the organism.
  • Provide clean, dry housing.
  • Practice good sanitation.

Equine Herpes Virus (EHV-1) and (EHV-4)
Equine Herpes virus types one and four are closely related viruses. They are highly contagious and easily transmitted via the respiratory route. The herpes virus infection is lifelong. The incubation period is 2 to 10 days. The organism can be spread to horses by humans and contaminated grooming equipment. Infection can be reactivated from latency by stress or other infection or may reoccur periodically with the virus actively replicating. Once a horse has had EHV it becomes a carrier. Even though the horse may not show signs of he disease, it can still shed the virus and be a source of respiratory infection in other horses.
EHV-1 (reproductive), also known as Rhinopneumonitis, can cause abortion, stillbirths, and weak foals that die soon after birth, as well as neurologic disease and paralysis. Abortion usually occurs in the last trimester of pregnancy. Near-term foals may be born alive but die due to sudden pneumonia within a few days. It also causes respiratory disease in young horses and mild respiratory infections in older horses.
EHV-4 (respiratory) can also cause abortion and neurologic disease. Clinical signs include fever, congestion, nasal discharge, discharge from the eye, depression, loss of appetite, cough, edema of the mandibular or retropharyngeal (facial) lymph nodes or constipation followed by diarrhea.

Exposure: Contaminated humans, grooming equipment, new horses, frequent travel to shows or areas with other horses.

Examples: Clothes, shoes, brushes, shared water buckets, nose-to-nose contact, traveling to horse shows, towels and blankets.

Biosecurity Control Points:

  • Isolate new horses or horses returning from other farms or racetracks a minimum of 21 days.
  • Keep horses on breeding farms or racetracks in small groups.
  • Vaccinate and booster appropriately and regularly.