Vaccinations Seminar-How to Protect Your Horse

April 26, 2024 32 view(s)



In-Depth Conversation about Core Vaccinations by Dr. Sean Allison, DVM from Cleveland Equine Clinic


What core vaccinations does your horse need?

Why is a coggins important?

Talk about EHV-1 and what precautions you should take


What is a vaccine?

  • Per Britannica a vaccine is a suspension of weakened, killed, or fragmented microorganisms or toxins or other biological preparation, such as those consisting of antibodies, lymphocytes or messenger RNA, that is administered primarily to prevent disease…
  • Basically a weakened version of a disease that is given to promote an immune response and cause the body to create antibodies for that disease
  • It causes an immune response but does not cause the disease itself

What can they protect and treat?

  • Viruses: West Nile, Herpes 1-4, EEE/WEE
  • Bacteria: Tetanus, strangles, botulism
  • Fungus: Treatment of Equine Pythiosis
  • Melanoma: Treatment of equine melanoma (Oncept)

Vaccine Types

  • Live (attenuated): Weakened form of disease
  • Modified Live
  • Recombitant: Uses small piece of bacteria or virus
  • Inactivated/killed: Also use a piece or part of a virus/bacteria

A few facts

  • Vaccines do NOT prevent an animal from contracting a disease, rather minimize the risk
  • Immunity decreases with lack of proper vaccination
  • Typically vaccines initially require a booster(s)
  • Vaccines do not afford immediate protection to a disease
  • Occasionally there can be reactions to the vaccine, very rarely can be severe

Core Vaccines

  • American Veterinary Medical Association (AVMA) defines as those that protect from disease that are endemic to a region, those with potential public health significance, required by law, virulent/highly infections, and/or those that posing a risk of significant disease
  • These types of vaccines show enough benefit and low enough level of risk to justify their use
  • Core Vaccines: West Nile Virus (WNV), Eastern and Western Encephalitis (EEE/WEE), Tetanus, Rabies (per AAEP)

Risk Based Vaccines

  • Equine Influenza
  • Equine Herpes 1-4 (Rhinopneumonitis) i.e. EHV 1-4
  • Potomac Horse Fever (PHF)
  • Strangles
  • Botulism
  • Leptospirosis
  • Anthrax, Rotavirus, Snake bite, Venezuelan Encephalitis, Equine Viral Arteritis (EVA) (per AAEP)

Broodmare Vaccination Schedule

  • EHV 1→ Pneumabort:
    Give at 3, 5, 7, and 9 months
  • Pre-foaling vaccines:
     Tetanus, WNV, EEE &WEE, Rabies, PHF, EHV 1/4
    Give 4-6 weeks prior to foaling

CEC Protocol

  • Potomac Horse Fever (annual)
  • Rabies (annual)
  • Eastern/Western Encephalitis (annual)
  • West Nile Virus (annual)
  • Equine Herpes 1-4 (bi-annual)
  • Influenza( bi-annual)
  • Tetanus (*annual)

West Nile Virus

  • Virus
  • Leading cause of arboravirus encephalitis (inflammation of tissue of brain) in humans and horses
  • Transmitted by mosquitos but carried by birds
  • Not directly contagious from horse to horse
  • Highly unlikely a horse with disease can pass to another horse via mosquito
  • Vaccine- annually (spring):
  • Diagnosed with blood or tissue sample



West Nile Virus Clinical Signs

  • Neurologic signs:
    Hind limb weakness, circling, muscle fasciculations, impaired vision, inability to swallow, hyperexcitability, paralysis, seizures, death
  • Loss of appetite
  • Depression (impaired mentation)
  • Fever
  • Blindness

West Nile Treatment

  • Supportive care:
    Oral/intravenous feeding
  • Anti inflammatory drugs
  • Slinging

Eastern & Western Equine Encephalitis

  • Transmitted via mosquito
  • Virus
  • Birds are reservoir
  • Horses dead end host (as are people)
  • EEE fast acting and highly fatal
  • WEE less deadly compared to EEE
  • Vaccine- annually (spring):
  • Diagnosed by blood test or cerebral spinal fluid (CSF)

WEE and EEE Clinical Signs

  • Fever
  • Impaired vision
  • Depression
  • Ataxia
  • Head pressing
  • Paralysis
  • Convulsions
  • Coma and death

WEE and EEE Treatment

  • Supportive care
  • Corticosteroids


  • Virus
  • Zoonotic
  • Carried by mammals and passed via bites, scratches, and saliva
  • Horses are very susceptible but relatively rare
  • Once clinical signs seen, death is typically inevitable
  • Reportable disease in the US
  • Vaccine:

Rabies Clinical Signs

  • Ataxia and muscle weakness
  • Sensitivity to touch
  • Loss of sensory perception
  • Fever
  • Self mutilation
  • Aggressive behavior
  • Drooling and inability to swallow
  • Death
  • Furious vs paralytic (stuporous) form**

Rabies Treatment

  • No treatment
  • IF properly vaccinated post vaccine booster dose needed

Equine Influenza

  • One of the most common respiratory diseases of horses
  • Virus
  • Highly contagious
  • Transmitted via coughing, droplets and fomites
  • Diagnosed via nasal swab PCR
  • Vaccine options:
    Inactivated given in muscle
    Modified live given intranasal

Equine Influenza Clinical Signs

  • Virus effects cells of throat and causes horse to be susceptible to bacterial infection
  • Fever
  • Nasal discharge
  • Cough
  • Lethargy and loss of appetite

Equine Influenza Treatment

  • Supportive care
  • Treatment of secondary bacterial infection

Equine Herpes 1 & 4

  • Rhinopneumonitis
  • Virus
  • Many horses may be infected with EHV 1 early on in life and lies latent:
    Some studies say 80-90%
  • Can vary from subclinical to severe
  • EHV 1 can cause abortion in mares as well as mutate into Equine Herpes Myeloencephalopathy (EHM)
  • Vaccines:
    Modified live
  • Diagnosed nasal swab or blood test

EHV 1-4 Clinical Signs and Treatment

  • Biphasic fever:
    Peaking at 1-2 days and then again at 6 days
  • Enlarged lymph nodes
  • Discharge from eyes and nose
  • Typically not much of a cough
  • Treatment includes supportive care


  • Equine Herpes Myeloencephalopathy
  • Form of EHV 1 (and rarely EHV 4)
  • Signs start approximately 7 days post infection:
    Incubation typically 2-10 days
  • Can cause incoordination, weakness, urine dribbling, head tilt, fever, loss of tail tone, inability to rise:
    Typically starts at hind end and moves forward
  • IMPORTANT to remember that the EHV 1-4 vaccine does not protect against the neurologic form
  • Can be diagnosed by blood test or nasal swab:
    Important to not to screen for EHV 1
  • Treatment includes supportive care


  • Bacteria Clostridium tetani, neurotoxin
  • Also called “lock jaw”
  • Attacks nerves controlling muscles and causes muscle stiffness and spasm
  • Live in GI tract of horses as well as in the soil
  • Not contagious between horses
  • Comes form punctures, wounds, surgical incisions
  • Vaccine- annually:
    Inactivated, toxoid
  • Diagnosed by clinical signs or culture

Tetanus Clinical Signs

  • Stiffness and difficulty moving, “saw horse” appearance
  • Third eyelid protrusion especially when startled
  • Tail may stick out
  • Loud sounds and bright lights can worsen symptoms
  • May have “anxious” look as facial muscles stiffe
  • Inability to open mouth (lock jaw)
  • May die from respiratory failure (diaphragm cannot move)

Tetanus Treatment

  • Antibiotic (typically penicillin)
  • Tetanus antitoxin
  • Typically kept in dark quiet stalls that may be padded
  • If disease is significant enough a sling may also be used

Potomac Horse Fever

  • Neorickettsia risticcii (bacteria)
  • Late spring to early fall but can be seen later into year:
    Have had diagnosed cases in December in this region
  • Ingest aquatic insects that have bacteria inside them (typically mayfly)
  • If found on farm it will mostly occur in the future
  • Vaccine-annually:
    Killed (many times combined with Rabies)
  • Diagnosed by blood or feces

PHF Clinical Signs

  • Fever
  • Colitis/diarrhea
  • Laminitis
  • Abortion in pregnant mares

PHF Treatment

  • Antibiotics
  • Anti-inflammatories
  • Anti-diarrhea medications
  • Treatment of laminitis
  • Fluid therapy


  • Streptococcus equi subspecies equi (bacteria)
  • Horse infected via inhalation or ingestion
  • Highly contagious
  • Diagnosed by blood, or culture/swab/tracheal wash
  • Currently an intra-muscular and intra-nasal vaccine
  • Discussion of whether horses should be vaccinated for strangles:
    Many horses may have contracted the disease early on in life.  Pulling a titer in older horses may be more ideal.

Strangles Clinical Signs

  • Fever
  • Nasal discharge
  • Lymph node swelling and/or abscessation:
    Especially in the jaw area
  • Purpura hemorraghica
  • “Bastard” strangles:
    Metastatic abscessation in other lymph nodes in the body

Strangles Treatment

  • Isolation
  • Antibiotics:
  • Anti-inflammatories
  • Tracheotomy

Purpura hemorraghica

  • Sequela to strangles
  • Swelling of head, legs and under belly
  • Blood vessels swell to immune response to strangles
  • Treatment include corticosteroids, antibiotics, tracheostomy in advanced cases
  • Difficult to predict cases
  • If horse has had previous reactions to strangles vaccine recommend not doing again


  • Clostridium botulinum
  • Can be found in soil and decaying animals
  • Hay can be contaminated
  • Horse is infected by ingestion or less likely a wound
  • “Shaker foal syndrome”
  • 8 types (A,B,C effect horses)
  • Diagnosed off clinical signs and history (no blood test etc.)

Botulism Clinical Signs

  • Flaccid paralysis:
    Difficulty standing
    Bladder paralysis and colic
    Paralysis of respiratory system
  • Normal mentation*

Botulism Treatment

  • Antitoxin
  • Supportive care
  • Mechanical ventilation in foals

Botulism Clinical Signs

  • Flaccid paralysis:
    Difficulty standing
    Bladder paralysis and colic
    Paralysis of respiratory system
  • Normal mentation*


  • Leptospira bacteria (pomona, interrogans)
  • Zoonotic (passed through urine)
  • Can be infected via mucus membranes of mouth, eyes, or nose with urine
  • Also infected via cuts or scratches
  • Can also be ingested
  • Diagnosed by blood or other tissues

Leptospirosis Clinical Signs

  • Fever
  • Depression
  • Lack of appetite
  • Uveitis (moon blindness)
  • Severe infections can cause kidney and liver issues and potentially death
  • Abortion
  • Treatment of Leptospirosis:
    Treatment of uveitis

Equine Melanoma

  • Common nodular tumors typically found in grey horses
  • May or may not be malignant
  • Can develop at any age
  • Melanoma in non grey horse should be considered much more dangerous
  • Can occur around mouth, eyes, sheath, vulva, behind jaw, internal organs
  • Malignant form can be more severe and effect horse to greater extent

Equine Melanoma Clinical Signs

  • Varied size of black “bumps”
  • Firm swelling particularly in the jaw area
  • Can break open and ooze a black substance
  • Can be locally invasive which may cause more severe issues like:
    Colic, compression of spinal cord, not allow penis to retract, cause horse to have difficulty passing manure

Equine Melanoma Treatment

  • Oncept:
    Made for oral melanoma in dogs
    Stimulates body to mount immune response against melanoma

Equine Pythiosis

  • Pythium insidiosum
  • “Swamp cancer”
  • Fungus like infection that can affect skin, bones, intestines etc.
  • Wounds develop kunker (not canker)
  • Diagnosed by presentation or blood test
  • Cannot be spread from horse to horse
  • Vaccine can help acute as well as chronic cases
  • **Has also some application of being used to help equine sarcoids

Autologous Vaccines

  • Immunotherapy
  • Equine Melanoma:
    Sample of melanoma removed and sent to specialty lab and made into injectable vaccine
  • Torigen:
    Melanoma, sarcoid, squamous cell carcinoma
    Administered once a week for 6 weeks


Autologous Vaccines


Equine Infectious Anemia

  • Coggins test
  • Swamp fever
  • Virus (lentivirus)
  • Potentially fatal blood borne disease causing persistent infection (life long carriers)
  • Can affect horses, ponies, zebras, donkeys, mules and found worldwide
  • Passed by biting flies (i.e. horsefly, deerfly)
  • Edema, weight loss, anemia, depression, petechia, epistaxis, death, fever

Equine Infectious Anemia Protocol

  • No treatment
  • No vaccine
  • With testing has dropped from 4% to .004%
  • If a horse is confirmed positive:
    Quarantine at least 200 yards from any equid species for life

Biosecurity & Isolation

  • When in doubt contact veterinarian
  • New arrivals to facility isolate for 7-14 days
  • When disinfecting know your products
  • Bleach/alcohol vs Accel/Rescue, Intervention
  • Isolation of suspect infected animal(s)
  • Foot baths, protective clothing, independent cleaning items and tack
  • Serial testing


CLICK HERE to Check out the entire presentation from the seminar on March 23rd, 2024 

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