Prevention of disease is the foundation for health. No medical treatment, or even cure, for an illness, is more important than that which may help us avoid disease in the first place. Vaccines (immunizations) are preeminent in maintaining good health, without which our horses are susceptible to numerous disease-causing pathogens.
Here are some of the equine diseases for which approved vaccines are available. Your veterinarian will help you to decide which of these are significant threats in your area and which vaccination schedules you should institute in your herd.
Core Vaccines:
Core vaccines are considered to be part of every horse’s regular vaccination regimen. The diseases they prevent pose significant health risks and are endemic to every part of the U.S., regardless of the use of the animal or housing situation. The vaccines may also be required by law where there is a risk of zoonoses, or possible transmission of disease from animals to humans.
Tetanus
Cause:
Clostridium tetani (spore-forming, toxin-producing bacteria) by contamination and infection of a wound, surgical incision, or umbilical stump in foals
Symptoms:
Third eyelid prolapse; classical grinning expression with teeth exposed, ears turned backwards, and nostrils flared; rigid paralysis of the neck and face muscles; and tetanic spasms (especially after stimulation with loud sounds), where limbs are further extended than normal, neck is arched back, and tail is pointed straight out
Prognosis:
Guarded to poor once neurological symptoms have occurred. 50 -70% fatality rate despite treatment
Vaccination Protocol:
Broodmares before foaling
Adults boostered annually after primary series
At time of any penetrating injury or pre-surgically if last booster was more than 6 months prior
Foal series according to mare’s vaccine status
Eastern/Western Equine Encephalomyelitis (EEE/WEE)
Cause:
Arbovirus of the familyTogaviridae spread by mosquito bites
Symptoms:
Anorexia, fever, hyper-excitability (pacing), depression, blindness, head tilt, inability to rise
Prognosis:
20-40% fatality rate (WEE); 70-90% fatality rate (EEE)
Vaccination Protocol:
Broodmares before foaling
Adults boostered annually after primary series especially prior to vector (mosquito) season
6 month boosters in endemic areas
Foal series according to mare’s vaccine status
*Note: Venezuelan Equine Encephalitis (VEE) vaccine is administered to horses in the southern states. Consult a veterinarian on risk / recommendations for your area.
Rabies
Cause:
Rabies virus from bite wounds of other mammals
Symptoms:
Ataxia (incoordination), aggression, depression, circling, fear, tremors or seizures, trouble swallowing, hyperesthesia (increased sensitivity to stimuli)
Prognosis:
100% fatality rate
Vaccination Protocol:
Broodmares before foaling (extra-label use);
Prior to breeding
Adults boostered annually
Foal series according to mare’s vaccine status
West Nile Virus
Cause:
Arbovirus of the family Flaviviridae spread by mosquito bites
Symptoms:
Ataxia (incoordination), anorexia, fever, depression, inability to rise, wandering, sweating, teeth grinding, swallowing difficulty, tremor / seizure activity, facial paralysis
Prognosis:
Guarded (35% fatality rate); poor for recumbent horses due to secondary complications; persistent symptoms despite survival
Vaccination Protocol:
Broodmares annually and before foaling
Adults boostered annually after primary series especially prior to vector (mosquito) season
4-6 month boosters in endemic areas
Foal series according to mare’s vaccine status
Non-Core Vaccines:
Other vaccinations are given based upon the risk of exposure to a particular disease in your horse’s specific environment or in an area to which the animal may travel. The factors that may play a role in determining whether or not your horse should receive the immunizations will include geographic region, exposure to other horses and animals, immune health, and breeding status.
Rhinopneumonitis
Cause:
Equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4)
Symptoms:
Nasal discharge, fever, cough, anorexia, lymph node enlargement, spontaneous fetal abortion, hind-limb ataxia (incoordination), urinary incontinence, fecal retention, dog sitting position, inability to rise
Prognosis:
Good, guarded, or poor depending upon progression of symptoms, aggressiveness of treatment, and secondary complications
Vaccination Protocol:
Recommended for at risk herds and known exposures, to stop viral shedding and disease transmission to stable-mates. Very short duration and limited protection. The abortion strain vaccination is given to the pregnant mare at 5, 7 and 9 months of gestation.
Influenza Virus
Cause:
Influenza type A virus
Symptoms:
Nasal discharge, fever, cough, lymph node enlargement
Prognosis:
Generally good; guarded if secondary bacterial infection (pneumonia) occurs
Vaccination Protocol:
Recommended series of vaccinations followed by semi-annual boosters for horses that travel, before exposure to other horses, and for known exposures within a herd
Potomac Horse Fever
Cause:
Neorickettsia risticii – rickettsial organism that originates in parasites of freshwater snails and insects which may be ingested by the horse by accident
Symptoms:
Reduced appetite, anorexia, colic, fever, depression, laminitis, diarrhea, spontaneous abortion
Prognosis:
Good with early treatment; guarded to poor if laminitis occurs, usually 3 to 5 days after diarrhea begins
Vaccination Protocol:
Very short duration and limited protection – may reduce severity of symptoms, but may not prevent infection; yearly boosters after initial series recommended in endemic areas
Botulism
Cause:
Exposure to botulinum toxin; ingestion of Clostridium botulinum bacteria by foals; rarely from infected wounds, incisions, or umbilical stumps
Symptoms:
Flaccid paralysis of the face and tongue, upper and lower GI tract, and respiratory muscles; muscle fasciculation (shaker foal syndrome); difficulty ingesting food and water; recumbency (inability to rise)
Prognosis:
Guarded at best; poor to grave prognosis if horse cannot eat, drink, goes down, and / or has respiratory distress
Vaccination Protocol:
Series and boosters for broodmares, foals, and other adults in endemic areas
Viral Arteritis
Cause:
Equine arteritis virus spread venereally or by respiratory secretions
Symptoms:
Fever, edema (swelling) in the limbs, genital swelling, nasal discharge, conjunctivitis, abortion
Prognosis:
Good for non-breeding animals; abortion or low survival rate of foals
Vaccination Protocol:
Recommended pre-breeding for broodmares (not safe for use while pregnant); all breeding stallions (all stallions should be tested and documented negative prior to vaccination)
Strangles
Cause:
Streptococcus equi bacteria from respiratory secretions and fomites (contaminated objects and equipment)
Symptoms:
Colored or milky nasal discharge, fever, reduced appetite, cough, abscessed lymph nodes, depression
Prognosis:
Good when treated aggressively; persistent complications possible
Vaccination:
Broodmares if foal will be at high risk; contraindicated in recently exposed or infected animals; vaccine may cause significant side effects; annually or semi-annually in endemic areas
Anthrax
Cause:
Bacillus anthracis bacteria ingested from soil or from biting flies – highly contagious to animals and people
Symptoms:
Higher fever; edema in the ventral thorax; sudden death lacking rigor mortis; dark blood from anus, mouth, and nostrils of carcass
Prognosis:
Certainly fatal unless treated early and aggressively; non-febrile (normal temperature) members of the herd are treated prophylactically
Vaccination Protocol:
Vaccinate non-febrile members of an exposed herd; prevent human exposure to vaccine and carcasses
Rotavirus
Cause:
Equine rotavirus in foals by ingestion of feces contaminated soil, feed, bedding, etc.
Symptoms:
Mild to severe diarrhea, loss of appetite, dehydration, colic
Prognosis:
Good with supportive treatment
Vaccination Protocol:
Recommended series for pregnant mares in order to protect foals through colostrum in high-risk environments and on farms with a history of rotavirus infection
