I. Tetanus (Lockjaw)
Caused by a toxin produced by the bacteria Clostridium tetani. The bacteria, always present in soil and manure, can enter the horse by a deep cut or puncture, bone fracture, retained placenta (foaling), or after surgery. Once in the body the bacteria release their toxin which affects the central nervous system. Common symptoms include paralysis of the jaws, body spasms or convulsions. The disease is usually fatal from paralysis, dehydration and starvation. The vaccine, tetanus toxoid is free from complications and very effective. It is noteworthy to differentiate between Tetanus toxoid & Tetanus antitoxin

Tetanus Toxoid: A Vaccine, not a treatment

• Stimulates a horses immunity approximately 3-4 weeks after vaccination

Tetanus Antitoxin: A Treatment, not a vaccine.

• Gives immediate protection which lasts 2-3 weeks

• Although rare, some horses experience fatal serum hepatitis a few weeks after injection. This is not a problem with foals, therefore reserved for:

• Nonvaccinated horses following injury
• Nonvaccinated mares at foaling & their foals.

First time vaccinates. NO surgery or injury

• Tetanus toxoid, & booster 1 month later
• Yearly with tetanus toxoid

Brood mares

• Tetanus toxoid 4-6 weeks before due date
• If unvaccinated at foaling: Toxoid & Antitoxin (see notes on antitoxin above)
• booster with tetanus toxoid 1 month later, then yearly

Following surgery or injury

Vaccinated horses

• tetanus toxoid if not vaccinated within 6 months

Unvaccinated horses, injury only

• tetanus toxoid AND ANTITOXIN, see notes below on antitoxin
• booster with tetanus toxoid 1 month, then yearly

Foals

From unvaccinated mares or lack of colostrum

• birth: tetanus toxoid and antitoxin
• booster at 1 & 3 months old with tetanus toxoid
• annual boosters with tetanus toxoid

From vaccinated mares

• ensure adequate colostrum
• booster at 3-4 months of age with tetanus toxoid
• booster 3-6 weeks later with tetanus toxoid
• annual boosters with tetanus toxoid

II. Equine Encephalomylitis (sleeping sickness)
Caused by a virus, transmitted by mosquito (therefore vaccinate before mosquito season) and other biting insects from birds to horses. Horse to horse transmission (except VEE) is not possible. Causes severe neurological symptoms which include blindness, convulsions, head pressing, severe depression, and coma like signs. Milder signs are also possible exhibiting as fever, depression, sleepiness, and or aggression. The disease is usually fatal in EEE less so in WEE but may result in permanent brain damage. Three varieties of the virus are found, Eastern (EEE) found in the East & Southeast states, Western (WEE) found in Western & Midwestern states, Venezuelan (VEE) found in South & Central America, Mexico. Humans are susceptible (rare disease) if bitten by infected mosquito but transmission is only possible from birds to humans, not horse to human (except VEE). The vaccine is free from complications and very effective.

Eastern & Western (EEE, WEE)

Pleasure or performance horses

• Annual booster in springtime

Brood mares

• 4 – 6 weeks before foaling, also springtime

Foals

• protection from colostrum can last 6-7 months
• first dose at 3-4 months old
• booster 1 month, followed by annual boosters
• If 1^st vaccinated at a younger age, 3^rd booster at 6 months

Venezuelan (VEE)

• currently not in the U.S., repeated outbreaks in Mexico and Venezuela
• consider vaccinating if transporting to Texas, Florida, southern California

III. Influenza (Flu)
Very common respiratory infection caused by influenza virus. Results in mild to severe: fever, lethargy, decreased appetite, coughing, nasal discharge, and muscle aches. Very contagious, spreads rapidly through groups of horses. Transmitted by aerosol from coughing horses and can travel at least 35 yards! Prevention of disease is complicated by recently vaccinated horses acting as symptom free carriers, short-lived immunity following infection, and a continually changing virus. This means that vaccination against one type of virus will not necessarily protect against another. Because of the constantly changing virus, vaccines are not as effective as we would like and therefore frequent vaccination is required.

The disease continually cycles through the U.S. horse population and large outbreaks occur when the virus has changed sufficiently so that current vaccines are not very effective. Never the less (because it is the only protection we can give them) vaccination is highly recommended for horses exposed to others, or horses which travel frequently, or horses exposed to horses which travel frequently. In other words boarding stables, training centers, shows, competitive events, group rides, breeding farms, racetracks, state or county fairgrounds. Because vaccine can cause muscle aches and discomfort, and because the effect of a vaccine doesn’t occur for several weeks, vaccination is recommended at least 2-3 weeks prior to an event.

As is true every time you transport your horse, bring your horse’s water and feed buckets if possible. AVOID group water troughs, feeding. Don’t allow strange horses to use your horses’ buckets.

FIRST TIME VACCINATE: best immunity with a minimum 3 doses at monthly intervals.

Performance & Show Horses, Weanlings & Yearlings

• Every 2-3 months 

Foals (Note: current research indicates 1^st vaccination at 6 mo. of age!)

From unvaccinated mares or lack of colostrum

• If high exposure, start at 1 month old
• If not high exposure start at 3 months old
• Booster every 4-6 weeks until 7 months old

From vaccinated mares

• if high exposure, start at 3 months old
• Booster every 4-6 weeks until 7 months old
• if not high exposure, can start at 6 months old
• Booster every 4-6 weeks 2 more times

Pleasure horses

• Booster yearly 2-4 weeks before exposure e.g. group trail rides, shows, fairgrounds etc.
• in public stables: same as performance horses

Brood mares

• Same as performance horses
• Booster 4-6 weeks before anticipated foaling date

IV. Rhinopneumonitis (Rhino)
Less common than flu. Caused by 2 types of Herpes virus (EHV-1, EHV-4). Both cause respiratory disease with mild to severe flu-like symptoms. Frequently leads to a secondary bacterial infection. EHV-1 also causes abortion, weak foals, and paralytic nervous disease.

Transmission of respiratory disease is by aerosol from coughing horses, by direct contact with nasal discharge, by touching nasal discharge with fingers and tack then touching another horse. Abortion Herpes virus are difficult to control because they can live inactive in carriers (without symptoms) and shed virus during times of stress.

Respiratory infection is most common in young horses especially when starting training and in groups of horses. Virus is present in nearly all horse populations and repeated exposure leads to mature horses not routinely experiencing severe disease. No immunity is developed from exposure to abortion or neurological forms.

Primary use of vaccine is to prevent EHV-1 abortion and EHV-4 respiratory disease in foals, weanlings, yearlings, and young performance and show horses.

Performance and show horses

• every 2-3 months
• best to vaccinate all horses on premises at the same time

Foals

• first dose at 2-4 months old
• booster 3-6 weeks
• afterwards booster as in performance horses

Weanlings, yearlings

• same as performance horses

Pleasure horses (living isolated from groups of horses, or travelling horses)

• optional, every 6 months if vaccinating

Brood mares

Abortion prevention: use approved EHV-1 vaccine. Vaccines don’t provide total protection but appear to reduce the severity and frequency of disease.

• Manufacturer recommends during 5th, 7th, & 9th months of pregnancy
• We recommend beginning during the 3rd month.

Respiratory disease prevention: EHV-1 & EHV-4 vaccine

• at breeding time
• 1 month before foaling

V. Potomac Horse Fever (PHF)
Caused by a bacteria-like parasite Ehrlichia risticii. More prevalent in the east, but has been seen in the Pacific Northwest and many regions in the U.S. Although transmission is not completely understood it doesn’t appear to be horse to horse and an insect (tick?) is highly suspected. The disease is often seasonal from late spring to early fall and single horse infections as well as groups of horses contract the disease. Symptoms include fever (often missed because it can be transient), lethargy, profuse diarrhea, loss of appetite, and colic. Affected horses die (20-35%) or are euthanised because of serious complications (laminitis) or dehydration from diarrhea. Blood tests show that horses sharing premises with affected horses become infected without showing symptoms. Once PHF is in an area it is likely to recur. Vaccination is recommended if in such an area or travelling there. The vaccine is free from complications and is fairly effective.

Pleasure, performance, weanlings, yearlings

• booster ever 6 months

Brood mares

• booster every 6 months
• booster 4-6 weeks before anticipated foaling date

Foals

• 3-4 months of age
• booster 1-2 months later
• If 1st vaccine was at less than 3 months old: booster monthly until 5 months
• Afterwards booster as in pleasure, performance horses

Rabies

Caused by a virus transmitted from infected wildlife which include skunk, raccoon, fox, badger, and bats. Always fatal, the virus is shed through the saliva of an infected animal. Although rabies is not a significant problem in pets, it is spreading widely throughout most of the U.S. and Canada through susceptible wildlife. The symptoms are not (as commonly believed) typical and can include colic, lameness, paralysis, muscle spasms, and depression. Aggression is not usually seen in the horse. Although at the present time it is not a serious problem in the Pacific Northwest we recommend vaccination because of the danger to humans, horses, cattle, and pets. The vaccine is free from complication or side effects, is cheap, and very effective.

All horses

• 2 injections 3-4 weeks apart
• start foals at 3 months, booster in 3-4 weeks
• annual booster

VI. Strangles (Distemper)
Caused by bacteria Streptococcus equi. A very contagious disease seen most frequently in breeding farms but also reported in public stables and fairgrounds. In breeding farm environments it affects weanlings and yearlings most often but horses of any age are susceptible. Transmitted by direct contact with infected horses or carriers without symptoms. Also transmitted via indirect contact with water troughs, feed buckets, pastures, stalls, trailers, tack, grooming equipment, bottom of human shoes, clothing etc. contaminated with pus from draining lymph nodes or nasal discharge.

The organism is very hardy and survives in the environment for months if not exposed to direct sunlight or disinfectants. This route can act as a source of infection for new horses on a farm.

Symptoms include cough, fever, large amounts of cloudy nasal discharge, enlarged abscessed and or draining lymph nodes under the jaw. Sore throat, pain on eating, decreased appetite, breathing and swallowing difficulty gave rise to its name "strangles".

Several types of vaccine exist, none are completely effective at preventing the disease but will decrease severity and number of horses affected by 50%. The vaccines tend to cause marked local reaction especially when given in the neck. Because of these sometimes-severe local reactions the recommendation is to only vaccinate horses living where the disease exists or traveling to such a facility. Routine vaccination is not recommended.

A new intranasal vaccine has just been introduced and seems to offer protection without any of the sideffects mentioned. This appears to make vaccination for this disease an easy option.

Adults

• 3 doses, booster 2-3 weeks apart
• twice yearly afterwards

Brood mares

• 4-6 weeks before foaling
• twice yearly afterwards

Foals

• 2-3 months old
• 3 doses, 2-4 weeks apart
• booster at weaning or at 6-8 months
• twice yearly afterwards