Help for you and your veterinarian in determining what vaccines your horses need, and when they should be given.

Spring means vaccination time. In 2008, the American Association of Equine Practitioners (AAEP) Infectious Disease Committee released a revised online version of their "Guidelines for the Vaccination of Horses."

Developing a vaccination schedule is not as straightforward as it sounds. So much of what you should vaccinate for depends upon such factors as where you live, how often your horse travels, how old he is, his vaccination history, and what infectious diseases he might encounter. The full guidelines, for adults and foals, are available at aaep.org/vaccination_guidelines.htm.  

Why Create Guidelines?

The AAEP is an international association of more than 9,000 equine veterinarians. Its mission is to promote the health and welfare of the horse. "Vaccination is a core principle of any horse health program, and providing quality information to caregivers is a very important part of the AAEP's mission to protect the health and welfare of the horse," says Sally Baker, AAEP director of Marketing & Public Relations.

 

The AAEP Infectious Disease Committee includes researchers in academics, practitioners, regulators, and vaccine experts. This year's chair is Mary Scollay, DVM, track veterinarian for Calder Race Course and Gulfstream Park in Florida.

"The Guidelines allow us to put out good information that has data to support it," Scollay says.

She says infectious diseases have been a hot topic lately, and some bad information is floating around.

There is a distinct "difference between vaccination and immunization," she says. "You really want to maximize the horse's immune response to get the protection you really want. In order to do that, you have to have a plan which takes into account multiple factors. I really encourage everyone to read the entire document, not just reference the tables."

What's in the Guidelines

According to a AAEP press release, highlights of "Guidelines for the Vaccination of Horses" include:

  • The identification of tetanus, Eastern/Western equine encephalomyelitis, West Nile virus, and rabies as "core" vaccines. Researchers have clearly demonstrated that core vaccines are safe and effective, and the vaccines exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients.
  • The addition of a vaccination protocol for anthrax.
  • Recommendations for the storage and handling of vaccines, as well as information on vaccine labeling and adverse reactions.
  • Inclusion of the AAEP's Infectious Disease Control Guidelines, which provide an action plan for containing infectious disease during an outbreak.

One of the reasons for the inclusion of the four core vaccines is the American Veterinary Medical Association (AVMA) has chosen to identify certain vaccines as core. According to the AVMA, core vaccinations are those "that protect from diseases that are endemic to a region, those with potential public health significance, required by law, virulent/highly infectious, and/or those posing a risk of severe disease."

Since anthrax is new to the list, following is more detailed information on it.

Anthrax

Anthrax spreads quickly and is often fatal in animals and man. Anthrax is caused by eating, inhaling, or having a wound come in contact with spores of the bacterium Bacillus anthracis. If an animal dies from the disease and the carcass isn't properly disposed of, the bacteria will lie dormant in the soil and can resurface under specific weather conditions. The bacteria can also be transmitted via horseflies, which feed by cutting the skin and using a spongelike tongue to absorb pooled blood. If the fly moves on before ingesting a complete blood meal, it will repeat the process with another animal, thus, transmitting bacteria on its mouthparts.

Luckily, anthrax is typically found only in areas that have alkaline soil conditions in which the organism can thrive. Primarily, the risk is in the central Plains states.

There is one anthrax vaccine available on the market, and it has been proven to be effective in horses. Vaccination in pregnant mares is not recommended, and some adverse events such as swelling have been reported in young animals. Vaccination is indicated only for horses pastured in endemic areas.

Storage and Handling

Especially with the advent of some new vaccine technologies, such as modified-live vaccines, and those administered in ways other than injection, such as intranasals, it is more important than ever to be aware of proper handling and storage of vaccines.

Each vaccine is packaged with specific recommendations, which should be followed carefully. For all vaccines it is important to clean the area where you are going to vaccinate and use a new, clean needle for each administration (if applicable). The Guidelines point out that you need to make sure you are administering the vaccine in the way it is intended, noting that intranasal vaccines should be administered up the nose and never intramuscularly, as it could cause unintended reactions and not be protective. The committee offered the following vaccine management recommendations:

  • Have a designated individual responsible for handling and storing vaccines.
  • Maintain a vaccine inventory log, documenting the vaccine name, manufacturer, lot number, expiration date, date and number of doses received, and arrival condition of vaccine.
  • Store vaccines in a refrigerator with a separate freezer compartment because some vaccines can easily freeze and lose their potency, and it's good to keep them at a constant temperature.
  • Keep a working thermometer in the refrigerator and monitor the temperature twice daily. Maintenance of a log is advisable, particularly if multiple people share responsibility for temperature monitoring.
  • Store vaccines in the middle of the refrigerator, not in the door or against the back of the refrigerator.
  • Organize vaccines according to expiration date, avoiding wastage by ensuring that products with earlier expiration dates are used before products with later dates.
  • In the event of refrigerator failure, promptly remove vaccines to an adequately refrigerated container.
  • In the event of a power failure, keep the refrigerator door closed until power is restored or a suitable location for the vaccines has been identified. Refrigeration can be maintained in a kitchen-sized refrigerator (20-24 cubic feet) for six to nine hours if the door remains closed. Once power is restored, promptly check refrigerator temperature to determine if vaccines have been exposed to temperatures outside of the recommended range. If the power outage is expected to be longer than six to nine hours, remove vaccines to a container that is maintained with ice and monitor the temperature in the container.
  • Ambulatory vehicles should have a thermometer in the refrigeration unit or portable cooler in which vaccines are carried. Temperature should be checked each time the container is opened. (Note: A freezer pack placed in a cooler generally is not sufficient to maintain vaccines in the proper temperature range throughout an entire day.)
  • Consult the manufacturer if vaccines are exposed to temperatures outside of the recommended range.

Infectious Disease Control

An important addition to the Guidelines is a section dedicated to infectious disease control. An effective vaccination program should be an integral part of an overall infectious disease management program. There are many things you can do in addition to vaccination to reduce the risk of horses getting sick. According to the Guidelines, any infectious disease management program should focus on, "reducing the exposure to infectious agents in the horses' environment, minimizing factors that decrease resistance or increase susceptibility to disease, and enhancing resistance to those diseases by vaccination."

If a disease flare-up does occur, proper sanitation and quarantine measures should be observed. A full listing of infectious disease control measures is available at www.aaep.org/control_guidelines_nonmember.htm.

The guidelines are available online only because, Baker explains, "The Infectious Disease Committee felt very strongly that the guidelines are a dynamic document that should be updated as soon as new information becomes available." An online document ensures the latest information can be disseminated quickly.

Vaccinations for Adult Horses
Disease/Vaccine Broodmares Other Adult Horses (>1 year of age) previously vaccinated against the disease indicated Other Adult Horses (>1 year of age) unvaccinated or lacking vaccination history Comments
Tetanus

Previously vaccinated:

• Annual, 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:

• 2-dose series
2nd dose 4-6 weeks after 1st dose
Revaccinate 4-6 weeks pre-partum

Annual

• 2-dose series 2nd dose 4-6 weeks after 1st dose.

• Annual revaccination

Booster at time of penetrating injury or prior to surgery if last dose was administered over 6 months previously
Eastern/Western Equine Encephalomyelitis (EEE/WEE)

Previously vaccinated:

• Annual, 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:

• 2-dose series
2nd dose 4 weeks after 1st dose
Revaccinate 4-6 weeks pre-partum

Annual--spring, prior to onset of vector season

• 2-dose series 2nd dose 4-6 weeks after 1st dose

• Revaccinate prior to the onset of the next vector season

Consider 6-month revaccination interval for:

1) Horses residing in endemic areas

2) Immunocompromised horses

West Nile Virus (WNV)

Previously vaccinated:

• Annual, 4-6 weeks pre-partum

Unvaccinated or lacking vaccination history:

• It is preferable to vaccinate na•ve mares when open

In areas of high risk, initiate primary series as described for unvaccinated, adult horses

Annual--spring, prior to onset of vector season

Inactivated vaccine:

• 2-dose series
2nd dose 4-6 weeks after 1st dose
Revaccinate prior to the onset of the next vector season

Recombinant canary pox vaccine:

• 2-dose series
2nd dose 4-6 weeks after 1st dose
Revaccinate prior to the onset of the next vector season

Flavivirus chimera vaccine:

• Single dose
Revaccinate prior to the onset of the next vector season

When using the inactivated or the recombinant product, consider 6-month revaccination interval for:

1) Horses residing in endemic areas

2) Juvenile (<5 yrs of age)

3) Geriatric horses (>15 yrs of age)

4) Immunocompromised horses

Rabies

• Annual, 4-6 weeks pre-partum

OR

• Prior to breeding (see "Guidelines" for criteria used in risk assessment)

Annual

• Single dose

• Annual revaccination

Due to the relatively long duration of immunity, this vaccine may be given post-foaling, but prior to breeding, to reduce the number of vaccines given to a mare pre-partum
Anthrax Not recommended during gestation Annual

• 2-dose series 2nd dose 3-4 weeks after 1st dose

• Annual revaccination

Do not administer concurrently with antibiotics.

Use caution during storage, handling, and administration. Consult a physician immediately if human exposure to vaccine occurs by accidental injection, ingestion, or otherwise through the conjunctiva or broken skin.

Botulism

Previously vaccinated:

• Annual, 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:

• 3-dose series 1st dose at 8 months gestation
2nd dose 4 weeks after 1st dose
3rd dose 4 weeks after 2nd dose

Annual

• 3-dose series
2nd dose 4 weeks after 1st dose
3rd dose 4 weeks after 2nd dose

• Annual revaccination

 
Equine herpesvirus (EHV)

3-dose series with product labeled for protection against EHV abortion

Give at 5, 7, and 9 months of gestation

Annual

3-dose series

2nd dose 4-6 weeks after 1st dose

3rd dose 4-6 weeks after 2nd dose

Consider 6-month revaccination interval for:

• Horses <5 years of age

• Horses on breeding farms or in contact with pregnant mares

• Performance or show horses at high risk

Equine viral arteritis (EVA) Not recommended unless high risk.

Annual

Stallions, teasers:
Vaccinate 2-4 weeks before breeding season

Mares:
Vaccinate when open

Single dose Prior to initial vaccination, intact males and any horses potentially intended for export should undergo serologic testing and be confirmed negative for antibodies to EAV (equine arteritis virus). Testing should be performed shortly prior to, or preferably at the time of, vaccination.
Influenza

Previously vaccinated:

Inactivated vaccine: Semi-annual with one dose administered 4-6 weeks pre-partum

Canarypox vector vaccine: Semi-annual with one dose administered 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:

Inactivated vaccine: 3-dose series
2nd dose 4-6 weeks after 1st dose
3rd dose 4-6 weeks pre-partum

Canary pox vector vaccine: 2-dose series
2nd dose 4-6 weeks after 1st dose, but no later than 4 weeks pre-partum

Horses with ongoing risk of exposure:
Semi-annual

Horses at low risk of exposure:
Annual

Modified live vaccine:

• Single dose administered intranasally

• Revaccinate semi-annually to annually

Inactivated vaccine:

• 3-dose series
2nd dose 4-6 weeks after 1st dose.
3rd dose 3-6 months after 2nd dose

• Revaccinate semi-annually to annually

Canary pox vector vaccine:

• 2-dose series
2nd dose 4-6 weeks after 1st dose

• Revaccinate semi-annually

 
Potomac Horse Fever (PHF)

Previously vaccinated:
Semi-annual, with one dose given 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:

• 2-dose series
1st dose 7-9 weeks pre-partum
2nd dose 4-6 weeks pre-partum

Semi-annual to annual

• 2-dose series
2nd dose 3-4 weeks after 1st dose

• Semi-annual or annual booster

A revaccination interval of 3-4 months may be considered in endemic areas when disease risk is high.
Rotavirus

• 3-dose series
1st dose at 8 months gestation
2nd and 3rd doses at 4-week intervals thereafter

Not applicable Not applicable  
Strangles (Streptococcus equi)

Previously vaccinated:
Killed vaccine containing M-protein:

• Semi-annual with one dose given 4-6 weeks pre-partum

Previously unvaccinated or having unknown vaccination history:
Killed vaccine containing M-protein:

• 3-dose series
2nd dose 2-4 weeks after 1st dose
3rd dose 4-6 weeks pre-partum

Semi-annual to annual

Killed vaccine with M-protein:

• 2-3 dose series
2nd dose 2-4 weeks after 1st dose
3rd dose (where recommended by manufacturer) 2-4 weeks after 2nd dose

• Revaccinate semi-annually

Modified live vaccine:

• 2-dose series administered intranasally
2nd dose 3 weeks after 1st dose
Revaccinate semi-annually to annually

Vaccination is not recommended as a strategy in outbreak mitigation

About the Author

Liza Holland

Liza Holland is a freelance writer and voice talent based in Lexington, Ky.

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