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Dr. Judy Marteniuk

Michigan State University

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Judy Marteniuk, DVMEquine Medicine and Extension

Michigan State University

Vaccinating Your HorseVaccinating Your Horse

Preventive Program• Nutrition• Environment

– Housing– Pasture/Fencing

• Vaccinations• Parasite control• Farrier• Dental

How do I decide on a Vaccination Program?• What does the disease do?

– Mortality– Complications– Down time

• Prevalence of the disease in the area?– Limited vector season versus continuous vectors

• What do the horses do?– Pleasure/show/race

• What age are the horses?

How do I decide on a Vaccination Program?

• Cost of the vaccine• Risk Factors

– Horse • Isolated versus travel/exposure• Vaccine reaction - benefits versus risk

– Human health risk - Zoonotic disease (passed from animal to people - Rabies)

• Vaccine concerns– No vaccine is 100% - prevents or reduces severity of disease

• The vaccinated animal may still be a vector for disease– Must follow protocol

• Timing of vaccination –seasonality, age• Time to protection after vaccination/booster

Vaccination Considerations• Initial series of injections is needed if vaccination status is

negative or unknown• If available, use combination vaccines

– 4-way, 5-way = a ‘generic name’ – doesn’t reveal contents

– Cannot assume anything – know what is given!• Do not administer more than 2 or 3 injections at a time. If

more injections are needed to complete a vaccination program, wait a week between injections

Vaccination SitesWhat determines vaccination site to be used? - Preference of veterinarian/owner - Temperament of horse - Risks of area versus safetyVaccines are primarily administered IM, but not always (strangles, influenza)KNOW YOUR VACCINE

NEVER inject inthe neck of aNursing foal

Vaccines available:• Encephalomyelitis ** • Strangles

EEE/WEE/VEE • Equine Viral Arteritis (EVA)West Nile Virus • Rotavirus

• Tetanus ** • Botulism• Rabies ** • Anthrax• Influenza• Equine Herpes (Rhinopneumonitis) (E H V 1 & 4)• Potomac Horse Fever ** Core Vaccines

aaep.org

Core Vaccines

Tetanus• Bacterial disease - Clostridium tetani

– Spore forming organism producing toxins– Found in intestinal tract as well as soil– Present on all horse facilities - worldwide

• Incidence is low, but mortality is nearly 100%• Tetanus toxoid

– Long-term protection • Tetanus antitoxin

– Short-term protection– Associated with Serum hepatitis (Theiler’s Disease) in horses over 1

year of age

Tetanus• Vaccine very effective and cheap• Clinical signs

– General stiffness (saw horse stance)– Ears pricked forward– React to sudden noise– As disease progresses:

• Unable to eat• Lateral recumbancy• Death

• Occurs after injury or surgery• Booster? Depends on age and last

vaccination• TAT concerns

Encephalomyelitis (EEE, WEE, VEE, WNV)

• Viral disease• Transmitted by mosquitoes• Birds are the reservoirs

– Can over-winter in birds/mosquitoes • Horses and humans are dead-end hosts

– VEE may be an exception• Disease of mid-to-late summer/fall in Michigan• VEE is rarely a problem in USA

– Central/South America

Encephalomyelitis

Encephalomyelitis• Clinical signs

– Neurologic - circling, head pressing, uncoordinated, depressed – Fever– Recumbency (laying down)

• Morbidity/Mortality• EEE, WEE, VEE - very high, especially young/old• West Nile - 30 - 40% die• Immune system status important

• Survival • West Nile - horses normal or only slight residue effects• EEE, WEE, VEE - rarely normal, if survive

Encephalomyelitis• Vaccines are very effective and cheap

• WNV is currently more expensive then EEE, WEE, VEE• WNV is currently available from your veterinarian

(Fort Dodge, Merial and Intervet)– Fort Dodge has a combination vaccine that has WNV present– Intervet has protection after one dose

• Vaccines should be given in the late spring or twice a year in warm climates (EEE,WEE,VEE, WNV)

• VEE not necessary in northern areas

Rabies• Viral disease• Zoonotic disease - can be spread to other species • Fatal disease• Clinical signs

– Neurological - presentation can vary greatly• Vaccination

– use approved product – annual vaccination– check the dosage – 1cc to 2cc– effective vaccine – Veterinarian – document usage

Other Vaccine Considerations

Equine Influenza• Common viral equine disease• 2 most common strains (A1 & A2)

– subject to antigenic drift, A2• Vaccine immunity is short-lived

– Killed product – need to select the most recent strain– Modified live vaccine – seems to be more protective, Intranasal

vaccine; not available in combination product– Re-vaccinate ?? times/yr (vaccine dependent/ use of horse, but

usually 1-2X/year)– Research – start foals later

• Vaccinated dam – 9, 10, 11 mo. (aaep changes)• Non vaccinated dam – 6, 7, 8 mo.

Equine Influenza• Clinical signs

– Primarily concerned with down time– 1 - 3 day incubation– Elevated temp (up to 1050F) for up to 5 days– Can cause loss of appetite and dullness– Dry cough that can last for several weeks– Nasal discharge – initially clear > cloudy (secondary bacterial

infection?)– Low secondary complications

• Severe pneumonia• Death

Equine RhinopneumonitisEquine Herpes Virus ( EHV 1 & 4)

• Viral disease• Clinical presentations vary depending on virus

– Respiratory disease – EHV 1 & 4– Reproductive

• Late-term abortions – EHV 1 & ocassionally EHV 4• Equine Colital Exanthema – EHV 3 • (venereal)

– Keratoconjunctivitis – EHV 2– Neurological – EHV 1

• Primarily due to viral mutation, but not all

Equine Rhinopneumonitis• Clinical signs

– Similar to influenza for respiratory disease– Concerns:

• Down time (respiratory)• Quarantine of facilities• Abortion of fetus • Severe neurological disease and possible

death/euthanasia

Equine Rhinopneumonitis• Vaccine available (EHV 1 & 4)

– Immunity short-lived – Modified live vaccine - use in performance horses only!– Killed vaccine - use in pregnant mares / performance

horses ([3],5,7,&9 months gestation)– Vaccination does not prevent the neurological form, but

may reduce the amount and time the virus is shed– Foals – may want to start later as with influenza

Strangles• Bacterial disease - Streptococcus equi• Clinical Signs

– Primarily respiratory with swollen draininglymph nodes and purulent nasal discharge

– Fever– Incubation: 3 - 10 days– Depression/reduced appetite– Normally recover from uncomplicated form– Complications

• Bastard Strangles• Purpura Hemorragica(vascular changes – oozing legs)• Pneumonia• Persistent infection (Nasal Discharge) - Chondroids

Strangles• Treatment antibiotics ?

– Penicillin drug – Varies by veterinarian/owner– Uncomplicated

• +/- of choice– Need at least 10 -14 days treatment

– Complicated• Antibiotics: long-term• Supportive care: tracheotomy, surgical drainage

• Immunity: long-term• Disease of young/naïve horses• Disease outbreak usually lasts about 3 months on a farm

Strangles• Extremely contagious• Vaccine available

– Vaccinate? Consider risk factors– Killed

• M protein• Efficacy is about 50%• Use in broodmares to provide colostral antibodies

– Modified live intranasal• Efficacy appears to be better• Should not be given at same time as any IM injections - ABSCESSES

Potomac Horse Fever• Caused by Ehrlichia risticii (Neorichetsia risticii)

– Multiple strains now known– Transmission involves snails, trematodes and flying aquatic insects (eaten on

pasture)– Associated with water, warm and humid/wet weather

• Clinical Signs– ADR (ain’t doin right) and decreased appetite– Fever – may miss initial fever– Colic – Diarrhea – immediate attention required when 1st noticed– Possible laminitis, can be mild to severe, may require euthanasia– Abortion

Potomac Horse Fever• Treatment

– Maintain hydration-drinking/oral/IV– Oxytetracycline– Banamine– Laminitis treatment - if occurs

• Outcome depends on keeping horse hydrated and laminitis if it occurs; severity?• Prevention

– Move horses if in endemic areas – Turn off barn light to reduce insect attraction– Vaccine available

• Only to one strain, efficacy is questionable• Vaccinate in spring and booster??• Can contract disease even if vaccinated

Anthrax• Use in endemic areas only• Consult with your veterinarian• Initially two doses subcutaneously, then

annually• Do not use in pregnant mares or foals• Live vaccine – human health risk

Broodmares

Rotavirus• Treatment is primarily

supportive: IV fluids, oral feeding

• Prevention– Vaccination of the

mare prior to foaling– Providing the foal with

colostrum from vaccinated mare at birth

– Clean mare and stall before foaling

Botulism• Treatment

– Antitoxin - expensive– Supportive care – long-term needed

• Prevention– Vaccine available (B toxin)

• efficacy is good, but other toxins (8) with no vaccines or cross protection

• Initially, 3 doses for broodmare or foal, then annually– Consideration, if traveling to endemic areas

• Kentucky, mid-atlantic areas

What is best for my farm?• Work with your veterinarian

– What vaccines should I use?– When is the best time to give them?– How many doses are needed to give adequate

protection initially?– Do all horses develop protection?– How often do they need to be boostered - once,

twice or more per year?

General VaccinationProgram Considerations

• Young foal– Vaccinated Dam: Do not begin foal vaccinations until at

least 5 - 6 mo of age– Non-vaccinated dam: Begin foal vaccinations at 3 - 4 mo of

age– Booster at 3 - 4 week interval(s) – 2 vs 3 boosters

• Adult horse– Unknown vaccination status – requires boosters as for foal– Annually (minimally) after initial series – disease and local

considerations

General Vaccination Program Considerations

• Broodmares– To prevent abortion

• EHV vaccine is given multiple times during gestation (killed products only)

• EVA vaccine is given in high risk situations– Rotavirus vaccine: multiple boosters (8, 9, 10 mo) before

foaling– Annual vaccines to mare 4 - 6 weeks before foaling to

boost colostral immunity– Additional boosters may be needed, especially if foaling

early

Vaccination Guidelines• http://www.aaep.org/

vaccination_guidelines.htm

Questions

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