equine vaccinations
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Equine Vaccinations. Equine Health Management September 21, 2011. Controlling Infectious Disease. What is an infectious disease ? Contagious disease Virus, bacteria, parasite, fungi and protozoa When is infectious disease a problem? - PowerPoint PPT PresentationTRANSCRIPT
Equine VaccinationsEquine Health Management
September 21, 2011
Controlling Infectious Disease What is an infectious disease?
Contagious disease Virus, bacteria, parasite, fungi and protozoa
When is infectious disease a problem? When a horse or group of horses experience a
challenge from an infectious agent at a dose sufficient to overcome resistance
Where do horses acquire resistance? Previous natural exposure or vaccination
Protecting Against Infectious Disease Three goals when it comes to protecting your
horses against infectious disease:1. Reduce exposure in the environment2. Minimize factors that decrease resistance3. Enhance resistance through the use of
vaccines** What causes increased incidence?
Management Animal Environment
Vaccinations Vaccination minimizes risk but does not
prevent disease Follow instructions re: primary series
(vaccines and boosters) before likely exposure
Not all horses respond the same or are protected for the same length of time
All horses in a herd should be vaccinated on the same schedule when possible to optimize herd immunity
Tetanus WNV EEE/WEE/VEE EHV1&4 Influenza Rabies Strangles Potomac Horse
Fever Botulism Rotavirus
• Killed or inactivated
• Modified live or attenuated
• Genetically engineered
• Mono or multi-valent
• IM / IN
Types of Immunity Humoral Immunity:
B lymphocytes and plasma cells produce antibodies to foreign agents and stimulate T lymphocytes to attack them
Cellular Immunity: Immune response that involves enhanced activity by
phagocytic cells and does not imply lymphocyte involvement.
Mucosal Immunity: Resistance to infection across the mucous membranes.
Dependent on immune cells and antibodies present in the lining of the urogenital tract, gastrointestinal tract and other parts of the body exposed to the outside world.
Contagious: Horse to Horse Spread horse to horse
Influenza virus: respiratory secretions, equipment Herpes virus: respiratory secretions, equipment, aborting
mares shed via uterine fluids, latent infections, asymptomatic shedders
Strangles: nasal discharge, draining abscesses, equipment, water troughs, environment , asymptomatic shedders
Rotavirus: manure, fomites Salmonella: manure, fomites (people, stall cleaning
equipment)
Population Dynamics Closed herd
Only resident horses Uniform vaccination/
deworming protocols Open herd
Outside horses Recipient or Nurse mares Performance/
show horses Young horses
Vaccinations Core Vaccines
Tetanus, EEE, WEE, WNV, EHV1&4, Influenza, Rabies
Regional Botulism: Mid-Atlantic area PHF: areas of fresh water
Endemic Strangles Rotavirus
Breed (WmB) EVA
Inactivated (Killed) Vaccine
Organisms not replicating Adjuvants added to boost
immune response Advantages:
Safety, stability Disadvantages:
Slower onset of protection, shorter duration of immunity
Reactions associated with adjuvants
Adjuvants Immunomodulation
Stimulate or slow the immune response
Increase response to vaccine No antigenic effect itself
Interaction between adjuvants? Different companies use different
adjuvants Local reaction to adjuvants Wide variety
Aluminum salts. Saponins, Oil emulsions, Liposomes
Attenuated (MLV) Vaccine Attenuated: organism is modified so it is non-pathogenic but still
causes immune response - replicates within the host Advantages:
Rapid onset of immunity Longer duration of immunity No adjuvant
Disadvantages: Potential for inactivation Reversion to virulence Requires reconstitution
Examples: Flu-AVERT® intranasal influenza vaccine Pinnacle® intranasal Strangles vaccine Rhinomune® intramuscular EHV-1 vaccine
Genetically Engineered Vaccines: A new breed of vaccines! Category I: Subunit Category II: Gene deletion Category III: Clone genes into vector (bacteria or
virus); vector transports genes & expresses the antigens when administered to host Recombitek®: Canary pox virus vector used
Advantages: Safety Antigenic specificity Longer duration
Toxoids vs. Antitoxins Toxoid: Deactivated toxin - vaccine
Tetanus toxoid Antitoxin: preformed antibody - treatment
Tetanus antitoxin Botulinum antitoxin R. equi hyperimmune serum Rapid, but short-lived protection
Immunization Failures Host:
Compromised host; steroids? Maternal antibody interference
Vaccine: Inappropriate strain (PHF) Improper storage & handling; outdated Bell curve: some horses respond better than others!
Human Error: Misuse Too frequent administration: wait a minimum of 2 wks
between doses or between different vaccines
Foal Vaccination Program:
Dam’s vaccination status Colostrum quality/FPT Risk of diseases
Regional Endemic to farm Husbandry practices
Vaccine used/age at initial vaccination/ number of doses
Foal’s immune response
Foal Immunity Passive Immunity
Maternally derived antibodies in colostrum Temporary protection Immunity gap / window of susceptibility: the
period during which MDA have fallen below protective levels but still interfere with the foal’s response to immunization Varies with different antigens (diseases) and different
vaccines
Impact of MDA on Immune Function in the Foal Maternally derived antibodies (MDA) provide
passive protection while suppressing the foal’s ability to synthesize its own antibodies
Rate of decline of MDA varies for both individuals and antigens
[MDA] fall below protective levels for most antigens by 3 months of age, but remaining antibody levels may still block the foal’s response to vaccination
Maternal Antibody Interference
EEE / WEE Tetanus EHV-1&4 Influenza Rabies Rotavirus
Misdirected Immune Response Inactivated vaccines administered to young foals
(< 6mos) stimulate mostly IgG(T) and little to no IgGb which is the most immunoprotective antibody
Immunosuppression by high levels of colostral IgGb Foal [IgGb] lagged behind adult levels for > 6mos Recommend delaying primary vaccination
with inactivated vaccines until foals are at least 6 mos old
Diseases: What protects? Humoral antibody
EEE / WEE / WNV Tetanus Rabies Botulism
Combination EHV1&4: Humoral, cellular, mucosal Rotavirus: IgA, humoral Influenza: Humoral, mucosal Streptococcus equi: Humoral, mucosal
EHV-1: What we know… EHV-1 becomes latent in ~80% of horses infected
Latency established in trigeminal ganglion & lymphocytes
Natural immunity is short lived (3 – 6 months) but may increase after repeated exposure
In broodmares, immunity against abortion appears to be more durable following natural infection.
Infection is spread by direct contact between horses and infected equipment
“
EHV-1
Fetal Infection
Fetal death
Abortion of virus (+) fetus or dying foal
Maternal endothelial cell infection
Endometrial vasculitis, thrombosis, ischemia
Abortion of virus (-) fetus
Placenta
“Red Bag”
EHV: Vaccines Killed Vaccines: Respiratory claim
Prestige®: IM Calvenza®: IM / IN Innovator®: IM
Modified Live: Respiratory claim Rhinomune®: IM
Killed Vaccines : Abortion claim; approved for pregnant mares Prodigy®: IM Pneumabort K® : IM
Herpes vaccines Should I use a vaccine with EHV-1 and 4 or
just EHV-1? EHV-4 causes the majority of herpes respiratory
disease in young horses EHV-1 causes abortion and CNS disease as well
When should I use a EHV-1 only vaccines? During pregnancy: months 5, 7, 9 To reduce the risk of neurological EHV-1 disease? There is cross protection between EHV-1 and 4
NO vaccine has a label claim to prevent the neurological form of EHV-1!!
Influenza Not a clinical problem in foals No longer necessary to have Influenza A type
1 in vaccines; should have clinically relevant A/equine 2 subtype in current vaccines
MLV Intranasal provides rapid onset of immunity (within 7 days) & longer duration of immunity
Use IM influenza vaccines to booster dam’s immunity
Modified Live Influenza Vaccine Stimulates local immunity Rapid onset of immunity within 7 days Safe in stressed animals (e.g., transportation,
weaning) Single dose for primary immunization
Begin vaccination at 11 months; booster every 6 months
Strangles: Immunity & Vaccination Immunity following recovery from disease
Dependent upon inoculum dose, virulence, and pre-existing immunity
Solid immunity for 5 yrs or longer in 75% of animals Foals born to recovered mares
Colostrum contains IgG & IgA; milk contains IgA Foals generally protected until weaned
Foals born to vaccinated mares Varies depending upon mare’s response Variable protection for 3-6 months
Strangles: Vaccination Vaccines
SeM protein extract vaccines (Bacterins) Intramuscular Reactive: use hindlimb
Attenuated live vaccine Intranasal Accidental contamination
of other injection sites
Complications Purpura Hemorrhagica
Necrotizing vasculitis – immune complex
Edema, petechial & ecchymotic hemmorrhage
May develop after vaccination or exposure to clinical disease
High titers predispose Do not over-vaccinate!
Strangles Protection on Hi-Risk Farms Yearlings and Performance horses:
IN every 6 mos; IM every 4-6 mos Broodmares:
IM booster last 4-6 wk of pregnancy Foals:
IN begin at 6 mos with 2 doses @ 3wk intervals IM begin at 4-6 mos with 3-dose series
Avoid vaccinating horses with high serum titers Horses with very high titers due to natural infection or
vaccination are at increased risk of purpura and other immune mediated complications
TETANUS (Lock-jaw) Not contagious; organism lives in the
environment in low oxygen conditions C. tetani enters via puncture wounds
(especially in the foot), lacerations, surgical incisions (e.g. castrations), umbilicus of foals
Horses are the most susceptible species
Very high mortality (80%)
Tetanus Vaccine is safe Good immunity; at least 1 year, probably longer
• Disease can be fatal and is expensive to treat
• All horses should be vaccinated for tetanus
• Check vaccination status before any surgery and after any deep penetrating wound
Eastern & Western Encephalomyelitis
Affects all ages; uncommon in foals < 3 mos
Viral infection Spread by ticks &
mosquitoes; wild birds & rodents are reservoirs
Seasonal and geographic disease; year to year variation based on rainfall and temperatures
EEE / WEE Vaccine is safe and
effective; USE IT Foals receive an initial series
of 3 doses beginning at 4 – 6 months of age
Booster 1 - 2 (3) times/yr depending on risk of disease and length of mosquito season
Booster before mosquito season begins
Insect control
Potomac Horse Fever: Distribution
• Cases reported in over 40 states, Canada and Europe
• Disease appears to be spreading• Cases tend to occur near bodies of water
Potomac Horse Fever Vaccination Commercial vaccines contain an older strain of
PHF; Field strains of E. risticii continue to change More than 28 new E. risticii isolates have been
identified in field cases of PHF Vaccinated horses often showed a milder form of
PHF when exposed Adults: Vaccinate once or twice a year depending on
risk of disease and length of vector season Booster pregnant mares 4 – 8 wks pre-foaling
Rabies: Important Facts It is a ZOONOTIC DISEASE that can be
spread from animal to man as well as from animal to animal
Public health concernNo treatment available once neurologic
signs developVaccinate ALL horses
Rabies Vaccine Killed intramuscular vaccine: safe,
effective Duration of immunity at least 1 yr;
annual boosters recommended Unvaccinated animals: primary series of 2 doses Colostral antibodies interfere with foal’s immune
response: Foals born to vaccinated mares: 1st dose at 6mo,
2nd dose 1 mo later, 3rd dose at 1yr of age
Rotavirus: MDA
Highly contagious Fecal-oral transmission Damages tips of villi in SI;
self-limiting Vaccinate pregnant mares: mos
8, 9, 10; repeat for each pregnancy; no “annual booster”
Herd immunity waxes and wanes
Botulism: Vaccine is safe and effective Protect foal by vaccinating mare & ensuring foal
ingests adequate colostrum Initial series of 3 doses given to 4 – 6 wks apart;
administer during last trimester Thereafter, annual booster for mares 4 – 8 wks pre-
foaling Can begin foal vaccinations at 3 – 4 mos if risk of
disease is high Series of 3 doses given 4 wks apart Foal relies on MDA for protection against “Shaker
Foal” syndrome