Transcript Vaccination

Equine Vaccinations
Equine Health Management
September 21, 2011
Controlling Infectious Disease
What is an infectious disease?
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Contagious disease
Virus, bacteria, parasite, fungi and protozoa
When is infectious disease a problem?
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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?
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Previous natural exposure or vaccination
Protecting Against Infectious
Disease
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Three goals when it comes to protecting your
horses against infectious disease:
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Reduce exposure in the environment
Minimize factors that decrease resistance
Enhance resistance through the use of
vaccines**
What causes increased incidence?
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Management
Animal
Environment
Vaccinations
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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
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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
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Humoral Immunity:
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Cellular Immunity:
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B lymphocytes and plasma cells produce antibodies to
foreign agents and stimulate T lymphocytes to attack them
Immune response that involves enhanced activity by
phagocytic cells and does not imply lymphocyte
involvement.
Mucosal Immunity:
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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
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Spread horse to horse
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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
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Closed herd
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Only resident horses
Uniform vaccination/
deworming protocols
Open herd
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Outside horses
Recipient or Nurse mares
Performance/
show horses
Young horses
Vaccinations
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Core Vaccines
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Regional
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Botulism: Mid-Atlantic area
PHF: areas of fresh water
Endemic
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Tetanus, EEE, WEE,
WNV, EHV1&4, Influenza,
Rabies
Strangles
Rotavirus
Breed (WmB)
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EVA
Inactivated (Killed) Vaccine
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Organisms not replicating
Adjuvants added to boost
immune response
Advantages:
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Safety, stability
Disadvantages:
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Slower onset of protection,
shorter duration of immunity
Reactions associated with
adjuvants
Adjuvants
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Immunomodulation
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Interaction between adjuvants?
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Stimulate or slow the immune response
Increase response to vaccine
No antigenic effect itself
Different companies use different
adjuvants
Local reaction to adjuvants
Wide variety
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Aluminum salts. Saponins, Oil
emulsions, Liposomes
Attenuated (MLV) Vaccine
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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!
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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
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Recombitek®: Canary pox virus vector used
Advantages:
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Safety
Antigenic specificity
Longer duration
Toxoids vs. Antitoxins
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Toxoid: Deactivated toxin - vaccine
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Tetanus toxoid
Antitoxin: preformed antibody - treatment
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Tetanus antitoxin
Botulinum antitoxin
R. equi hyperimmune serum
Rapid, but short-lived protection
Immunization Failures
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Host:
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Vaccine:
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Compromised host; steroids?
Maternal antibody interference
Inappropriate strain (PHF)
Improper storage & handling; outdated
Bell curve: some horses respond better than others!
Human Error: Misuse
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Too frequent administration: wait a minimum of 2 wks
between doses or between different vaccines
Foal Vaccination Program:
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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
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Passive Immunity
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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
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Varies with different antigens (diseases) and different
vaccines
Impact of MDA on Immune
Function in the Foal
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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
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EEE / WEE
Tetanus
EHV-1&4
Influenza
Rabies
Rotavirus
Misdirected Immune Response
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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?
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Humoral antibody
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EEE / WEE / WNV
Tetanus
Rabies
Botulism
Combination
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EHV1&4: Humoral, cellular, mucosal
Rotavirus: IgA, humoral
Influenza: Humoral, mucosal
Streptococcus equi: Humoral, mucosal
EHV-1: What we know…
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EHV-1 becomes latent in ~80% of horses infected
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Latency established in trigeminal ganglion & lymphocytes
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Natural immunity is short lived (3 – 6 months) but
may increase after repeated exposure
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In broodmares, immunity against abortion appears
to be more durable following natural infection.
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Infection is spread by direct contact between horses
and infected equipment
EHV-1
Fetal Infection
Maternal
endothelial cell
infection
Placenta
Fetal death
Abortion of
virus (+) fetus
or dying foal
Endometrial vasculitis,
thrombosis, ischemia
“Red “Bag”
Abortion of virus (-) fetus
EHV: Vaccines
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Killed Vaccines: Respiratory claim
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Modified Live: Respiratory claim
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Prestige®: IM
Calvenza®: IM / IN
Innovator®: IM
Rhinomune®: IM
Killed Vaccines : Abortion claim; approved for
pregnant mares
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Prodigy®: IM
Pneumabort K® : IM
Herpes vaccines
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Should I use a vaccine with EHV-1 and 4 or
just EHV-1?
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When should I use a EHV-1 only vaccines?
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EHV-4 causes the majority of herpes respiratory
disease in young horses
EHV-1 causes abortion and CNS disease as well
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
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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
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Stimulates local immunity
Rapid onset of immunity within 7 days
Safe in stressed animals (e.g., transportation,
weaning)
Single dose for primary immunization
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Begin vaccination at 11 months; booster every 6
months
Strangles: Immunity &
Vaccination
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Immunity following recovery from disease
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Dependent upon inoculum dose, virulence, and preexisting immunity
Solid immunity for 5 yrs or longer in 75% of animals
Foals born to recovered mares
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Colostrum contains IgG & IgA; milk contains IgA
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Foals generally protected until weaned
Foals born to vaccinated mares
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Varies depending upon mare’s response
Variable protection for 3-6 months
Strangles: Vaccination
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Vaccines
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SeM protein extract vaccines
(Bacterins)
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Intramuscular
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Reactive: use hindlimb
Attenuated live vaccine
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Intranasal
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Accidental contamination
of other injection sites
Complications
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Purpura Hemorrhagica
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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 HiRisk Farms
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Yearlings and Performance horses:
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Broodmares:
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IM booster last 4-6 wk of pregnancy
Foals:
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IN every 6 mos; IM every 4-6 mos
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
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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)
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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
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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
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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
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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
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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 concern
 No treatment available once neurologic
signs develop
 Vaccinate ALL horses
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Rabies Vaccine
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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
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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:
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Vaccine is safe and effective
Protect foal by vaccinating mare & ensuring foal
ingests adequate colostrum
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Initial series of 3 doses given to 4 – 6 wks apart;
administer during last trimester
Thereafter, annual booster for mares 4 – 8 wks prefoaling
Can begin foal vaccinations at 3 – 4 mos if risk of
disease is high
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Series of 3 doses given 4 wks apart
Foal relies on MDA for protection against “Shaker
Foal” syndrome