Vaccines & Biosecurity

What core principles should guide vaccination decisions in horses?

• Risk of exposure to infectious agents

• Consequences of disease

  • Morbidity

  • Mortality

  • Zoonotic potential

• Potential for adverse reactions

• Cost-benefit analysis

  • Cost of immunization vs cost of disease

• Vaccination reduces risk, but does not guarantee protection

• Vaccines require time to induce immunity

  • Often need an initial priming series

• Protection varies between horses and over time

• Vaccination benefits:

  • Individual immunity

  • Herd immunity

What factors influence infectious disease control and spread in horse populations?

• Core goals of disease control programs:

  • Place infected horse in isolation

  • Reduce exposure to pathogens

  • Minimize factors that decrease resistance

  • Enhance resistance through vaccination

• Disease risk increases with:

  • High population density (boarding barns, breeding farms, racetracks)

  • Movement of horses on/off facilities

  • Mixing horses from different origins and age groups

• Stressors that increase susceptibility:

  • Stress

  • Overcrowding

  • Parasitism

  • Poor nutrition

  • Inadequate sanitation

• Additional risk factors:

  • Contaminated water sources

  • Concurrent disease

  • Poor rodent, bird, and insect control

  • Mechanical transfer via people, vehicles, equipment

What are best practices for vaccine use at equine facilities?

• Maintain accurate vaccination records

• Establish facility-wide vaccination policies

  • More effective than horse-by-horse decisions

• Preserve vaccine efficacy through:

  • Proper storage

  • Proper handling

  • Proper administration and use

What do vaccine label claims mean?

• Claims must be data-supported

• USDA protection categories include:

  • Prevention of infection

  • Prevention of disease

  • Aid in disease prevention

  • Aid in disease control (↓ severity, duration, or delayed onset)

• Some vaccines claim reduced pathogen shedding

How are veterinary biologics regulated in Canada?

• Regulated by the Canadian Centre for Veterinary Biologics (CCVB) under the Health of Animals Act

• Oversight includes:

  • Manufacturing and testing

  • Labelling

  • Import/export

  • Distribution and use

  • Adverse reaction monitoring

• Veterinary biologics include:

  • Vaccines

  • Plasma

  • Tetanus antitoxin

  • EIA cELISA test kits

  • Immunomodulators (e.g., Immunocidin, EqStim)

What are characteristics of killed (inactivated) vaccines?

• Contain inactivated pathogens (phenol, formalin, β-propiolactone)

• Non-pathogenic

• Require:

  • Multiple initial doses

  • Regular boosters

• Adjuvants are critical

  • Enhance and modulate immune response

• Types include:

  • Whole killed organisms

  • Protein/subunit vaccines

How do live and modified-live vaccines differ from killed vaccines?

• Attenuated but capable of replication

• Induce broader and longer-lasting immunity

• Stimulate:

  • Surface (mucosal) immunity

  • Cytotoxic T-cell responses

• Produced by:

  • Cell culture attenuation

  • Cross-species variants

  • Temperature-sensitive mutants

What are recombinant vaccines?

• Use genetic engineering rather than whole organisms

• Types include:

  • Live attenuated vector vaccines

  • Chimeric vaccines

  • DNA vaccines

What adverse reactions can occur following vaccination in horses and how are they managed?

• Common reactions:

  • Local swelling and soreness

  • Fever

  • Anorexia

  • Lethargy

• Severe reactions:

  • Aseptic or septic inflammation

  • Urticaria

  • Purpura hemorrhagica

  • Anaphylaxis

• Management strategies:

  • Short-term vs long-term planning

  • Staging vaccines

  • Using monovalent vs polyvalent vaccines in sensitive horses

What is the role of epinephrine in vaccine reactions?

• Used for anaphylaxis

• Common concentration: 1:1000 (1 mg/mL)

• Often diluted before use

• Routes of administration:

  • IV

  • IM

  • Intratracheal (IT)

How are equine vaccination programs structured?

• Divided into:

  • Core vaccines

  • Risk-based vaccines

• Guidelines are recommendations, not mandates

• Veterinarians must consider:

  • Individual horse risk

  • Facility management

  • Product availability

  • Professional judgment

• USDA-licensed vaccines form the basis of guidelines

• Use in non-horse equids is discretionary

Which vaccines are considered core for all horses?

• Tetanus → 3 boosters before 1year of age

• Rabies → yearly booster

• EEE/WEE → yearly killed vx given in the spring in canada, water climate 2x/year

• West Nile Virus (WNV)

What vaccines are considered risk-based in horses?

• Influenza

• Equine herpesvirus

• Potomac Horse Fever

• Strangles

• Botulism

• Equine viral arteritis

• Rotavirus

• Anthrax

• Others:

  • Snake bite

  • Venezuelan Equine Encephalitis (VEE)

What newer or future vaccines are being explored in horses?

• Rhinitis virus

• Leptospirosis

• Lawsonia intracellularis

• Lyme disease

• Rhodococcus equi

What is the foundation of equine biosecurity?

• Anything contacting a horse can transmit pathogens

• High-risk materials include:

  • Manure, urine

  • Nasal, ocular, vulvar secretions

  • Fetal fluids and tissues

  • Abscess drainage

• Humans can act as vectors

How should personnel and protective equipment be managed during outbreaks?

• Ideal: separate staff for sick vs healthy horses

• Practical order of care:

  1. Healthy animals

  2. Exposed animals

  3. Sick animals

• Use of PPE:

  • Gloves

  • Gowns/coveralls

  • Shoe covers

  • Eye protection

• Proper disposal of contaminated materials

What hygiene and containment measures support biosecurity?

• Hand hygiene:

  • Soap and water ≥15 seconds

  • Alcohol-based sanitizers (≥62% ethanol)

• Animal containment:

  • Controlled movement

  • Clear boundaries and signage

  • Footbaths and wash stations

• Footbaths:

  • May be inactivated by organic matter

  • Less effective in cold temperatures

  • Must be safe if contacted or ingested

How should facilities manage environmental contamination?

• Solid stall barriers to reduce aerosol spread

• Avoid shared equipment and water sources

• Proper manure and bedding disposal

• Separate equipment for contaminated areas

• Cleaning protocol:

  • Rinse → wash → rinse → disinfect → rinse → dry

• Disinfectant categories include:

  • Alcohols

  • Chlorhexidine

  • Halogens

  • Oxidizing agents (Virkon-S)

  • Phenols

  • Quaternary ammonium compounds

Why must non-horse animals be considered in biosecurity plans?

• Dogs, cats, rodents, and birds can act as reservoirs or mechanical vectors

• Vermin control is essential to disease prevention