Veterinary Vaccine
A vaccine is a biological preparation that provides active acquired immunity to a particular
disease.
A vaccine typically contains an agent that resembles a disease-causing micro-organism and is often
made from weakened or killed forms of the microbe, its toxins or one of its surface proteins.
The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and
keep a record of it, so that the immune system can more easily recognize and destroy any of these
micro-organisms that it later encounters.
Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection
by any natural or "wild" pathogen), or therapeutic (e.g., vaccines against cancer are also being
investigated). The administration of vaccines is called vaccination.
The terms vaccine and vaccination are derived from Variolae vaccinae (smallpox of the cow), the
term devised by Edward Jenner to denote cowpox. In 1881, to honour Jenner, Louis Pasteur
proposed that the terms should be extended to cover the new protective inoculations then being
developed.
Veterinary Vaccine
Vaccinations of animals are used both to prevent their contracting diseases and to prevent
transmission of disease to humans. Both animals kept as pets and animals raised as livestock are
routinely vaccinated. In some instances, wild populations may be vaccinated. This is sometimes
accomplished with vaccine-laced food spread in a disease-prone area and has been used to attempt
to control rabies in raccoons.
Types of Vaccines
• Modified live vaccines (MLV)
– Replicate in host, mild clinical signs
• Killed inactivated vaccines
– All or part of inactivated pathogen
– Require adjuvant
• Novel vaccines - include
– Gene-deleted vaccines
– Live vectored vaccines
– Plant-derived vaccines
– DNA vaccines
Inactivated (“killed”) vaccines contain bacteria or viruses that have been inactivated by heat or
chemicals. Whichever method is used needs to completely render the microbe incapable of
growing and reproducing, while maintaining the microbe’s structure enough to be recognized by
the body. Because inactivated organisms do not multiply inside the body, substances called
adjuvants are included in such vaccine suspensions. Adjuvants are compounds (such as aluminum
salts or oil-in-water emulsions) that non-specifically stimulate the immune system to respond to—
and slow down the body’s elimination of—the injected inactivated microbes.
Subunit vaccines, which contain only parts of the bacteria or virus of interest, and toxoids,
vaccines created from inactivated toxins released from certain disease-causing bacteria, are also
examples of inactivated vaccines. Antitoxins, preparations of antibodies against bacterial toxins,
are not technically vaccines: they passively tie up toxins instead of actively stimulating an immune
response, as is the case with toxoids. However, like most components of vaccines, antitoxins are
protein molecules, and the issues regarding handling and care of those products are the same as
for vaccines.
Modified-live virus (MLV) vaccines contain whole viruses that have been altered such that, while
they are able to multiply within the body, their ability to cause disease has been taken away.
Vaccine manufacturers typically achieve this by making the microbe grow under prolonged or
slightly abnormal growing conditions. Because the modified microbes actively grow within the
host—stimulating the immune system in the process—fewer of them are needed in a vaccine dose
compared to inactivated vaccines. MLV vaccines are typically packaged in two vials—one
containing a freeze-dried cake that contains the modified microbes, and the other containing the
diluent, which re-suspends the microbes.
The importance of animal medicines and vaccines
The main aims of animal medicines and vaccines are:
- To prevent animal disease and treat it when it occurs;
- To ensure animal welfare and healthy food;
- To preserve a healthy environment;
- To foster economical livestock rearing, for food and recreation;
- To protect public health and control animal diseases which threaten people through contact
with animals or food contamination.
• Vaccines play an important role in meeting these aims: Vaccines and antisera are most
commonly used to prevent diseases caused by pathogens such as bacteria and viruses. They
can also be used to control diseases caused by other organisms, such as parasitic worms and
fungi (e.g. ringworm).
• Maintaining animal health is vital: Vaccines contribute to the welfare of food-producing and
companion animals, the prosperity of farming, the safety and availability of food, and the
health of animal owners. They play an important role in the fight against illness and have
achieved great success in controlling many diseases of vital importance in farm and companion
animals or those which threaten human health (e.g. smallpox, rabies and salmonella).
• Healthy animals lead to a safer environment: Healthy animals make a positive contribution
to the environment by reducing the chance of zoonotic disease (e.g. salmonella poisoning), the
spread of diseases from the increase in movement of goods, animals and people, as well as
making better use of resources in feeding an increasing world population.
• Vaccines enhance consumer safety: Food coming from vaccinated animals is potentially
healthier, as it means that the animal has not suffered from that disease. Particularly for
zoonotic disease organisms, e.g. salmonella poisoning, vaccination can reduce the health risk
for the consumer.
• Vaccines contribute to world health: Vaccination has profoundly influenced and improved
world health, and will continue to be a fundamental tool to meet future health challenges. It
has eliminated smallpox and can control many other health scourges against which no other
treatment exists, such as human polio, foot-and-mouth disease in cattle, canine distemper and
rabies in man and animals.
Species Diseases Controlled by Vaccines
• Cattle: Blackleg, tetanus, 'husk' (lungworm disease), rotavirus, infectious bovine
rhinotracheictis (IBR), respiratory syncytial virus, pasteurellosis, enteritis, leptospirosis,
mastitis, ringworm, BVD, coronavirus, salmonella, E Coli.
• Sheep & Goats: Clostridial diseases (8 different species including tetanus), pasteurellosis,
ovine abortion (chlamydiosis and toxoplasmosis), louping ill, contagious pustular dermatitis
(orf), footrot
• Poultry: Avian coccidiosis, avian encephalomyelitis, avian infectious bronchitis, avian
infectious bursal disease, avian reovirus, chicken anaemia virus, duck virus enteritis, egg drop
syndrome 1976, erysipelas, infectious laryngotracheitis, Marek's disease, Newcastle disease,
pasteurellosis, post-natal colibacillosis, salmonellosis, swollen head syndrome, turkey
haemorrhagic enteritis, turkey rhinotracheitis
• Fish: Enteric redmouth disease, furunculosis, vibriosis (vibrio anguillarum, vibrio salmonicida
and Vibrio viscosus (now named moratella viscosus)
Vaccine Delivery
• Routes
– Parenteral Injection
– Needle-Free
– Intranasal
– Ocular
– Oral
– Spray/Topical
Parenteral Injection
• Delivered with a syringe and needle
– In muscle (intramuscular)
– Under skin (subcutaneous)
– Use a new needle for each animal
Needle-Free Injection
• Transdermal
– Drives vaccine into skin by a burst of air or gas
– Minimal bodily fluid contamination
– Delivery of vaccine to dermis may enhance efficacy
Intranasal and Ocular
• Methods mimic natural route of infection
• Intranasal
– Delivered with a squeeze bulb attached to intranasal device
• Ocular
– Primarily used for fowl (chickens)
– Applied to surface of the eye
Oral Vaccines
• May be diluted in drinking water or sprayed onto food
• Convenient for mass vaccination
• Limited to fowl (chickens) and pigs
Spray/Topical Vaccines
• Diluted in water or diluted and misted, sprayed, or nebulized onto a large group of animals
• Convenient for mass vaccination
Vaccine Handling
Cold Chain
• Appropriate temperature range to ensure efficacy
• During transport, storage, and all handling
• Do not freeze vaccines intended to be refrigerated
• Do not subject to freeze-thaw cycles
• Store in box until needed
Transporting and Receiving
• When transporting:
– Minimize the number of times transported
– Ensure cold chain is maintained
• When receiving vaccines:
– Inspect immediately on arrival
– Look for signs of physical damage
– Check expiration dates
Storage Units
• Dedicated to vaccine storage
• Avoid temperature fluctuations
• Do not use an outlet controlled by a wall switch or power strip
Maintaining Sterility
• When using multi-dose vials:
– Use sterile technique to withdraw vaccine
– Never remove rubber stopper
– Disinfect rubber stopper before piercing
– Use a sterile needle each time
– Clearly mark vials with date, time, and user’s initials
