Vaccine are regulated by...
the center for veterinary biologics, a division of the USDA
How are vaccines approved for use? (3)
- tested under controlled experimental conditions in healthy, non-stressed animals; controlled exposure to a single infectious agent
- vaccinated group must have significantly less disease than control group
- does not mean complete immunity, especially for stressed animals or those with concurrent disease
What is the most efficient and cost-effective method of controlling infectious diseases in animals?
Why is it important to customize vaccine protocols to each animal?What so you consider?
- determine the risk:benefit ratio because vaccination is not always an innocuous procedure and may cause illness or death [the risk of vaccination does not exceed the chance of contracting the disease]
- consider the seriousness of the agent, the animals exposure risk, and any legal requirements
Describe "core vaccines".
vaccines that are strongly recommended in that they protect against common, dangerous diseases and failure to use them would place an animal at significant risk of disease or death
Describe "optional/ non-core vaccines".
directed against diseases for which the risk associated with not vaccinating are low
Describe the third category of vaccines, which are only used in special circumstances.
directed against diseases of little clinical significance or vaccines whose risks outweigh their benefits
Describe the category of vaccines that are used to control disease in a population, rather than in individuals.
herd immunity- 75% of the herd is immunized to protect those who cannot be immunized or don't respond properly to immunization
What vaccines are available in intranasal formulations? (4)
- IBR in cattle
- equine influenza and strangles
- feline/ canine/ poultry respiratory diseases
What are methods of vaccinating fish? (2)
- immersing the fish in a dilute antigen solution
What are the properties of an ideal vaccine? (9)
- inexpensive to produce
- consistent in formulation
- stable without requirement for special storage
- long shelf life
- able to induce the most appropriate type of immune response
- activation of multiple clones of antigen specific T and B cells
- ability to induce a long-lived immune response
- ability to induce immunological memory
- no adverse side effects
What are the principals of passive vaccination? (4)
- rarely used
- uses preformed antibodies specific to a particular antigen
- ex. tetanus antitoxin, antivenoms, rabies immunoglobulin
- antiserum raised in large animal species then harvested from hyperimmunized animals
Why must care be taken when deciding to use a compound for passive immunization?
immunoglobulins are antigenic in other species, and repeated injections can sensitize to recipient for a future hypersensitivity reaction or serum sickness
What are the principals of active immunization? (2)
- more common method of vaccination
- antigen is administered to induce an immune response and immunologic memory
The most effective vaccines are those that...
retain the ability to infect an animal, without causing disease
Non-infectious (killed) vaccines are less effective (compared to live vaccines) and therefore...
- up to 3 doses given several weeks apart
- first dose primes the immune system
- second dose immunizes
- third dose boosts
- [versus modified live vaccines which can prime, immunize, and booster in one dose]
Describe live virulent vaccines.
- incorporate the live and virulent form of an infectious agent
- uncommonly used d/t risk of causing disease
- orf vaccine is an example
Describe live attenuated vaccines.
- [MLV] use of intact and viable organism that has been attenuated to reduce its virulence
- capable of inducing low level infection and replicating within the host, but do not induce significant tissue pathology or clinical disease
- most common vaccine type
What are the advantages of MLVs? (5)
- induces more effective immunity than killed vaccines
- limited replication of live vaccine increases antigen conc immediately after vaccination
- more likely to replicate intracellularly (T cell response)
- fewer doses required
- greater safety than live virulent vaccines
MLVs induce a _______ response, while killed vaccines are more likely to induce a _______ response.
What is a recombinant organism vaccine?
- benign carrier organism genetically modified to incorporate a gene from an unrelated pathogen; cannot revert to virulence b/c they don't contain the live target virus
- ex. canary pox virus is a carrier for FeLV, CDV, rabies, WNV, and Eq influenza
What types of vaccines can induce immunity in the face of maternally derived immunoglobulins?
- recombinant organism vaccines
- naked DNA vaccines
Describe Marker vaccines.
- discriminate between vaccinated and exposure titers with parallel development of an appropriate diagnostic test
- ex. IBR in cattle
Describe subunit vaccines.
- do not use whole organisms but rather specific structural proteins
- require an adjuvant
- the immunity is very restrictive
Describe naked DNA vaccines.
- gene of interest from pathogen is inserted into a bacterial plasmid--> injected directly into an animal
- triggers a very potent mixed cell-mediated and humoral immune response
What are the 10 commandments of vaccination?
- 1. it's a medical procedure and not every animal requires all vaccines
- 2. all animals should get core vaccines but not non-core vaccines
- 3. vaccines should be administered to as many animals as possible- herd immunity
- 4. maternal antibodies interfere with the ability of young animals to respond to vaccines properly (ie. so many boosters)
- 5.adult animals should be vaccinated as infrequently as possible (based on DOI)
- 6. preg animals should only be vaccinated if it is supported by data
- 7. do not vaccinate ill or immunosuppressed
- 8. consult with client first
- 9. follow data sheet instruction
- 10. detailed records should be kept and animals monitored for adverse effects
Describe autogenous vaccines. (4)
- comprised of agents or antigens derived from the individual herd or area in which they intend to be used
- molecular techniques are used to differentiate the field strains from those in commercial vaccines
- letting an infection (rather than a vaccine) generate an immune response
- ex. live PRRSV to infect certain populations of pigs or salmonella in poultry
Describe vaccination in the face of an outbreak.
- use of modified live vaccines (intranasal- resp outbreak) is ideal
- one dose of MLV results in immediate replication and you immediately have protection from IFN-gamma within 24 hours and large amounts of IgA in 72 hours [in contrast, killed vaccines result in IgG and very little IgA]
Criteria for a vaccine program. (5)
risk for disease, consequences of the disease, anticipated effectiveness of the product, potential for adverse effects, cost of immunization versus cost of disease
Infectious disease control programs should be directed towards: (3)
- reducing exposure
- minimizing factors that decrease resistance or increase susceptibility
- enhance resistance by vaccination
What protocols should be put in place for moving horses? (3)
- copies of vaccination and health maintenance records
- owners of equine facilities should establish health entry prereqs (not just vaccine requirements)
- horses should be vaccinated no later than one month prior to entering or leaving a facility in order to produce adequate antibody levels
What are some potential adverse effects of vaccines in horses? (7)
- IM vaccines may cause systemic or localized adverse reactions
- local reactions are often non-descript and self limiting
- severe reactions may require prolonged treatment
- systemic reactions include purpura or anaphylaxis (stay on the farm for 10 minutes following vaccination of an animal)
- adverse reactions should be reported to the USDA center for veterinary biologics
- administration of vaccines containing multiple antigens/ adjuvants may increase the risk of adverse reactions
- don't give a MLV and a killed vaccine in the same location b/c the killed vaccine will inactivate the live one
Where shouldn't you give an IM injection in a horse and why?
- gluteal/ hip muscles
- abscesses can be obscured along fascial planes, leading to severe tissue damage and prolonged time to heal
When should you vaccinate brood mares?
- 4-6 weeks before foaling- maximizes Ig in the colostrum
- foals will have maternal antibody interference to vaccines- make sure to minimize exposure and do a series of 3 shots
What are the core vaccines for horses? (5)
- easter equine encephalomyelitis
- western equine encephalomyelitis
- west nile virus
Describe the EEE vaccine in horses.
- killed vaccine
- 3 doses in foals, 2 doses when starting in older horses- boostered yearly
- high morbidity and mortality with EEE, horses that do survive often have permanent neurologic deficits
Describe the WEE vaccine in horses.
- vaccine very effective
- mortality lower than EEE
- horses that survive infection rarely have permanent deficits
Describe the WNV vaccine in horses.
- vaccine very effective
- leading cause of encephalitis in the US
- moderate morbidity and mortality, 40% chance of showing residual deficits after recovery
Describe the tetanus vaccine in horses?
- one of the most deadly infections in horses
- antibody alone is protective- annual revaccination
- revaccinate in the case of a laceration or surgery
Describe the rabies vaccine in horses.
- fatal disease
- foals should be tested for titers at 24hours old- if +, don't vaccinate until 6 months old, followed by a second dose 4-6 weeks later
- foals from unvaccinated maresshould be vaccinated at 3-4 months old and repeated at 4-6 weeks later
- mares should be vaccinated 4-6 weeks before foaling or before breeding
What are some risk-based vaccines that we give to horses?
Describe anthrax in horses.
- serious and rapidly fatal septicemic disease
- acquired through ingestion, inhalation, or contaminated of wound with soil-borne spores
- vaccination only recommended for horses pastured in endemic areas
- vaccine is a modified live; not recommended in pregnant mares
Describe botulism in horses.
- disease is due to potent toxins
- wound botulism, shaker foal syndrome (spores ingested), forage poisoning (preformed toxin ingested)
- botulinum toxin type B prevents transmission of impulses in nerves--> flaccid paralysis
- Equine grass sickness is overgrowth of C. botulinum type C in intestinal tract
- no cross protection between type B and C
Describe Equine herpesvirus.
- The primary use of the vaccine is to prevent abortion and reduction of signs and spread of resp disease in young animals at high risk of exposure
- non of the vaccines prevent the myeloencephalitic form of EHV-1
- MLV vaccine
- frequent vaccination of mature horses is no recommended
- outbreak mitigation with MLV
Describe equine influenza.
- horses 1-5 years old are at the most risk and are therefore usually the vaccinates
- another risk factor is frequent contact with large numbers of horses
- available as MLV, inactivated (recommended), and vector vaccine (recommended for pregnant mares)
- outbreak mitigation with MLV or vector vaccine
Describe equine viral arteritis.
- causes abortion in pregnant mares, uncommonly causes death in young foals; spread by resp secretions or venereally
- highly attenuated MLV
- consult with state or fed animal health official before using this vaccine
- Neorickettsia risticii
- late spring early fall- infections
- may cause abortion
- killed adjuvant vaccine (does not prevent abortion)
- major cause of foal diarrhea
- focus on strict biosecurity and cleanliness during foaling season
- vaccinate pregnant mares to increase colostral antibodies
- most commonly occurs in weanlings and yearlings
- 2 types of vaccines- killed give IM, MLV given intranasally
- killed vaccine attenuates the svereity of clinical signs
- MLV stimulates high level of immunity but there are side effects
- all parenteral vaccines should be given prior to administration of IN vaccine (advised to give IN vaccine on a different day)
- purpura hemorrhagica is a potential side effect of vaccination