Topic 4 - Prevention and control of infectious diseases. Flashcards
What is the aim of preventing or controlling an infectious disease?
To prevent introduction of the disease, and to prevent spread.
If the disease is introduced, the aims is to localize and eliminate the epidemy.
Which methods are used in prevention and control of infectious diseases?
- Veterinary administration methods
- Immune prophylaxis
- Chemo prophylaxis
What is meant by “veterinary administration methods”?
there are administration rules, general epidemiological rules and specific measures which are variable for each disease.
Name “veterinary administration rules”:
- We have notifiable disease
- rules for international transport
- Import restrictions
- Identification of animals
- Certificates
- Traceability of the animal
Name the general epidemiology rules:
VERY IMPORTANT FOR THE EXAM
- All-in-all out, WITH disinfection
- Isolated keeping of different animal species and age groups
- Closed keeping, limited traffic (personal, vehicles)
- Introduction of animals: diagnostic tests, quarantine
- Isolation from wild living animals, rodents, birds
- Rendering dead animals, waste
- Rules of hatching, transport of day-old chicken
- Excluding carrier people
Name some specific epidemiologic measures:
This is specific for each disease, we have two different method:
- Great economic impact
- Smaller economic impact
Specific epidemiological measures for diseases of GREAT economic impact:
- Strict rules
- Closed herd
- protection zone
- observation zone
- stamping out
Specific epidemiological measures for diseases of SMALLER economic impact:
- Movement restriction
- Closed herd
- Diagnostic examination
- Treatment + vaccination
What is immune prophylaxis?
We have two types:
- Passive immunisation
- Active immunisation
What is passive immunisation under immune prophylaxis treatment?
We have:
1. Hyperimmune serum
2. Maternal immunity
What is hyperimmune serum of passive immunisation under immune prophylaxis treatment?
the animal is given a high level of antibodies through a vaccine.
Homologous half-life = 2-3 weeks
Heterologous half-life = 7-10 days
What is maternal immunity of passive immunisation under immune prophylaxis treatment?
It is a passive immunity. Depending on the type of placenta, the significant of the colostrum is varying. Also the colostrum quantity and quality changes over time
good colostrum immunity = the mother is vaccinated
Significance of colostrum with Epitheliochorial:
colostrum
horses, pigs
Significance of colostrum with Syndesmochorial:
mainly colostrum
ruminant ungulates
Significance of colostrum with Endotheliochorial:
diaplacental + colostrum
cat and dog
The number of maternal antibodies depends on?
- The antigen
- Nutrition of the dam
- General state of the dam
Why is it important to measure the colostrum level before vaccinating?
If the animal have high colostrum immunity level, the vaccination efficiency can be decreased, because the antibodies bind the antigens of the vaccine
What is active immunisation?
Immunisation provided by the veterinarian, such as the vaccine
Factors influencing the efficacy of the active immunisation:
- the agent
- Vaccine type
- Amount of antigen
- Method of vaccination
- age of animal
- health of animal
Different types of vaccine, name them and the subunits of them.
- Live vaccines
a. Avirulent
b. Attenuated - natural and artificially - Inactivated vaccines
- Polyvalent vaccines
What helps the efficiency of the vaccine?
the adjuvant, they have a longer antigen release
What is a live vaccine?
Fast effect and more effective, they induce a faster immune reaction
What is an AVIRULENT live vaccine?
there are no pathogenic opportunity, they can be used in vaccines
What is an ATTENUATED live vaccine?
virulent, but after passaging they can be attenuated artificially
What is inactivated vaccine?
They contain viruses whose genetic material has been destroyed by heat, chemicals or radiation so they cannot infect cells and replicate, but can still trigger an immune response
What types can the inactivated vaccine be?
- Complete agent
- Partial antigen extract
- Subunit
- Toxoid = inactivated toxin
What is a polyvalent vaccine?
more than one agent is present in the vaccine
What does the DIVA principle stand for?
DIVA = Differentiation Infected and Vaccinated Animals. Also called marker vaccine
What is the DIVA principle?
= induce an immune response which is different from that induced by natural infection.
Difference between the field and the vaccine strains
Name different marker vaccines:
- Deletion markers
- Subunit markers
- Non-structural marker
What is a deletion marker vaccine?
Gene-deletion-lack of certain non-important protein
What is a subunit marker vaccine?
Vector-produced, different structure
What is a non-structural marker vaccine?
Viral enzymes, no-replication, no immune answer
What is Chemo prophylaxis?
refers to the administration of a medication for the
purpose of preventing disease or infection. Antibiotics, for example, may be administered to patients with disorders of immune system function to prevent bacterial infections.
Which methods are used for control and eradication of an infectious disease?
- Selection
- Generation shift
- Herd replacement
- SPF method
- Embryo transfer
- Eradication with antibodies
- Eradication of infectious disease of animals
What is selection as a control and eradication method?
In small herds we can select the animals, selection test and removal of the infected animal and we have a high chance of removing the disease. To test we a useful tool, the DIVA marker vaccine
What is generation shift as a control and eradication method?
Generation shift is a method where we isolate the keeping of new-born animals, and then we replace the infected parent stock with the new-born when they are old enough. In optimal conditions we will then have a new herd without the disease.
What is herd replacement as a control and eradication method?
This is a VERY expensive method, we eliminate the herd, disinfect the area and buy new livestock.
What is SPF method as a control and eradication method?
SPF = Specific Pathogen Free
It is a health state, there is a risk of pathogens – that is why it is specific.
What is embryo transfer as a control and eradication method?
Embryo transfer can be used, but with the restriction that deep frozen embryos can harbour infections as well. In some diseases this will work
What is eradication with antibodies as a control and eradication method?
Is not preferred, because of the resistance issues. In case of leptospirosis it can work
How was Rinderpest eradicated?
Rinderpest was the only disease with sterile immunity, so if the animals was vaccinated the immunity would cause sterility so the virus couldn’t cause infection anymore – this is why it was possible to eradicate the disease
