4. Prevention and control of infectious diseases.

Question 1

Aim for prevention and control of infectious disease?(3)

Answer 1

Aim:

• Prevention of introduction of the agents
• Localisation of the epidemic: prevent spread
• Elimination of the epidemic

Question 2

Vet administration rules: Notifiable diseases?

Answer 2

Vet administration methods

• Vet admin rules

Notifiable diseases

• most severe diseases
• Great economic impact, public health importance
• National Lists, EU lists, OIE lists

Question 3

1)Vet admin rules : International transport + General epidemiological rules?

Answer 3

International transport

• intro of certain infections, only certified transportations can happen,
• import bans can be implemented
• Certificates, traceability
• Import restrictions
• Quality requirements

General epidemiological rules

• All-in, all-out, disinfection
• Isolated keeping of different animal sp/age groups e.g. dog carries Brucella and can
• infect Su/Ru (younger may be more susceptible/older may have more resistance)
• Closed keeping, limited traffic (authorised personnel, vehicles)
• Introduction of animals to the farm: diagnostic tests, quarantine (at least 30 days)
• Isolation from wild living animals, rodents, birds e.g. ASF wild boar contact
• Arthropod control is important
• Rendering dead animals, waste
• Rules of hatching, transport of day-old chicken ʹ can only put marked eggs from
• 1 farm in the hatchery, has to be disinfected (easy place for infection)
• Disinfection very important, hatching boxes must be disinfected/use
• trays that can be disinfected
• Don’t mix the boxes
• Excluding carrier people: avoid unnecessary exposure and only healthy people can
• work/regular xray(TB),
• if have diarrhoea not allowed in poultry -salmonella/examinations

Question 4

1) Vet admin - specific measures, international cooperation regarding infectious diseases?

Answer 4

Specific measures (different in the case of different diseases)

• Specific for each disease
• Notifiable/Zoonotic/Diseases of great economic impact: strict measures
• closed herd, protection zone, observation zone, eradication/stamping out
• Diseases of smaller economic impact
• Movement restriction, closed herd
• Diagnostic examination
• Treatment, vaccination

International cooperation regarding infectious diseases

• OIE (Office International des Epizooties, World organisation for animal health) 1924
• International animal health code
• Manual of standards for diagnostic tests & vaccines
• FAO (Food & Agricultural Organisation) 1948

Question 5

2) Immune Prophylaxis- passive immunisation?

Answer 5

Passive immunisation

• Hyper-immune serum (artificial): homologous 2-3 weeks, heterologous 7-10 (horse in dog ʹ can cause allergy/hyperimmune reaction) days t1/2 ʹ high number of immunoglobulins
• Maternal immunity (natural) (yolk immunity in birds)
• Epitheliochorial placenta: colostrum
• Syndesmochorial: mainly colostrum
• Endotheliochorial: diaplacental + colostrum
• Immune globulin content of the colostrum is decreasing
• Enteral absorption of Ig is decreasing: 1st day is still good, then sharp decline at end of 1st day (calf) by 27th hr, is no absorption of Ig ʹ
• epithelial layer of gut is CLOSED: give 10% of weight of animal on first day! Calf =: 50kg, give 5kg colostrum
• enteral lymphocytes can be transferred
• Half life
• The number of maternal antibodies depends on: the antigen, nutrition of the dam
• Certain antibodies can inhibit the active immunisation
• Ig content of the serum can be detected

Question 6

Active Immunisation?

Answer 6

Active immunisation

• Factors influencing efficacy:
• agent, vaccine type, amount of antigen, method of vaccination, age & health state of the animal
• Live vaccines: give faster immune response,
• less antigen needed, stronger immune response
• Avirulent/Attenuated strains
• Naturally or artificially attenuated strains
• Inactivated vaccines: contain complete agent in inactivated (killed), Ag extract or subunit
• Adjuvants: help the immune response (longer release of the antigen) e.g. gel
• Polyvalent vaccines ʹ several agents are included in a single shot
• New generation vaccines
• Live vaccines:
• deletion vaccines (certain part of gene deleted that are responsible for the virulence) IBR
• vector vaccines(gene inserted into the gene of the pox virus that doesnt cause disease) BVDV
• Not living vaccines:
• Inactivated deletion vaccines
• Recombinant vaccines
• Virus like particle (VLP) vaccines: ISCOM
• Synthetic vaccines e.g. in case of FMD vaccine
• Nucleic acid vaccines (DNA, ss+RNA)
• Transgenic plant vaccines

Question 7

Chemoprophylaxis?

Answer 7

Chemoprophylaxis:

• Antibacterial - mostly only leptospirosis
• Control, eradication: 3 main eradication methods, others are less used but still possible
• 1. Selection (test & remove)
• used in small herds and if has low level of infection (if 80% should be slaughtered, farmer wont be happy
• repeated and controlled
• With vaccine: DIVA can combine with Vaccine
• 2. Generation shift:
• isolated keeping of new-borns
• replace infected parent stock with disease free young animals
• continuous production (dairy farm)
• 3. Herd replacement: quite expensive, all infected are slaughtered/get new to repopulate
• changing infected stock with disease free animals
• SPF method: specific pathogen free (free from certain diseases, efficient way of eradication),
• strict isolation
• Embryo transfer: expensive but reliable, more used in very valuable animals
• implantation of washed embryos into disease free dams
• Eradication with antibiotics: limited, leptospirosis
• Eradication of human infectious diseases: smallpox (1959-1979), poliomyelitis (some years),
• rubella, mumps
• Eradication of infectious diseases of animals: Rinderpest (2011)