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EPIDEMIOLOGY, INFECTIOUS DISEASES
Department of Microbiology and Infectious Diseases
Budapest, XIV. Hungária krt. 23-25.
Telephone: 251.9900
Internal phone: 8090, 8091
Fax: 251.9260
E-mail: Fodor.Laszlo@aotk.szie.hu
Department of Microbiology and Infectious Diseases
Lectures
• Bakonyi, Tamás: Associate Professor
• Fodor, László: Professor
• Makrai, László: Associate Professor
• Tuboly, Tamás: Professor
• Varga, János: Professor
• invited speakers
Department of Microbiology and Infectious Diseases
Plenary practicals
• Bakonyi, Tamás: Associate Professor
• Fodor, László: Professor
• Hornyák, Ákos: Head of Department
• Makrai, László: Associate Professor
• Tuboly, Tamás: Professor
• Varga, János: Professor
Diagnostical practical
• 4 weeks
Importance of infectious diseases
• all areas of veterinary medicine
• great economic impact (avian influenza 20 bn $)
• trade of animal and animal products
• zoonoses
• food hygiene, food safety
• 25% of human death cases is because of infective agents
Subject of „Epidemiology, infectious diseases”
• Structure
• lectures
• plenary practicals (from 10th October, 2011)
• practice at diagnostic institute
• midterm exam (24th October, 21st November)
• Content
• general epidemiology
• diseases caused by viruses
• diseases caused by prions
• diseases caused by bacteria
Literature
• Hagan and Brunner’s Microbiology and Infectious Diseases. 8th
Ed. Comstock Publishing Associates 1988.
• Kahn (Ed.): The Merck Veterinary Manual. 10th Ed. Merck & Co.
2010. www.merckvetmanual.com
• http://www.oie.int
• Straw, B. et al. (Eds.): Diseases of swine. 9th Ed. Blackwell. 2006.
• Saif, Y.M. (Ed.Ch.): Diseases of poultry. 12th Ed. Blackwell. 2008.
• Radostits, O.M. (Ed.): Veterinary Medicine 10th Ed. Elsevir. 2007.
HISTORY OF INFECTIOUS DISEASES
• Varro (2nd cent B.C.): living agents
• Fracastoro (16th cent.) „contagium vivum”
• Leeuvenhoek (17th-18th cent.): microscope
• Pollender (19th cent.): bacteria in the blood of animals with anthrax
• Pasteur-Koch (19th-20th cent.)
• Ivanovsky (19th cent.): virus
• Löffler and Frosch (1897): foot and mouth disease virus
• Jenner (1796): pox
• Mechnikov (1884): phagocytosis
• Behring (1890): antibodies in the blood
• eradication of infectious diseases
Infectious disease
• agent (lower ranked)
• host (higher ranked)
• exposition - disposition
• phases of infection
Sources of infection
• source: generally infected animals / humans
• direct
• indirect
•excretions, secretions (blood, faeces, urine, saliva, milk,
semen,)
•products of animal origin (meat, milk, skin, wool, hair)
•drinking water, feed
•soil, environment
• aerogenic
• arthropods
• iatrogenic infections
•nosocomial
Transmission of diseases
• vertical
• germinative
• intra uterine
• galactogen
• horizontal
Zoonoses
• orthozoonoses
• cyclozoonoses
• metazoonoses
• sapronoses
Infection
• ways of infection
• per os, intra nasal, genital tract, udder
• conjunctiva,
• per cutan, wound
• optimal entrance
• source of infection: animal (carrier), environment, feed, water, etc.
Forms of infection
• reinfection
•exacerbation
•superinfection
• secondary infection
• mixed infection
Outcome of the infection (agent – host – environment)
• agent
• relationship of the agent and the host (pathogenicity, virulence)
• amount of the agent
• way of infection
• host
• species, age
• species related resistance
• non specific resistance
• specific resistance
• environment
• nutrition
• management
Outcome of the infection (agent – host - environment)
Agent
• host-parasite relationship
• normal microflora
• pathogenicity (euryxen / stenoxen, obligate / facultative pathogen)
• virulence (virulence factors, MLD, LD50, change of the virulence)
• invasiveness (intra cellular, extra cellular)
• amount of the agent
• way of infection (optimal!)
• Henle-Koch postulates
Outcome of the infection (agent – host – environment)
Host
• species, age (species specific resistance)
• race, individual resistance (lines)
• production (feeding, laying)
• non specific resistance
• skin, mucous membranes, excretions (HCl, fatty acids, bile, etc.
• macrophag-phagocyte system (MPS)
• complement, properdin, opsonin
• IL, IF, TNF
• specific resistance
• passive immunity (natural, induced)
• active immunity (natural, induced)
•specific resistance
• humoral resistance (IgA, IgG etc.)
• cellular resistance (i.c. bacteria, viruses)
• effect of immune suppression (toxicosis, medicine,
micotoxins, some agents, parturation etc.)
• foetal immune reaction (hierarchy, age)
• immune reaction of newborns (age related)
•calf: Ig 4-32 days
•calf, piglet: local immune reaction immediately
(disappears, no immune memory)
•cellular immune reaction: 0-2 weeks weaker
Outcome of the infection (agent – host – environment)
Environment
• survival in the environment
• environmental effects on animals
• predisposes to facultative pathogens
• nutrition
• management
• technology (weaning, grouping, treatment, castration, sheering,
transport)
• physiological effects, use of animals
Course of an infectious disease
1. local infection
2. infections of different organs (localised)
3. generalised infections
• incubation: infection, colonisation, replication
• generalisation: spreading (blood, lymphatic vessels,
perineural)
• foetus:
• resorption, embryonic death, abortion
• teratogenic
• decreased resistance
• tolerated infections
• manifestation: clinical signs, lesions (virulence factors)
Course of infectious diseases caused by viruses
• replication at the place of entry and in the regional lymph node
• localisation by macrophages
• replication in infected macrophages, lymphocytes, blood
(viraemia)
•replication in lymphoid cells: immune suppression, damage of
blood vessels
• secondary replication in tissues
•damage of cells: clinical signs
• reactive inflammation, allergic reactions
•clinical signs
Start and course of infectious diseases
Course of the disease
• incubation time
• course of an infection in time
• peracute
• acute
• subacute
• chronic
Outcome of the disease:
• recovery (full or partial), carrier
• death
Infections without clinical signs
• forms of infections without clinical signs
•abortive infection
•inapparent (sub clinical) infection
•persistent infection (virus)
•latent infection (virus)
•tolerated infection (virus)
• importance of infections without clinical signs
Epidemiology of infectious diseases
Characteristic of infectious diseases
• infectious diseases
• contagious diseases
• soil infections
Statistical evaluation of infectious diseases
• morbidity
• mortality
• lethality
• incidence
• prevalence
Analysing methods of infectious diseases
• data collection to diagnostic work
•monitoring
•surveillance (passive, active)
•screening
• control of hypothesis
•statistical methods
•blind examinations
Extension of infectious diseases
• endemic diseases (enzootia)
• epidemic diseases (epizootia)
• pandemic diseases (panzootia)
Notification
International cooperation regarding infectious diseases
• OIE (Office International des Epizooties, World Organisation for
Animal Health) 1924.
• FAO (Food and Agricultural Organisation) 1948.
• WHO (World Health Organisation) 1948.
Factors influencing infections
• geographical factors (island, desert, mountain, river, soil)
• climatic factors (sunshine, wind, vapour content, season)
• management (overcrowding, mixing, contact, draught, NH3)
• nutrition (pasture, stable, starvation)
• transport (road, rail, harbour)
• biological factors (mating, leave of the offspring)
Diagnostics of infectious diseases
• complex
• epidemiological data
• clinical signs
• pathological lesions
• allergic examination
• laboratory examinations (diagnostic institutions)
• evaluation, diagnosis
Diagnostics of infectious diseases
• epidemiology – clinical signs – pathological lesions
• allergic tests (tuberculin, mallein)
• laboratory diagnosis
•sampling, letter
•histological examination
•microscopic examination (smear)
•electron microscopic examination
•isolation (medium – cell culture – egg – laboratory animal)
•serological tests
•classical: agglutination, precipitation, elfo, PAGE, CFT
•virus serology: VN, HAI
•marked immunological methods: IF, ELISA, RIA, IRMA
Diagnostics of infectious diseases
• cellular tests
•lymphocyte stimulation test
•immune rosette formation
•cytotoxic reaction
•macrophage migration
• -interferon test
• methods detecting nucleic acids (DNA hybridisation, PCR)
• more diagnostic methods have to be used
• complex evaluation
Treatment of diseased animals
• aetiological treatment
• symptomatic treatment
• bacteria: antibacterial treatment (appropriate medicine)
• individual / mass treatment
• treatment of certain diseases is not allowed
• some chronic diseases cannot be treated or treatment is not
reasonable
• prevention of complications (diseases caused by viruses)
• hyperimmune serum
Prevention and control of infectious diseases
1. veterinary administration, rules
• general rules
• specific measures
2. immune prophylaxis
3. chemoprophylaxis
Prevention and control of infectious diseases
1. rules, veterinary administration
• international transport, certificates
• import restrictions
• quality requirements
• localisation
Prevention and control of infectious diseases
• general rules
•all in, all out, disinfection
•isolated keeping of different animal species / age groups
•closed keeping, limited traffic (personal, vehicles, avoiding mixing)
•isolation from wild animals, rodents, birds
•rendering dead animals, waste
•rules of hatching, transport of day-old chicken
•excluding carrier people
Prevention and control of infectious diseases
1. veterinary administration
• general rules
• specific rules
• specific measures concerning a certain disease
2. immune prophylaxis
1. passive immunisation
2. active immunisation
3. chemoprophylaxis
Immune prophylaxis
Passive immunisation
• hyperimmune serum
• maternal immunity
• epitheliochorial: colostrum
• syndesmochorial: mainly colostrum
• endotheliochorial: diaplacentar + colostrum
• immuno globulin content of the colostrum is decreasing
1st day 3rd day Commercial milk
Protein 18.8 7.5 3.25
Ig 13.1 1.0 0.09
Colostrum (%)
• enteral absorption of Ig is decreasing
• enteral lymphocytes can be transferred
• bisection time
• effect of the antigen on the amount of maternal antibodies
• can inhibit immunisation
Immunprophylaxis
Active immunisation
• factors influencing efficacy
• live vaccines (attenuated)
• inactivated vaccines
New generation vaccines
• live vaccines
•deletion vaccines
•vector vaccines
• not living vaccines
• subunit vaccines
• inactivated deletion vaccines
• ISCOM vaccines, virus like particles
• synthetic vaccines
• nucleic acid vaccines (DNA, ss+RNA)
• transgenic plant vaccines
• not replicating vector vaccines
• anti-idiotype vaccines
•DIVA: Differentiation Infected and Vaccinated Animals
Prevention and control of infectious diseases
1. veterinary administration
• general rules
• specific rules
• specific measures concerning a certain disease
2. immune prophylaxis
1. passive immunisation
2. active immunisation
3. Chemoprophylaxis
• antibacterials
Control, eradication
• selection (test and remove) (+ vaccine)
• generation shift
• herd replacement
• SPF method
• embryo transfer
Eradication of human infectious diseases
• smallpox (1959-1979)
• polyomyelitis (some years)
• rubella, mumps (target: 2010-2015)
Eradication of infectious diseases of animals
• Rinderpest (2011): 2010-2015)
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