Transmission and control of infectious diseases (6) Flashcards
What is an infection?
The invasion, spread, and multiplication of a micro-organism in the body of an animal, resulting in a host response.
What is a disease?
A condition of the living animal or plan (or of one of its parts) that impairs normal functioning and is typically manifested by distinguishing signs and symptoms.
What are the general phases of infection?
1) Incubation period
*Entering and multiplication at the porte d’entrée
*No symptoms
*Activation of immune system
2) Prodromal period
*Spread through host
*A-specific symptoms
*Activation of immune system
3) Acute stage
*Infection and multiplication in specific organ(s)
*Specific (organ related) symptoms
*Tissue immunity
4) Convalescence (two stage options)
*Further implication (till death) or
*Restriction (chronic infection, carrier, or healing)
*Humeral immunity (antibodies)
What are the two types of infection?
Inapparent
*Still in the incubation period
*Subclinical (no symptoms visible for the ‘untrainedʼ senses)
*Persisting
-Latent
-Tolerated
-Occult
Apparent (local or general/systemic)
*Per acute
*Acute Subacute
*Chronic
*Abortive
What factors determine if an infection leads to a disease?
Infectiously of MO
*Infection pressure/transmission
Host immunity Stock density
Environmental factors → climate and housing
Management
What is the definition of infectious?
The ability of a micro-organism to cause an infection.
What is the definition of contagious?
The ability of a specific type of micro-organism to go from an
infected host to a non-infected host by direct contact.
What is the definition of pathogenic?
The ability of a specific type of micro-organism to cause
disease in a host.
What is the definition of virulence?
The severity of pathogenic action of a certain strain of micro- organism in a specific host under specific circumstances.
What is the definition of serotype?
A group of intimately related micro-organisms distinguished by a common set of antigens.
What is the definition of prevalence?
The number of diseased animals in a population at a certain moment
What is the definition of incidence?
The number of new disease cases in a population over a period of time
What is the definition of morbidity?
Amount of disease animals in a population
What is the definition of mortality?
Amount of death cases in a population
What mechanisms of transmission are there?
Direct
*Horizontal → host to host
-Contact infection
-By droplets
-By dust
-By lesions
-By mating
*Vertical → mother to young
-In uterus
-By milk
Indirect
*Horizontal
-By vehicle (dead)
-By vectors (alive)
What is the difference between a viral and bacterial infection?
Bacteria
*Discovered by the innate immune response
Viruses
*Can easily slip through tissues with minimal disruption
*Do not result in pus formation
*Phagocytosis is not important in defence
*An engulfed virus will often continue replicating in the phagocytes and actually be carried therein via the bloodstream to the preferred tissue
*When at the site it will begin to destroy the tissue or cells Circulating in the bloodstream → viraemia
*The first phase of the infection of animals is most dangerous for other animals → contagiousity
Why are foreign animal diseases a threat?
The animal population has no prior experience with the disease and therefore has no immunity, this makes them highly susceptible
What are the characteristics of equine infectious anaemia?
Transmission through fly bites -> Summer season
Not contagious → infectious
Incubation 3-30days
Fever, blood changes, anaemia, and can be fatal
Carrier animals
No available vaccine
