Topic 1 - Definition of infectious diseases, sources of infection, factors influencing infectious diseases (pathogen-host relationship, protection of the host, environmental factors) Flashcards
What is epidemiology?
It is the study of diseases in populations and of factors that determine their occurrence.
With which steps do we investigate a disease?
- Occurrence
- Aetiology: Which pathogen is responsible?
- Epidemiology: What are the circumstances, how the disease evolves, how is it spread
- Pathogenesis
- Clinical signs
- Post mortem lesions: pathology
- Diagnosis
- Treatment
- Prevention: vaccines
- Control
- Eradication
- Public health
What is the Epidemiologic triangle?
Used to investigating how a disease spreads and how to combat it
What is included in the Epidemiologic triangle?
- Agent
- Host
- Environment
What is the “agent” in the Epidemiologic triangle?
The agent is the microorganism that actually causes the disease
Name the 4 main classes of infectious agents:
Bacteria, virus, fungi, parasites
What is the “host” in the Epidemiologic triangle?
The agent infects the host, which is the organism that carries the disease.
A host doesn’t necessarily get sick; hosts can act as carriers for an agent without displaying any outward symptoms of the disease.
Hosts get sick or carry an agent because some part of their physiology is hospitable or attractive to the agent
What is the “environment” in the Epidemiologic triangle?
Outside factors can affect an epidemiologic outbreak as well.
The environment includes any factors that affect the spread of the disease but are not directly a part of the agent or the host. For example: temperature, feed, management
Name the PHASES of infection:
- Entry
- Colonisation
- Replication
- Host damage
- Transmission
What is the “entry” phase of infection?
The entry is where the organism enter the body. It need to be optimal for the infection to be effective. Entry can be natural orifices or per cutaneous
What is the “colonisation” phase of infection?
Pathogens are present on the body site, but cause no harm - they cause no symptoms of infection
What is the “replication” phase of infection?
Create new infectious virons that are able to infect other cells of the body
What is the “transmission” phase of infection?
The spreading of the disease.
What are the sources of disease?
Direct of indirect route
What is “direct” route of infection?
Animal to animal, through contact
Give example of direct route of infection:
- Teeth of rabid animal get in contact with the animal of the susceptible host
- Sexual transmitted diseases
What is “indirect” route of infection?
No direct contact between the animals
Give example of direct route of infection:
- Excretions/secretion
- Artropods
- Water/food
- Soil/environment
- Animal products
What are the main directions of transmission of a disease?
Vertical
Horizontal
What is the horizontal direction of transmission of a disease?
Transmission between same generation. adult to adult
What is the vertical direction of transmission of a disease?
Transmission between to generation.
What are the different vertical direction of transmission of a disease?
- Germinative = birds
- Intrauterine = inhertied
- Galactogen = through milk
What is zoonosis?
A disease or infection that is naturally transmissible from vertebrate animals to humans
Name the different types of zoonosis:
- Ortho zoonosis
- Cyclo zoonosis
- Meta zoonosis
- Sapronoses
