2 Disease Terms and concepts

Incubation period

Time interval between invasion by an infectious agent and the appearance of the first sign or symptom of the disease ie. Time infected to time you begin to feel sick

Infectivity

Ability of an agent to get in. The capacity of an agent to enter and multiply in a susceptible host and this produce infection or disease

Pathogenicity

Refers to the capacity of a microorganism to cause damage in a host (NOT degree of damage or severity)

Virulence

Refers to the severity of the disease produced, the degree to which the disease has severe clinical manifestations or is fatal in a large number of cases

Influenza, E. coli, ebola

What are some diseases which can vary in their virulence even from year to year?

Immunogenicity

The ability of a foreign substance (ex. antigen on a pathogenic organism) to provoke an immune response in the body of a human or other animal host species

NO. For ex. Prion and HIV do not trigger an immune response

Are all pathogens immunogenic? What does this mean?

Exposure status: Unexposed and exposed
Infection status: OF THOSE EXPOSED: can be uninfected or infected
Disease status: OF THOSE INFECTED: can be clinical or subclinical.
OF THOSE WITH CLINICAL DISEASE: can be morbid (severe) sickness or face mortality (fatal)

Describe the disease spectrum starting with exposure status, going to infection status, then disease status.

Latent period

The period of time between the infection of the host by the agent and the ability to transmit the agent. Animal may appear healthy and asymptomatic ie. time point of infection to time you can communicate disease to someone else, normally before you present as sick

Incidence

Term for "new cases"

R-naught (R0)

Term for "average number of secondary cases from each case" or "ability to spread disease"

Prevalence

Term for "all existing cases"

Infectvitiy

Term for "ability to enter and establish in body"

Virulence

Term for "how severe disease is"

Pathogenicity

Term for "ability to cause disease"

Zoonosis

Any disease or infection that is naturally transmissible from vertebrae animals to humans

Zoonotic disease

A disease that can be passed between animals and humans

Pathogens with high R naught values are often not incredibly virulent (or severe/fatal). This is because "nature" does not want to kill off all the hosts, only survive in the host and be infected. So, we have immunity.

If we have pathogens with high R naught values, like 20, why are we not all dead?

Passive and natural/active

What are the two types of individual immunity?

Natural/Active immunity

Which immunity refers to getting a disease and getting over it yourself or through vaccination?

Natural/Active immunity

This type of immunity refers to the production of antibodies against a specific disease organism by the host immune system. Often permanent

Immunity

Refers to protection against a disease. Indicated by the presence of antibodies in the blood and can usually be determined with a laboratory test

Passive immunity

Refers to protection against a disease through antibodies produced by another human being or animal. Diminishes over time

Maternal antibodies passed from mother to offspring either prior to birth or via colostrum

What is an example of passive immunity?

First 12 hours (follows similar patterns with other animals)

When specifically talking about cats, colostrum can only be absorbed within how many hours of life?

In the time that the residual maternal antibodies are receding and the puppy is making it's own anitbodies, there is a window of susceptibility where the maternal antibodies may still be fighting off diseases, not allowing the puppy to build its own immunity or the puppy's immunity is not yet strong enough

What is the largest window of susceptibility to disease when considering a newborn puppy which has recently come off its mothers colostrum?

Maternal antibodies fight off introduced disease but this does not allow puppy to build up its own immunity. This is a window of susceptibility

Describe vaccine failure and why we give serial vaccinations at the beginning of life

Seroconversion

The development of antibodies in an animal can produce evidence of infection with that specific disease agent. Use tests to determine this

Rose bengal and brucellosis card test

What are two types of seroconversion tests?

Determinants of health

The range of personal, social, economic, and environmental factors that influence health status

Social determinant of health

Refers to the availability of resources to meet daily needs, such as educational/job opportunities, living wages, or healthful foods

Social norms/attitude, exposure to crime/violence/social disorder, social support/interaction, food deserts, exposure to media/technology, socioeconomic conditions, quality schools, transportation options, public safety, residential segregation, etc.

What are some social determinants of health?

Physical social determinants of health

Refers to exposure to toxic substances and other physical hazards, physical barriers (especially for the disabled), or aesthetic elements (such as good lighting, trees)

Agent, host, environment

What are the components of the epidemiologic triad?