Herd Immunity

What is the state of specific resistance to an infectious agent?

immunity

Immunity is achieved partially through the presence of antibodies to that disease. What type of immunity is this called?

Humoral immunity

What are the TWO ways that active immunity is achieved?

- vaccination ( artificial)

- natural expose (natural exposure)

In ___ immunity, the body has "memory" of the antigen so it can produce its own antibodies now or in the future

active

How do vaccines work?

presenting the immune system with a harmless form or component of a pathogen, allowing the body to rehearse its defense without risking disease

What does the exposure from vaccines acitivate?

activates B cells and T cells,

leading to the production of

pathogen-specific antibodies

and the development of long-

lived memory cells

look at slide 4 for other information on the types of vaccines

okay girl

What are THREE ways that passive immunity occur when an individual is given antibodies?

1) Fetus acquires antibodies via the placenta

2) A baby acquires antibodies by nursing

3) Antibodies may be given intravenously for treatment of a disease

In ____ immunity, your body has NO "memory" of the antigen; you are protected only as long as the antibodies remain in your system.

passive

What is resistance to the spread of disease in a population when a certain proportion of the population is immune to it due to vaccination or

previous infection?

Herd immunity ("community immunity")

T/F When herd immunity is achieved by vaccination programs, this helps protect susceptible individuals from illness.

True

The ___ ___ ___, the minimum proportion of individuals that must be immune to reach herd immunity, varies by pathogen (or strain of pathogen).

herd immunity threshold

Herd immunity can only be attained by ____

immunity, how is this done?

ACTIVE- created via vaccination or natural infection

T/F A certain % of the population must be vaccinated or immune to the disease

to prevent onward transmission. This % differs for every pathogen.

True

Once achieved, herd immunity acts to ___ ___ ___ by reducing the probability that they will come into contact with a shedder

protect susceptible individuals

WHEN YOU VACCINATE INDIVIDUAL ANIMALS, YOU ARE PROTECTING

THE ___ ___ , NOT JUST THE ANIMAL YOU VACCINATE.

ENTIRE POPULATION

What is the average number of individuals infected by an infectious individual when the whole population is susceptible to the disease?

basic reproductive rate (R0)

R 0 tells us how ___ or ____ the pathogen is.

contagious, transmissible

What do high and low levels of the basic reproductive rate mean?

High values mean the disease

is easy to transmit, and low values mean the disease is more difficult to transmit

What is R0 meant to measure what?

potential for epidemic spread

What is the proportion of the population that must be immune to the disease for herd immunity to be achieved?

Herd immunity threshold

We use R 0 to help us figure out what proportion of the population we need to

____ to stop onward transmission/spread of disease.

vaccinate

What is the most infectious agent we know in veterinary medicine?

Measles

chart of BASIC REPRODUCTIVE RATE (R0) OF

VETERINARY PATHOGENS is on slide 17, she kinda talked about it but not really

okay ill go an look at it (jk <3)

There are examples of how to calculate herd immunity threshold, i think it is on the formula sheet!

herd immunity threshold= 1- 1/Ro

There's a (indirect/ direct) relationship between how contagious a pathogen is and the level (%) of protection needed for herd immunity.

direct

The more contagious a pathogen is, the (lower/higher) the percentage of individuals that must be immune (vaccinated) to achieve herd immunity

higher

T/F Successes of vaccines are so profound that they've become invisible - people rarely see the diseases vaccines prevent and, as a result, sometimes fail to appreciate their value.

True

What is tis the average # of secondary cases per infectious case in a population made up of both susceptible and non-susceptible (immune) hosts?

effective reproductive rate

If Rt >1, what does this mean?

EPIDEMIC

If Rt = 1, what does this mean?

EQUILIBRIUM /ENDEMIC

If Rt <1, what does this mean?

ERADICATION

We have the power to change Rt, what is the goal?

The goal is to get Rt down to < 1.

What animal is known as an amplifier?

pigs

What does effective reproduction number Rt determine?

potential for epidemic spread at

a specific time t under the control measures in place

If the threshold for herd immunity is surpassed, then R t <1 and the number of cases of

infection _____

decreases

What decreases effective reproductive rate? (4)

• Vaccination

• Natural infection (if confers durable immunity to infection)

• Control practices: isolation & quarantine, minimize contact between groups, improved ventilation, travel/movement restrictions, basic biosecurity, C&D

• Testing (awareness of disease status)

What must we do to reduce the effective reproductive rate (Rₜ) in herds or populations?

reduce contact between animals, reduce susceptibility, or reduce the chance of transmission per contact