Dynamics of disease

Lectures 14-15

Parasite-definition

Organism that consumer part of its host without necessarily killing it

Pathogens-definition

Parasites that cause diseases

Parasitoid-definition

Insect whose larvae live in hosts that they consume

Transmission-definition

Movement of parasites from one host to the next

SIR Model diagram

SIR Model equations

SIR assumptions

• Susceptibles become infected at rate Bxy

• Recovery is permanent and conveys immunity

• Infected individuals can recover

SIR threshold behaviour

SIR R(x)

R(x) is the number of individuals affected by one infected individual during its lifetime

• If R(x)>1, the infection persists

• R(x) depends on lifetime of infected individuals and the infection rate

SIR Lifetime of infected individuals

Reproductive number in a population of susceptibles (R₀)

Vaccination strategies

Mechanisms to explain cyclic dynamics of disease

• Latency

• Seasonality

• Dispersal limitation

Host-parasitoid dynamics

Fluctuations in interactions explained by:

• Parasitoids kill their host

• Generations do not overlap