Table 1 Definition of variables and parameters used in the transmission model
State variables | Description | Â |
S | Susceptible humans | Â |
I T | Humans with taeniasis only | Â |
I C | Humans with cysticercosis only | Â |
I TC | Humans with taeniasis and cysticercosis | Â |
S P | Susceptible pigs | Â |
I PL | Pigs with cysticercosis (low cyst burden) | Â |
I PH | Pigs with cysticercosis (high cyst burden) | Â |
R p | Recovered (immune) pigs | Â |
V p | Vaccinated pigs | Â |
E | Taenia solium eggs (in the environment) | Â |
Demographic rates | Description | Units |
b H | Human births (net rate, set to maintain stable population size) | Month-1 |
d H | Human death rate (per capita) | Month-1 |
b P | Pig births (net rate, set to maintain stable population size) | Month-1 |
d P | Pig death rate (per capita) | Month-1 |
d E | Egg removal/death rate (per capita) | Month-1 |
Transmission parameters | Description | Units |
α | Human recovery rate from taeniasis (reciprocal of the average lifespan of the adult Taenia solium worm) | Month-1 |
Ï„ | Egg to pig transmission coefficient (product of the contact rate and the probability of infection upon consumption of a Taenia solium egg) | Month-1 |
ϕ | Proportion of pigs with low cyst burden; (1-ϕ) is the proportion of pigs with high cyst burden | – |
δ | Egg production rate | Month-1 |
ε | Rate of loss of immunity in pigs | Month-1 |
χ | Rate of human pork meal procurement | Month-1 |
π L | Probability of human becoming infected having consumed infected pork with a low cyst burden | – |
r consumption | Risk multiplier of discarding high cyst-burden pork (relative to discarding low cyst-burden pork) | – |
r infection | Risk multiplier of infection on consuming high cyst-burden pork (relative to consuming low cyst-burden pork) | – |
π H | Probability of human becoming infected having consumed infected pork with a high cyst burden, π H   = π L (1 + r consumption + r infection) | – |
β L | Pig (low cyst burden) to human transmission coefficient (a product of the contact rate and the probability of infection upon consumption of infected pork, β L  = χπ L | Month-1 |
β H | Pig (high cyst burden) to human transmission coefficient (a product of the contact rate and probability of infection upon consumption of infected pork, β H  = χπ H | Month-1 |
θ | Egg to human cysticercosis transmission coefficient (a product of the contact rate and probability of infection upon consumption of Taenia solium eggs) | Month-1 |
r Cysticercosis | Risk multiplier for cysticercosis (applied to theta if the individual has taeniasis) | – |
η | Human recovery rate from cysticercosis (reciprocal of the average duration of cysticercosis infection in humans) | Month-1 |