Fig 1.
Compartmental diagram of the dynamics of Newcastle disease in a homogeneous population of white-winged parakeets (model 1).
Five transition states include: susceptible (S), exposed (E), acutely-infected (IA), chronically-infected (IC) and recovered (R). See Table 1 for parameter descriptions.
Fig 2.
Compartmental diagram of the dynamics of the dynamics of Newcastle disease in an age-structured population of white-winged parakeets (model 2).
Transition states for juvenile parakeets are: susceptible (Sj), exposed (Ej), acutely-infected (IAj), chronically-infected (ICj) and recovered (Rj) and for adult parakeets the states are: susceptible (Sa), exposed (Ea), acutely-infected (IAa), chronically-infected (ICa) and recovered (Ra). See Table 1 for parameter descriptions.
Table 1.
Definitions and values of parameters for the model of Newcastle disease (ND) transmission in a homogeneous (model 1) and age-structured (model 2) population of wild white-winged parakeets.
Table 2.
Scenario analysis of the effect of uncompensated additional harvest (h1) on the basic reproduction number (R0) and population size following introduction of Newcastle disease into a homogeneous (model 1) and age-structured (model 2) populations of white-winged parakeets.
a
Fig 3.
Deterministic two-year time trajectories for Newcastle disease transmission.
Simulated outbreak dynamics from homogeneous (model 1) and age-structured (model 2) populations of white-winged parakeets with (A-B) no additional harvest (hl = 0%) and (C-D) 10% additional (uncompensated) harvest (hl = 10%). Here uncompensated additional harvest means that the population natality did not increase to compensate population decline due to additional harvest. Depicted states of infection are: susceptible (S), exposed (E), acutely-infected (IA), chronically-infected (IC) and recovered (R). Age-structured panels (B, D) show summed juvenile and adult parakeets for each infection state. See S1 Fig for separate juvenile and adult trajectories for model 2.
Fig 4.
Population decline during two years post Newcastle disease introduction.
Population decline in (A) homogeneous (model 1) and (B) age-structured (model 2) populations of white-winged parakeets with no additional harvest (hl = 0) and three additional, uncompensated harvest rates (h1; 0-blue, 2%-orange, 5%-black, and 10%-red). Here uncompensated additional harvest means that population natality did not increase to compensate the population decline due to additional harvest.
Fig 5.
Population decline during 100 years post Newcastle disease introduction.
Population decline in (A) homogeneous (model 1) and (B) age-structured (model 2) populations of white-winged parakeets with no additional harvest (hl = 0) and three additional uncompensated harvest rates (h1; 0-blue, 2%-orange, 5%-black, and 10%-red). Here uncompensated additional harvest means that population natality did not increase to compensate the population decline due to additional harvest.
Fig 6.
Influence of additional harvest (hl) on mean estimates of the basic reproduction number, R0.
Comparison of mean R0 estimates under assumptions of compensated (red) and uncompensated (blue) additional harvest rates for (A) homogeneous and (B) age-structured populations of white-winged parakeets following introduction of Newcastle disease. Here compensated and uncompensated additional harvest means respectively that population natality did and did not increase to compensate the population decline due to additional harvest.
Fig 7.
Spearman’s correlation coefficient values for models 1 and 2.
Spearman’s coefficients indicating the strength of the relationship between parameters of the (A) homogeneous (model 1) and (B) age-structured (model 2) models and the basic reproduction number (R0) with 10% additional harvest from 10,000 simulations. Only parameters with statistically significant coefficients are shown. See Table 1 for parameter descriptions.
Fig 8.
Classification trees for Newcastle disease.
Classification tree for disease-free (basic reproduction number, R0 < 1) or endemic (R0 ≥ 1) conditions of Newcastle disease (ND) in (A) homogeneous and (B) age-structured populations of white-winged parakeets. The rule for data partitioning is on top of each node. For example, in panel (A), the root node rule is the duration of the acute infectious stage (Dδ) less than 11.08 days; the subset of simulations satisfying this rule partitioned to the left daughter node and consecutively down the nodes. The terminal nodes represent disease-free (DF) or endemic (E) conditions for ND. See Table 1 for parameter descriptions.