Table 1. Model input parameters, values, and sources.
| Parameter | Value | Source |
|---|---|---|
| Transmission Model | ||
| Probabilities (% per month) | ||
| Developing chronic Chagas disease given indeterminate phase (% over 20 years) | 25 | [58] |
| Proportion time spent in domestic settings for humans (%) | 90 | Assumption |
| Proportion time spent in domestic settings for dogs (%) | 23 | [59] |
| Transmission to dogs given bite of infected vector (% per bite) | 0.00274 | Calibrated |
| Transmission to humans given bite of infected vector (% per bite) | 0.00012 | Calibrated |
| Transmission from acute stage to triatomine (% per bite)° | 49.28 | Calibrated |
| Transmission from indeterminate/chronic stage to triatomine (% per bite)° | 1.62 | Calibrated |
| Transmission from dog to triatomine (% per bite)° | 19.00 | Calibrated |
| Triatomine feeding proportion for humans in domestic settings | 91.7 | Calibrated |
| Triatomine feeding proportion for humans in peridomestic settings | 46.7 | Calibrated |
| Ratio of triatomine feeding proportion for chickens:dogs in peridomestic settings‡ | 51.7:48.3 | Calibrated |
| Congenital transmission given birth from infected mother (% per birth)° | 16.7 | Calibrated |
| Relative prevalence of women of reproductive age as compared to the general population | 93.3 | Calibrated |
| Transmission via infected blood transfusion or organ transplant° | 14.7 | Calibrated |
| Human receiving a blood transfusion or organ donation |
0.0042 | Calibrated |
| Benznidazole treatment efficacy (per treatment) | ||
| Acute stage | 71.5 | [60] |
| Indeterminate stage | 57.6 | [60] |
| Rates (per month) | ||
| Triatomine biting rate | 6 | [61] |
| Triatomine birth rate (eggs hatching per month)^ | 32.13 | [62] |
| Triatomine death rate* | 0.036959468 | [62, 63] |
| Triatomine in peridomestic habitat moves to domestic habitat | 0.0205936 | [64] |
| Triatomine in domestic habitat moves to peridomestic habitat | 0.0205936 | [64] |
| Human death rate†† | 0.001111111 | [65] |
| Chagas related mortality during the acute stage | 0.007178811 | [66] |
| Movement from the acute phase to the indeterminate phase | 0.04688 | [58, 66] |
| Movement from the indeterminate phase to chronic phase | 0.001198675 | [58, 67] |
| Rate of Chagas-related mortality during chronic stage | 0.00680 | [68] |
| Dog death rate†† | 0.013888889 | [69] |
| Numbers | ||
| Number of humans | 2,000 | Assumption |
| Number of dogs | = NH/3.24 | [59, 70] |
| Number of chickens† | = (NH/4)*0.5 | [71] |
| Carrying capacity (per person) | 50 | Assumption |
| Clinical and Economic Model | ||
| Costs (2018 $US) | ||
| Hourly wage | 6.82 | [72] |
| Case identification overhead | 1.92 | [50] |
| Diagnostic tests | 10.80 | [73] |
| Case identification laboratory work | 1.81 | [50] |
| Benznidazole (100mg) | 0.14–0.33 | [74] |
| Adverse events (antihistamines) | 2.19 (0.77–5.25) | [75] |
| Chronic Chagas case (annual healthcare, Lee) | 457 (247–759) | [15] |
| Chronic Chagas case (annual societal, Lee) | 4,847 (4,262–5,294) | [15] |
| Chronic Chagas case, undiagnosed (annual societal, Ramsey) | 19,857 (17,871–21,843) | [1] |
| Chronic Chagas case, diagnosed (annual societal, Ramsey) | 29,359 (26,423–32,296) | [1] |
| Probabilities (%) | ||
| Interrupt treatment/adverse events | 11.25 (1.06) | [76, 77] |
| Disability-adjusted life years (DALYs) | ||
| Chronic Chagas disease (annual) | 0.51 (0.38–0.6) | [15] |
| Numbers | ||
| Case identification personnel hours | 1.54 | [50] |
| Patient weight (kg) | 52.1 (2–188) | [40] |
| Treatment duration (days) | 60 | |
‡Calibrated values for remainder of feeding proportion after humans, where chicken proportion is higher than for dogs following the literature[81, 82]
^Assumes maximum number of eggs laid per day and egg hatching rate (90%) from literature[62] and assumes 7% of vector population are adult females
*Calculated using the adult life span and days from egg to adult to determine total life span
††Model assumes constant populations, such that human birth rate is equal to natural death rate and Chagas death rate and dog birth rate is same as death rate
†Assumes 50% of households have chickens and that there are 4 to 5 persons per household