Table 3 Scenario-specific input variables used to estimate disease costs (schistosomiasis-related disease effects and the reaction to the disease)
Variable | Unit | Notation | Cattle | Sheep and goats | Explanation | References | ||
|---|---|---|---|---|---|---|---|---|
Scenario 1 | Scenario 2 | Scenario 1 | Scenario 2 | |||||
Average duration of clinical illness before animal is sold | d | DCIS | 14.0 | 7.0 | 14.0 | 7.0 | Number of days animals stay in the herd/flock before being sold; this reflects the observation and decision time of the farmer. It is assumed that they will observe the animal to see whether it recovers and then sell it. It is also assumed that those sold are sold early to get a better market price, when they still have some condition | Assumption |
Proportion of sick animals tested | % | PTS | Pert (0.24, 0.31, 0.36) | 0.00 | Pert (0.24, 0.3, 0.36) | 0.00 | Only a handful of the animals showing clinical signs will be tested. Those who have health-seeking behaviour might not be able to afford the cost of testing for all sick animals | Assumption based on literature [13] |
Proportion of tested animals that are treated | % | PTT | Pert (0.40, 0.50, 0.60) | 0.00 | Pert (0.40, 0.50, 0.60) | 0.00 | Not all farmers who test will be able to afford the treatment costs for all the animals; hence only some will treat | Assumption |
Proportion of untested animals that are treated | % | PUTT | Pert (0.64, 0.80, 0.96) | 0.00 | Pert (0.64, 0.80, 0.96) | 0.00 | It is assumed that farmers with health-seeking behaviour will treat some of the sick animals | Assumption |
Proportion of sick animals sold among those not treated | % | PSUT | Pert (0.90, 0.95, 1.00) | Pert (0.90, 0.95, 1.00) | Pert (0.90, 0.95, 1.00) | Pert (0.90, 0.95, 1.00) | Farmers reported in the survey that they sell all types of animals (young, adult, old, production and breeding animals). Many also indicated selling animals when they are sick. It is assumed that farmers will sell both the treated and untreated sick animals | Survey and assumption |
Proportion of sick animals sold that are replaced | % | PSAR | Pert (0.56, 0.70, 0.84) | Pert (0.40, 0.50, 0.60) | Pert (0.56, 0.70, 0.84) | Pert (0.40, 0.50, 0.60) | Because farmers like to maintain their herds (their asset), it is assumed that a proportion of the animals sold will be replaced. Because farmers in scenario 2 have more animals to sell, their replacement rate is lower, as they will not have the means to replace so many animals | Assumption |
Rate of reduced lactation duration in sick females (due to disease) | Year−1 | RLF | Pert (0.032, 0.04, 0.048) | Pert (0.032, 0.04, 0.048) | Pert (0.10, 0.12, 0.15) | Pert (0.10, 0.12, 0.15) | The lactation duration of sick females will be shortened | |
Rate of reduced milk yield in sick females (due to disease) | Year−1 | RMY | Pert (0.08, 0.1, 0.12) | Pert (0.08, 0.10, 0.12) | Pert (0.08, 0.10, 0.12) | Pert (0.08, 0.10, 0.12) | The milk yield of sick females will be reduced | Survey, FGD |
Mortality rate young animal among those sick and not sold | Year−1 | MtY | Pert (0.032, 0.04, 0.048) | Pert (0.032, 0.04, 0.048) | Pert (0.40, 0.50, 0.60) | Pert (0.40, 0.50, 0.60) | Information by respondents and expert opinion. Mortality due to schistosomiasis in cattle/sheep/goats is low in regular production years | Survey, expert opinion |
Mortality rate adult animal among those sick and not sold | Year−1 | MtA | Pert (0.032, 0.04, 0.048) | Pert (0.032, 0.04, 0.048) | Pert (0.40, 0.50, 0.60) | Pert (0.40, 0.50, 0.60) | ||