Statistical methods
REGRESSION
The data statistically analyzed using Minitab for windows (Minitab Inc., 2013, Pennsylvania, USA), the continues data represented as mean (SD) or median (IQR), while categorical data as number and percentage, independent t-test, or Kruskal Wallis test was used to compare between parametric data, while Chi square test was used with non parametric data. Logistic regression model with and without adjustment for age, sex and bird exposure was used to find the independent predictors for PHT. All tests were two sided, 