Sample collection
Wild ducks from the Lerma marshes and the surrounding backyard farms were sampled during the winter and the early spring season 2016 – 2017. Each wild bird species was identified based on the descriptions provided by Howell & Webb (2010) and classified according to Clements et al. (2019). The sample selection was done by a convenience sampling method. Cloacal swabs from 597 hunter-harvested wild ducks, nasal swabs from 175 pigs, as well as cloacal and oropharyngeal swabs from 103 poultry (hens, cocks, ducks, geese, and turkeys) were collected and stored in cryovials containing 1 ml of Brain Heart Infusion (BHI) broth and 1ml of Eagle’s Minimum Essential Medium (EMEM) in wild duck/poultry and pig samples, respectively. The biological samples were kept refrigerated at 4 °C during transportation and stored at −80 °C until analysis.