Eight-year monitoring of Mycobacterium avium subsp. paratuberculosis (MAP) infection in a herd of farmed sika deer (Cervus nippon) following known pasture contamination

We report on the 8-year close monitoring of a small sika deer herd on year-round grazing to investigate MAP transmission after a subclinically MAP infected stag had been inadvertently introduced. Whole genome sequencing identified the MAP isolate as Type C (cattle) strain. The infection status of all animals from the herd (n = 36) was investigated by MAP liquid culture on faeces (n=36), ileocaecal lymph nodes (n=33) and ileum samples (n=29). Further ELISA on serum samples (n=29) was conducted and representative samples of ileum and ileocaecal lymph nodes were examined by histopathology (n=36). Despite identifying the stag as a moderate and low shedder on two occasions, none of the other deer got infected over the 8 years of monitoring. This suggests that a subclinically infected sika deer may pose a lower risk for transmission of MAP than anticipated and raises the question of other possible sources to initiate disease in deer herds.