Pervasive shedding of Mycobacterium tuberculosis complex at the wildlife-livestock interface revealed by hierarchical models

This study investigated shedding by animal tuberculosis maintenance host species, using hierarchical models to quantify Mycobacterium tuberculosis complex in swabs collected from oral, nasal, and faecal routes of naturally infected hosts. Replicated quantitative real-time PCR of MTBC DNA concentration in pooled swabs were analysed using zero-inflated Poisson N-mixture models to correct for the species-specific sensitivity of the method. The detection probability in cattle was lower than in wild boar (Sus scrofa), red deer (Cervus elaphus), fallow deer (Dama dama), or Eurasian badger (Meles meles) swabs. The abundance was mainly insensitive to the covariates included in the state model (species, sex, age, MTBC genotype, Normalised Difference Vegetation Index - NDVI, and its interaction with species). Shedding was higher in wild boar (2.87 ± 0.73 colony-forming units (cfu)/ml) and red deer (2.04 ± 0.95 cfu/ml) and lower in badger (1.27 ± 1.66 cfu/ml). Such differences, although small, can affect the species-specific epidemiological roles in multi-host communities.