Mycobacterial vaccination of fish and human tuberculin skin test reactivity: a testable One Health interface.

Screening with tuberculin remains widely used in humans and livestock for detecting mycobacterial immune sensitization, but tuberculin skin test (TST) interpretation is influenced by Bacillus Calmette-Guérin vaccination, environmental non-tuberculous mycobacteria (NTM), cutoff selection, and epidemiological context. The TST uses purified protein derivative (PPD), a complex mycobacterial antigen preparation, to elicit delayed-type hypersensitivity measured as local skin induration. Aquaculture vaccination is established for farmed fish, whereas vaccines targeting fish mycobacteriosis remain largely experimental, including BCG, attenuated or heat-inactivated mycobacteria, DNA vaccines, mycolic acids, and defined antigen combinations. This Perspective asks whether experimental mycobacterial vaccination of fish could plausibly influence human TST interpretation in occupationally exposed aquaculture workers. Such an interaction would require antigenic overlap with PPD, environmental release or persistence of mycobacterial material linked to vaccination, repeated worker exposure through water, biofilms, fish tissues, surfaces, or skin microtrauma, immune sensitization or amplification, and an induration shift sufficient to alter classification at operational cutoffs. The article defines this as a testable One Health interface and proposes construct-level antigen mapping, environmental monitoring around vaccination events, and prospective worker studies using continuous TST measurement with parallel IGRA testing.