Mycobacterial Infection in Laboratory-Maintained Atlantic Menhaden

Abstract

Mycobacteriosis can be a chronic wasting disease found in many species of fish examined from wild-caught, cultured, and aquarium-reared populations. An Atlantic menhaden Brevoortia tyrannus with an open ulcer from a wild-caught, laboratory-maintained population was sampled for microbiology. Mycobacterium spp. was recovered from the ulcer and M. fortuitum complex was recovered from the spleen of this fish. Subsequently, 20 additional fish were subsampled from this population to determine the prevalence of the infection. Bacteriology samples were taken from the brain, liver, and kidney. Spleens were homogenized and plated on media enriched for mycobacterial growth, full necropsies were performed, and samples were taken for histology. Bacteriology results showed 100% of the fish in the subsample were infected with mycobacteria. Three species of mycobacteria were isolated from the spleen tissues: M. marinum, M. fortuitum complex, and M. gordonae. Histology results revealed that granulomas, characteristic of mycobacteriosis, were most prevalent in livers but were also found in spleens, posterior kidneys, and hearts. This report adds Atlantic menhaden to the list of species susceptible to mycobacteria.