Fatal coinfection by Mycobacterium fortuitum and Epicoccum sp. with concurrent severe coccidial enteritis in an olive ridley sea turtle (Lepidochelys olivacea)

Abstract Sea turtles are susceptible to opportunistic infections, particularly when debilitated, injured, or exposed to environmental stressors. Although nontuberculous mycobacteria are increasingly recognized as emerging pathogens in marine wildlife, documented cases in sea turtles remain limited, and coinfections involving mycobacteria and uncommon environmental fungi are rarely reported. Here, we describe a fatal multisystemic disease involving Mycobacterium fortuitum infection, Epicoccum sp.-associated coelomitis, and severe coccidial enteritis in an adult olive ridley sea turtle ( Lepidochelys olivacea ) stranded in Southeastern Brazil. The turtle was admitted with marked emaciation, dehydration, and lethargy and died six days after admission despite supportive care and antimicrobial therapy. Necropsy revealed multiple disseminated granulomas over the serosal surfaces of the coelomic viscera, along with pneumonia, hepatitis, cystitis, orchitis, and severe enteritis. Histopathological examination demonstrated granulocytic coelomitis with abundant intralesional septate fungal hyphae, necrosis, and aggregates of unidentified bacterial bacilli. Severe coccidial enteritis associated with intralesional bacilli was also observed. Culture and molecular analyses identified M. fortuitum from tissue samples, while sequencing of fungal DNA recovered from fresh and formalin-fixed tissues identified Epicoccum sp. These findings support a complex multisystemic disease process characterized by mycobacterial infection, opportunistic fungal coelomitis, and severe coccidial enteritis. Chronic debilitation and severe coccidial enteritis may have predisposed the turtle to systemic M. fortuitum infection, with Epicoccum sp. subsequently acting as a secondary opportunistic invader. This case reinforces the pathogenic potential of M. fortuitum in free-ranging sea turtles and contributes to the growing recognition of nontuberculous mycobacteria as relevant pathogens in marine wildlife. In addition, the detection of Epicoccum sp. expands the known host range and pathological spectrum of this rarely reported opportunistic fungus.