An adult female captive-born Atlantic guitarfish (Rhinobatos lentiginosus) was found acutely moribund on exhibit and died soon after presentation. Abnormalities on necropsy were focal skin erythema on the tail, a small liver, many variably sized friable ovarian follicles, and coelomic effusion. Histologic exam revealed systemic bacterial embolization, yolk coelomitis and systemic mycobacteriosis with minimal associated inflammation and some mineralization. Bacterial culture of blood and coelomic effusion grew rapid-growing Mycobacterium sp. The coelomic effusion culture was further identified as Mycobacterium chelonae using PCR amplification and sequencing of the RNA polymerase subunit beta (rpoB) gene of isolated genomic DNA. Although common in teleosts, there have been no reports of mycobacteriosis in elasmobranchs until very recently, including a single Atlantic guitarfish case with splenic M. chelonae granulomas.1-3 Our case was an acute process with no granulomatous disease, with embolic lesions similar to those seen in syngnathids with mycobacteriosis. Mycobacteriosis is apparently uncommon to rare in elasmobranchs.4 Guitarfish may have greater susceptibility to mycobacteriosis than other elasmobranchs, and acute and chronic manifestations of the disease may exist in this species.
1. Anderson ET, Frasca S, Asakawa MG, Fatzinger MH, Johnson J, Marchetere K, Goodale L, Risatti GR, Harms CA. Splenic mycobacteriosis in an Atlantic guitarfish, Rhinobatos lentiginosus Garman. J Fish Dis. 2012;35:541–544.
2. Clarke EO, Dorn B, Boone A, Risatti G, Gilbert-Marcheterre K, Harms CA. Mycobacteriosis, Mycobacterium chelonae, in a captive yellow stingray (Urobatis jamaicensis). J Zoo Wildl Med. 2013;44:470–474.
3. Janse M, Kik MJ. Mycobacterium avium granulomas in a captive epaulette shark, Hemiscyllium ocellatum (Bonnaterre). J Fish Dis. 2012;35:935–940.
4. Garner MM. A retrospective study of disease in elasmobranchs. Vet Pathol. 2013;50:377–89.