Fusarium solani Species Complex in a Collection of Captive American Horseshoe Crabs (Limulus polyphemus)
American Association of Zoo Veterinarians Conference 2013
Kathryn A. Tuxbury1, MS, DVM; Gillian C. Shaw2, MS, DVM; Richard J. Montali2, DVM, DACVP, DACZM; Leigh Ann Clayton1, DVM, DABVP (Avian, Reptile/Amphibian); Nicole P. Kwiatkowski3, MS; Michael J. Dykstra4, MS, PhD; Joseph L. Mankowski2,3, DVM, PhD, DACVP
1Department of Animal Health, National Aquarium, Baltimore, MD, USA; 2Department of Molecular and Comparative Pathobiology, Johns Hopkins University, Baltimore, MD, USA; 3The Johns Hopkins Microbiology Laboratory, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; 4Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA


Captive American horseshoe crabs (Limulus polyphemus) at the National Aquarium, Baltimore presented with severe shell and gill lesions over a 3-year period (2006 to 2009). Carapace lesions were located on both the dorsal and ventral prosoma and opisthosoma. Carapace lesions included multifocal circular areas of tan discoloration, ulcerations, and/or pitting lesions extending from superficial to full thickness. Gill lesions involved both the book gill cover and individual book gill leaflets and included multifocal circular areas of tan discoloration, tan to off-white opaque proliferative lesions, and/or areas of black discoloration. Histopathology revealed septate, irregularly branched fungal hyphae throughout the thickened and irregular cuticle of the carapace with associated amebocytic inflammation, and occasional penetration into subcuticular tissues. Book gill leaflets were infiltrated by fungal hyphae and contained necrotic debris and amebocytes. Thirty-nine animals had histopathologic analyses performed with 38 (97.4%) having evidence of fungal hyphae. Fungal cultures of carapace and gill lesions were attempted in 26 tissue samples from 15 individuals and grew in 13 samples (50%), with ten cultures (76.9%) having successful genus identification. Fusarium sp. was identified in eight of the ten cultures (80%). Fusarium solani species complex was identified in six of these cultures via polymerase chain reaction amplification of two different ribosomal specific sequences of isolated fungal DNA. Histopathology revealed fungal disease was more prevalent than fungal cultures indicated and was a major cause of morbidity and mortality in this collection. Based on anecdotal reports from other facilities, the condition may be common in captive American horseshoe crabs.


Speaker Information
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Kathryn A. Tuxbury, MS, DVM
Department of Animal Health
National Aquarium
Baltimore, MD, USA

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