Hepatopancreas Necrosis in the Caribbean spiny lobster, Panulirus argus

Hannah M. Bennett,1*+ Matt Griffin,3 Craig A. Pelton,4,5 Ruth Francis-Floyd,4 Jennifer Dill-Okubo,2,4

 1School of Forest, Fisheries, and Geomatic Sciences, University of Florida, Gainesville, Florida, 32603, USA; 2 Bronson Animal Disease Diagnostic Laboratory, Florida 34741; 3 College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, 39762, USA; 4 College of Veterinary Medicine, University of Florida, Gainesville, Florida, 32610, USA; 5 SEA LIFE Orlando Aquarium, Florida, 32819, USA 

ABSTRACT

A Caribbean spiny lobster, Panulirus argus was received for necropsy after increased fatalities in a local public aquarium. Mortalities occurred in a multi-species system and spanned multiple tanks connected to the same life support system. There was an absence of clinical signs and post-mortem decomposition limited investigation to an arbitrary individual, which was euthanized and submitted immediately for diagnostics. The Caribbean spiny lobster is named for the protective spines that span their body. The Caribbean spiny lobster fishery is exceptionally valuable generating over $450 million per year. Wild populations are largely affected by overfishing, but disease outbreaks have also been reported, including Panulirus argus Virus 1 (PaV1).

At necropsy there was no external shell disease or trauma, the hemolymph was mildly opaque and did not clot, and the hepatopancreas was tan to green with multifocal small, firm white foci. The lobster's gonads were immature and was sexed a female. Microscopic findings revealed significant multifocal necrosis of the hepatopancreas centered on myriad gram-negative bacteria. PaV1 polymerase chain reaction (PCR) was negative, but Vibrio harveyi was cultured from multiple organs, identified initially by MALDI-TOF MS and confirmed by MLSA gene sequencing. Susceptibility testing was conducted.  The genus Vibrio is salt-tolerant, found in temperate climates and commonly associated with human illness through the consumption of seafood. Vibrio spp. result in morbidity for many aquaculture animals and are the most frequently encountered pathogen of cultured shrimp. Vibrio harveyi causes necrosis of the striated tail muscle in shrimp, while several other Vibrio spp. are implicated in limp lobster disease and luminous vibriosis. In addition, toxins produced by the family Vibrionaceae produce clinical manifestations, such as hepatopancreatic necrosis disease (AHPND/EMS) in aquacultured shrimp, which is caused by plasmid mediated PirA and PirB genes carried by certain strains of Vibrio parahaemolyticus.  Since it has been reported that Vibrio harveyi isolates from marine organisms can have virulence-variation and genetic diversity with the production of toxins such as haemolysin and protease toxin, a PCR was performed but negative for the CTX gene. The hepatopancreas was sent to the University of Georgia for laser capture microdissection (LCMD) for confirmation of the bacterial sequence within the lesions. Genomic analysis is being conducted and we have partial sequences of gyrB, pyrH, recA, and rpoB.

In conclusion, this lobster had significant hepatopancreas necrosis, likely associated with Vibrio harveyi, which may produce toxins resulting in clinical morbidity similar to AHPND/EMS.  As Caribbean spiny lobsters continue to be used for consumption and aquariums, it is prudent to expand diagnostic techniques and to develop management strategies to reduce the incidence of infectious diseases.