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Butler Leads Project on Spread of Marine Pathogens

Mark Butler

Old Dominion University marine biologist Mark Butler leads a research team that has won $1.4 million in support from the National Science Foundation (NSF) to explore new evidence they have developed to explain the spread of a deadly viral disease among spiny lobsters in the Caribbean and waters off Florida.

Don Behringer, a researcher at the University of Florida who was a Ph.D. student of Butler's at ODU, is a co-principal investigator together with Jeff Shields of the Virginia Institute of Marine Science, and Claire Paris and Robert Cowen of the University of Miami.

The three-year grant, "Connectivity of Disease in Marine Ecosystems: Multi-scale Dynamics of a Viral Disease Infecting Caribbean Spiny Lobster," builds upon two previous NSF-funded projects in which the investigators have studied the dynamics and ecological consequences of the lobster virus known as PaV1 (Panulirus argus virus 1). Altogether, the NSF has invested nearly $2.5 million in their work on this problem.

Spiny lobsters support the most valuable fishery in the Caribbean, and the threat to them from PaV1 has hastened the need for scientific research to better explain how the virus is spread among distant populations, Butler said.

Recent research by the ODU scientist and his collaborators has found that many lobster postlarvae settling into coastal nurseries in Florida are already infected with PaV1.

"This latest grant from the NSF will allow us to examine this stunning new evidence that long-distance pathogen dispersal in the sea via infected larvae is possible," Butler said.

Scientists have long understood that pathogens spread much differently in marine systems than they do in terrestrial systems. In water they have no barriers to dispersal. "Yet the movement of pathogens in the sea and its importance to disease dynamics in marine metapopulations is virtually unstudied," according to Butler.

What is known is that pathogens free-living in the water are subject to rapid dilution and have no means of targeting distant hosts.

An "underappreciated mechanism for dispersal," as Butler calls it, involves infected larvae. Most marine animals produce larvae that float as plankton in the sea and can potentially be carried for great distances. If they are infected by a virus "these larval vectors would provide an efficient mechanism for distributing pathogens at high concentrations directly into habitats where hosts dwell," he said.

Butler and research collaborators described the PaV1 virus in 1999 and since then have studied its pathology, epidemiology, transmission and effects on juvenile lobster populations in the Florida Keys. "Our focus has been on local pathogen-host dynamics, but PaV1 infections in lobsters are now confirmed in distant areas of the Caribbean such as Belize, Mexico and St. Croix," Butler said. "These regions are demographically linked only by dispersing larvae that spend more than six months in the open ocean."

The researchers believe that their findings will have an impact beyond spiny lobster-PaV1 associations, providing a better understanding of how dispersal of infectious agents affects the spread and maintenance of disease in marine populations in general.

Research findings will be shared with fishermen and resource managers in Florida and the Caribbean via workshops and consultations, Butler said.

He said the work with spiny lobsters in the Caribbean complements another project he and colleagues at VIMS have undertaken-with $2.25 million in support from the NSF-to study blue crab disease dynamics on the Virginia Eastern Shore.

Chris Platsoucas, dean of the ODU College of Sciences, noted that Butler has the distinction of having two decades of continuous research support from NSF. "This is a remarkable accomplishment," the dean said. "The competition for these awards is stiff, and for Professor Butler to have been an NSF investigator for 20 straight years is a tribute to the quality of his research."

This article was posted on: September 21, 2009

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