The Status of Oyster Diseases

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The Status of Oyster Diseases in Chatham County,
Georgia.
Alan Power, Ph.D. Marine Extension
Service Shellfish Research Laboratory University
of Georgia 20 Ocean Science Circle Savannah, GA
31411-1011
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The Eastern Oyster Crassostrea virginica

• Gulf of St. Lawrence to Gulf of Mexico
• In southern range grows primarily intertidally
• Salinity range 15 to 30 ppt
• Form reefs

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Oyster Ecological Functions

• Keystone species critical to healthy coastal
  ecosystem
• Reefs provide essential fish habitat
• Water filtration
• Reduce shoreline erosion
• Food source

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Georgias Oyster Populations

• Oyster resources once immense
• 1908 landings highest in the country
• Populations depleted by
• Commercial fishing
• Habitat degradation
• Fishery virtually non-existent today

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Oyster Disease

• Pollution reduces health resulting in increased
  susceptibility to parasites and disease
• Environmental factors temperature salinity
• Recent drought encouraged the spread of
  Haplosporidium nelsoni (MSX) and Perkinsus
  marinus (dermo)
• Extensive mortalities in mid 80s due to disease
• No disease surveys in last 10 years
• Present status unknown, survey timely now that a
  prolonged drought period is ending.

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Haplosporidium nelsoni MSX

• MSX is a protozoan pathogen
• Lethal to oysters, not harful to humans
• Early infection found in gill tissue
• Spreads to digestive tissue and then all tissues
• Highest mortalities in the warm summer months
• Transmission mechanism unknown

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Perkinsus marinus Dermo

• Dermo is another intracellular parasite
• Infects oyster hemocytes not harmful to humans
• Transmission through the release of parasites
  from the disintegration of dead oysters. These
  are then ingested by uninfected oysters and
  invade the epithelium of the stomach and
  intestine.
• Again most mortalities occur in the warm summer
  months.

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Our Survey Goal Objectives

• Goal to provide a timely assessment of
  biological response to a rising coastal
  population, prolonged drought period and
  decreasing water quality
• Objectives (a) water quality assessment of
  Chatham County, (b) oyster health assessment at
  65 major oyster beds in the area, and (c)
  correlation analysis to assess relationship
  between water quality conditions and oyster
  disease prevalence and intensity.

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Project Value

• Oyster farming Recent interest in developing
  techniques to produce single oysters for half
  shell trade, more areas being tested by DNR to
  become classified for shellfish harvesting.
• G.E.O.R.G.I.A. Generating Enhanced Oyster
  Resources for Georgias Inshore Areas.
• A community based oyster shell recycling and reef
  restoration program.

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