Wellfleet Harbor and Dermo

PICTURE AND NOTES

Overview

– What is the Oyster disease, Dermo?– What do we know /don’t know about Dermo?– How does Dermo effect the oyster?– What does this mean for Wellfleet Harbor?– Questions

Oyster Disease

• Dermo Perkinsus marinus• MSX Haplosporidium nelsoni• JOD/ROD Roseovarius oyster disease

Dermo Background

• Dermo originally thought to be a fungus, reclassified as a protozoan parasite Perkinsus marinus in 1978. (Ewart and Ford, 1993)

• Originally Dermo was restricted to southern waters • Usually spread to the North (Cape Cod) by introducing infected

seed

Parasite / Host Interaction

What happens when the oyster is infected with Dermo:

• Oysters ingest cells infected with Dermo from water-column

• In vivo, Dermo occurs as a unicellular trophozoite displacing the nucleus of cells appearing as signet ring (Perkins, 1996)

• Cells are most commonly found in the gut, connective tissues, digestive glands, and the gill

• As infection grows shellfish become emaciated, ceases growing, and eventually die

• Oysters die releasing infected cells back into the water column to be filtered by neighboring oysters

Environmental Factors

• Since Dermo has been partially cultured since the 1960s, there is a wealth of information on physiological needs, life cycle stages, and growth characterisitics. (Ray, 1966)

• For Dermo, temperature and salinity are known to be the dominant environmental variables dictating the suvival prevalence, intensity, and influence of the host parasite interaction (Soniat 1985; Soniat and Gauthier 1989; Chu and La Peyre 1993)

Temperature

Dermo’s prevalence and intensity increases with increasing water temperature

Abnormally warm winters have been shown to correlate with a greater proportion of overwintering cells (Makin, 1962; Quik and Mackin, 1971)

Wellfleet Temp: June, July, August, and September > 20 c (Mass DMF, 1972)

Temperature Dermo Response

0° C Infections decline

15-19.9° C Infections decline

20° C Threshold

20.1-24.9 ° C Intensifies / Mortality

25° C + Rapid multiplication / MM

Salinity

• Dermo increases in prevalence and intensity as salinity (ppt) increases

• 9 ppt or < infections remain low (Mackin, 1956; Scott et. al 1985)

• 12 ppt is required for full epizootics (Ewart and Ford, 1993)

• 15 ppt have high intensity of infections and mortality (Mackin, 1956)

• Wellfleet salinity: 28-34 ppt, Herring River 18-33 ppt

(Mass DMF, 1972)

Seasonal Cycles

• Intensity and persistence of Dermo exhibits seasonal cycles. Increases throughout summer and a peak in late summer /early fall coinciding with the seasonal fluctuations in temperature. Mortalities are usually seen in late summer early fall (Ford and Tripp, 1996).

Other influences on Dermo infections

• Density

• Stress

• Age

Testing for Dermo

Ray’s Fluid Thioglcollate Media Assay- 1952

Gold standard due to sensitivity, speed, and expense– Shuck oyster + cut slice from mantle/ and end organ

of digestive tract– Place in RFTM media for 5-10 days– Media causes trophozoites to form sporangia and

enlarge, forming thick walled hypnospores that don’t replicate

– Slice tissue even thinner and stain with iodine. Place under microscope and observe.

– Perkinsus visible as perfect spheres stained black

Slide of Infected Oyster

• Perkinsus spores stained with lugols solution

Mackin Scale

0 1 2 3 4 5

Uninfected --------Heavy infection

Light infections (1 or 2) seen microscopically, counting spores

3 visible to naked eye

Heavier infections (4 and 5), majority of tissue will appear blue black in color (Mackin, 1952; Markey, 2007)

Dermo in Wellfleet Harbor

• Dermo first appeared in Wellfleet around the same time as MSX. Mid to late 70sish. (Anonymous, pers com)

• It is generally accepted that cold conditions reduce the impact of, and unless there is extensive global climate warming, these northern extensions are not likely to remain (Eastern Biological Review Team, 2007)

(Ewart and Ford, 1993)

Future of Dermo in Wellfleet Harbor/ Solutions?

• As global warming increases so will temperature optimizing conditions for a Dermo outbreak

• Reducing the (3 in.) legal limit for aquaculture raised animals will reduce numbers of susceptible animals

• No cure for Dermo so removal of infected animals is the best management practice

• Monitoring program? – May-September– 10 locations in harbor– 25 samples per location per month

– $1 per sample plus labor (plus microscope)

$$

SummaryDermo poses no health risk to

humans

Years of research we know many things about Dermo (Temperature, Salinity, Seasonal Cycles)

If this warming trend continues we are likely to see more outbreaks of Dermo

There is no Dermo resistant strain, only Dermo tolerant

A monitoring program should be economically feasible if needed

Belding, D. 1909. The Works of David L. Belding M.D. Re-Print Cape Cod Cooperative Extension of Barnstable County (2004).

Bellantoni, N.F. & Harty, c. 2001. The Eastern Oyster. Changing Uses from an Archaeological Perspective. CRM 24, no. 4 (2001): 30.

Burreson, E.M., & Ragone-Calvo, L.M. 1996. Epizootiology of Perkinsus marinus disease of oysters in Chesapeake Bay, with emphasis on data since 1985. Journal of Shellfish Research 15 (1): 17-34.

Curley, J.R., Lawton, R.P., Whittaker, D.K; and J.M. Hickey. 1972. A Study of the Marine Resources of Wellfleet Harbor. Massachusetts Division of Marine Fisheries Number 12.

Eastern Oyster Biological Review Team. 2007. Status Review of the Eastern Oyster. Report to the National Marine Fisheries Service, Northeast Regional Office. February 16, 2007. 105 p

Ewart, J.W., and Ford, S.E. 1993. History and Impact of MSX and Dermo Diseases. Oyster Stocks in the Northeast Region. Northeast Regional Aquaculture Center Fact Sheet No. 200.

Ford, S.E. and Tripp, M.R. 1996. Diseases and Defense Mechanisms. In. Kenedy VS Newell RI, EbleAE (eds) The Eastern Oyster, Crassostrea virginica. Maryland Sea Grant, College Park, MD, pp 581-660.

Galtsoff, P.S. 194. The American Oyster. Bull Fish Wildl Service. US Department of Interior. Vol 64: 480.Gomez, M. Personal Communication 11/14/08Harvell et al. 1999. Emerging Marine Disease- Climate Links and Anthropogenic Factors. Science. Vol 285.Leavitt, Dale. Personal Communication. 11/5/08Mackin, J.G. 1956. Dermocystidium marinum and salinity. Proc National Shellfish Association 46: 116-128.Markey, Kathryn 2007. Traditional and Novel Diagnostic Techniques For Three Diseases Affecting the Eastern Oyster,

Crassostrea virginicaMckenzie, Clyde. 2007. Causes Underlying the Historical Decline in Eastern Oyster (Crassostrea Virginica Gmelin, 1791)

Landings.Perkins, F.O., 1996. The Structure of Perkinsus marinus (Mackin, Owen and Collier, 1950) Levine, 1978 with comments on

taxonomy and phylogeny of Perkinsus marinus spp. Journal of Shellfish Research 15:67-87.Quick, J.A., Jr., & Mackin, J.G. 1971. Oyster parasitism by Labyrinthomyxa marina inFlorida, Fla. Dept. Nat. Resources.

Mar.Res. Lab. Prof. Pap. Ser. No. 13. 55 p. Ray, S.M. 1952. A Culture Technique for the diagnosis of infections with Dermocystidium marinum, Mackin, Collier, in

oysters. Science. 166:360-361.Soniat, T.M. 1985. Changes in levels of infection by Perkinsus marinus, with special references to interaction of

temperature and salinity on parasitism. Northeast Gulf Science. 7:171-174.Soniat, T.M., Gauthier, J.D. 1989. The prevalence and intensity of Perkinsus marinus from the mid northern gulf of Mexico,

with comments on the relationship of the oyster parasite to temperature and salinity. Tul Stud Zool Bot 27 21-27

References

Thank You

Dad, Mom, Bill and Alice, Barbara, Kate, Dale, Marta, Scotty, Clint, Sky, and Belding