Researcher questions shellfish standards 



In 1973. 263 people in Houston. Texas, and 15 people in 

 Calhoun. Georgia caught infectious hepatitis after all of 

 them had eaten oysters harvested from the lower Mississippi 

 River. The oysters were virally contaminated. Yet according 

 to the bacteriological standards set by the National Shellfish 

 Sanitation Program, the oysters were safe for consumption. 



Deduction? The standards are not adequate indicators of 

 viral contamination in shellfish. Answer? Better tests and 

 more research are needed. Enter: Mark Sobsey, one of sev- 

 eral scientists around the country working to improve shell- 

 fish sanitation. 



Sobsey. a UNC Sea Grant researcher and an associate 

 professor in the department of environmental sciences and 

 engineering at the University of North Carolina at 

 Chapel Hill, has 

 been conducting 

 research since 1974 

 to improve shellfish 

 standards and learn 



more about the vi- 

 ral contamination 

 in oysters and 

 clams. 



How do oysters 

 and clams become 

 contaminated? Sob- 

 sey says that 

 frequently sewage 

 treatment plants 

 and malfunctioning 

 septic tanks allow 

 partially treated or 

 untreated sewage to 

 flow or seep into 



shellfishing waters. Fecal wastes in this sewage con- 

 tain bacteria and often enteric or intestinal viruses 

 such as those causing infectious hepatitis and gas- 

 troenteritis. The shellfish pick up these viruses and 

 bacteria as they feed on suspended particles in the 

 water. The viruses can, in turn, be passed to people 

 when they eat raw or cooked oysters or clams. 



How do we know if oysters are contaminated? 

 They don't necessarily look or taste different. Areas 

 are surveyed for waste sources and tests must be 

 run on the shellfish or their harvesting waters to de- 

 termine the level of total or fecal coliform bacteria. If 

 the bacterial levels are high, the shellfish are un- 

 marketable; if they are low. the shellfish are fit for 

 consumption. Or are they? Not always. Sobsey says. 

 He points to the hepatitis outbreak in Texas and 

 Georgia, other documented viral outbreaks, and his 

 own research to make his point — bacteria counts are 

 not reliable indicators of viral contamination. 



In 1974 at Baylor College of Medicine in 

 Houston. Sobsey began developing a method that 

 directly detected and measured the presence of vi- 

 ruses in oysters. When he moved to North Carolina 

 he continued, through Sea Grant funding, to im- 

 prove his methods and expand them to include viral 



detection in clams. Using a blender, centrifuge, filters and 

 other simple laboratory equipment, Sobsey is able to recov- 

 er enteric viruses from oysters. Now other scientists through- 

 out the country have adopted his detection method, with 

 some variations of their own. The Food and Drug Adminis- 

 tration is currently testing methods used at various labora- 

 tories, including Sobsey's, to see which is the most accurate. 



Using his methods of viral detection and the older meth- 

 ods for bacterial detection, Sobsey has been testing the rela- 

 tionship between viral and bacterial contamination in shell- 

 fish, water and sediment. He has set up testing stations at 

 various intervals downstream from a sewage treatment plant 

 on the North Carolina coast. 



"So far, we've found no consistent relationship be- 

 tween virus and 

 bacteria levels," 

 Sobsey said. 

 "Sometimes we 

 have oysters with 



ICLOSED SHELLFISH AREA 



SHELLFISH FROM THIS AREA MAY 

 ICAUSE SERIOUS ILLNESS IF EATEN 



N.C. COMM I SPORTS FISHERIES 



a high virus count 

 yet a low bacteria 

 level. Other times 

 we have just the 

 opposite. How can 

 we use these bac- 

 terial standards 

 to measure viral 

 quality of the 

 shellfish if they 

 can't even indicate 

 ■ i viral presence?" 



^^^^^^^^^^^^^^^^^^^^^^^^^B ! he 

 ^^^^ ^^^^^^^^^^^^^^^^^^^^^^ Sobsey has 



found that the re- 



' ; * y lationship between water, sediment and shellfish is in- 

 j H consistent. Oysters taken from a testing area, for exam- 

 ple, may contain viruses, while the water and sediment 

 taken from the same test area may show no viral con- 

 tent. It is inconsistencies like these that leave scientists 

 puzzled, and Sobsey is the first to say that more tests 

 are needed before any conclusions can be made. 



When an oyster or a clam is virally contaminated, 

 will it remain unfit for eating until it dies? No it does 

 not. Oysters and clams are tidy creatures. Once placed 

 in clean water, they will purge themselves of contam- 

 ination. Fishermen are allowed to relay oysters and 

 clams from contaminated waters to clean waters, and 

 then harvest the shellfish when the cleansing process is 

 completed. 



Although shellfish clean themselves of contami- 

 nants, the cleansing rates seem to vary during the year. 

 Throughout 1979, Sobsey conducted relay experi- 

 ments with oysters to find out when they flushed out 

 contaminants most quickly. He would experimentally 

 place them in large baskets in clean water. In several 

 30-day periods, oysters were removed periodically to 

 see how fast they were eliminating viruses and bacteria. 

 Sobsey found that in winter months when water 

 Continued on next page 



temperatures are low, the oysters were 

 only modest housekeepers. After three 

 days in clean water, 5.5 percent of the 

 viruses remained in the oysters; after 

 30 days .006 percent of virus remained. 

 The oysters tested in April and May. 

 however, did their spring cleaning at 

 faster rates. Only .04 percent of the 

 viruses remained after three days and 

 after thirty days .005 percent 

 remained. Sobsey also tested for bac- 

 terial elimination and found similar 

 cleansing rates. 



Sobsey expected the oysters to 

 eliminate viruses and bacteria at faster 

 and faster rates as the water tem- 

 perature rose. But the oysters became 

 lazy in hot weather. 



"I was surprised", says Sobsey. 

 "The viral elimination dropped off 

 drastically when water temperatures 

 were high, and I am not sure why." 

 Sobsey says the warmer water could 

 cause the oyster to become extremely 

 sluggish and therefore reduce the rate 

 at which they flush water through 

 their bodies. Or the viruses could 

 become sequestered in the shellfish 

 tissue because of changes in the 

 shellfish physiology during spawning. 



Mark Sobsey at work 



Sobsey intends to continue his relay 

 experiments this year. 



In the relay experiments, Sobsey 

 again found the inconsistent relation- 

 ship between viruses and bacteria. 

 During the summer months, when 



viruses were persistent in the oysters, 

 bacteria were not. Bacterial elimina- 

 tion in oysters during summer con- 

 tinued at similar rates as in the spring 

 tests. These findings led Sobsey to 

 question how fast the shellfish became 

 contaminated with viruses and bac- 

 teria, in which body organs the con- 

 taminants settled, and how conditions 

 like temperature, salinity and tur- 

 bidity affected how long the bacteria 

 and viruses persisted. This year, Sob- 

 sey and graduate students will be try- 

 ing to answer these questions. The 

 answers could have implications for 

 regulations governing shellfish relay. 



As development continues along our 

 nation's coastlines, more pollution is 

 being dumped into our bays, rivers and 

 sounds. This pollution is contaminat- 

 ing thousands of acres of shellfish 

 growing waters. One-fifth of North 

 Carolina's shellfishing waters have 

 been closed. Will more shellfishing 

 waters need to be closed? Or once the 

 tests for contaminants are improved, 

 will some waters be closed while others 

 are re-opened? The work of Sobsey and 

 others may soon help answer these 

 questions. 



Pollution hits Brunswick County fishermen hard 



In Brunswick County, numbers tell 

 a sad story. The county has 22,500 

 acres of shellfish waters, and 18,830 of 

 them, or 83.5 percent, are closed 

 because of pollution — pollution from 

 sewage treatment plants, malfunction- 

 ing septic tanks, farms, drainage areas, 

 construction sites and industry. 



Many long-time Brunswick County 

 shellfishermen are hanging up their 

 gear for other occupations or moving 

 to other counties because of the 

 problem, says Loyd Ward, president of 

 the Brunswick County Commercial 

 Fishermen's Association, a 550- 

 member association organized to draw 

 attention to the fishermen's plight. 



"Out county is a disaster area," he 

 says. "And if something isn't done in 

 the next two years, the seafood in- 

 dustry will become non-existent in 

 Brunswick County." 



Officials aren't as pessimistic, but 

 everyone agrees the problem is serious. 

 The N.C. Department of Natural 

 Resources and Community Develop- 

 ment has developed a ten-point "ac- 

 tion plan" for the county. 



Among other things, the plan calls 

 for relaying oysters from polluted to 

 non-polluted waters and depositing 

 empty shells or cultch to make beds on 

 which the spat can attach themselves. 

 The plan asks for careful monitoring 

 by the state Division of Marine 

 Fisheries and the Shellfish Sanitation 

 Division to allow conditional openings 

 when coliform counts meet FDA stan- 

 dards and for a study to be conducted 

 into opening some inlets so estuarine 

 waters could better be flushed by tidal 

 fluctuations. 



The plan also suggests a study be 

 made by the Environmental Protec- 

 tion Agency to see what effect sewage 

 disposal along South Carolina's Grand 

 Strand has on North Carolina waters. 

 In a 1972 study, the EPA found some 

 of Brunswick County's problems com- 

 ing from inadequate sewage disposal 

 along the Grand Strand. Since then, 

 some improvements have been made 

 and an update is needed. 



Brunswick County fishermen, 

 however, aren't the only ones suffering. 

 In nearby New Hanover County, 58 



percent of the shellfish waters are 

 closed. But Fentress "Red" Munden. 

 shellfish coordinator for the state Divi- 

 sion of Marine Fisheries, offers some 

 hope. In 1974, 668,335 acres of es- 

 tuarine waters were closed, he said. In 

 1979, the acreage had decreased to 

 419.676. 



Michael Marshall, a shellfish 

 biologist with the Division of Marine 

 Fisheries, says the state is not only 

 helping Brunswick County, but other 

 counties as well. "Last year, we spread 

 200,000 bushels of cultch material from 

 Manteo to the South Carolina line," he 

 says. And in addition to relaying con- 

 taminated shellfish, the state also 

 transfers undersized shellfish to better 

 waters. Marshall says the division calls 

 its oyster programs "oyster rehabilita- 

 tion." 



Marshall says the state also allows 

 fishermen to do their own relaying 

 from polluted waters to clean waters as 

 long as they obtain a permit, lease ap- 

 proved bottom areas and meet state re- 

 quirements for leasing and relaying. 



