Douglas Wait

Enteric Bacterial and Viral Pathogens and Indicator Bacteria in Hard Shell Clams

Enteric bacteria and virus levels were determined in hard shell clams, Mercenaria mercenaria , harvested from areas open or closed for commercial shellfishing on the basis of total coliform levels in water. Four pairs of open and closed stations were sampled seasonally over a 1-year period. Enteric viruses were isolated from 3 of 13 100-g clam samples from open beds and 6 of 15 samples from closed beds. Salmonella was found in 1 of 15 samples from closed areas, but not in any samples from open areas. No Shigella or Yersinia were isolated from clams taken from either open or closed beds. Levels of Vibrio parahaemolyticus , an indigenous estuarine microorganism, were similar in clams from open and closed areas. No statistically significant difference was found in the occurrence of enteric viruses in clams from open and closed areas. Product-moment correlations between concentrations of enteric viruses and bacteria in clams or water demonstrated no statistically significant correlations between virus concentrations in clams and total coliforms or fecal coliforms in water or total coliforms, fecal coliforms, fecal streptococci or aerobic plate counts in clams.

Isolation and Characterization of Circulating Type 1 Vaccine-Derived Poliovirus from Sewage and Stream Waters in Hispaniola

Twenty-one cases of acute flaccid paralysis (AFP) were reported on the island of Hispaniola in 2000. Laboratory analysis confirmed the presence of circulating vaccine-derived poliovirus (cVDPV) type 1 in stool samples obtained from patients. As a complement to the active search for cases of AFP, environmental sampling was conducted during November and December 2000, to test for cVDPV in sewage, streams, canals, and public latrines. Fifty-five environmental samples were obtained and analyzed for the presence of polioviruses by use of cell culture followed by neutralization and reverse-transcription polymerase chain reaction. Of the 23 positive samples, 10 tested positive for poliovirus type 1, 7 tested positive for poliovirus type 2, 5 tested positive for poliovirus type 3, and 1 tested positive for both poliovirus type 2 and type 3. By sequence analysis of the complete viral capsid gene 1 (VP1), a 2.1%-3.7% genetic sequence difference between 7 type 1 strains and Sabin type 1 vaccine strain was found. Phylogenetic analysis showed that these viruses are highly related to cVDPV isolated from clinical cases and form distinct subclusters related to geographic region. Our findings demonstrate a useful role for environmental surveillance of neurovirulent polioviruses in the overall polio eradication program.