Strains of Vibrio cholerae, both O1 and non-O1 serovars, were found to attach to the surfaces of live copepods maintained in natural water samples collected from the Chesapeake Bay and Bangladesh environs. The specificity of attachment of V. cholerae to live copepods was confirmed by scanning electron microscopy, which revealed that the oral region and egg sac were the most heavily colonized areas of the copepods. In addition, survival of V. cholerae in water was extended in the presence of live copepods. Attachment of viable V. cholerae cells to copepods killed by exposure to -60 degrees C was not observed. Furthermore, survival of V. cholerae was not as long in the presence of dead copepods as in the live copepod system. A strain of Vibrio parahaemolyticus was also seen to attach to copepod surfaces without effect on survival of the organism in water. The attachment of vibrios to copepods was concluded to be significant since strains of other bacteria, including Pseudomonas sp. and Escherichia coli, did not adhere to live or dead copepods. Attachment of V. cholerae to live copepods is suggested to be an important factor of the ecology of this species in the aquatic environment, as well as in the epidemiology of cholera, for which V. cholerae serovar O1 is the causative agent.

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BACKGROUNDUntil the late 1970s and early 1980s, Vibrio cholerae was believed to be highly host-adapted and incapable of surviving longer than a few hours or days outside the human intestine. This view, enunciated by Felsenfeld,' was that "some authors claimed that cholera vibrios may survive in water, particularly seawater, for as long as 2 months. This is, however, scarcely possible under natural conditions, if reinfection of the water does not take place." This perspective of cholera ecology dominated the literature since the organism was first identified by Robert Koch in 1884.2 For V. chohae the term ''survival" had been viewed to reflect a high degree of host-adaptation, ea., "cholera vibrios" being able to exist for only very short periods of time outside the human intestine. But Koch's speculation that multiplication takes place in river water, without any assistance, has proven to be prescient, since the most recent data show that toxigenic V. cholerae 01 exist for long periods in laboratory microcosm water.' In fact, the evidence accumulated over the ast decade shows that V. chohae is an tochthonous nature of V. choferae 0 1 is an important factor in the epidemiology of cholera, significantly so in endemic areas. Thus, the very early studies of V. cholerue, prior to 1970, were aimed at identifjring environmental conditions associated with unusual delays in the inevitable "death" of the "cholera vibrios," in order to establish the length of time after which an environment could be considered cholera-free, unless recontaminated with infected stool. The remarkable discoveries of the past decade have revealed the existence of the dormant or somnabulant ( i e . , viable but non-culturable) state into which V. cholerae 01 and V. cholerae non-01 enter in response to nutrient autochthonous inhabitant of brac L 'sh water and estuarine ~ystems.~ The aua The work reported here was supported,