The white band disease type II pathogen in Puerto Rico
The white band disease type I (WBD-I) epizootic event of the early 1980’s resulted in significant changes in the structure and composition of coral communities throughout the wider Caribbean. The disease decimated populations of acroporid corals throughout their geographic distribution and it is still affecting the surviving and recovering populations of these corals in a number of localities in the wider Caribbean. The putative pathogen for this syndrome (WBD-I) was never identified. A second pattern of white band was described later as white band type II (WBD-II). A potential pathogen named Vibrio charchariae was identified but Koch’s postulates were never fulfilled. In this work, we present results of a preliminary approach to confirm the identity of the pathogen of WBD-II. During the fall months of 2004, samples of Acropora cervicornis with signs of WBD-II were collected from a small population in Mario reef, an isolated patch reef off La Parguera, southwest coast of Puerto Rico. Bacteria extracted from these samples were isolated in TCBS agar, grown in Glycerol Seawater agar, and then used to inoculate separated, healthy-looking colonies of the same population in the same reef. Isolation, culture, and inoculations of bacteria were conducted under controlled conditions within hours of collection, and no microorganisms that were not already in the reef community were introduced with these experiments. Some of the newly inoculated colonies developed the disease signs within 24 hr. These were subsequently sampled and bacterial re-isolated to be identified, thus complying with the first steps to fulfill Koch’s postulates for this disease. Rates of advance of the disease signs varied between 0.5 and 2 cm/day. Preliminary analyses indicated that the potential cause of WBD-II is a Vibrio species very close to Vibrio harveyi, a synonymy of V. charchariae. All inoculated coral colonies that developed the signs of WBD-II, behaved as the naturally infected colonies, and all of them showed no signs of the disease after two months of the inoculation when water temperatures dropped due to winter in the area. Rev. Biol. Trop. 54 (Suppl. 3): 59-67. Epub 2007 Jan. 15.
Keywords: White Band Disease Type II, Acropora cervicornis, Vibrio harveyi, Vibrio charchariae, Koch’s postulates, field Inoculations