Perkinsus, a protistan parasite of abalone in Australia: A review

Perkinsus parasites are widespread in molluscs around the world. In 1985 and 1986, a die-back of greenlip abalone, Haliotis laevigata, occurred along part of the South Australian coast. Perkinsus olseni was abundant in H. laevigata from the die-back area and widespread around the Yorke Peninsula in other hosts. After the epizootic had passed, two attempts were made to repopulate the area by transplanting adult H. laevigata; the second attempt, in 1989, appears to have been successful. Laboratory experiments showed that abalone infected with P. olseni had a higher mortality rate than did uninfected abalone and that stress such as high temperature predisposed the abalone to disease. During winter, abalone appear able to contain and possibly eliminate the infection. Molecular studies have indicated that there is a single species of Perkinsus in Australia that is widespread in abalone and bivalves from the Great Barrier Reef and South Australia but is not found in molluscs in Tasmania. This parasite, P. olseni, is similar to P. atlanticus from Portugal but different from P. marinus in North America. P. olseni was shown to be highly infectious to a range of molluscs in the laboratory. P. marinus can be cultured in vitro; this will facilitate investigation into the susceptibility of the parasite to therapeutic agents, the mechanisms of host defence, and the affinities of Perkinsus parasites isolated from Australia and elsewhere.