Hematodinium-Like Disease of Dungeness Crabs

crustacean Protozoa Hematodinium-like Disease of Dungeness Crabs

I. Causative Agent and Disease developmental stages if confirmed to be Obligate parasitic dinoflagellates Hematodinium sp. that belong to the genus Hematodinium sp. are in the protozoan phylum Alveo- V. Diagnosis lata, subphylum Dinoflagellida, order Stained blood smears contain myriad Syndinida and family Syndiniceae. numbers of apparent prespore stages, A major feature of classification for some of which have dinokaryon type all dinoflagellates is the biflagellated condensed chromosomes in V-shaped grooved dinospore stage. Hematodimium configuration. Tissues were not available parasites have been described from for further diagnostic analysis. several species of crustaceans, certain fishes and cephalopods. In crustaceans VI. Prognosis for Host the type species is H. perezi parasitizing The single parasitized crab was one the European shore crab. All Hema- of several being held in crowded 10 todinium described from crustaceans foot circular tanks for a size at maturity parasitize the hemolymph causing study. Minor mortality, beginning in systemic disease and mortality affecting early July, occurred in the captive crab at least 26 species of crustacean hosts in groups, some of which was due to stress- Europe, Australia and North America caused bacterial septicemia while other including many commercially important mortality was reportedly caused by this crab species and 13 species of benthic Hematodinium-like parasite. amphipods. VII. Human Health Significance II. Host Species There are no zoonotic human health A Hematodinium-like parasite was concerns regarding dinoflagellate para- observed in a single captive subadult sitism in crabs. However, parasitized Dungeness crab collected from the crabs often have an unpalatable flavor waters of Kodiak Island, Alaska in and undesirable meat texture. mid-May of 2003. It is the only known case of dinoflagellate parasitism in the Dungeness crab on record in the Pacific Northwest.

III. Clinical Signs Clinical signs include lethargy fol- lowed by death associated with milky white hemolymph and grossly abnormal viscera characterized by pallid color and a white viscous exudate.

IV. Transmission The mode of transmission is un- known but likely complex (see bitter crab disease section) involving several

90 91 crustacean Protozoa

Milky-white viscera and exudate of a Dungeness crab parasitized by a Hematodinium- like organism



Stained hemolymph smear of parasitized Dungeness crab showing Hematodinium-like prespores with dinokaryon type condensed chromosomes in V-shaped configuration (arrow)

90 91