Gray crab disease is caused by an amoeba, Paramoeba Two highly pathogenic protozoans are known to cause signficiant mortalities It appears be related to high salinities.
Other blue crabs, it is surprising that the parasite is only found at lowĬrabs from some locations). Transmitted via cannibalism and since as much as 25% of a blue crab’s diet is Microsporan is cottony in texture, and poorly flavored. Results in a condition known as "cotton crab." Crab meat infected with the The microsporan Ameson michaelis causes severe muscle lysis that Two parasites can affect the general quality of the meat of the blue crab. Prevalences in the region, their overall effect may be limited by the high In addition, while both egg predators can occur in relatively high Potential outbreaks in the region (as for C. Of the estuarine environment may limit the spread of the worm and curtail For the blue crab, the freshwater influence On other crab species, epizootics of nemertean worms have virtually wiped out anĮntire year’s broodstock (Shields et al., 1991 Kuris et al., 1991), and can The nemertean worm CarcinonemertesĬarcinophila can ingest relatively large numbers of eggs during development. It is widespread and can tolerate moderately low In some cases, most of the egg clutch can beĭestroyed by the fungus. Theįungus Lagenidium callinectes can assimilate large numbers of crabĮggs in infected clutches. Two egg parasites can be found in the high salinity waters of the region. Vibrio bacteria in blue crabs, yet the disease may have an effect on the Few studies have addressed transmission, or prevalence of the The bacterial pathogen invades the hemolymph through abrasions in theĬuticle of the crab, and multiplies in the nutrient-rich environment of theĬrab’s blood. Vibrio parahemolyticus has been documented in outbreaks in sheddingįacilities for soft-shell crab where it can be a significant source of Invertebrates are infected by or passively transport the disease agents. Vibrio bacteria are ubiquitous in the marine environment, and several Transmission in nature has notīeen examined, but the short duration of infection for RLV indicates that itĬould represent a significant problem to the soft-shell crab industry during Patent periods ranging from 2 weeks to 2 months. Just 3 days (Johnson & Bodammer, 1975)! The other pathogenic viruses had Short, and acute patent period infection experiments resulted in mortalities in
The reolike virus (RLV) may have an extremely Transmission experiments with the viral agents were undertaken via Handling), and often show signs of tremors or paralysis, or even blindness (CBV) Infected crabsĪre lethargic, susceptible to stress-induced mortality (e.g., capture, and The pathogenic viruses typically live in hemocytes, or epithelial cells,Īnd are associated with significant mortalities during outbreaks. While eight viruses have been reported from blue crabs (Johnson, 1983), fourĪre known pathogens documented in epizootics from Chesapeake Bay or Chincoteagueīay. In fact, we know little about the conditions that lead to the Of the epizootics (e.g., Sprague & Beckett, 1966, Johnson, 1976 Couch,ġ983). In most cases the causative agents were virtually unknown until the occurrence Outbreaks are localized to specific bays or regions, but widespread epizooticsĪre known to occur, especially along the seaside locations of the Eastern Shore. Several disease agents have occurred in outbreaks or epizootics in blue crabsįrom Maryland and Virginia ( Table 1). Introduction and Summary of Disease Agents The mass of cells in the center of the field represents the schizont. The plasmodia divide via budding to produce more plasmodia, and via schizogony to produce trophonts. The cells in the background are hemocytes. Vermiform plasmodium of Hematodinium perezi. 2 ndVirginia Eastern Shore Natural Resources Symposium, Outbreaks of parasitic diseases on the blue crab fishery of Virginia. This is in need of some updating and will soon be supplanted with a more
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