Fungi of Penaeidae Boas 1880 and Pandalidae Dana 1852
'Black-gill disease' is caused by deuteromycete fungi belonging to the genus Fusarium (principally F. solani). The disease affects P. japonicus, P. duoraraum, P. setiferus, P. aztecus, P. vannamei, P. stylirostris and P. californiensis (Brock and Lightner, 1990) and can cause significant mortality. Under intense culture, over 90 cumulative mortalities of P. japonicus and P. californiensis may occur over 4-5 months (Lightner et al., 1979). Infections are initiated via epicuticle abrasion and...
Introduction
Some of the earliest records of mass mortalities of shellfish were caused by microbial disease agents, e.g. the phycomycete fungus, Ostracoblabe implexa, responsible for 'maladie du pied' in European oyster (Ostrea edulis) (Montauge, 1878) and the iridoviral agent of 'maladie des branchies' in Portuguese oysters (Crassostrea angulata) (Comps, 1988). Many excellent reviews cover the literature on microbial disease agents of shellfish (Lauckner, 1980, 1983 Sparks, 1985 Sindermann and Lightner,...
Cellular defence mechanisms
Pathogenesis and immunity in lobsters, shrimps, prawns, crabs and crayfish are, generally speaking, similar and are discussed together under the heading Crustacea. The initial response to tissue damage (traumatic or due to infection) is haemocyte infiltration. Perforations in the cuticle are sealed by plugging the opening with haemocytes. Subsequent repair involves envelopment of the exposed soft tissues by migrating epidermal cells and melanocytes (Fontaine and Lightner, 1973 Sparks, 1985). If...
Biomolecular factors
The mechanism of immunity and defence responses to microbial infections in shrimps, crabs and crayfish is less well understood than in other invertebrates. Lectin- or enzyme-mediated mechanisms are known to play a role in insect defences and may be involved in crustacean immunity (Soderhall and Unestam, 1979 Bang, 1983 Olafsen, 1988 Adams, 1991). Lightner and Redman (1977) clearly demonstrated the chemical link between phenol oxidases in the cirulating haemolymph and the melanization response...
Birnaviruslike viruses
A double-stranded ribonucleic acid (RNA) virus, with characteristics similar to infectious pancreatic necrosis virus (IPNV), was isolated from the digestive gland of diseased Tellina tenuis (Tellin clams) (Buchanan, 1973 Hill, 1976a) on bluegill fibroblast cell lines (Hill, 1976a,b Hill and Alderman, 1979). Tellina virus (TV) is a member of the Birnaviridae (bisegmented, double-stranded, RNA viruses) (Dobos et al., 1979), which includes IPNV (Francki et al, 1991). Similar viruses have also been...
Nonspecific techniques Tissue squash
Certain microbial infections can be detected in fresh tissue squashes, using light microscopy. Virions cannot be seen directly however, tissue pathology may allow presumptive diagnosis. For example, loss of the velar epithelium can be used for presumptive diagnosis of OVVD (Elston, 1989). Nuclear polyhedrosis viruses (NPV) (Baculoviridae) of shrimps and crabs can also be identified presumptively, using light microscopy. The spherical or polyhedral intranuclear occlusion bodies fluoresce under...
Gramnegative bacteria
A number of disease problems in bivalve hatcheries are attributed to Gramnegative bacteria (Walne, 1958 Tubiash et al., 1965, 1970 Elston et al., 1981, 1982 Lodeiros et al., 1987 Dungan and Elston, 1988 Dungan et al, 1989 Elston, 1989 Nicolas et al., 1992b), especially Vibrio spp. Although some have been identified to species (Vibrio anguillarum, V. alginolyticus and V. tubiashii), most are identified only to genus (Hada et al., 1984). Severity of infection is related to suboptimal growing...
Fungi of Brachyura Latreille 1803
Chitinolytic fungal disease ('black-mat syndrome') caused by Trichomaris invadens, was originally described as the coelomycete, Phoma fimeti (Van Hyning and Scarborough, 1973) and is the only ascomycete infection reported from crustaceans. The tanner crabs, Chionoecetes bairdi and, to a lesser extent, C. opiJio and C. tanneri (Sparks and Hibbits, 1979) are infected off Alaska (Sparks, 1985), British Columbia (Bower et aJ., 1994a) and the east coast of Newfoundland (Dr J. Brattey, Northwest...
Bacteria of Nephropidae Dana 1852 genera Astacus Camabrus Cherax Austropotamobius and Orconectes
The only rickettsial-like organism reported in crayfish infects Cherax quadricarinatus from freshwater streams and culture facilities in northern Australia (Ketterer et al., 1992). Mass mortalities are linked to basophilic, granular inclusions, which cause hyperplasia and hypertrophy of endothelial and interstitial cells of the gills and other organs. The inclusions consist of thin-walled microcolonies, containing rod-shaped, Rickettsia-like, organisms (0.16 mm x 0.5 mm). Poor water quality and...
Grampositive bacteria
One of the best-studied bacterial diseases of marine invertebrates is gaffkemia (or 'red-tail disease') of Homarus americanus and H. gammarus, (see reviews by Stewart, 1980, 1984, 1993, Sindermann, 1990 Brock and Lightner, 1990). Gaffkemia is caused by Aerococcus viridans var. homari (syn. Gaffkya homari and Pedicoccus homari) and causes problems primarily in captive lobsters. The sources of infection include wild lobsters and other decapod crustaceans, which can serve as reservoirs of...
Rickettsia Chlamydia and Mycoplasmalike organisms
To date, RLOs have been described from only two species of crabs, but asymptomatic infections most probably have a broad host distribution. An RLO isolated from Carcinus mediterraneus from the Mediterranean coast of France caused pathogenic lesions in the hepatopancreas, gill, gonad and intestinal connective tissue of experimentally inoculated crabs (Pappalardo and Bonami, 1980). Feulgen-positive microcolonies (10-20 mm in diameter), containing rod-shaped organisms (0.7 mm x 2 mm) with a plasma...
Fungi of Nephropidae Dana 1852 Genus Homarus Weber 1795
Three fungal diseases have been reported from captive lobsters. Lagenidium sp. (oomycete) infects cultured lobster (Homarus americanus and H. gammarus ( H. vulgaris)) larvae in California (Nilson et al., 1976) and appears to be related to Lagenidium callinectes in crabs and shrimps (Fisher, 1988c). The fungus penetrates the carapace of young lobsters and spreads through the soft tissues, giving them an opaque, milky appearance. Light-microscopy reveals dense networks of finely branched mycelia,...
Epibiont bacteria
Low levels of epibiont bacteria occur naturally on the surfaces of aquatic crustaceans and are usually controlled by preening. Since larval shrimp cannot preen, they are more susceptible to epibiont proliferation, which impedes feeding, respiration and swimming. Nutrient accumulation in holding facilities accelerates epibiont fouling, especially by species such as Leucothrix mucor, Thiothrixsp., Flexibacter spp., Cytophaga spp., Flavobacterium spp. (Lightner, 1988b) and a filamentous species...
Fungi of Cephalopoda Cuvier 1797
Polglase et al. (1984) described the first fungus from a cephalopod. Cladosporium sphaerospermum was isolated from experimentally induced wounds in the octopus, Eledone cirrhosa. Mycelia penetrated the underlying dermis and radiated out from the surface of the wound. The possibility that C. sphaerospermum is a secondary saprobiont was not ruled out (Polglase et al., 1984). Two thraustochytrid-like organisms, Schizochytrium sp. and Ulkenia ammoeboidea were associated with an ulcerative condition...
Culture of microorganisms
Multigeneration or self-replicating mollusc and shrimp cell lines have yet to be developed however, recent reports indicate progress in this area (Mialhe et aJ, 1988b Chen, 1990 Rosenthal and Diamant, 1990 Kleinschuster and Swink, 1992). Explants of cardiac tissue have been kept alive for up to 117 days (Tripp, 1963) and cell lines of heart tissue from C. gigas and O. eduJis have been subcultured for 4 days. Monolayer production from heart and mantle cells from C. virginica was enhanced by use...
Bacteria of Cephalopoda Cuvier 1797
Young octopuses held at high densities in recirculated sea water suffer severe bacterial ulceration (Hanlon et al., 1984). Erosion of the mantle epidermis destroys the underlying chromatophores, leaving bare, white patches. Subsequent necrosis of the underlying musculature and internal organs leads to death within as few as 4 days. Bacteria isolated from lesions on Octopus joubini and O. briareus were all Gram-negative Vibrio alginolyticus, V. damsela, V. parahaemolyticus, Pseudomonas stutzeri...
Fungal Infections Fungi of Bivalvia Linn 1758
The phycomycete fungus, Ostracoblabe implexa, is responsible for severe shell damage in European oysters O. edulis , known as maladie de la charni re 'hinge disease' , maladie du pied 'foot disease' erroneously , shell disease and Dutch shell disease Fig. 20.15 . Less severe infections occur in C. gigas, Fig. 20.15. Opposite a Conchiolin warts in the shell of Ostrea edulis infected by the fungus Ostracoblabe implexa 'shell disease' . Note lesions at the adductor muscle attachment point of the...
Husbandry practices
The principal method of disease control in hatcheries is destruction of the infected shellfish and disinfection of the tanks and equipment with which they were in contact Elston, 1990, 1993 . In some cases, however, early detection and removal of individuals with clinical signs may control pathogen proliferation or enhance effective chemotherapeutant treatment of remaining stocks see 'Treatment and protection' below . All prophylactic measures involve risk benefit examination of production...
Bacterial Infections Bacteria of Bivalvia Linn 1758
Rickettsia-, Chlamydia- and Mycoplasma-like organisms Bacteria belonging to the orders Rickettsiales, Chlamydiales and Mycoplasmatales class Mollicutes infect a wide range of bivalves and crustaceans Table 20.2 . With certain exceptions, described below, Rickettsiaceae are Gram-negative, intracytoplasmic, membrane-bound, oval to rod-shaped bacilli, measuring 0.3-0.6 mm x 0.8-2.0 mm. Chlamydiales are also Gram-negative, but have a complex developmental cycle, multiplying within cytoplasmic...
Fungi of Nephropidae Dana 1852 genera Astacus Pacifastacus Cambarus Cherax Austropotamobius and Orconectes
One of the best-known fungal diseases of crustaceans is crayfish plague Krebspest or Kraftpest or la peste or crayfish aphanomyciasis , caused by Aphanomyces astaci Saprolegniales . This fungus is common in North American crayfish Pacifastacus leniusculus and Procambarus clarkh , where it causes superficial lesions, but is not associated with epizootic mortality. In contrast, crayfish in Europe Astacus astacus, A. leptodactylus and A. pallipes have been decimated by A. astaci infections...
Chemotherapy
Chemotherapeutants have long been used in fin-fish aquaculture Meyer and Schnick, 1989 Michel and Alderman, 1992 however, there is increasing awareness of the risks associated with their indiscriminant or continuous application. These risks include drug-resistant pathogens, overdosage and impacts on the environment, consumer health and market perception and aquaculturist handling and economics . Moreover, increased restrictions on aquaculture imports between countries with non-complementary...
Bacteria of Gastropoda Cuvier 1797
Juvenile vibriosis in red abalone, Haliotis rufescens, from a hatchery in California Elston and Lockwood, 1983 and H. kamtschatkana from a hatchery in British Columbia Bower et al., 1994a was responsible for swollen patches of epipodial tissue, which became necrotic and ruptured. Small numbers of bacteria were detected on sloughed-off epithelium Elston and Lockwood, 1983 , as well as from the intramuscular vascular sinuses and along peripheral neurons. Nine isolates from the Californian...
Quarantine and disinfection
Quarantine is commonly used to control disease spread. Types of quarantine range from high-technology facilities, with automated fail-safe containment and treatment equipment, to tanks with disinfected effluent. The first documented quarantine for a shellfish disease was for Malpeque disease in American oysters, C. virginica from PEI, Canada, in 1915 and 1916. Although the cause of the mortalities was not known, oyster transplants out of the Malpeque Bay were prohibited geographical quarantine...
Viruses of uncertain affinities
A virus or group of viruses of undetermined affinity occur s in six penaeid species P. vannamei, P. stylirostris, P. monodon, P. semisulcatus, P. chinensis orientalis and P. japonicus , as well as four experimentally infected species Fig. 20.7. and Opposite a Yellow-head baculovirus YHB in the cytoplasm of an infected lymphoid organ in Penaeus monodon. Photograph courtesy of S. Boonyaratpalin. TEM, x 7700. b Gill lamellae of Penaeus monodon infected by YHB. Note aggregations of viral particles...
Baculoviral and baculoviruslike viruses
The first baculovirus described from shrimp was baculovirus penaei BP in Penaeus duorarum from Florida Couch, 1974a,b . J.-R. Bonami, L.D. Bruce, B.T. Poulos and D.V. Lightner unpublished, cited in Bruce et al., 1993 propose changing BP to 'PvSNPV' 'the most characterised variant, from Penaeus vannamei, in the singly enveloped nuclear polyhedrosis virus group' , in compliance with the guidelines for virus nomenclature designated by the International Committee on Taxonomy of Viruses. For the...
Histology
The standard disease-screening technique applied to shellfish is histology Howard and Smith, 1983 Bell and Lightner, 1988 Bucke, 1989 . Although frequently insufficient for species identification of microbial pathogens especially those with a non-specific host response , histology provides a useful record of infection foci and host response. The host-parasite interaction at the tissue and cellular level is essential for interpreting pathogenic effects. Furthermore, light microscopy is...
Baculoviruses and baculoviruslike viruses
A non-occluded baculovirus named Tau t , after the lagoon in southern France from which infected Mediterranean shore, Carcinus mediterraneus, were collected Pappalardo and Bonami, 1979 , induced 100 mortality in experimentally inoculated crabs Pappalardo et al., 1986 . Infections developed faster at 23 C than at 18 C and crabs fed infected tissues developed heavier infections than those which were inoculated. Clinical signs of Tau infections were non-specific increased lethargy, decreased...
Herpesviruslike viruses
Farley et al. 1972 found a herpes-like infection in the haemocytes of moribund American oysters, C. virginica, held in thermal effluent 28-30 C, within the temperature tolerance range of C. virginica from a power plant in Maine. Mortalities of 52 were attributed to this infection, which was characterized by Feulgen-positive nuclear inclusions in the haemocytes of all moribund specimens Fig. 20.1 . Similar inclusions were found in wild, apparently healthy, oysters at the site of collection...
Iridoviruslike viruses
The first viral disease recorded from bivalves was 'maladie des branchies' gill disease , which appeared in Portuguese oysters C. angulata in France in 1966 Marteil, 1969 . The disease spread throughout Atlantic populations of Portuguese oysters until stocks reached a non-exploitable level in the early 1970s. The gills of infected oysters demonstrated intense haemocyte infiltration, abscessing and necrosis. Iridovirus-like viral particles, subsequently named gill necrosis virus GNV Comps and...
