Epizootic mortality in the pilchard Sardinops sagax neopilchardus in Australia and New Zealand in 1995. I. Pathology and epizootiology

A large-scale epizootic occurred in the Australasian pilchard Sardinops sagax neopilchardus between March and September 1995 over more than 5000 km of the Australian coastline and 500 km of the New Zealand coastline. Affected fish died within a few minutes of clinical signs of respiratory distress and death was associated with hypoxaemia and hypercapnea. Significant lesions were confined to the gills and comprised acute to subacute inflammation followed by bizarre epithelial hypertrophy and hyperplasia. The lesions were initially focal but progressed to become generalised over about 4 d. Pathological changes in affected fish from western Australia, eastern Australia and New Zealand were similar, suggesting a common aetiology The lesions were unlike those associated with ichthyotoxic algae, siliceous algae, physicochemical factors, fungi, bacteria, dinoflagellates, amoebae, other protozoa and metazoa. A herpesvirus was consistently present in gills of affected fish and absent from unaffected pilchards and is proposed as the aetiological agent The rate of spread of the mortality front (approximately 30 km d -1) in relation to the migration rate of pilchards and prevailing currents suggests that a vector was involved. The disease may have been newly introduced into Australian waters

A New Species of Mugilicola Parasitic on South African Elvers (Copepoda, Therodamasidae)

A new species of parasitic copepod belonging to the genus Mugilicola Tripathi, I960 (CYCLOPOIDA: THERODAMASIDAE) is described. The copepods were embedded in the buccal cavity of elvers of Anguilla mossambica caught in South African rivers

Bonamia and other aquatic parasites of importance to New Zealand

The degree to which the parasites and diseases of New Zealand fish and shellfish have been studied reflects the commercial importance of the host concerned and the severity of infection. As New Zealand aquaculture is largely based on farmed bivalve molluscs and salmonids, most attention has been given to these groups. However, by far the most serious parasitic disease of bivalves, Bonamia sp. in flat oysters (Tiostrea chilensis), is primarily a problem in wild fisheries. The importance of Bonamia sp. is such that this review will deal largely with bonamiasis but will also mention other parasites of New Zealand fish and shellfish. Crustaceans have received very little attention, because only rock lobsters (Jasus edwardsii) support a substantial fishery, and there are no known parasitic diseases of this species. Marine fishes have been poorly surveyed for parasites, but the presence of Anisakis spp. larvae and cestode plerocercae in fillets are of increasing public health concern

Ergasilus rotundicorpus n. sp. (Copepoda: Ergasilidae) from Siganus guttatus (BLOCH) in the Philippines

A new species of Ergasilus is described and illustrated from the gills of juvenile (c. 70 mm total length) Siganus guttatus raared in a Philippine fish farm. Of 15 fish examined, all were infested and nine had concurrent lymphocystis infections

Observations on the blood of the Australian lungfish, neoceratodus forsteri Kief ft II. enzyme cytochemistry of blood cells, peritoneal macrophages and melano-macrophages

Peroxidase, alkaline and acid phosphatases, esterases, neutral proteases and PAS reactivity were examined in the peripheral blood leucocytes and peritoneal and melano-macrophages of the Australian lungfish. Eosinophils contained partly cyanide-inhibited peroxidase, and monocytes and blasts showed weak peroxidase staining, but other blood leucocytes were negative. Only neutrophils and heterophils showed alkaline phosphatase reactivity, but acid phosphatase was ubiquitous in leucocytes and macrophages. Alpha-naphthyl acetate esterase and naphthol AS-D chloroacetate esterase occurred, and were often strong, in all cell types but particularly neutrophils; a-naphthyl butyrate esterase was only observed in monocytes, macrophages, and in the latter stained moderately to strongly. Beta-glucuronidase, β-galactosidase and N-acetyl-β-glucosaminidase were also confined to the monocyte/macrophage lineage. The neutral protease acetyl-L-tyrosine-α-naphthyl esterase was moderate to strong in monocytes and macrophages. All leucocytes except monocytes stained moderately to strongly by pas. Leucocytes showed similarities in enzyme content to those of elasmobranchs, but less so to those of teleosts. They also resembled leucocytes of mammals, particularly in monocyte-macrophage enzyme profiles, in the heterogeneous response for peroxidase, and the restriction of a-naphthyl butyrate esterase to that lineage

Ultrastructure of sporulation in Haplosporidium armoricanum

An ultrastructural study was carried out on the tissues of an oyster (Ostrea edulis), heavily infected with Haplosporidium armoricanum (van Banning, 1977), that had been fixed in Carson¿s fixative. The well-fixed tissues revealed details of sporulation and of the spores, which had not been previously reported from H. armoricanum. These include the initial presence of sparse haplosporosomes after thickening of the plasma membrane in early sporonts, division of sporont nuclei by multiple fission, cup-like indentations in the nuclear surface associated with putative nuclear material in both the sporonts and spores, and cytoplasmic multi-vesicular bodies in the cytoplasm of sporonts and spores. The spore wall and operculum were formed from a light matrix that occurred in short cisternae of smooth endoplasmic reticulum in the episporoplasm, and parallel bundles of microfibrils were present in some spores. Spores were rarely bi-nucleate with the nuclei occurring as a diplokaryon, with putative nuclear material at the junction of the 2 nuclei. Nuclear membrane-bound Golgi (NM-BG) cisternae were common in spores, and they appeared to synthesise a light granular material into lysosome-like granules. Dense bodies similar to those reported from H. lusitanicum, H. pickfordi and H. monforti occurred in, or outside, the peripheral endosporoplasm, which was closely apposed to the spore wall. Spore haplosporosomes were frequently axehead-shaped, more like those of H. costale than those previously reported from H. armoricanum, and in some haplosporosomes there was a small round lucent patch with a dark point near the centre of the lucent patch. Overall, H. armoricanum appears to be closely related to H. costale and Bonamia spp. Although the endosporoplasm of H. armoricanum has NM-BG and it resembles the uni-nucleate stage, it appears to be unlikely that they are the same, as the axehead-shaped haplosporosomes of the spore differ considerably from the spherical haplosporosomes of vegetative stages

Fusobacterium necrophorum leukotoxoid vaccine for prevention of liver abscesses

The efficacy of Fusobacterium necrophorum crude leukotoxoid vaccine to immunize and protect steers against experimentally induced liver abscesses was evaluated. The vaccine consisted of cell-free culture supernatant of a high leukotoxin-producing strain of F. necrophorum, inactivated with formalin and homogenized with an oil emulsion adjuvant. Vaccine was injected subcutaneously on days 0 and 21. Blood samples were collected weekly to monitor immune response. Three weeks after the second vaccination, steers were injected intraportally with F. necrophorum culture to induce liver abscesses. Three weeks later (day 63), steers were euthanatized and necropsied; livers were examined, and protection was assessed. Anti-leukotoxin antibody titers in the control steers generally did not differ from the baseline (week 0) titers. The titers in the vaccinated groups increased, more so after the second injection, and the increase was generally dose dependent. At necropsy, all steers in the control group had liver abscesses. In the vaccinated groups, two out of five steers in the 1.0 ml group and one each in the 2.0, 5.0, and 2.25 ml (concentrated) groups had liver abscesses. The difference suggests a protective effect of antileukotoxin antibodies against experimentally induced liver abscesses