ALBERT

Notes: An intranuclear microsporidium is described from hemoblastic cells of the chinook salmon, Oncorhynchus tshawytscha. The infection is associated with an acute anemia in the fish. Up to 47% of the hemoblast nuclei were infected in anemic fish. The organisms, found only in spleen and kidney tissues, were 1–2 μm in diameter and consisted of vegetative and early sporulation forms. This microsporidium differs from known species which parasitize fish in its tissue location; however, the absence of mature spores and other life cycle stages precludes determination of its precise taxonomic identity.

Notes: . Sphaerospores were found among three species of fish examined from waters known to be enzootic for proliferative kidney disease (PKD) of salmonids. They were detected in the renal tubules of both hatchery-reared rainbow trout (Salmo gairdneri) exposed to the infectious stage of PKD and in chubs (Gila bicolor) in the headwaters of a hatchery where PKD is enzootic. Sticklebacks (Gasterosteus aculeatus) collected near net pens where Pacific salmon had experienced a PKD epizootic were also found to harbor sphaerospores in the lumen of the kidney tubules. The latter two host species contained developmental stages of a myxosporidan in the blood and in the lumen of the kidney tubules which are similar to those of PKX, the causative agent of PKD in salmonid fish. The sphaerospores observed in the rainbow trout are the first to be observed in this species. The similarity to previously observed developmental stages, rarity, and presence of these sphaerospores in salmonid fish from a hatchery where PKD is enzootic suggest that they are the most mature stage of the PKX myxosporidan yet observed.

Notes: A previously unknown virus was isolated from juvenile Atlantic salmon (Salmo salar) reared in fresh water. The virus induced syncytia in CHSE-214 cells at 10–20°C. Optimum replication occurred at 15°C. Virions, purified from infected CHSE-214 cells, were hexagonal to round with a mean diameter of 39.5 run (n = 20 SD = 0.32 nm). Virions did not possess an envelope as shown by resistance to chloroform treatments. Replication was not appreciaby inhibited by 50 pg/d 5-bromo-2'-deoxyuridine indicating that the virus has a RNA genome. Waterborne exposures and intraperitoneal injections of the virus into juvenile Atlantic salmon did not cause mortality nor was virus detectable at 33 and 76 d post-exposure. Similar results were obtained when rainbow trout (Oncorhyncbhus mykiss) were exposed to waterborne virus.〈section xml:id="abs1-2"〉〈title type="main"〉ZusamrnenfassungEin kleiner RNA-Virus, vom Atlantischen Lachs (Salmo salar) isoliertEin bisher unbekannter Virus wurde von Jungtieren des Atlantischen Lachses (Salmo salar) isoliert, die im Süßwasser aufgezogen wurden. Der Virus induzierte Synzytem in den CHSE-214-Zellen bei 10–20°C. Oprimale Vermehrung trat bei 15°C auf. Virionen, die gereinigt aus infizienen CHSE-214-Zellen isoliert wurden, waren hexagonal bis rund, mit einem Durchmesser von 39,5 nm (n=20; SD=0,32 μm). Die Virionen besaßen keine Hülle, wie durch die Resistenz gegenüber Chloroform nachgewiesen wurde. Die Vermehrung wurde durch 50 μg/ml 5-bromo-2'-deoxyuridine nicht nennenswert beeinträchtigt, was darauf schließen läßt, daß der Virus ein RNA-Genom besitzt. Exposition von Junglachsen gegenüber virushaltigem Wasser und intra-peritonale Injektion des Virus hat keinerlei Sterblichkeit verursacht. Auch konnte der Virus in den Fischen 33 und 76 Tage nach der Behandlung nicht nachgewiesen werden. ähnliche Ergebnisse wurden mit Regenbogenforellen (Oncorhynchus mykiss erzielt, die virushdtigem Wasser ausgeserzt waren.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméUn petit virus RNA isolé sur le saumon atlantique (Salmo salar)Un virus auparavant inconnu a été isolé sur le saumon juvénile (Salmo salar) élevé en eau douce. Le virus provoquait des syncytíums dans les cellules CHSE-214 sà 10–20°C. Une réplication optimum avait lieu sà 15°C. Les virions, purifiés des cellules CHSE-214 infectées, étaient de forme hexaonale sà ronde avec un diamètre moyen de 39,5 nm (n=20 SD4,32 nm). Les virions ne possédaient pas d' enveloppe comme la résistance aux traitemenu chloroformes l' a montré. La réplication n' a pas été inhibée de faqçon appréciable avec 50 μg/ml 5-bromo-2'-déoxyuridine, ce qui montre que le virus a un génome RNA. Des expositions sà l' eau infectée et des injections intrapéritonéales du virus chez le saumon atlantique juvénile ne causaient pas de mortaité et le virus n' était pas détectable aprés un délai de 33 et 76 jours apés l'exposition. Des résultats semblables ont été obtenus lorsque la truite (Oncorhynchus mykiss) a été exposée sà un virus transporté par l' eau.

Notes: Abstract. Inflammatory bacteraemia was found in 27–31% of Pacific oysters in two bays over 2 years in Puget Sound, Washington, USA. Mantle discolouration and raised yellow to green nodules are associated with the disease in 52% and 85% of the observed cases, respectively. The disease is caused by systemically distributed, branching. Gram-positive, acid-fast bacteria suggestive of an actinomycete. Clusters of the bacteria elicit a marked inflammatory response. Glycogenic degeneration of host vesicular cells occurs in the advanced infections and results in the formation of the characteristic nodules comprised of lipid filled cells. The disease is, thus, significant to the health of individual oysters and also appears to be an important factor in the historically observed phenomenon of summer mortality in certain areas of Puget Sound.

Notes: Infections of Ichthyophonus hoferi, a cosmopolitan parasite of marine fish, have recently been reported in rockfish, Sebastes spp., from the north-eastern Pacific. Because I. hoferi also infects Pacific herring, Clupea pallasi Valenciennes, and salmonids in this region, we wanted to determine if Ichthyophonus parasites from rockfishes, Pacific herring and chinook salmon, Oncorhynchus tshawytscha (Walbaum), were the same. Small subunit ribosomal deoxyribonucleic acid sequence data revealed two haplotypes that were fixed among host species in geographic sympatry, one from rockfish and the other from both Pacific herring and salmon. These isolated populations of Ichthyophonus could be part of the same species that are ecologically separated because of host behaviours, or they could be distinct species that are host specific. Dietary patterns of the hosts indicate that ecological separation among hosts is possible, but the presence of distinct species may better explain the observed Ichthyophonus haplotype association with host species.

Notes: The use of fumagillin-DCH, a natural product of Aspergillus fumigatus, has proven successful for the control of microsporidian infections, including Nucleospora salmonis Hedrick, Groff & Baxa (Hedrick, Groff & Baxa 1991) and Loma salmonae (Putz, Hoffmann & Dunbar) (Kent & Dawe 1994). Fumagillin has also been used to treat various myxosporean diseases of fishes, including proliferative kidney disease (PKD), which is caused by the PKX organism (Molnár, Baska & Székely 1987; Hedrick, Groff, Foley & McDowell 1988; Székely, Molnár & Baska 1988; Wishkovsky, Groff, Laurén, Toth & Hedrick 1990; Yokoyama, Ogawa & Wakabayashi 1990; El-Matbouli & Hoffmann 1991; Sitjá-Bobadilla & Alvarez-Pellitero 1992; Higgins & Kent 1996). An analogue of fumagillin, TNP-470, has been shown to be effective in in vitro studies against the mammalian microsporidian pathogens Encephalitozoon intestinalis (Cali, Kotler & Orenstein), Vittaforma corneae (Shadduck, Meccoli, Davis & Font) (Didier 1997), E. cuniculi Levaditi, Nicolau & Schoen and E. hellem Didier, Didier, Freidberg, Stenson, Orenstein, Yee, Tio, Davis, Vossbrinck, Millichamp & Shadduck (Coyle, Kent, Tanowitz, Wittner & Weiss 1998). Higgins, Kent, Moran, Weiss & Dawe (1998) tested TNP-470 against two microsporidian diseases of salmonids, N. salmonis and L. salmonae, and showed a significant reduction in parasitism after oral treatment with 0.1 or 1.0 mg kg-1 fish day-1 for 5 weeks. Therefore, the present authors investigated the efficacy of TNP-470 against the PKX myxosporean in naturally exposed sockeye salmon, Oncorhynchus nerka (Walbaum). This host was chosen as it has been found to be particularly susceptible to the infection.

Notes: The results of comparative immunohisto-chemical staining studies with two lectin probes, GS-I and SBA, and five monoclonal antibodies raised against the PKX myxosporean are presented. In order to investigate the postulated link between PKX and Sphaerospora spp., the lectins and monoclonal antibodies were tested against PKX, Sphaerospora renicola, Sphaerospora oncorhynchi, Sphaerospora elegam, Sphaerospora truttae and Sphaero-spora sp. from Atlantic salmon, Salmo salar L., and Ceratomyxa shasta. SBA appears a useful tool for tbe diagnosis of all Sphaerospora spp. infections and was also positive for C. shasta. GS-I and monoclonal antibodies (12, C5, D4 and A3) appear to be specific for both the extrasporogonic and sporogonic stages of PKX. Although MabB4 was raised to PKX, it appears to stain some of the sporogonic stages of Sphaerospora spp. but not C. shasta. The results of the lectin and monoclonal staining of PKX and Sphaerospora oncorhynchi indicated that further work was required to prove or disprove the hypothesis that PKX and S, oncorhynchi are the same organism.