Pancreas disease (PD) of farmed Atlantic salmon Salmo salar has been recognised in Scotland, Ireland, Norway, the USA, France and Spaln and can cause severe economlc loss Thls paper reports the ~solatlon, flom PD-affected f~s h , of a virus with physicochemlcal characteristics and moiphology resembling members of the Togavirldae When Inoculated into Atlantic salmon post-smolts it causes pathological changes in pancreas h e a~t and muscle tlssues which are ind~stinguishable from those piesent in fleld outbreaks of PD I t is proposed that the virus be named salmon pancreas disease vlrus (SPDV) KEY WORDS. Pancreas d~s e a s e . PD Atlantlc salmon Toga-like SPDV

Experimental pancreas disease in Atlantic salmonSalmo salar post-smolts induced b y salmon pancreas disease virus (SPDV) ' ABSTRACT: Disease-free Atlantic salmon Salrno salarpost-smolts (mean weight 87 g) were maintained in a flow-through ozone-sterilized sea water system at 12 to 15'C and ambient salinity. One hundred fish were intraperitoneally inoculated with 0.1 m1 of salmon pancreas disease virus (SPDV) of a titre 107 TCIDSO ml-' Fifty fin-clipped uninoculated smolts were placed in-contact in the same tank. One hundred fish were kept in another tank as controls and were inoc.ulated with a lysate from un-infected Chinook salmon embryo (CHSE-214) cell cultures. Blood and tissues for virus isolation, serum neutralisation tests and histological examination were taken at intervals up to 42 days post inoculation (dpi). Virus was re-isolated from SPDV inoculated smolts at 7, 10. 15 and 21 dpi and in-contact fish at 14 and 21 dpi. Neutralising antibody was first detected in the inoculated fish at 10 dpi and in the in-contact fish 11 d later. Clinical signs and microscopic lesions indistinguishable from naturally occurring pancreas disease (PD) were observed in SPDV inoculated and in-contact smolts. No lesions were detected in the negative controls. These results provide strong evidence that SPDV is the etiologic agent of PD in farmed Atlantic salmon in Ireland.

Using the equine infectious anemia virus (EIAV) lentivirus model system, we previously demonstrated protective effects of broadly neutralizing immune plasma in young horses (foals) with severe combined immunodeficiency (SCID). However, in vivo selection of a neutralization-resistant envelope variant occurred. Here, we determined the protective effects of purified immunoglobulin with more potent broadly neutralizing activity. Overall, protection correlated with the breadth and potency of neutralizing activity in vitro. Four of five SCID foals were completely protected against homologous challenge, while partial protection occurred following heterologous challenge. These results support the inclusion of broadly neutralizing antibodies in lentivirus control strategies.

Parr of Atlantic salmon Salmo salar (mean weight, 25.49 g) were maintained in recirculated freshwater and injected intraperitoneally with one of four inocula . Inoculum 1 was prepared from tissue homogenates taken from Atlantic salmon smolts with acute-stage pancreas disease . Inoculum 2 was a 0.22-um-filtered preparation of inoculum 1 Inoculum 3 was prepared from tissues harvested from Atlantic salmon parr 8 and 10 d after inoculation with inoculum 1 Inoculum 4 (negative control) was prepared from tissues from Atlantic salmon smolts from a farm with no previous history of pancreas disease . The sequential development of lesions is described up to 23 d postinoculation . Inocula 1-3 produced pancreatic and cardiac lesions similar to those previously described in Atlantic salmon with naturally occurring pancreas disease . Negative-control fish developed no lesions . This is the first description of cardiac lesions resulting from experimentally induced pancreas disease . The results support the theory that a transmissible agent is the cause of pancreas disease .

Antigenic variation in the ILDar 1 serodeme of the naturally rodent-infective stock of West African Trypanosoma vivax has been investigated following cyclical transmission. The immunofluorescent and immune lysis tests were employed with a panel of 39 variant-specific mouse antisera. When antigenically homogeneous, or mixed, populations were transmitted by tsetse flies to goats, the first peak parasitaemias arising in the goats were antigenic mixtures (up to 9 major, and several minor variants being recognized in some cases) from which the ingested variant was absent. Although first peak parasitaemias in similarly infected goats showed some variants in common, there was no obvious relationship between the VAT profiles in different goats. When these populations were expanded in irradiated mice, VAT heterogeneity was maintained with a tendency towards the development of predominant variants in some, but not all, instances. Six additional variants, derived following the growth of bloodstream form ILDat 1.9 in 37 degrees C culture, were also represented in goat and mouse populations. Two further variants, isolated after cyclical development of ILDat 1.9-derived trypanosomes in vitro, were not present in the early parasitaemias in goats and mice.