Emergence of MD type infectious hematopoietic necrosis virus in Washington State coastal steelhead trout.

Infectious hematopoietic necrosis virus (IHNV) occurs in North America as 3 major phylogenetic groups designated U, M, and L. In coastal Washington State, IHNV has historically consisted of U genogroup viruses found predominantly in sockeye salmon Oncorhynchus nerka. M genogroup IHNV, which has host-specific virulence for rainbow and steelhead trout O. mykiss, was detected only once in coastal Washington prior to 2007, in an epidemic among juvenile steelhead trout in 1997. Beginning in 2007 and continuing through 2011, there were 8 IHNV epidemics in juvenile steelhead trout, involving 7 different fish culture facilities in 4 separate watersheds. During the same time period, IHNV was also detected in asymptomatic adult steelhead trout from 6 coastal watersheds. Genetic typing of 283 recent virus isolates from coastal Washington revealed that the great majority were in the M genogroup of IHNV and that there were 2 distinct waves of viral emergence between the years 2007 and 2011. IHNV type mG110M was dominant in coastal steelhead trout during 2007 to 2009, and type mG139M was dominant between 2010 and 2011. Phylogenetic analysis of viral isolates indicated that all coastal M genogroup viruses detected in 1997 and 2007 to 2011 were part of the MD subgroup and that several novel genetic variants related to the dominant types arose in the coastal sites. Comparison of spatial and temporal incidence of coastal MD viruses with that of the rest of the Pacific Northwest indicated that the likely source of the emergent viruses was Columbia River Basin steelhead trout.

Sphaerospora elwhaiensis sp.n. (Myxosporea: Sphaerosporidae) from landlocked sockeye salmon Oncorhynchus nerka (Salmoniformes: Salmonidae) in Washington State, USA.

A new species of sphaerosporid myxosporean, Sphaerospora elwhaiensis sp. n., is described from kidney of non-anadromous sockeye salmon (kokanee) Oncorhynchus nerka (Walbaum) from Lake Sutherland in the northern Olympic Peninsula, Washington, USA. Infection with the parasite was detected in 45% of 177 kokanee examined over 5 years. While conforming to the morphological criteria by which members of the genus are defined, the parasite is distinguished from congeners in salmonids of western North America by a unique combination of valvular sculpting of the myxospore, the relatively large size of the myxospore and monosporous development within the pseudoplasmodium. In addition, nucleotide sequences of the parasite's small and large subunit ribosomal RNA gene are unique. Phylogenetic analyses of these sequences suggested that the parasite is most closely related to freshwater Myxidium spp. and Zschokkella spp. The molecular data have provided further evidence for a polyphyletic association previously recognized among members of the genus and emphasize the need for a taxonomic revision of Sphaerospora Thélohan, 1892 and related genera.

Adaptations of subpalpebral lavage systems used for llamas (Lama glama) and a harbor seal (Phoca vitulina).

Subpalpebral lavage systems (SPLSs) were adapted for use in zoo llamas (Lama glama) and a wild harbor seal (Phoca vitulina) during therapy for severe ulcerative keratitis or corneal perforation. One llama presented with a melting corneal ulcer caused by Pseudomonas aeruginosa, which necessitated frequent application of a topical ophthalmic antibiotic. The lavage system was used routinely during the day and was connected to a balloon infusion system at night to allow for continuous medication administration. The ulcer healed soon after therapy was extended to include overnight treatment with the infusion system. A SPLS system was also combined with a balloon infusor during postoperative treatment of a second llama that had sustained a corneal perforation. Both llamas tolerated the infusor/lavage systems well and regained vision. One llama had minor conjunctival irritation from the SPLS that resolved quickly without treatment. Bilateral SPLS were placed in a wild harbor seal for treatment of severe ulcerative keratitis associated with Candida albicans infection. The seal tolerated the lavage systems well throughout 14 wk of their use in an aquatic environment with other seals. Partial detachment of the lavage systems from the skin of the seal occurred a few times during treatment and was easily corrected. Severe keratitis resolved with administration of antimicrobials through the lavage systems, and the seal was returned to the wild. The use of SPLSs alone or in ombination with balloon infusion systems warrants consideration for exotic, wild, and aquatic animals that cannot tolerate repetitive manual applications of topical ophthalmic medication.

Comparison of individual and pooled sampling methods for detecting bacterial pathogens of fish.

Examination of finfish populations for viral and bacterial pathogens is an important component of fish disease control programs worldwide. Two methods are commonly used for collecting tissue samples for bacteriological culture, the currently accepted standards for detection of bacterial fish pathogens. The method specified in the Office International des Epizooties Manual of Diagnostic Tests for Aquatic Animals permits combining renal and splenic tissues from as many as 5 fish into pooled samples. The American Fisheries Society (AFS) Blue Book/US Fish and Wildlife Service (USFWS) Inspection Manual specifies the use of a bacteriological loop for collecting samples from the kidney of individual fish. An alternative would be to more fully utilize the pooled samples taken for virology. If implemented, this approach would provide substantial savings in labor and materials. To compare the relative performance of the AFS/USFWS method and this alternative approach, cultures of Yersinia ruckeri were used to establish low-level infections in groups of rainbow trout (Oncorhynchus mykiss) that were sampled by both methods. Yersinia ruckeri was cultured from 22 of 37 groups by at least 1 method. The loop method yielded 18 positive groups, with 1 group positive in the loop samples but negative in the pooled samples. The pooled samples produced 21 positive groups, with 4 groups positive in the pooled samples but negative in the loop samples. There was statistically significant agreement (Spearman coefficient 0.80, P < 0.001) in the relative ability of the 2 sampling methods to permit detection of low-level bacterial infections of rainbow trout.