First cases of amoebic gill disease (AGD) in Norwegian seawater farmed Atlantic salmon, Salmo salar L., and phylogeny of the causative amoeba using 18S cDNA sequences.

Amoebic gill disease (AGD) was observed in seawater farmed Atlantic salmon at four geographically distant locations on the western coast of Norway. To the best of our knowledge, these are the first detected AGD outbreaks in Norway. The outbreaks lasted for 7-12 weeks in late autumn 2006 and were for the most part concurrent. The crude, cumulative mortality was in the range of 12-20% at three farms and 82% at a fourth. The histopathology showed uniform parasomal amoebae in lesions characteristic for AGD. Another gill disease, proliferative gill inflammation (PGI), was also present to a variable degree and the distinction between the two gill problems is discussed. Seawater temperatures were 3.5 degrees C higher than average before disease outbreaks, which subsided in early winter. The geographical and time pattern of these outbreaks strongly indicates simultaneous infection from the marine environment. Two contiguous 18S cDNA sequences, obtained by reverse transcriptase PCR from gill tissue with AGD-related lesions, showed highest similarity (99.2%) to a newly recognized species designated Neoparamoeba perurans and maximum likelihood analysis demonstrates that they represent Norwegian strains of this Neoparamoeba lineage.

Muscle characteristics in Thoroughbreds of different ages and sexes.

Muscle biopsies were taken from the middle gluteal muscle in 163 healthy Thoroughbreds aged one to six years. The horses were separated according to sex and divided into four different age groups (one, two, three and four to six years). Muscle biopsies were analysed for fibre type (I, IIA and IIB), and the enzyme activities of citrate synthase, 3-OH-acyl-CoA dehydrogenase, lactate dehydrogenase and hexokinase were measured. The percentage of Type I fibres of all horses increased with age, irrespective of sex (from 9 to 16 per cent). The percentage of Type IIA fibres varied with age and sex, increasing in stallions from 34 to 53 per cent and in mares from 27 to 45 per cent, respectively. Correspondingly, the proportion of Type IIB fibres decreased with age and differed between sexes (stallions from 56 to 29 per cent and mares from 65 to 40 per cent) Muscle oxidative capacity increased with age as indicated by significant increases in the activities of citrate synthase (from 32 to 67 mmol/kg/min) and 3-OH-acyl-CoA dehydrogenase (from 20 to 34 mmol/kg/min). The activity of hexokinase increased with age (from 2.4 to 4.8 mmol/kg/min), whereas the activity of lactate dehydrogenase decreased (from 1,754 to 1,444 mmol/kg/min). No differences were seen between stallions and mares in enzyme activities. This study shows that age is one factor influencing enzyme activities, the percentage of Type I fibres and the Type IIA/IIB ratio in M. gluteus medius of Thoroughbreds, and that stallions have a higher Type IIA/IIB ratio compared with mares.