The effect of temperature on ability of Lepeophtheirus salmonis to infect and persist on Atlantic salmon

The salmon louse (Lepeophtheirus salmonis) is an ecologically and economically important parasite of salmonid fish. Temperature is a strong influencer of biological processes in salmon lice, with development rate increased at higher temperatures. The successful attachment of lice onto a host is also predicted to be influenced by temperature; however, the correlation of temperature with parasite survival is unknown. This study describes the effects of temperature on infection success, and survival on the host during development to the adult stage. To accurately describe infection dynamics with varying temperatures, infection success was recorded on Atlantic salmon (Salmo salar) between 2 and 10°C. Infection success ranged from 20% to 50% and was strongly correlated with temperature, with the highest success at 10°C. Parasite loss was monitored during development at eight temperatures with high loss of lice at 3 and 24°C, whilst no loss was recorded in the temperature range from 6 to 21°C. Sea temperatures thus have large effects on the outcome of salmon louse infections and should be taken into account in the management and risk assessment of this parasite. Improving understanding of the infection dynamics of salmon lice will facilitate epidemiological modelling efforts and efficiency of pest management strategies.     

Increased dietary protein‐to‐lipid ratio improves survival during naturally occurring pancreas disease in Atlantic salmon,Salmo salar L.

This study demonstrated that increased dietary protein‐to‐lipid ratio (P/L‐ratio) improved survival of farmed Atlantic salmon naturally affected by pancreas disease (PD). In addition to diet, body weight (BW) and delousing mortality prior to the PD outbreak also contributed significantly (p < 0.05) to explain the observed variation in PD‐associated mortality. Subsequent to the PD outbreak, large amount of fish failed to grow and caused thin fish with poor condition (runts). At the end of the trial, significantly (p < 0.05) lower amounts of runt fish and increased amount of superior graded fish where detected among fish fed increased P/L‐ratio and within the fish with the largest BWs prior to PD. Diet, BW and delousing mortality contributed significantly (p < 0.05) to explain the variation in the amount of superior graded fish, whereas BW and diet explained the variation in the amount of runt fish. A significant (p < 0.01) negative linear relationship was observed between the amount of superior graded fish and the total mortality, whereas a positive linear relationship was detected between percentage of fillets with melanin and the total mortality. Thus, increased dietary P/L‐ratio seem to reduce the mortality and impaired slaughter quality associated with PD.     

Effects of tractor weight,wheel placement and depth of ploughing on the infestation of perennial weeds in organically farmed cereals

To ensure optimum conditions for organic cereal growing, it is important to minimize both compaction and soil inversion depth. The relative effects of using light versus heavier tractors, shallow versus deeper ploughing and on-land versus in-furrow wheel placement during ploughing were investigated in three-year organic rotations dominated by cereals with naturally infested stands of perennial weeds. The second part of the experiments was carried out in continuous barley with transplanted root fragments of Cirsium arvense (L.) Scop. and rhizome pieces of Elymus repens (L.) Gould. Ploughing was performed in spring under favourable weather conditions. Neither tractor weight nor wheel placement influenced decisively the numbers and above-ground biomass of perennial weeds. Depth of ploughing, on the other hand, affected both perennial weed infestation and yield levels consistently. Weed numbers and the total above-ground weed biomass were mostly 50% lower with deep ploughing (25 cm) than with shallow ploughing (15 cm). The greatest advantage of deep ploughing appeared in the control of C. arvense, which in some cases was reduced by more than 90% compared to shallow ploughing. In organic rotations dominated by cereals, therefore, combating of perennial weeds by deep ploughing may be more important than factors such as tractor weight and wheel placement.     

Colour Doppler sonography of cystic ovarian follicles in cows

The goals of the present study were to investigate whether colour Doppler sonography can be used to differentiate temporary from persistent ovarian follicles and follicles with luteal tissue from follicles without luteal tissue and to assess the response of follicular cysts to administration of a gonadotropin releasing hormone (GnRH) analogue. Fifty-four cows having ovarian follicular structures with a diameter of >15 mm but no corpus luteum were included. These cows were examined via B-mode and colour Doppler sonography. The same examinations were repeated 10 to 12 days later, and the cows with follicular cysts (n=17) received a GnRH analogue. Blood flow was measured before and 30 min after treatment. Ten to 12 days later, the response to treatment was assessed using B-mode sonography. While 31 of 54 follicles disappeared spontaneously (temporary follicles), 23 follicles persisted and were diagnosed as cystic ovarian follicles (COFs). There was no difference between temporary follicles and COFs in regard to total area, wall thickness or the perfused area. In the luteinized follicles (n=13), based on the plasma progesterone concentration, total area was twice as large, wall thickness was three times greater and the perfused area was 4.5 times larger than those of the non-luteinized follicles (n=41). The sensitivity of diagnosing luteinized follicles was 61.5% using B-mode sonography and 92.3% using colour Doppler sonography. Twelve cows responded to GnRH, and five cows did not. There was a trend (P=0.07) toward higher (59.3%) blood flow in the cyst wall 30 min after treatment in the responding cows compared with the non-responding cows. Our results showed that the perfused area more accurately reflects active luteal tissue than wall thickness. Thus, colour Doppler sonography is superior to B-mode sonography for differentiating follicular and luteal cysts and aids in the selection of treatment. However, exact prediction of COFs destined to regress or persist and the response of COFs to treatment with a GnRH analogue were not possible using colour Doppler sonography.     

Detection of respiratory pathogens in porcine lung tissue and lavage fluid

The objective of this study was to compare the detection rate of bacterial agents in bronchoalveolar lavage fluid (BALF), taken without visual control, to that in affected lung tissue obtained from the same pig at necropsy. BALF and affected lung tissue were examined for Mycoplasma hyopneumoniae using PCR, and standard cultural methods were used for Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, Haemophilus parasuis, Pasteurella multocida and Streptococcus suis. All pigs with a history of respiratory symptoms were submitted as live animals for routine diagnostic examination. In each animal the site of lavage, marked by injecting methylene blue, differed from the site of pneumonic lesions. M. hyopneumoniae was detected more frequently in lung tissue than in BALF in cases with moderate or severe lung lesions. The detection rates of M. hyopneumoniae were higher in the BALF of pigs with mild lesions. Cultural examination of BALF was at least as satisfactory as affected lung tissue for detecting B. bronchiseptica, H. parasuis and P. multocida.     

The risk of individual fish being captured multiple times in a catch and release fishery

The proportion of angled Atlantic salmon Salmo salar L. being caught and released has increased. If individuals are repeatedly captured, this may have fish welfare consequences. Of 995 Atlantic salmon tagged during catch and release in eight Norwegian rivers, 10% were captured twice, while 3% were captured three times within the same fishing season. The probability that released salmon were captured again decreased with decreasing time left of the fishing season, decreased for larger‐sized fish and varied among rivers/years. Increased exploitation rates within the river, indicating an increased fishing pressure, strongly increased the probability that fish would be recaptured. However, the proportion of salmon caught a second time was much lower than the total exploitation rates in the same rivers (which was on average 46%). For fish tagged in the sea, the likelihood of being angled decreased with time since entering the river, which may explain why the recapture rates of caught and released fish were lower than the total exploitation rates.     

Equine herpes virus 1 (EHV-1) in liver, spleen, and lung as demonstrated by immunohistology and electron microscopy

Ten aborted foals, diagnosed as infected with Equine Herpes Virus 1 (EHV-1) on histopathological criteria, were examined for the presence of EHV-1 using immunohistology as the investigative instrument. The primary reagent was an antiserum specific for viral envelope glycoproteins. Immunohistology localised EHV-1 to areas of liver necrosis and to the cytoplasm of infected Kupffer cells and hepatocytes. Cytoplasmic immunolabelling was also prominent in reticular cells of the red pulp of the spleen and in intact and degenerated bronchiolar epithelium. Cytoplasmic immunolabelling was seen in morphologically unchanged cells and in cells containing intranuclear inclusion bodies. Three aborted foetuses with no histological signs of EHV-1 infection were negative when immunostained for EHV-1. Detection by electron microscopy of EHV-1 virions confirmed the EHV-1 specificity of the immunolabelling procedure.