Toxicity of aqueous aluminium to the ectoparasitic monogenean Gyrodactylus salaris

Both laboratory and field experiments have demonstrated that aqueous aluminium can act as a paraciticide to the monogenean Gyrodactylus salaris Malmberg, 1957 infecting freshwater salmonids. However, the reproductive conditions of gyrodactylids surviving to cessation of an aluminium exposure is unknown. Therefore, Atlantic salmon (Salmo salar L.) parr infected with G. salaris was experimentally exposed to elevated concentrations of aqueous aluminium for more than 1 month. During this period, the infection increased the first week before it peaked and started to steadily decline approaching elimination. When almost all parasite specimens were eliminated, the water quality was adjusted to normal aluminium-poor freshwater. During the next 3 weeks, the surviving G. salaris were shown to clearly resume their reproduction. The experiment demonstrates the potential of the gyrodactylids to reproduce after cessation of an aluminium exposure. Thus, the as-yet unknown mechanism behind the toxic effects of aluminium on G. salaris survival and reproduction might to some extent be reversible. The present study gives further support for this metal as a parasiticide to G. salaris but demonstrates at the same time that in order to eliminate the parasites totally, the aluminium treatment must eradicate all G. salaris from the skin of the infected hosts. Furthermore, the potential development of resistance to aluminium should also be studied.     

Evaluation of the effect of commercially available plant and animal protein sources in diets for Atlantic salmon (Salmo salar L.): digestive and metabolic investigations

The present study investigated the effect of various alternative diet ingredients partially replacing fishmeal (FM) on digestive and metabolic parameters in Atlantic salmon (Salmo salar L.) post-smolts (initial body mass 305 ± 69 g) following 12 weeks of feeding. Experimental diets containing 20 % extracted sunflower (ESF), pea protein concentrate (PPC), soy protein concentrate (SPC), feather meal (FeM) and poultry by-product (PBY) were compared to a reference diet containing FM as the main protein source. For the different intestinal compartments trypsin, lipase, bile salts, dry matter and chyme-associated leucine aminopeptidase (LAP) were measured from the content and LAP was measured in the tissue. Selected metabolites were measured in plasma samples. In general, use of plant proteins resulted in low C-LAP activity, low plasma cholesterol and high plasma magnesium. The plasma levels of cholesterol and Mg reflecting were most likely reflections of the composition of the diet, while the LAP activity in chyme may indicate lower epithelial cell turnover. Other responses varied depending on the plant protein source. Results from the animal protein substitution also varied both between diets and compartments; however, both materials increased lipase activity in DI. FeM resulted in a significant increase in both total and specific LAP activities suggesting an attempt to increase the digestive capacity in response to low digestibility of the diet while PBY showed very little difference from the FM-fed control fish. The present trial indicates that 20 % PPC, SPC and PBY can partially replace FM in diets for Atlantic salmon. The qualities of ESF and FeM used in this trial show little promise as FM replacement at 20 % inclusion level.     

An Investigation of Ovine Pneumonia in Four Herds from Central Norway: I. Prevalence of Pneumonia and Microbiological Findings

In a study of 4 sheep herds, 1 apparently healthy and 3 having respiratory problems, lesions typical of subacute or chronic pneumonia were found in 3–36 % of slaughtered lambs. Occurrence appeared to be related to certain environmental factors such as pasture, whereas moderate lungworm invasion was not found to contribute to subacute or chronic pneumonia. Relation between pneumonia and low carcass weight was established only in 1 herd.Lungs were subjected to microbiological examination. Mycoplasma ovipneumoniae was isolated from both normal and pneumonic lungs from all 4 herds. The prevalence was far higher in pneumonic (98 %) than in normal ones (28 %). Bacteria, mostly Pasteurella haemolytica, were also found in both pneumonic (49 %) and normal (18 %) lungs from all 4 herds. These results confirm the conclusions of a previous study that M. ovipneumoniae is of etiological significance in subacute or chronic pneumonia, whereas bacteria mainly occur as secondary invaders. M. ovipneumoniae appears, however, only to be a potential pathogen. Examinations for Mycoplasma arginini and virus were negative and these agents are considered to be of less significance in subacute or chronic pneumonia under Norwegian conditions.     

Prevalence of gastrointestinal helminths,lungworms and liver fluke in sheep and goats in Norway

The present study describes the occurrence of various gastrointestinal helminths, lungworms and liver flukes in Norwegian sheep and goats as assessed from faecal samples and post mortem examinations performed between 2007 and 2010. Faecal samples for gastrointestinal nematode egg counts were collected from 77 sheep flocks and 30 dairy goat flocks from three geographical regions in Norway. Additionally, thirty-two lambs and 16 adult goats were euthanized for necropsy examination and for identification of adult gastrointestinal nematodes and tapeworms, lungworms and liver flukes. The survey showed that there was a higher mean excretion of trichostrongyle eggs in sheep than in goats at the individual level (392 EPG vs. 154 EPG, p < 0.001). For both host species, the mean prevalence and intensity of excreted trichostrongyle eggs were significantly higher in the southern coastal region compared with the inland and northern regions (p < 0.001). Third stage larvae of Trichostrongylus/Teladorsagia, Haemonchus and Nematodirus type were the most prevalent ones in the coprocultures from sheep, whereas larvae of Trichostrongylus/Teladorsagia and Nematodirus type dominated in goats. The most prevalent gastrointestinal nematode species found at necropsy was Teladorsagia circumcincta (75.0 and 81.2% respectively in sheep and goats), while the largest mean worm burdens were recorded for Haemonchus contortus in sheep (724 ± 623) and T. circumcincta in goats (377 ± 529). Other gastrointestinal nematode species were present at low prevalence or in low numbers.     

Performance and carcass characteristics of lambs fed diets with increasing levels of <Emphasis Type="Italic">Mimosa tenuiflora</Emphasis> (Willd.) hay replacing Buffel grass hay

This study evaluated the performance and carcass characteristics of lambs fed diets with increasing levels of Mimosa tenuiflora (Willd.) hay replacing Buffel grass (Cenchrus ciliaris). Twenty-eight Santa Inês male lambs with an average body weight (BW) of 20.3 ± 1.49 kg(mean ± SD) were allocated in individual stalls and distributed in a completely random design with four treatments (0, 20, 40, and 60 g/100 g total DM M. tenuiflora hay replacing Buffel grass hay in diet) with seven replications. M. tenuiflora hay at the level of 20% dry matter (DM) total replacing Buffel grass hay increased final weight (P = 0.006), total weight gain (P < 0.001), average daily weight gain (ADWG; P < 0.001), DM intake (P < 0.001), and feed efficiency (P < 0.001). Intake of crude protein, NDF_ap, ADF_ap, ash, ether extract, total and non-fibrous carbohydrates, and total digestible nutrients presented a positive quadratic effect with M. tenuiflora hay replacing Buffel grass hay and 40 g/100 g total DM level presented greater intake. There were positive quadratic effects by M. tenuiflora hay inclusion at 20 g/100 g total DM level on slaughtering weight (P = 0.005), hot carcass weight (P = 0.002), cold carcass weight (P = 0.002), empty body weight (P = 0.001), hot carcass yield (P = 0.002), cold carcass yield (P = 0.003), and increase linear on biological yield (P = 0.003). There was no influence on cooling weight loss (P = 0.284). M. tenuiflora hay may be included in lamb diets at amounts up to 20 g/100 g total DM substitution of Buffel grass hay because increase in the nutrients intake, growth performance, and carcass characteristics.     

A morphological and molecular study of Anaplasma phagocytophilum transmission events at the time of Ixodes ricinus tick bite

Background

Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis (HGA) in humans and tick-borne fever (TBF) in ruminants. The bacterium invades and replicates in phagocytes, especially in polymorphonuclear granulocytes.

Methods

In the present study, skin biopsies and ticks (Ixodes ricinus) were collected from tick feeding lesions on 38 grazing lambs between two and three weeks after access to pastures. The histopathological changes associated with tick bites and A. phagocytophilum infection, were described. In addition the skin biopsies were examined by immunohistochemistry. Furthermore, samples from blood, skin biopsies and ticks were examined by serology, PCR amplification of msp2 (p44), genotyping of rrs (16S rRNA) variants, and compared with the results obtained from histological and immunohistochemical investigations.

Results

Tick bites were associated with chronic and hyperplastic inflammatory skin lesions in this study. A. phagocytophilum present in skin lesions were mainly associated with neutrophils and macrophages. Bacteria were occasionally observed in the Tunica media and Tunica adventitia of small vessels, but were rarely found in association with endothelial cells. PCR and genotyping of organisms present in blood, ticks and skin biopsies suggested a haematogenous and a local spread of organisms at the tick attachment sites.

Conclusions

The present study describes different aspects of A. phagocytophilum infection at the site of tick bite, and indicates that A. phagocytophilum rarely associates with endothelium during the early pathogenesis of infection.     

A comparative study of clinical manifestations,haematological and serological responses after experimental infection with Anaplasma phagocytophilum in two Norwegian sheep breeds

Background

It has been questioned if the old native Norwegian sheep breed, Old Norse Sheep (also called Norwegian Feral Sheep), normally distributed on coastal areas where ticks are abundant, is more protected against tick-borne infections than other Norwegian breeds due to a continuously high selection pressure on pasture. The aim of the present study was to test this hypothesis in an experimental infection study.

Methods

Five-months-old lambs of two Norwegian sheep breeds, Norwegian White (NW) sheep and Old Norse (ON) sheep, were experimentally infected with a 16S rRNA genetic variant of Anaplasma phagocytophilum (similar to GenBank accession number {"type":"entrez-nucleotide","attrs":{"text":"M73220","term_id":"148293"}}M73220). The experiment was repeated for two subsequent years, 2008 and 2009, with the use of 16 lambs of each breed annually. Ten lambs of each breed were inoculated intravenously each year with 0.4 ml A. phagocytophilum-infected blood containing approximately 0.5 × 10⁶ infected neutrophils/ml. Six lambs of each breed were used as uninfected controls. Half of the primary inoculated lambs in each breed were re-challenged with the same infectious dose at nine (2008) and twelve (2009) weeks after the first challenge. The clinical, haematological and serological responses to A. phagocytophilum infection were compared in the two sheep breeds.

Results

The present study indicates a difference in fever response and infection rate between breeds of Norwegian sheep after experimental infection with A. phagocytophilum.

Conclusion

Although clinical response seems to be less in ON-lambs compared to NW-lambs, further studies including more animals are needed to evaluate if the ON-breed is more protected against tick-borne infections than other Norwegian breeds.