Cells, cytokines and other molecules associated with rejection of gastrointestinal nematode parasites

Infections with gastrointestinal nematodes represent a major problem for human health and animal health and production. The physical size of the parasite, its changing life-cycle stages and the relative inaccessibility to host cells pose unique challenges to the immune system, which has evolved specialized strategies for parasite control. This paper reviews the work performed in the authors' laboratories to identify components that are involved in the natural rejection response against ruminant gastrointestinal nematode parasites, in particular Haemonchus contortus in sheep. The results of these studies indicate that stage-specific antibodies act in concert with effector cells, in particular globular leukocytes (intraepithelial mast cells) and eosinophils, appropriately activated/primed by type 2 (T2) cytokines, to initiate different mechanisms of parasite expulsion and killing. In addition, other molecules, in particular carbohydrate binding galectins, may be involved in strengthening the final effector phase of the rejection response.     

An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves.

Splenectomized vaccine donor calves undergoing primary reactions to Babesia bovis infections may develop cerebral babesiosis which leads to death if not treated in time. A brain biopsy was performed on an artificially-infected animal showing nervous symptoms and the tissue was immediately processed for electron microscopic examination. Virtually every erythrocyte in the brain capillaries sectioned was infected with B. bovis. Intra-erythrocytic merozoites, trophozoites and dividing trophozoites were indentified. Important features of the piriform merozoites included a reduced apical complex consisting of the anterior polar ring, microtubules, rhoptries and micronemes. Unidentified membrane-bound bodies, mostly spherical in shape, were observed anterior to the nucleus. The trophozoites showed very little structural differentiation and no food vacuoles or micropores could be detected. Each trophozoite produced 2 identical merozoites and the parent cell became totally incorporated in the daughter merozoites in the multiplication process. Projections were seen radiating from the surface of infected erythrocytes which appeared to adhere to other surfaces on contact. This probably resulted in the sludging of infected erythrocytes in the capillaries. The latter observations coincide with those described for Babesia argentina.     

Do citizens and farmers interpret the concept of farm animal welfare differently?

Animal welfare is of increasing importance in livestock production and consumption debates. However, discordance exists between citizens' and farmers' perception of animal welfare. Since the search for, and the realization of improvements towards farm animal welfare is strongly driven by citizen expectations, it is of utmost importance to better understand this perceptual discordance. A quantitative study was done in Flanders, Belgium during 2006, including citizens as well as farmers, to obtain a detailed insight in the way the multi-dimensional concept of farm animal welfare is valued. This allowed to discriminate between issues of agreement and disagreement. In general, a similar interpretation of farm animal welfare in terms of animal welfare related aspect's ranking was found. Differences were mainly related to aspects dealing with the ability to engage in natural behaviour on the one hand and with production process-related aspects on the other hand. Citizens evaluate the current state of animal welfare as rather problematic, while farmers report a more satisfactory evaluation of the present condition of farm animal welfare. Especially differing opinions regarding the ability to engage in natural behaviour, together with aspects related to pain, stress and the availability of space seem to contribute to the discordance between farmers and citizens in terms of evaluative beliefs.     

The possibility of positive selection for both F18(+)Escherichia coli and stress resistant pigs opens new perspectives for pig breeding

F18(+)Escherichia coli infections causing post-weaning diarrhoea and/or oedema disease are a major cause of economic losses in pig industry. To date, no preventive strategy can protect pigs from F18(+)E. coli infections. One of the most attractive approaches to eliminate F18(+)E. coli infections is the selection for pigs that are resistant to F18(+)E. coli infections. However, this strategy was not believed to be favourable because of reports of genetic association with the stress-susceptibility gene in the Swiss Landrace. To investigate this potential association more thoroughly, 131 randomly selected Belgian hybrid pigs were genotyped for both the F18(+)E. coli resistance alleles (FUT1(A)) and the stress-susceptibility alleles (RYR1(T)) and their association was investigated by determining the linkage disequilibrium. This linkage disequilibrium (LD=-0.0149) is close to zero and does not differ significantly from 0 (likelihood ratio test chi(1)(2)=1.123, P=0.29), demonstrating no association between the FUT1(A) and RYR1(T) alleles. Furthermore, only a small fraction (4.6%) of the Belgian pigs was found to be resistant to F18(+)E. coli infections. Our results suggest that selection for F18(+)E. coli resistant pigs might be an attractive approach to prevent pigs from F18(+)E. coli infections, unlike to what has previously been postulated.     

Site‐fidelity and movement patterns of bottlenose dolphins (Tursiops truncatus) in central Argentina: essential information for effective conservation

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The Development of a Functional Digestive System in the African Catfish Clarias gariepinus (Burchell)

The morphological and physiological development of the intestine, stomach, liver and pancreas of the African catfish, Clarius guriepinus (Burchell 1822), was investigated from hatching until 9 days after the start of exogenous feeding by histological, histochemical and immunohistochemical procedures. During the yolk sac period, lasting 48 hours at 30 C, the digestive system develops from a rather undifferentiated system into a distinct liver and pancreas and a segmented intestine (parts I to III). Insulin and glucagon producing cells were clearly found in the endocrine pancreatic islets from 14 hours after hatching onwards, while at the start of exogenous feeding, the exocrine pancreas showed an intense zymogen colouration. Exogenous feeding started three days after fertilization, i.e., 48 hours after hatching. At that moment, the rearing temperature was lowered to 27.5 C. The first day of feeding was referred to as day zero, changing into day 1 when the first 24 hours of feeding were completed. From the start of exogenous feeding onwards, aminopeptidase, non-specific esterase and ATP-ase were detected in the digestive system. Morphologically, the stomach was completed at day 4 of exogenous feeding. Gastric acid secretion started on day 4 and lead to a pH below 3.3 in the stomach on day 5. During the first four days of exogenous feeding, C-t-gastrin immunopositive cells were found throughout the gut, including the gastric epithelium. After day 4, the C-t-gastrin cells were only detected in the anterior intestine. The completeness of the stomach development was also marked by the appearance of non-specific esterase activity in the stomach epithelial cells on day 5. All data together clearly indicate that in Clarius gariepinus , the ontogeny of a functional digestive system has been completed on day 5 after the start of exogenous feeding, marking thereby the end of the larval period.     

Assessing biosecurity practices, movements and densities of poultry sites across Belgium, resulting in different farm risk-groups for infectious disease introduction and spread

The existing diversity within poultry systems affects the potential risk of infectious disease introduction and spread. Population data on the level of biosecurity and between-farm contacts is scarce, despite its importance for identifying possible routes of disease transmission. A study was carried out in Belgium to investigate and differentiate professional and hobby poultry sites based on their biosecurity levels and farm movements. Questionnaire data from a total of 37 professional poultry farms, 19 hatcheries and 286 hobby poultry sites were analyzed using a combination of a linear scoring system, a Categorical principal component analysis (CATPCA) and a Two-Step cluster analysis (TSCA). In general, the level of biosecurity was lower in hobby poultry flocks, mainly due to the poor confinement against the outdoor environment and the poor infrastructural hygiene. Most Belgian professional poultry farms and hatcheries had an acceptable level of adoption of standard biosecurity practices, however less attention was given to the way transportation vehicles and employers were brought onto farms and professional visitors welcomed. Considerable variation in the movements and in the structure of the networks arising from these movements was found. Movement frequencies were higher at professional farms compared to hobby farms. Results showed that multiple category farming systems had the highest total movement frequencies. Monthly frequencies of professional visits often exceeded those of poultry and egg movements. Professional and hobby poultry sites were also connected, but movements of poultry and eggs were found only to occur from professional to hobby sites. However, hobby poultry keepers were personally purchasing the poultry and eggs on the professional poultry sites. Six groups of poultry sites were differentiated, which are interpreted as very low to very high risk groups, based on the potential of infectious disease introduction and spread.     

Toxin variation among salamander populations: discussing potential causes and future directions

Amphibians produce defensive chemicals which provide protection against both predators and infections. Within species, populations can differ considerably in the composition and amount of these chemical defenses. Studying intraspecific variation in toxins and linking it to environmental variables may help us to identify the selective drivers of toxin evolution, such as predation pressure and infection risk. Recently, there has been a renewed interest in the unique toxins produced by salamanders from the genus Salamandra: the samandarines. Despite this attention, intraspecific variation has largely been ignored within Salamandra-species. The aim of this study was to investigate whether geographic variation in profiles of samandarines exists, by sampling 4 populations of Salamandra atra over its range in the Dinaric Alps. In addition, we preliminary explored whether potential variation could be explained by predation (counting the number of snake species) and infection risk (cultivation and genomic analyses of collected soil samples). Salamanders from the 4 populations differed in toxin composition and in the size of their poison glands, although not in overall toxin quantity. Nor predation nor infection risk could explain this variation, as populations barely differed in these variables. Sampling over a much broader geographic range, using better estimators for predation and infection risk, will contribute to an improved understanding of how environment may shape variation in chemical defenses. Nevertheless, as the 4 populations of S. atra did differ in their toxin profiles, we propose that this species provides an interesting opportunity for further ecological and evolutionary studies on amphibian toxins.     

Effects of bruise type on discrimination of bruised and non-bruised ‘Golden Delicious’ apples by VIS/NIR spectroscopy

Visual (VIS) and near-infrared (NIR) spectroscopy was applied to discriminate bruises and non-bruised healthy spots on ‘Golden Delicious’ apples. Two types of bruises were examined; those created by controlled impact and those by compression. Reflectance spectra of apples were measured in the range from 400 to 1700 nm. The data were analysed with canonical discriminant analysis (CDA). The squared canonical correlation (CR²) was 0.74 for discriminating impact bruises and non-bruised tissue, and a CR² of 0.68 was obtained for distinguishing compression bruises and sound tissue. Based on the linear discriminant functions, built with canonical components, the misclassification errors for non-bruised apples were mainly due to the presence of compression bruises. The classification accuracy was improved by taking the type of bruises into account in the model.