Effectiveness of treatment with lincomycin hydrochloride and/or vaccination against Mycoplasma hyopneumoniae for controlling chronic respiratory disease in a herd of pigs

A herd of pigs infected with Mycoplasma hyopneumoniae was used in a double-blind randomised trial to assess the effectiveness of three control strategies against chronic respiratory disease in growing-finishing pigs. One group of 61 pigs received 220 ppm lincomycin hydrochloride in the feed from day 71 to day 91, a second group was vaccinated against M. hyopneumoniae at four and 28 days of age, and a third group received both treatments; a fourth group was left untreated as a control. Throughout the nursery-finishing period (day 29 to slaughter) the average daily weight gain and feed conversion rate of all the treated groups were slightly better than in the controls, but there were no significant differences between them. There were no significant differences between the treated groups in terms of clinical signs, serology, pathology or mortality, which was very low throughout the trial.     

The Control of Rinderpest in Tanzania between 1997 and 1998

In January 1997, Tanzania requested international assistance against rinderpest on the grounds that the virus had probably entered the country from southern Kenya. Over the next few months, a variety of attempts were made to determine the extent of the incursion by searching for serological and clinical evidence of the whereabouts of the virus. At the clinical level, these attempts were hampered by the low virulence of the strain, and at the serological level by the lack of a baseline against which contemporary interpretations could be made. Once it became apparent that neither surveillance tool was likely to produce a rapid result, an infected area was declared on common-sense grounds and emergency vaccination was initiated. The vaccination programme had two objectives, firstly to prevent any further entry across the international border, and secondly to contain and if possible eliminate rinderpest from those districts into which it had already entered. On the few occasions that clinical rinderpest was subsequently found, it was always within this provisional infected area. Emergency vaccination campaigns within the infected area ran from January to the end of March 1997 but were halted by the onset of the long rains. At this time, seromonitoring in two districts showed that viral persistence was still theoretically possible and therefore a second round of emergency vaccination was immediately organized. Further seromonitoring then indicated a large number of villages with population antibody prevalences of over 85%. These populations were considered to have been `immunosterilized'. Although no clinical disease had been observed in them, it was decided to undertake additional vaccination in a group of districts to the south of the infected area. Serosurveillance indicated that rinderpest could have been present in a number of these districts prior to vaccination. Serosurveillance in 1998 suggested that numerous vaccinated animals had probably moved into districts outside the infected and additional vaccination areas, but did not rule out the continued presence of field infection.     

F4 receptor-independent priming of the systemic immune system of pigs by low oral doses of F4 fimbriae

Oral administration of F4 fimbriae of Escherichia coli induces intestinal mucosal immune responses in F4 receptor-positive (F4R(+)) pigs, but not in F4R(-) pigs. We examined whether F4 fimbriae in F4R(-) animals behave like a food antigen and can induce oral tolerance. Therefore, F4R(+) and F4R(-) pigs were fed 2mg of F4 and challenged i.m. to evaluate the effect of oral F4 on the systemic immune system. As control antigen, two different oral doses (2 and 600 mg) of OVA were used. Thirty days after the i.m. OVA challenge, the OVA-specific serum IgG titre in 600 mg-fed pigs was lower than that in non-fed animals, indicating that tolerance was induced. Conversely, in the 2mg-fed pigs a rapid increase of OVA-specific IgG with higher titres than those in non-fed pigs was seen following challenge, indicating a priming of the systemic immune system. A similar priming was seen in both F4-fed F4R(-) and F4R(+) pigs. Upon challenge, non-fed pigs displayed a primary immune response with a slow increase of F4-specific serum IgG, whereas F4-fed F4R(-) and F4R(+) pigs showed secondary responses with a rapid increase of serum IgG. This was expected in F4R(+) pigs, as in these animals oral F4 induces F4-specific antibody-secreting cells in the spleen, suggesting a priming of the systemic immune system. However, also the F4-fed F4R(-) pigs displayed a secondary response, despite the failure to detect a response upon oral F4 administration. These findings suggest that the F4 antigen, at a dose of 2 mg, behaves like a common food antigen in F4R(-) pigs, namely it induces a systemic priming.     

Present Concepts on the Inflammatory Modulators with Special Reference to Cytokines*

The pro- and anti-inflammatory cytokines create a network of interactions between cells that lead to both stimulatory and inhibitory responses that maintain an effective homeostatic regulation. The anti-inflammatory cytokines are a family of peptides that modulate the pro-inflammatory cytokine response. Cytokines act in concert with non-cytokine mediators, such as prostaglandin E₂, glucocorticosteroids, lipocortins, and catecholamines. This review highlights new developments in our understanding of the pathophysiology of inflammation and gives an example of a more recent approach to the modulation of acute systemic inflammatory disorders: activation of ₂-adrenergic receptors on macrophages. In this respect the potent ₂-adrenergic agonist clenbuterol seems of therapeutic interest.     

Effect of acetic acid consumption on clinical laboratory values in the dog

To investigate the influence of food enriched with acetic acid on the clinical, biochemical, electrolyte, blood gas, haematological and urinary variables in the dog, a cross-over study was carried out with periods of approximately 2 weeks involving six healthy, adult dogs. Another objective was to determine the maximum concentration of acetic acid that the dogs found to be palatable. The dogs were maintained on a commercial meat-based food with added acetic acid and/or glucose. The administered acetic acid was increased in stages. All dogs accepted the diet containing acetic acid at a level of 5% of metabolizable energy. Except for a decrease in plasma total protein, none of the variables were significantly affected by acetic acid consumption. Acetic acid feeding did not affect plasma acetate concentration and urinary acetate excretion, indicating that dogs efficiently metabolize ingested acetic acid.     

Clinico-pathological aspects of canine cutaneous and mucocutaneous plasmacytomas

In this study the clinico-pathological aspects of cutaneous and mucocutaneous plasmacytomas were investigated in 63 dogs (one dog with two tumours). The tumours were most commonly observed in the skin of the trunk and legs. Yorkshire Terrier (n = 8) was the most commonly affected breed and males were affected more commonly than females (36 versus 23, respectively). Plasmacytomas were histologically classified into mature, hyaline, cleaved, asynchronous, monomorphous blastic and polymorphous blastic cell types. Monomorphous blastic cell type was the most frequent type (n = 21), followed by cleaved (n = 19) and asynchronous (n = 11) cell types. Secondary amyloid depositions were observed in eight cases. Immunohistochemical staining showed monoclonal lambda light chain positivity in all cases. In the immunohistochemical staining for cyclin D1, which is a prognostic marker in human plasma cell tumours, moderate numbers of positive tumour cells were observed in only one case of (muco)cutaneous plasmacytoma. All other cases were negative or contained few positive tumour cells. On the other hand, high numbers of tumorous plasma cells reacted positively with cyclin D1 in three out of six cases of canine multiple myelomas. Prognosis of the (muco)cutaneous plasmacytomas was good, except in one dog which developed a lymphoma afterwards. No significant correlations were observed between the cell type and the location of the tumour, presence of amyloid or prognosis.     

Small intestinal morphology and disaccharidase activities in early-weaned piglets fed a diet containing spray-dried porcine plasma

The purpose of this study was to test whether dietary spray-dried porcine plasma (SDPP) in early-weaned piglets prevents small intestinal villus atrophy by trophic or protective activity. Fifty-four weaned, 18-day-old piglets were used to determine the effect of dietary SDPP on small intestinal villus length, crypt depth, enterocyt mitotic activity and brush border enzyme activities during the first week after weaning. The piglets were offered a diet containing either 8% SDPP or 8% casein. At 2 and 7 days after weaning, piglets were anaesthetized to provide samples of the small intestinal wall and killed immediately afterwards. There were no differences in daily gain and daily feed intake between the two dietary treatments. At day 2 after weaning, all piglets showed a marked reduction in villus height when compared with baseline values. In all piglets, small intestinal enterocyte mitotic activity had decreased by day 2 and was increased again on day 7. There were no significant effects of dietary SDPP on small intestinal villus length, crypt depth and enterocyt mitotic activity. This indicates that SDPP has no trophic effect on the small intestinal mucosa and that it does not protect against the damaging effect on the small intestinal villi that is associated with the process of weaning. There was no effect of SDPP on lactase-, sucrase- or maltase-specific activities that are a measure of the digestive function of the small intestine. It can be concluded that SDPP versus casein has no effect on small intestinal morphology and disaccharidase activities in early weaned piglets kept under low infection pressure.     

Growth performance and health status in weanling piglets fed spray-dried porcine plasma under typical Northern European conditions

The effect of inclusion of spray-dried porcine plasma (SDPP) in diets for weanling piglets was studied. The objectives were to determine whether SDPP would have positive effects on post-weaning piglet performance and health under typical Northern European conditions. In experiment 1, 160 weanling piglets were assigned randomly to a control diet or a diet containing 3% SDPP, which was added at the expense of both fishmeal and dried skim milk. In experiment 2, 264 weanling piglets were assigned to a control diet containing whey protein, a diet without whey protein but with SDPP or a diet containing both whey protein and SDPP. In essence, SDPP was added to the test diets at the expense of either whey protein or fishmeal. Piglets were fed the diets for 3 weeks. In experiment 1, the piglets fed the SDPP diet had a 7% higher average daily gain (ADG) and a 4% lower feed conversion ratio (FCR) (p < 0.05) during the first 3 weeks after weaning than did those fed the control diet. There were no differences in leucocyte counts or γ-globulin. In experiment 2 there were no significant differences in ADG and FCR among the dietary treatments. It is concluded that low amounts of SDPP in weanling diets can have positive effects on growth performance under Northern European conditions.     

Susceptibility of trypanotolerant West African Dwarf goats and F1 crosses with the susceptible Sahelian breed to experimental Trypanosoma congolense infection and interactions with helminth infections and different levels of diet

Forty pure West African Dwarf (WAD) goats and 35 of its F1 crosses with the Sahelian breed were used in a multifactorial experimental design to evaluate the effects of an experimental Trypanosoma congolense infection and interactions with natural helminth infections and different levels of diet on health and productivity of these two breeds. Trypanosome infection caused a severe drop in packed cell volume (PCV), but this was not significantly affected by breed. Neither deworming nor diet had any effect on the course of anaemia after trypanosome infection. The mean score of parasitaemia tended to be higher in crossbreeds than in WAD goats although this was not significant (P>0.05). Similarly, the antibody response to trypanosome infection was not significantly different between breeds. Parasitaemia level was significantly influenced by the level of diet with the group under high supplementation having a higher mean parasitaemia score than the group under low supplementation. Weight loss due to trypanosome infection tended to be greater in crossbreeds than in WAD goats (P>0.05).During this study, there was no difference in mean helminth egg output between crossbred and WAD goats. However, between weeks 4 and 10 after trypanosome infection (corresponding to a period of heavy rainfall and highly infective pastures), the mean egg output was higher in the crossbreeds.The immunosuppressive effect of trypanosome infections was revealed by a lower antibody response to Haemonchus contortus in infected animals compared to the uninfected controls. Trypanosome infection tended to increase strongyle egg output. This study did no reveal any superior trypanotolerance of WAD goats compared to crossbreeds.     

Antibody-induced internalization of viral glycoproteins in pseudorabies virus-infected monocytes and role of the cytoskeleton: a confocal study

Addition of pseudorabies virus (PrV)-specific polyclonal immunoglobulins to PrV-infected monocytes induces internalization of plasma membrane anchored viral glycoproteins. This process may interfere with antibody-dependent cell lysis and resembles the well-studied physiological endocytosis process. A confocal study was designed to investigate whether the major cellular components, involved in physiological endocytosis (clathrin, actin, dynein and microtubules), play a role in this virological internalization process. In order to visualize the interaction of endosomes, which contain the internalized viral glycoproteins, with clathrin, actin, dynein and microtubules, a double labeling of viral glycoproteins and different cellular proteins was performed. Porcine monocytes were inoculated with the PrV-strain 89V87 at a multiplicity of infection of 50 for 13h. After the addition of FITC-labeled porcine polyclonal PrV-specific antibodies, cells were fixed with para-formaldehyde at different time points and afterwards permeabilized. The different cellular components were visualized with monoclonal antibodies and a Texas Red-conjugate, with the exception of actin, which was stained with phalloidin-Texas Red. The cells were analyzed by confocal microscopy. A clear co-localization was observed between the viral glycoproteins and clathrin and dynein during the internalization process. The microtubules were in close contact with the internalized vesicles. For actin no co-localization could be observed. It can be stated that clathrin, dynein and microtubules, important components during physiological endocytosis, are also of importance during the antibody-induced internalization of viral glycoproteins.