Mycobacterium paratuberculosis and milk

The possibility that milk from cattle with Johne's disease could be a potential vehicle of transmission of Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) to humans has been the focus of a UK government-funded research programme at Queen's University, Belfast since 1993. The main findings of this research programme are reported and practical advice about the most appropriate methods for the isolation/detection of this organism in milk is given. The findings of several milk surveys during which optimised sensitive detection methods were employed (decontamination with 0.75% cetyl pyridinium chloride for 5 h prior to culture and a novel immunomagnetic PCR technique) have revealed that detectable levels of M. paratuberculosis are present in bulked raw cows' milk in the UK at both the farm level and at dairy processing plants prior to pasteurisation. Furthermore, results of three different experimental approaches to assess the effect of pasteurisation time/temperature conditions on the viability of M. paratuberculosis (laboratory pasteurisation studies, a national survey of commercially pasteurised milk, and processing of naturally infected milk through commercial-scale pasteurising plant) provide firm evidence that this organism is capable of surviving commercial milk pasteurisation on occasion. Hence, both raw and pasteurised cows' milk are potential vehicles of transmission of M. paratuberculosis to humans.     

Growth and Apparent Absorption of Minerals in Broiler Chicks Fed Diets with Low or High Tannin Contents

Sorghum grains with low (0.28 per cent catechin equivalent (%CE) or high (1.36 %CE)) tannin contents were used to study the effect of tannin on growth and on the apparent absorption of Ca, P, Mg, Na, K, Fe and Co by chickens. High-tannin sorghum caused a highly significant (p0.01) reduction in the weight gain and feed intake of broiler chicks compared to low-tannin sorghum and increased the feed conversion ratio (p0.01). The amount of tannin did not affect mortality. The apparent absorption of Ca, P, Mg, Na, K, Fe and Co was reduced (p0.01) by feeding sorghum grains with a high tannin content.     

Fat-Tailed Sheep Traits as Affected by Docking

The literature mostly indicates that docking fat-tailed lambs initially reduces growth but that post-weaning growth and feed conversion efficiency then increase. The amount of fat deposited, the total separable lean meat to fat ratio and the meat quality all increase, while the percentage of bone in the carcase either decreases or does not change in the carcases of the docked lambs. Wool growth and characteristics are, in general, not affected and reproductive traits in ewes and lambs are improved by docking. The rectal temperature, respiration rate and pulse rate are decreased following docking. The concentrations of immunoreactive beta-endorphin and cortisol in the plasma and the incidence of foot stamping and restlessness, as indicators of stress, increase after docking. Other constituents of the blood are not significantly altered following docking or by the methods of docking. Docking of fat-tailed sheep using rubber rings at one day of age can be recommended. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of dorsal hip loading,sedation, and general anesthesia on the dorsolateral subluxation score in dogs

OBJECTIVE: To determine whether dorsal loading of the pelvis and type of chemical restraint affected the dorsolateral subluxation (DLS) score of dog hips. STYDY DESIGN: In vivo testing of diagnostic method. ANIMALS: Labrador retrievers, Greyhounds, and crosses between both breeds (n = 119 dogs). METHODS: Dorsal load was applied to the hips through a strap that was placed over the hips, and the peak vertical and steady-state vertical, ground-reaction forces exerted on the stifles were measured in the DLS position. The DLS score was measured with their hips under dorsal load and compared with the DLS score without load. For 24 dogs, the DLS score was measured both under chemical restraint (medetomidine) and under general anesthesia. Wilcoxon-signed rank test and paired t test was used to compare effects of dorsal load and restraint method on the left and right DLS hip score, and P <.05 was considered significant. RESULTS: Both stifles together accepted median 15% body weight in the vertical plane in the unloaded steady state. Loading the hips increased the steady-state, vertical ground-reaction force to 34% body weight. At 8 months of age, loading significantly decreased the DLS score from 65% +/- 11% (mean +/- SD) to 60% +/- 12% for left hips and 66% +/- 11% to 63% +/- 13% for right hips. The left hip DLS score was affected by load more consistently than the right hip. In general, loading the hips decreased the DLS score in all breeds by 4% to 6% except for the greyhounds, in which the DLS score was unchanged by dorsal loading. When grouped by their DLS scores, load significantly decreased DLS scores in dogs with unloaded scores greater than 55% (nondysplastic), whereas DLS scores of dogs with unloaded scores between 55% and 45% (dysplastic) and less than 45% did not change significantly with load. Unloaded scores did not change significantly when compared under sedation versus general anesthesia. However, load significantly decreased the DLS score under general anesthesia for the left hip but not for the right hip. CONCLUSIONS: Less than half of the vertical ground-reaction force normally exerted by the hindlegs of a standing dog was sufficient to induce hip subluxation in the DLS position. Although dorsal loading approximately doubled the steady-state, vertical ground-reaction force, the decrease in the DLS score under load was never greater than 6%. Furthermore, the DLS scores of dogs most likely to be dysplastic (based on DLS scores <45%) were not affected by load, whereas load slightly decreased DLS cores of dogs with DLS scores greater than 55%. CLINICAL RELEVANCE: External influences can change the DLS score significantly, but the magnitude of change is unlikely to be of clinical importance, making the method useful as a field screening test for both dysplastic and nondysplastic hips in young dogs.     

The Effect of Anthelmintic Capsules on the Egg Output and Larval Viability of Drug-resistant Parasites

Challenge with an equal mix of drug-resistant and drug-susceptible larvae of Teladorsagia circumcincta resulted in infections in groups of lambs (n = 6) either untreated or given controlled-release capsules, containing either albendazole or ivermectin. Lambs treated with albendazole capsules contained similar numbers of adult worms at necropsy to the other groups but had no detectable faecal egg count. Animals treated with ivermectin capsules had similar worm burdens and faecal egg counts to the control group but the worms had significantly higher numbers of eggs in utero. These results provide evidence for suppression of egg production by both anthelmintic treatments. The observation that albendazole caused a significant reduction in the developmental success of parasite eggs also has implications for the use of faecal egg count as an indicator for pasture contamination with resistant parasites. In two further groups of lambs, either untreated or given albendazole capsules, treatment caused a significant reduction in egg count and adult worm burden of Trichostrongylus colubriformis. No significant effects were observed on in utero egg counts or egg viability and the apparent effect on the number of eggs produced in faeces per adult female was not significant (p = 0.077). There was, therefore, no evidence that albendazole controlled-release capsules caused suppression of egg output in this species.     

Comparison of antibody values in sera of pigs vaccinated with a subunit or an attenuated vaccine against classical swine fever

Ten pigs, aged 85 days, were vaccinated with a subunit vaccine containing 32 g of classical swine fever virus glycoprotein E2 (gp E2) (group 1), and a further 10 pigs were vaccinated with a C strain vaccine (10^4±0.15 TCID₅₀/ml), produced by amplification in minipig kidney (MPK) cell culture (group 2). Nine non-vaccinated pigs served as a control group (group 3). Serum samples were collected before (day 0) and at 4, 10, 21 and 28 days after vaccination and were analysed by two commercially available enzyme immunoassays and by a neutralizing peroxidase-linked assay (NPLA). At the same times, peripheral blood was taken for determining the total leukocyte count and the body temperature was taken daily. Antibodies were not detected in serum samples collected before vaccination (day 0), and no side-effects that could be connected with vaccination were observed during the trial. Ten days after vaccination 6/10 pigs vaccinated with the subunit vaccine were seropositive. On days 21 and 28, the ratios of serologically positive to vaccinated pigs were 9/10 and 10/10, respectively. Four of the ten pigs that were vaccinated with the C strain vaccine were positive on day 21 and 9/10 on day 28. However, the results of the NPLA showed that only 4/10 pigs had an antibody titre >1:32 at the end of the trial in both the vaccinated groups, even though the subunit vaccine initiated an earlier and higher level of neutralizing antibodies than the vaccine produced from the C strain. Challenge was performed 28 days after vaccination on four randomly selected pigs from both vaccinated groups. The pigs survived the challenge without showing any clinical signs of classical swine fever (CSF), while two nonvaccinated control pigs died on the 10th and 12th days after infection.     

Experimental vascular graft for liver transplantation

Hepatic artery thrombosis is a major cause of graft failure in liver transplantation. Use of donor interponates are common, but results are controversial because of necrosis or thrombosis after rejection. Reperfusion injury, hypoxia and free radical production determinate the survival. The aim of the study was to create an 'ideal' arterial interponate. Autologous, tubular graft lined with mesothelial cells, prepared from the posterior rectus fascia sheath, was used for iliac artery replacement in eight mongrel dogs for six months under immunosuppression. Patency rate was followed by Doppler ultrasound. Eight grafts remained patent and another two are patent after one year. The patency rate was good (median Doppler flow: 370 cm/sec) and there was no necrosis, thrombosis or aneurysmatic formation. The grafts showed viable morphology with neoangiogenesis, appearance of elastin, smooth muscle and endothelial cells. Electron microscopy showed intact mitochondrial structures without signs of hypoxia. Tissue oxygenation was good in all cases with normal (< 30 ng/ml) myeloperoxidase production. In conclusion, this autologous graft presents good long-term patency rate. Viability, arterialisation and low thrombogenicity are prognostic factors indicating usability of the graft in the clinical practice without the risk of rejection. Further investigations such as cell cultures and standardisation are necessary.     

Operation technique and healing process of telescopic ileocolostomy in dogs

The healing process of telescopic anastomoses was found in an animal experiment with 12 mongrel dogs. After the division of vessels an ileal segment of different length was invaginated into the lumen of the colon using single-layer interrupted sutures. The following four groups were used: Group A (n = 3): end-to-side ileocolostomy, single-layer interrupted suture (invagination length: 0 mm), survival time: 21 days. Group B (n = 3): invagination length: 20 mm, survival time: 7 days. Group C (n = 3): invagination length: 10 mm, survival time: 21 days. Group D (n = 3): invagination length: 20 mm, survival time: 21 days. At the end of the above survival times the anastomosis area was removed. The bursting pressure was measured and morphological as well as histological examinations were performed. In each case the 0-day look-alikes of anastomoses were performed using the remnant bowels, and bursting pressure measurements were done on these models as well. Anastomosis leakage did not occur. The serosal layer of the intracolonic part of the ileum disappeared during the healing process. The free surface of the intracolonic ileal segment became covered by the sliding mucosa of the colon and the prolapsing mucosa of the ileum. The following could be concluded after the experiments: The inner pressure tolerance of a telescopic ileocolostomy promptly after preparation is better than in case of another single-layer anastomosis. This fact results in increased safety against leakage on the first postoperative days. The inner pressure tolerance of the telescopic ileocolostomy increases during the healing process and it does not depend on the length of the invaginated part (0 day-20 mm: 56 mmHg +/- 6, Group A: 252 +/- 39, Group B: 154 +/- 19, Group C: 249 +/- 20, Group D: 298 +/- 2). There is no difference in pressure tolerance between the telescopic and the end-to-side single-layer interrupted anastomoses after the healing process. The invaginated section within the lumen of the large intestine does not suffer ischaemic or any other kind of damage. This inexpensive and simple anastomosis technique could be useful in the veterinary surgical practice as well.     

Characterisation of Hungarian porcine circovirus 2 genomes associated with PMWS and PDNS cases

The authors report the data of the first survey on the incidence of post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) in Hungary. A PCR method specific for the detection of porcine circovirus 2 (PCV-2) was developed, which proved to be suitable for diagnostic purposes. PCR screening of organ samples from pigs suspected to be affected with PMWS or PDNS revealed the presence of PCV-2 in 80% of the cases. Six PCV-2 genomes from Hungarian isolates were completely sequenced. Phylogenetic comparison with all the available PCV-2 sequences showed that porcine circoviruses circulating in Hungary are more variable than in several other European countries. Two Hungarian strains clustered together with the Spanish strains forming a distinct group; two others fell in a common group with the French, UK, and Dutch strains, whereas another two strains showed the closest relationship to two of the three known German PCV-2 sequences.     

Spontaneous antibiotic resistance mutation associated pleiotropic changes in Escherichia coli O157:H7

Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin--(Rif) and ampicillin--(Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rifr mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.