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Pig Journal Volume: 63
Publication date: August 2010

General Section

ANTIMICROBIAL CONCENTRATIONS IN PLASMA AND LUNG AND THEIR RELATIONSHIPS TO BACTERIAL RESPIRATORY INFECTIONS
D.G.S. BURCH

Abstract
Some antimicrobials, such as tiamulin, tilmicosin and tulathromycin, have been shown to concentrate in lung tissue and have also been reported to have shown good efficacy in the control of respiratory bacterial infections in the pig. The most common infection is caused by Actinobacillus pleuropneumoniae (App). Classical pharmacokinetic and pharmacodynamic relationships using plasma concentrations do not appear to apply, as the plasma concentrations for these substances are usually much lower than the minimum inhibitory concentration (MIC). It was the purpose of this paper to explore the relationship of lung concentrations in comparison with the MICs of the major respiratory bacteria, such as App as well as Pasteurella multocida (Pm) and Haemophilus parasuis (Hps) and correlate these with the results of artificial challenge studies and antimicrobial susceptibility/resistance patterns from field isolates. Actinobacillus pleuropneumoniae is a fastidious organism and its MICs can vary substantially with the culture method employed. Tiamulin administered in the drinking water shows good efficacy against App and the lung concentration correlated well with the MIC of the organism used and an epidemiological cut off value (ECOV) occurred around 8.0μg/ml and could be observed for App and Hps but not for Pm. Tilmicosin also showed an ECOV at 8.0μg/ml, which correlated with alveolar macrophage concentrations rather than lung concentration for Pm and Hps but not for App. This was thought to be due to the MIC determination and culture method, as strains with MICs of 16μg/ml were treated successfully. Tulathromycin’s ECOV was approximately 4.0μg/ml for Pm and Hps and correlated with lung concentration but not for App. Again there was great difficulty ascertaining the susceptibility of App, as there was a large variation in MIC depending on the method and conditions used. The MIC was markedly reduced when serum was included in the culture media. Plasma levels correlated well with Mycoplasma hyopneumoniae MICs and serum is also included in the medium as a routine. Recent data suggests that tiamulin’s MICs against App are also substantially reduced when serum is added to the medium. Further work is required to clarify these MIC anomalies.

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BARRIERS TO ADOPTION OF MEASURES TO CONTROL SALMONELLA IN PIGS IN THE UK: A STAKEHOLDER ANALYSIS
Y.K. VAN DAM, L.J. FREWER, E. MARIER, D. ARMSTRONG, A.J.C. COOK

Abstract
Salmonella infection in pigs may enter the pork chain and thus contribute to human salmonellosis. In 2002 the British Pig Executive (BPEX) launched the Zoonosis Action Plan (ZAP). ZAP is a monitoring scheme based on detecting antibodies to salmonella infection in meat juice sampled from pigs after slaughter. Farms were assigned a score (one to three) according to the test results. ZAP2 or ZAP3 farms had to act to control salmonella or potentially lose quality assured status. The aim of ZAP was to reduce the prevalence of salmonella infection in pigs at slaughter by 25%. However, prevalence of salmonella infection in pigs has not changed since ZAP was initiated. Stakeholder interviews in the UK (seven farmers, seven abattoir managers and two veterinarians) identified concerns regarding implementation of ZAP measures. General support for the implementation of measures to control salmonella in pigs and pork was identified, reflecting the perceived need to attain good food safety standards in order to generate consumer confidence in food safety and quality. The responsibility for prevention of human infection was perceived to be a consumer responsibility. Stakeholders thought that salmonella control measures should be adapted and related to individual farm conditions. The costs of implementation and maintaining control impeded implementation as the benefits were perceived to be indirect and unrelated to animal or human health. The voluntary implementation of ZAP was viewed favourably. Mandatory implementation was not. In conclusion, farmers considered that reduction of salmonella would be an achievable goal, but elimination was considered unfeasible.

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Case Studies

ERADICATION OF ENZOOTIC PNEUMONIA FROM A PIG UNIT WITHOUT PARTIAL DEPOPULATION USING A METHOD SELECTED BY CALCULATING EXPECTED PROJECT VALUE
M. DONADEU, K. SIEBERT, D. TRAMNITZKE, A.W. TUCKER

Abstract
Enzootic pneumonia (EP) remains one of the most costly diseases for the global pig industry. The options for control include adapted management of the environment and pig flow, medication, vaccination, and disease eradication by partial or total depopulation. Disease eradication methods are often not attempted because of the cash flow implications that follow from the interruption to pig flow. We adapted a formal cost benefit analysis (CBA) approach for comparison of different methods of EP eradication to produce an Expected Project Value (EPV) that took the probability of success or failure into account. This adapted CBA was applied to a 330 sow, farrow to finish, genetic nucleus herd with long standing EP to assess the economic implications of five different EP eradication methods. One of the options was eradication by use of a bubble system that did not require partial depopulation of all young pigs. Application of CBA and calculation of EPV for these options resulted in the selection of the bubble option. This option was implemented and took into account the following key principles; initial biosecurity assessment, maximisation of herd immunity by vaccination, and reduction of environmental load of Mycoplasma hyopneumoniae through the creation of a functional bubble (or gap) in pig flow, temporary offsite weaning for five weeks, strict and biosecure definition of clean and dirty areas, and finally blanket medication with intense cleaning and disinfection at the same time. A strategy was implemented to minimise impact on flow of replacement breeding stock. There has been no evidence to date (April 2009), from serological, PCR based, or slaughter assessment methods, of EP in the unit since the completion of eradication in November 2007. We concluded that CBA, including estimation of EPV, is an important and under used tool in swine disease control. Furthermore, the use of a bubble system that does not require partial depopulation of all young pigs can, on appropriate units, be a very cost effective approach to eradication of EP.

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MYELOPROLIFERATIVE DISEASE IN AN ADULT VIETNAMESE POT-BELLIED PIG
D.F. TWOMEY, J. BRADSHAW, G. SAYERS

Abstract
A case of myeloproliferative disease in a seven year old female Vietnamese pot-bellied pig is described. Leukaemia was suspected during a routine haematological screen, but this preceded clinical disease by three months. When clinical signs occurred, they included inappetance, lethargy and aggressive behaviour. The sow was euthanased and post-mortem examination was carried out. Lesions consistent with myeloproliferative disease were present and included multifocal pale lesions in the liver, and enlargement of hepatic and gastric lymph nodes, which were also pale. Histopathological examination demonstrated extensive involvement of multiple organs including liver, spleen, bone marrow and lymph nodes, by sheets of pleomorphic round cells, which were considered to be of granulocytic myeloid lineage. A putative diagnosis of chronic myeloid leukaemia was reached, and a predominance of basophils suggested the possibility of a chronic basophilic leukaemia. Immunohistochemistry using monoclonal antibody markers for CD3, CD79a, and MAC387 were used. Most of the infiltrating neoplastic cell population did not stain with any of these markers thus ruling out a lymphocytic or monocytic neoplasm and supporting the diagnosis of a granulocytic cell neoplasia.

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Research Papers

THE EFFECT OF INCLUSION OF FORMIC/PROPIONIC ACID BLEND AND PHYTASE IN WEANER PIG DIETS UPON FEED INTAKE, PIGLET PERFORMANCE AND GUT STRUCTURE
S.M. CARROLL, H.M. MILLER

Abstract
The main effects of the inclusion of a formic/propionic acid blend at 12 g/kg (6.50 g/kg formic, 2.55 g/kg propionic) and/or phytase (BASF Natuphos) at 500 FTU/kg in the diets upon feed intake, piglet performance and gut structure for the first 18 days post-weaning were investigated. A total of 256 indoor reared, mixed sex (JSR Healthbred) piglets were weaned at a mean weaning age of 27.5 ± 2.23 and weaning weight of 7.9 ± 1.61 kg. The experiment was designed as a 2x2 factorial to test the effect of the inclusion of acid and/or phytase and any acid x phytase interactions. Diets were fed ad libitum for 18 days post-weaning. On day six post-weaning eight pigs per treatment were sacrificed for tissue collection. There was no effect of acid and/or phytase upon piglet feed intake, performance or feed conversion efficiency nor were there any interactions. ADFI, ADG, and FCR for days one to 18 of the experiment were respectively 285 g/d, 217 g/d and 1.33 minus acid and 297 g/d, 222 g/d, and 1.35 plus acid. ADFI, ADG and FCR for days one to 18 of the experiment were respectively 292 g/d, 217 g/d and 1.36 minus phytase and 291 g/d, 222 g/d and 1.33 plus phytase. Treatment had no effect upon small intestine villus height and crypt depth. Litter of origin was found to have a significant effect upon small intestine structure. Mean stomach pH values ranged from 2.77 to 3.33, acid and/or phytase failed to lower the stomach pH as was hypothesised as the stomach content pH for all diets lay within the range required for optimum protease activity (2.0 to 3.5). This experiment showed that the inclusion of phytase to a diet 63% lower in dicalcium phosphate resulted in similar piglet performance, feed intake and gut structure to the diet containing no phytase for the first 18 days postweaning

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MYCOPLASMA HYORHINIS: DISCOVERED OR REDISCOVERED
R.A.J. NICHOLAS, R.S. ROSALES

Abstract
Mycoplasma hyorhinis is a common contaminant of the upper respiratory tract of pigs worldwide occasionally causing polyarthritis and polyserositis in young animals. It is often found in association with the more fastidious and economically more important M. hyopneumoniae, the cause of enzootic pneumonia, which it may overgrow in culture. It may exacerbate disease caused by other bacteria such as Actinobacillus species and has been implicated in the porcine reproductive and respiratory syndrome (PRRS). It has also been shown to be a primary cause of acute eustachitis and otitis in piglets. Evidence is accumulating from the field and from experimental infections that M. hyorhinis is a cause of enzootic pneumonia in its own right.

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EVALUATION OF EFFICACY OF ORAL TOLTRAZURIL (BAYCOX 5%®) FOR THE IMPROVEMENT OF POST WEANING GUT HEALTH IN PIGS
S. MCORIST, R. BLUNT, H. EL-SHEIKHA, A. MORILLO ALUJAS, M. OCAK, A. DENIZ

Abstract
Clinical studies of the anti-coccidial drug toltrazuril have not been comprehensive for issues such as possible beneficial effects on gut health in later production stages. The aim of this on farm study was to evaluate the efficacy of toltrazuril (Baycox® 5% oral suspension) for the improvement of gut health in a European grower finisher pig herd. Four day old matched piglets either received toltrazuril (Group A, n = 218) or placebo (Group B, n = 216). The subsequent diarrhoea scores, growth performance, gut health and entero-pathogen load in each group was monitored by blinded observations, feed and pig weighing, faecal PCR tests and Lawsonia immunofluorescence assay serology up to day 105 in the grower finisher stage of farming. The results showed markedly improved feed conversion in grower finisher pigs in Group A, particularly in the finisher period, but similar weight gains throughout. Lawsonia serology results indicated an early (before day 56) and moderate on farm exposure. Titres in Group B pigs were higher, with fewer negatives throughout (p < 0.01), suggesting that the intestines of these pigs were more receptive to pathogenic Lawsonia infections, just after weaning. Four Group B pigs, 77 to 105 days old, but no Group A pigs, had putative positive faecal PCR results for Brachyspira hyodysenteriae (swine dysentery). Salmonella, PCV2, Brachyspira pilosicoli, E coli and Clostridia results were not noteworthy. There was more diarrhoea noted (p < 0.05) in the piglets up to weaning age in group B (untreated), by blinded investigators. These results confirm the protective effect of toltrazuril for coccidiosis prior to weaning and demonstrate specific beneficial effects on gut health and feed conversion after weaning.

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INFLUENCE OF SPERM CELL CONCENTRATION AND SEMINAL DOSE VOLUME ON SOW FERTILITY
A. RUIZ, G. CASSAR, R.N. KIRKWOOD, R.M.FRIENDSHIP, M.E. WILSON, A.F. DEGRAU

Abstract
At an eCG induced oestrus, 212 sows were inseminated once with 3.5 x 109 sperm either in 80 ml extender (control) or in 56 ml extender followed by a flush with 24 ml sperm free extender (modified insemination technique, MIT). There was no significant effect of insemination management on subsequent farrowing rates or litter sizes although there was a trend for MIT sows of parities one and two to have a higher farrowing rate than controls (74.5% vs. 64.9%; p = 0.13).

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Clinical Practice

LAMENESS IN PIGLETS
M.ZORIC

Abstract
Lameness in piglets is one of the largest animal welfare issues in Sweden today. About every tenth piglet is treated with antibiotics for lameness before three weeks of age. This lameness is commonly associated with abrasions caused by contact to the floor and when given a laboratory diagnosis, these arthrites were found to be caused by ubiquitous microbes such as Streptococcus spp, Staphylococcus spp and E. coli.
There was no difference in prevalence of arthritis between the sexes, but piglets of both sexes that developed arthritis grew slower than healthy pigs, regardless of sex. Lameness may be prevented by relevant floor maintenance and by increasing the amount of straw. There was a sow influence, since lameness was diagnosed only in every second litter. In affected litters, from one to nine piglets were affected by arthritis.

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PMWS IN SWEDEN – FROM AN EXOTIC TO AN ENDEMIC DISEASE
P.WALLGREN

Abstract
Post-weaning multisystemic wasting syndrome (PMWS) was diagnosed for the first time in Sweden at a progeny test station in December 2003. By December 2006, 126 herds had been diagnosed with PMWS and the disease was regarded as endemic and was removed from the list of notifiable diseases. This manuscript describes the spread of PMWS in Sweden and gives some comments on the epidemiology of PMWS.

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PREVALENCE OF ENDEMIC PIG DISEASE IN ENGLAND: AN OVERVIEW SIX MONTHS INTO A LARGE SCALE CROSS SECTIONAL STUDY ON POST-WEANING MULTISYTEMIC WASTING SYNDROME (PMWS)
B. WEILAND, P. ALARCON, M. VELASOVA, A. NEVEL, H. TOWRIE, D. PFEIFFER, C. WATHES, D. WERLING

Abstract
In April 2008 the Royal Veterinary College implemented a large scale cross-sectional study investigating risk factors affecting severity of Post- Weaning Multisystemic Wasting Syndrome (PMWS) on farms. Six months into the study 114 farms have been recruited and on each farm blood samples of 20 pigs, including sows, weaners, growers and finishers were collected and tested for Porcine Circovirus type 2 (PCV2), Actinobacillus pleuropneumoniae (APP), Porcine Parvovirus (PPV) and Porcine Reproductive and Respiratory Syndrome virus (PRRS). All farms tested either positive for PCV2 antibodies or the presence of the virus was confirmed by PCR. For PCV2 and PPV, maternal antibodies were detected in samples from weaners, however low prevalence of maternal antibodies for APP was observed in this age group despite high prevalence in sows. Furthermore, presence of APP antibodies were associated significantly with a positive PCV2 PCR test result in weaners in logistic regression models. In addition, positive PCV2 PCR results were associated with poor growth in weaners, growers and finishers. Besides providing prevalence data of important endemic pig diseases in England the preliminary results of this ongoing study indicate the potential importance of other pathogens for the development of PMWS. This study further provides field data that can be used as a baseline to assess the efficacy of PCV2 vaccines.

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THE IDENTIFICATION OF RISK FACTORS FOR THE PRESENCE OF ENZOOTIC-PNEUMONIA LIKE LESIONS AND PLEURISY IN SLAUGHTERED FINISHING PIGS UTILISING EXISTING BRITISH PIG INDUSTRY DATA
M.J. SÁNCHEZ-VÁZQUEZ, R. SMITH, G.J. GUNN, F. LEWIS, W.D. STRACHAN, S.A. EDWARDS

Abstract
Abattoir monitoring in slaughtered finishing pigs is carried out as part of established health schemes. Enzootic pneumonia-like (EP-like) lesions and pleurisy are the two more prevalent conditions reported, being associated with reduction in performance traits.
This study combined records on EP-like lesions and pleurisy from 129,819 slaughtered pigs with information from the farms of origin in order to identify those production characteristics that may influence the prevalence of these lesions. Five hundred and five farms were recruited using the information available in national quality assurance programmes (QAPs); pig stocking levels, feeding practices, housing systems and geographical location.
Relevant epidemiological information common to these databases was extracted. Generalised linear mixed models were used for multivariable analysis, allowing for clustering at batch level. Geographical location of the finishing unit appeared to be a statistically significant risk factor for EP-like lesions and pleurisy. Part slatted floors also appeared as a potential risk factor for the presence of these two conditions, versus the use of solid floor with bedding which appeared protective.
This study demonstrated the potential of combining abattoir and QAPs’ data to perform epidemiological analyses which may lead the British pig industry to a better understanding of how the farm characteristics and geographic location could influence the prevalence of EP-like lesions and pleurisy.

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