enzootic respiratory diseases in the growing-finishing pig and control

infection pressure) in the different compartments of the herd, thus keeping the pathogen load at an acceptable level iewithin herd immunity level, easy to handle and finally, avoid disease expression.Although health would be easier to maintain in the absence of infection by specific pathogens, the presence ofthose associated with enzootic respiratory diseases is not incompatible with good levels of health and performance,provided that that adequate housing and herd management are provided.7. CONCLUSIONA vast amount of knowledge is available about enzootic respiratory disorders, and it is paradoxical that the lattershould remain a major concern in modern intensive pig farming. It is all the more surprising given that new technologiesare now available for both pathogen detection and disease prevention. This frustrating situation is probably , at least inpart, due to the multifactorial character of the problem; the scientists involved in different disciplines in their labs often donot work and intervene in direct collaboration with various advisers on the farms. A more integrated technical effort couldcertainly improve both the accuracy and the efficiency of the preventive programmes. The emphasis must be on reducingthe overwhelming challenges to the pig’s immune status due to bacteria and viruses. In this area reliable clues arealready known. However, further investigations should clarify certain points and respond to those currently -unansweredquestions: How to objectively assess the herd microbial load?; how to assess the dynamics of the pathogenic microflorain a herd ? what are the factors that trigger an outbreak of pleuropneumonia in a silently App infected herd? Newscientific acquisitions in these fields may help to understand the reasons of disease expression. Definitely theperspective of an effective prevention initiative must integrate all disciplines of animal sciences, including livestockbuilding design and herd management.8. REFERENCES- AJITO T., HAGA Y., HOMMA S., GORYO M., DKADA K., 1996. Immunohistological evaluation of respiratory lesionsof pigs intranasally inoculated with Actinobacillus pleuropneumoniae, serotype 1. J. of Vet. Red. Sci. 58, 297-303.- ALEXANDER T.J.L., 1980. Medicated earl weaning to obtain pigs free from pathogens endemic in the herd of origin.Vet. Rec. 106, 114-119.- AMASS S.E., CLARK L.K., VAN ALSTINE W.G., BOWERSOCK T.L., MURPHY D.A., KNOX K.E., ALBREGTS S.R.,1994. Interaction of Mycoplasma hyopneumoniae and Pasteurella multocida infections in swine. J. Am. Vet. Med.Assoc. 204, 102-107.- AMASS S.F., CLARK L.K., 1999. Biosecurity considerations for pork production units. Swine Health and Production7, 217-228.- ANDREASEN M., BAEKBO P., NIELSEN J.P., 1999. Effects of aerial ammonia on Porcine infection of therespiratory tract with toxigenic Pasteurella multocida. Acta Veterinaria Scandinavica 40, 197-203.- ARTIUSHIN S., MINION F.C. 1996 Arbitrarily primed PCR analysis of M. hyopneumoniae field isolatesdemonstrates genetic heterogeneity . Intern.J. of systematic Bacteriology 46, 324 –328- BASKERVILLE A. 1972. Development of the early lesions in experimental enzootic Pneumonia of the pig : anultrastructural and histological study. Res. Vet. Sei. 13, 570-578- BLAHA T. 1992 Proceedings 12th IPVS congress, the Hague, PP 126- BLANCHARD B., VENA M.M., CAVALIER A., LE LANNIC J., GOURANTON J., KOBISCH M.,1992. Electronmicroscopic observation of the respiratory tract of SPF piglets inoculated with Mycoplasma hyopneumonsae. Vet.Microbiol. 30, 329-341- CARUSO J.P., ROSS R.E., 1990. Effects of Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniaeinfections on alveolar macrophage functions in swine. Am. J. Vet. Res. 51, 227-231.- CIPRIAN A., PISOAN C., CRUZ T., CAMACHO J., TORTORA J., COLMENARES G., LOPEZ-REVILLA R., DE LAGARZA M. 1998. Mycoplasma hyopneumoniae increases the susceptibillity of pigs to experimental Pasteurellamultocida pneumonia. Can. J. Vet. Res. 52, 434-438.- DEE S., 1999. Bacterial respiratory diseases of nursery pigs. Compendium on Conti. Educ. for the pract. Vet. 21,5170-5176.- DESROSIERS R., MOORE C., 1998. Indirect transmission of Actinobacillus pleuropneumoniae. Swine Health andProduction 6, 263-265.- DIEKMAN M.A., SCHEIDT A.B., SUTTON A.L., GREEN M.L., CLAPPER J.A., KELLY D.T., VAN ALSTINE W.G.,1993. Growth and reproductive performance, during exposure to ammonia, of gilts afflicted with pneumonia andrhinitis. Am. J. Vet. Res. 54, 2128-2131.- DONE S. 1991 pneumonia, some aspects of treatment and control. Pig Vet. J. 27, 30-49.- DRUMMOND J.G., CURTIS S.E., MEYER R.C., 1981. Effects of atmospheric ammonia on young pigsexperimentally infected with Bordetalla bronchiseptica. Am. J. Vet. Res. 42, 963-968.5

- DRUMMOND J.G., CURTIS S.E., SIMON J., 1978. Effects of atmospheric ammonia on bacterial clearance in theyoung pig. Am. J. Vet. Res. 39, 211-212.- FLESJA K.I., SOLBERG I.1981. Pathological lesions in swine at slaughter. Acta Vet. Scand., 22, 272-282- GOODWIN RFW 1991. Clinical and Epidemiological aspects of respiratory disease in pigs. Proceedings RoyalVer./Pfizer Ltd symposium, Royal Vet. College, July 1991, pp.47-52- GUZYLACK S., MORVAN P., PABOEUF F., LABBE A., CHEVALLIER B., KOBISCH M., MADEC F., 1997. Infectiondes porcs charcutiers par Actinobacillus pleuropneumoniae. Etude séro-épidémiologique dans 5 élevages. J. Rech.Porcine 29, 31-38.- HALL W.F., BANE D.P., KILROY C. R., ESSEX-SORLIE D.L., 1990. A model for the induction of Pasteurellamultocida type A pneumonia in pigs. Can. J. Vet. Res. 54, 238-243.- HURNIK D.,DOHOO I.R., BATE L.A., 1994 . Types of farm management as risk factors for swine respiratorydisease. Prev. Vet. Red. 20, 147-157- JERICHO KWF 1968. Pathogenesis of pneumonia in pigs. The Vet. Record 82, 507.- JOBERT J.L., SAVOYE C., CARIOLET R., KOBISCH M., MADEC F., 2000. Experimental aerosol transmission of A.pleuropneumoniae to pigs. Can. J. Vet. Res., 64, 21-26.- JOLIE R., BACKSTROM L., OLSON L., CHASE C., 1999. A 15-week experimental exposure of pigs to airborne dustwith added endotoxin in a continuous flow exposure chamber. Can. J. Vet. Res. 63, 129-137.- KOBISCH M., BLANCHARD B., LE POTIER M.F., 1993. Mycoplasma hyopneumoniae infection in pigs : duration ofthe disease and resistance to reinfection. Vet. Res. 24, 67-77.- KOVACS F., NAGY A., SALLAI J., 1967. Concentrations of dust, airborne bacteria and ammonia in pig housing andtheir relationship to the incidence of pneumonia. Magyar Allotorvosok Lapja, 22, 496-505.- LARSEN I.P., 1998. Danish SPF herds: a lesson in precautions. Pig progress, June 1998, 46-47.- LARSSON K., EKLUND A.G., HANSSON L.O., I. SAKSSON B.M., MALMBERG P.O., 1994. Swine dust causesintense airways inflammation in healthy subjects. Am. J. Respir. Crit. Care Med., 150, 973-977.- LAVAL A., 1995. Respiratory diseases, vaccination principles: what strategy should be adopted? When and how touse vaccines? Pigs-Misset June 1995, 28-29.- LEON E.A, MADEC F., TAYOR N.M., KOBISCH M., 2001. Seroepidemiology of Mycoplasma hyopneumoniae inpigs from farrow-to-finish farms. Vet. Microbiol. 78, 331-341.- MADEC F., KOBISCH M., LEFORBAN Y., 1993. An attempt at measuring health in nucleus and multiplier pig farms.Livest. Prod. Sci. 34, 281-294.- MADEC F., TILLON J.P., 1986. The ecopathological approach in pig veterinary practice. Its application to the controlof enzootic respiratory diseases in intensive pigs units. Proceedings pig Vet. Soc. 15, 7-26.- MAES D.G., DELUYKER H., VERDONCK M., CASTRYCK F., MIRY C., VRIJENS B., DUCATELLE R., DE KRUIFA. Non- infections factors associated with macroscopic and microscopic lung lesions in slaughter pigs from farrowto-finish herds. The Vet. Rec. 148, 41-46- MEBUS CA., UNDERDAHL NR, 1977. Scanning electron microscopy trachea and bronchi from gnotobiotic pigsinoculated with Mycoplasma hyopneumoniae. Am. J. Vet. Res. 38, 1249-1254.- ROBERTSON J.F., 1993. Dust and ammonia concentrations in pig housing: the need to reduce maximum exposurelimits. Livest. Environment Ivth Intern. Symp. Univ. of Warrick, Coventry, England 6-9 July 1993, 4, 694-700.- SCHEIDT A.B., CLINE T.R., CLARK L.K., MAYROSE V.B., VAN ALSTINE W.G., DIEKMAN M.A., SINGLETONW.L., 1995. The effect of all-in/all-out growing-finishing on the health of pigs. Swine Health and Production 3, 202-205.- SEBUNYA TNK, SAUNDERS J.R., OSBORNE A.D. 1983. Dose response relationship of Haemophiluspleuropheumoniae aerosols in pigs. Can.J. Comp.Red; 47;54 –56- SOLANO G.I., BAUTISTA E., MOLITOR T.W., SEGALES J., PIJOAN C., 1998. Effect of Porcine Reproductive andRespiratory Syndrome Virus infection on the clearance of Haemophilus parasuis by porcine alveolar macrophages.Can. J. Vet. Res., 62, 251-256.- SORENSEN V. , AHRENS P., BARFOD K., FEENSTRA A. A., FELD N.C., FRIIS N.F, BILLE-HANSEN V., JENSENN.E., PEDERSEN M.W. 1997. Mycoplasma hyopneumonise infection in pigs : duration of the disease and evaluationof four diagnostic assays Vet. Microbiol; 54, 23-346

- STRAW B., 1986. A look at the factors that contribute to the development of swine pneumonia. Vet. Med. 81, 747-756.- TORREMORELL M., PIJOAN C., JANNI K., WALKER R., JOO H.S., 1997. Airborne transmission of Actinobacilluspleuropneumoniae and porcine reproductive and respiratory syndrome virus in nursery pigs. Am. J. Vet. Res. 58,828-832.- URBAIN B., NICKS B., MAST J., GODDERIS B., ANSAY M., GUSTIN P., 1997. Subacute effects of feed flour dustinhalation on the respiratory tract of pigs. Proceedings 9 th cong. of the Intern. Soc. for Anim. Hygiene. Helsinki,FINLAND 1, 188-191.- VAN DIEMEN P.M., HENKEN A.M., SHRAMA M., BRANSMA H.A., VERSTEGEN M.W.A., 1995. Effects of rhinitisinduced by Pasteurella multocida toxin on heat production and activity of pigs kept under different climaticconditions. J. Anim. Sci. 73, 1658-1665.- WISEMAN B.S., MORISSON R.B., DIAL G.B., 1991. Influence of weaning age on pathogen elimination and growthperformance of commingled pigs derived by medicated early weaning. Proceedings 12 th IPVS congress, pp500.7

Table 1 – Respiratory disorders in growing-finishing pigsName of the disease Clinical symptoms Lesions at necropsy Associated pathogen1. Enzootic pneumoniawith complicationsCough, reduced WGSevere cough, depression,anorexia2. Atrophic rhinitis Sneezing (first stage), twistedsnout (advanced stage)3. Pleuropneumonia Fever, malaise, anorexia,mortality4. Swine Influenza Fever, malaise, anorexia, highmorbidity (close to 100 %)5. Porcine Reproductive andRespiratory Syndrome(PRRS)Fever, anorexia “influenzalike”in some cases6. Aujeszky’s disease Fever, coughing, sneezing,anorexia, “influenza-like”symptoms7. Others :- Glasser’s disease- Strept. suis- Parasitic diseases- Salmonellosis- PMWSVarious:Fever, dyspnoea,sudden death, lameness,coughFever, dyspnoea, coughing,mortalityWastingLung consolidationBronchopneumonia, pleuritisTurbinates atrophyHemorragic lungFibrinous pleurisyPneumoniaPurple lung areasInterstitial pneumoniaPharyngitis, necrotic foci(liver), tonsillitisFibrinous pleuritispericarditis, arthritis, meringitisdiverse : hemorrhage,oedema…Congested lungs, oedemarubber-like aspect of lungs,enlarged lymph nodesMycoplasma hyopneumoniaePasteurella multocidaBordetella bronchisepticaToxigenic P. multocida (D)ActinobacilluspleuropneumoniaeInfluenza virusesPRRS VirusAujeszky’s disease virusHaemophilus parasuisStreptococcus suisAscaris,S. choleraesuis,Circovirus (PCV2)9

Table 2 - Gross lesions in pigs inoculated with M. hyopneumoniae and yielding M. hyopneumoniea alone or incombination with P. multocida (Sorensen et al 1997)Autopsy (days pi )14 28 57 85 controls% lungs consolidated100 100 71 10 8mean lesion score 5.9 8.3 1.5 0.2 0.1M. hyopneumoniaealone• % of total numberof lungs92 26 90 82 0• mean lesion score 5.5b 5.7b 0.8b 0.2b _-M. hyopneumoniae +P. multocida• % of total numberof lungs• mean lesion score8 74 10 0 010.8c 9.3c 7.6c 0b _b, c : different letters on the same day indicate significant difference in mean lesion scores between the two groups (P

Table 3 – Severely affected lungs in growing pigs subject to varying temperatures and draughts (TIELEN et al1978, adapted by DONE 1991)% of severely affected lungs 26 14 6Temperature-fluctuationindex0,78 0,60 0,48Draughtiness index 137 130 11411

Table 4 – Housing and herd management conditions which may be proposed for better control of enzooticrespiratory disorders in growing-finishing pigs raised on confined farrow-to-finish operations- Sow herd• excellent health status of replacement stock• adaptation phase (quarantine) for purchased replacement stock in comfortable accommodations• batch farrowing system• appropriate hygiene and air quality• in specific cases, segregated early weaning as far as permitted by regulation,adequate logistics needed- Post-weaning and finishing phases• all-in/all-out system ie only contemporary pigs (born from sows of the same batch) located in the same room• cleaning/disinfection in-between batches, empty pit below slatted floor• air quality : -NH3:

Level of respiratory disordersexpressionAmplification due to an“influenza” outbreakImpact of enzootic pbrecrudescence farm BFarm B (1)Backgroundnoise farm Bfarm AId.Farm A (2)TimeDuration of the problemFigure 1: Schematic general trend of respiratory disorders expression infarrow-to-finish farmsInterfering effect of enzootic and epizootic disorders(1) farm B: “heavy” background noise of respiratory disorders(2) farm A: “light”background noise of respiratory disordersgrowing-finishing pigs in confined intensive13