Mycoplasma hyopneumoniae Associated Respiratory Disease on the Farm Brad Thacker Iowa State University

Mhyo: General Characteristics Obligatory pathogen of the respiratory tract of the pig Infection is limited to the airways Mhyo by itself causes little if any reduction in performance Recognized as an initiator or potentiator of more serious respiratory diseases caused by other primary or opportunistic pathogens

Mhyo: General Characteristics Does Mhyo potentiate the impact of bioreactive environmental contaminants such as endotoxins and glucans? Mhyo infected herds are at greater risk for developing respiratory disease compared to Mhyo-free herds

Mhyo: General Characteristics Mhyo utilizes several mechanism to cause disease –Respiratory immune system modulation Attraction of lymphocytes Cytokine profile –Cilia atrophy resulting in reduced function of innate defense mechanisms

Impaired Innate Defenses Mucociliary apparatus dysfunction –Mycoplasma hyopneumoniae causes cilia atrophy –Dehydration decreases fluid layer => reduced cilia activity –Ammonia inhibits cilia movement resulting in reduced clearance of bacteria –Carbon dioxide/monoxide effects? Disruption makes pigs more prone to developing pneumonia

Mhyo: Historically Clinical presentation –Chronic, low-to-moderate grade pneumonia –Variable morbidity –Reduced growth rate –Low mortality –Recognized in finishing pigs Characterized as “enzootic pneumonia”

Mhyo: Historically Mhyo was believed to be the primary cause of enzootic pneumonia Opportunistic bacteria, especially Pasteurella multocida (Pm) were believed to be “secondary invaders” Relative contribution of each bacteria was difficult to ascertain Pm was not a concern in Mhyo free or “quite” herds

Mhyo: Historically Explosive outbreaks of respiratory disease were attributed to SIV, App or a “hot” Pasteurella –SIV was a minor, periodic problem Differentiate from PRV –App was the “profit robber” Mixed sources of feeder pigs Poor understanding of environmental triggers Poor understanding of vaccinology (ApX toxins)

Mhyo: Historically Diagnostics –Few laboratory capabilities –More veterinary contact => better clinical assessment –Fewer records => less production and economic data –Slaughter checks used but didn’t understand how to interpret the data very well –In total, relatively subjective evaluations

Mhyo: Historically Control –No vaccines –All-in-all-out by room –Periodic medication for secondary invaders Pulse one week every month (CTC/BMD rotation) During stress periods –Weaning –Move from nursery to finisher –Many farms had more than two phases Based on severity of disease: vet evaluated –Better diets, ventilation, pig flow

Mhyo: Historically Subjective evaluations => “Seat of the pants” approach Limited factors to control However, NOT uniformly ineffective!! –No PRRS virus –Smaller herd sizes –Smaller room sizes => better microenvironments?

Mhyo: Currently Evolution of swine respiratory disease –More explosive, but repeated outbreaks Somewhat older pigs (16-20 weeks of age) Predictable age at onset –High morbidity –Increased stall-out pigs –Variable, but sometimes high, mortality Designated as the “porcine respiratory disease complex” (PRDC)

Mhyo: Currently Common organisms isolated from PRDC cases besides Mhyo –PRRS virus –Swine influenza virus (SIV) –Pasteurella multocida (Pm) –Porcine circovirus Type 2 (PCV2) –Actinobacillus pleuropneumoniae, A. suis –Salmonella cholerasuis –Hemophilus parasuis and Streptococcus suis

Mhyo: Currently The main difference between enzootic pneumonia and PRDC? –Viruses!! PRRSV Changing pattern of SIV PCV2?

Mhyo: Currently Mhyo often plays a significant role in the underlying severity of PRDC or enzootic pneumonia Mhyo vaccination tends to be beneficial in herds with varying degrees and presentations of respiratory disease

Mhyo Vaccination Field Study 14 herds in Belgium Vaccinate at 1 and 4 weeks of age Improvements –Daily gain (+22g) and FCR (-.07) –Decreased medication costs ($1.02); greatest benefit –Prevalence (-14%) and lesions (-3%) at slaughter –None- mortality, coughing, carcass quality

Why PRDC vs. enzootic pneumonia? What has changed? New agents –PRRS virus!! Pig flow –Increasing herd size –Age segregated rearing, multiple site production –Reduced weaning age?! Less attention to pig comfort –Especially in the nursery => more poor pigs Phase feeding –Potentially more pigs on the wrong diet

Pig Flow Related Issues Benefits of AIAO and SEW were demonstrated in small herds and/or small scale research projects –Bacterial disease control is the primary benefit –Viruses have emerged as important contributors –Prevention of vertical transmission via early weaning results in highly susceptible populations of finishing pigs –Prevention of lateral transmission via AIAO results in highly susceptible populations of finishing pigs

Pig Flow Related Issues Applicability to large herds/systems –Continual pathogen circulation in breeding herd –Compliance with pig flow rules (weaning age) –Multiple sites: many finishers close together, viruses transmitted between sites (PRV, SIV, PRRSV) –High capital investment => keep facilities full => no flexibility to eliminate disease via sequential depopulation => continual disease

Pig Flow Based Disease Control Disease level will continue to increase unless the cycle is broken –Pre-PRRS: Sequential depopulation of rooms within a building was reasonably effective for bacterial diseases –Post-PRRS: Sites need to be depopulated to move disease out

PRDC Prevention and Control Multi-factorial approach is necessary –Management, sanitation, nutrition, pig flow, growth promoters and environment Improve disease status and productivity in a general sense –Medical: vaccination, acclimatization of new animals and therapeutics Reduce the impact of specific diseases

PRDC Prevention and Control Multi-factorial approach is necessary –Recognize that some diseases or deficiencies can be dealt with and some can’t Available technology Cost considerations: can’t afford every product –Strategy => success Aggressive = do everything possible Conservative = change one thing

Clinician’s View of Diagnostics Identifying all of the organisms present in a given situation is essential The clinician’s challenge is sorting out the relative role that each organism plays –Tissue level: histopath –Organ level: extent of lesions –Animal level: severity of signs, organs damaged –Herd level: number of animals affected and severity Determine economic impact to justify action

Clinician’s View of Diagnostics Gross (visible, macroscopic) lesions are of little diagnostic value except in App cases –Main decision in acute outbreaks: App or not? Lesions of Mhyo, SIV and in a recent case of PRRSV/circovirus look the same Must verify cause of lesion by histopath and organism identification

Question: Is this mycoplasma?

Swine Influenza Virus

Clinician’s View of Diagnostics Clinical signs are not characteristic of any one disease or disease combinations –Fever –Cough –Increased respiration rate –Dyspnea

Clinician’s View of Diagnostics With enzootic pneumonia, diagnosis was often limited to necropsy lesions with very little laboratory testing –Were our assessments correct? –Did we truly understand the role of the various organisms involved? –Likely not Are we doing better with PRDC diagnostics?

Diagnostic Sampling Strategies Small numbers of pigs tested will result in missed diagnoses –PRDC case: 21 finishing pigs of various ages submitted for necropsy –Pathology/microbiology: –No lesions =5Gastric ulcer = 2 –PMWS = 5PRRSV = 2 –SIV? = 1App? = 3 (non-typeable) –P. mult. = 2Bordetella = 2 –Strep suis = 1M. hyo = 8 –Serology: M. hyo+, SIV+, PRRSV(late +) –Slaughter check: Low average percent pneumonia, a few pigs with severe A-V pneumonia

Clinician’s View of Diagnostics The severity of pneumonia observed at slaughter may have little relationship to the impact of pneumonia on life time health status and growth performance Lesions resolve with time: –SIV => quickly (2-3 weeks) –Mhyo => slowly (2-3 months)

Clinician’s View of Diagnostics Few production systems can monitor daily feed and water intake, which can pinpoint when disease is affecting performance Unable to detect short time periods of reduced performance that significantly contribute to reduced close-out based performance Vaccination, prevention, control decisions ultimately are based on economics –Costs are relatively easy to determine –Benefits (reduced disease impact) are difficult to determine

Summary Still not smart enough to effectively control respiratory disease in swine –Pathogens –Environmental stressors –Economics Every herd situation is unique –Diagnostics and remedial actions need to be implemented on a farm-by-farm basis –“Cookie cutter” production/medical approach does not work very well

Summary Laboratory research and diagnostic testing frame the questions for and define the limits of the clinician’s approach to each situation The final answer ultimately lies with the attending clinician, who makes the diagnosis and formulates, implements and monitors treatment and control programs