Interactions Between Interactions Between M. M. hyopneumoniaehyopneumoniae and Other and Other

PathogensPathogens

Eileen L. ThackerEileen L. Thacker

DVM, PhD, DACVMDVM, PhD, DACVM

Iowa State UniversityIowa State University

Porcine Respiratory Disease Porcine Respiratory Disease Complex (PRDC)Complex (PRDC)

• EconomicallyEconomically significant to the significant to the swine industry in the swine industry in the U.S.U.S.

Pathogens Associated with Pathogens Associated with PRDCPRDC

• PRRSVPRRSV

• Mycoplasma hyopneumoniaeMycoplasma hyopneumoniae

• Swine influenza virus (SIV)Swine influenza virus (SIV)

• Actinobacillus pleuropneumoniaeActinobacillus pleuropneumoniae

• Streptococcus suisStreptococcus suis

• Pasteurella multocidaPasteurella multocida

• Aujeszky’s disease (Pseudorabies virus )Aujeszky’s disease (Pseudorabies virus )

Enzootic pneumoniaEnzootic pneumonia

• Mycoplasma hyopneumoniaeMycoplasma hyopneumoniae – Mycoplasmal pneumoniaMycoplasmal pneumonia

• M. hyopneumoniaeM. hyopneumoniae plus plus– Pasteurella multocidaPasteurella multocida– Bordetella bronchisepticaBordetella bronchiseptica– Haemophilus parasuisHaemophilus parasuis– Actinobacillus pleuropneumoniaeActinobacillus pleuropneumoniae– Etc.Etc.

M. hyopneumoniae & P. multocidaM. hyopneumoniae & P. multocida(Enzootic Pneumonia)(Enzootic Pneumonia)

PRDCPRDC

• Enzootic pneumonia +Enzootic pneumonia +

• PRRSVPRRSV

• SIVSIV

• PCV 2?PCV 2?

Which Diseases are Considered Which Diseases are Considered the Biggest Problem in PRDC?the Biggest Problem in PRDC?

• Varies from farm-to-farmVaries from farm-to-farm

• Porcine respiratory disease complex Porcine respiratory disease complex common problem in finishing pigscommon problem in finishing pigs

• NOT in the scope of this talk to discuss NOT in the scope of this talk to discuss all pathogensall pathogens– results of current research results of current research

Mycoplasma hyopneumoniaeMycoplasma hyopneumoniae

• Cause of “enzootic pneumonia”Cause of “enzootic pneumonia”– Other secondary pathogensOther secondary pathogens

• APPAPP• Pasteurella multocidaPasteurella multocida• PRRSVPRRSV

• Clinical signs-Clinical signs-M. hyopneumoniaeM. hyopneumoniae alone alone– mild, dry, nonproductive coughmild, dry, nonproductive cough

PathogenesisPathogenesis

• Very slow to colonize and multiplyVery slow to colonize and multiply

• 2 weeks+ to induce observable lesions2 weeks+ to induce observable lesions

• 4-6 weeks before serum antibodies 4-6 weeks before serum antibodies producedproduced

• 4-8 weeks to resolution4-8 weeks to resolution

• Organisms never eliminated from pig?Organisms never eliminated from pig?

• Adheres only to cilia of airwaysAdheres only to cilia of airways

• Does not invade lung tissuesDoes not invade lung tissues

DiseaseDisease

• Decrease the function of the mucociliary Decrease the function of the mucociliary apparatusapparatus– decrease clearance of other pathogens and decrease clearance of other pathogens and

debrisdebris

• Modulation of the immune systemModulation of the immune system– immunosuppression-macrophages - APPimmunosuppression-macrophages - APP– immunostimulation-lymphocytesimmunostimulation-lymphocytes– cytokine productioncytokine production

PathologyPathology

• Chronic pneumoniaChronic pneumonia– 2-3 weeks for pneumonic lesions to appear2-3 weeks for pneumonic lesions to appear– mildmild– focal, well-demarcated area of cranioventral focal, well-demarcated area of cranioventral

consolidationconsolidation

HistopathologyHistopathology

• BronchopneumoniaBronchopneumonia• Perivascular and peribronchiolar Perivascular and peribronchiolar

cuffingcuffing– Influx of lymphocytes and macrophagesInflux of lymphocytes and macrophages

• primarily B cellsprimarily B cells• non-specificnon-specific

Evasion of the Immune SystemEvasion of the Immune System

• Mucosal pathogenMucosal pathogen– locationlocation

• Structure and make up of surfaceStructure and make up of surface– slime layersslime layers– capsulecapsule– no cell wallno cell wall

a

Low Adherent High Adherent

Control

Proinflammatory CytokinesProinflammatory Cytokines

• TNF-TNF-• IL-1IL-1

• IL-6IL-6

• Important in further inducing inflammation Important in further inducing inflammation in the lungsin the lungs

Dual infection of Pigs withDual infection of Pigs with PRRSV and PRRSV and Mycoplasma Mycoplasma

hyopneumoniaehyopneumoniae

E.L. Thacker, P.G. Halbur, B.J. E.L. Thacker, P.G. Halbur, B.J. Thacker and R. F. RossThacker and R. F. Ross

Iowa State UniversityIowa State University

Porcine Reproductive and Porcine Reproductive and Respiratory Syndrome VirusRespiratory Syndrome Virus

PRRSVPRRSV

• An An ArterivirusArterivirus– Enveloped RNA virusEnveloped RNA virus– all infect macrophagesall infect macrophages– all cause prolonged infectionsall cause prolonged infections

• High mutation rate due to method of High mutation rate due to method of replication = constant minor changesreplication = constant minor changes– Accounts for differences between “isolates”Accounts for differences between “isolates”– No such thing as “strains”No such thing as “strains”

Clinical SignsClinical Signs

• Severe to no clinical disease in the fieldSevere to no clinical disease in the field

• In our experimental modelIn our experimental model– maximum pneumonia is 10 daysmaximum pneumonia is 10 days– fever, respiratory distress, lethargy, anorexiafever, respiratory distress, lethargy, anorexia– no coughno cough– pneumonia resolved by 21-28 dayspneumonia resolved by 21-28 days

PathologyPathology

• Diffuse, tan-mottled consolidation of the Diffuse, tan-mottled consolidation of the lungslungs

Evades the Immune SystemEvades the Immune System

• PersistsPersists– > 100 days > 100 days

• Very slow to ineffective systemic immune Very slow to ineffective systemic immune responseresponse– viremia in presence of antibodiesviremia in presence of antibodies– can be reinfected by different strainscan be reinfected by different strains– alteration of immune response by directing alteration of immune response by directing

cytokinescytokines

Experimental DesignExperimental Design

• Three different inoculation protocolsThree different inoculation protocols– PRRSV first (-10 days)PRRSV first (-10 days)– M. hyopneumoniaeM. hyopneumoniae first (-21 days) first (-21 days)– concurrent (0 days)concurrent (0 days)

• Three necropsy datesThree necropsy dates– 3 DPI3 DPI– 10 DPI – maximum PRRSV pneumonia10 DPI – maximum PRRSV pneumonia– 28 DPI – maximum mycoplasma pneumonia28 DPI – maximum mycoplasma pneumonia

Mycoplasma Pneumonia

0

1

2

3

4

5

6

7

8

9

M+P(0) M(-21) P(0)

P(-10) M(0)

M(-21) M(0) P(0) Negative

Groups (Trial Day)

Pe

rce

nt

Pn

eu

mo

nia

3 DPI

10 DPI

28 DPI

PRRSV Pneumonia

0

10

20

30

40

50

60

M+P(0) M(-21)P(0)

P(-10)M(0)

M(-21) M(0) P(0) Negative

Groups (Trial day)

Perc

en

t P

neu

mo

nia

3 DPI

10 DPI

28 DPI

ConclusionsConclusions

• Pigs infected with both Pigs infected with both M. hyopneumoniaeM. hyopneumoniae and PRRSV:and PRRSV:– SS– significantly increased clinical respiratory significantly increased clinical respiratory

diseasedisease– macroscopic lesions consistent with PRRSV-macroscopic lesions consistent with PRRSV-

induced pneumonia lasted significantly longerinduced pneumonia lasted significantly longer– increased increased M. hyopneumoniaeM. hyopneumoniae-induced -induced

pneumonia at 10 days post infection with bothpneumonia at 10 days post infection with both

PRRSV- 10 DPIPRRSV- 10 DPI PRRSV - 28 DPIPRRSV - 28 DPI

M. hyopneumoniaeM. hyopneumoniae - 28 DPI - 28 DPI Dual Infection - 28 DPIDual Infection - 28 DPI

Conclusions (cont.)Conclusions (cont.)

• No long term increase in No long term increase in M. M. hyopneumoniaehyopneumoniae-induced pneumonia -induced pneumonia macroscopicallymacroscopically

• Pigs with minimal to no macroscopic Pigs with minimal to no macroscopic mycoplasmal pneumonia lesions exhibited mycoplasmal pneumonia lesions exhibited potentiation of PRRSV-induced potentiation of PRRSV-induced pneumoniapneumonia

WHY? WHY?

• Pathogenesis complement each otherPathogenesis complement each other– M. hyopneumoniaeM. hyopneumoniae attracts macrophages for attracts macrophages for

PRRSV to infectPRRSV to infect– both induce inflammationboth induce inflammation– both direct the immune response from a Th1 both direct the immune response from a Th1

towards a Th2 responsetowards a Th2 response– production of IFN-production of IFN-γγ is correlated to virus is correlated to virus

clearanceclearance• delayed in pigs infected with both pathogensdelayed in pigs infected with both pathogens

Why?Why?

• Immune systemImmune system– both evade the immune systemboth evade the immune system– both modulate the immune systemboth modulate the immune system– both chronicboth chronic

• PRRSV-persistancePRRSV-persistance• M. hyopneumoniaeM. hyopneumoniae chronic chronic

Interaction between Interaction between M. hyopneumoniaeM. hyopneumoniae and SIV and SIV

E. Thacker, B. Thacker E. Thacker, B. Thacker

and B. Jankeand B. Janke

Iowa State UniversityIowa State University

What do we knowWhat do we know

• M. hyoM. hyo– infect epithelial infect epithelial

cells (cilia)cells (cilia)– causes a chronic causes a chronic

pneumoniapneumonia

• SIVSIV– infects epithelial infects epithelial

cellscells– causes acute causes acute

pneumonia – but pneumonia – but will last 3+ weeks will last 3+ weeks histologicallyhistologically

Experimental DesignExperimental Design

• M. hyopneumoniaeM. hyopneumoniae strain 232 strain 232 intratracheally (-21 Trial Day)intratracheally (-21 Trial Day)

• ISU SIV inoculum (H1N1) nebulized ISU SIV inoculum (H1N1) nebulized intranasally (0 Trial Day) intranasally (0 Trial Day)

• Pigs necropsied at 3, 7, 14 and 21 days Pigs necropsied at 3, 7, 14 and 21 days post SIV infectionpost SIV infection

Percent Pneumonia

0

2

4

6

8

10

12

14

16

Day 3 Day 7 Day 14 Day 21

Groups

Pe

rce

nt

Pn

eu

mo

nia

M. hyopneumoniae (-21)

SIV (0)

SIV (0), M. hyopneumoniae (-21)

Confusing AppearanceConfusing Appearance

ResultsResults

• Dual infected pigs had highest coughing Dual infected pigs had highest coughing scoresscores

• Pneumonia lasted longer-additive in Pneumonia lasted longer-additive in naturenature

ConclusionsConclusions

• Unlike with PRRSV, Unlike with PRRSV, SIV and SIV and M. M. hyopneumoniaehyopneumoniae appear to be additiveappear to be additive

• Both infect epithelial Both infect epithelial cells – important for cells – important for secondary pathogenssecondary pathogens

• Different Different pathogenesis than pathogenesis than with PRRSVwith PRRSV

Circovirus (PMWS)Circovirus (PMWS)

• PCV 2 alone induces minimal diseasePCV 2 alone induces minimal disease

• Combined with PRRSV, Porcine Combined with PRRSV, Porcine Parvovirus results in significant increase in Parvovirus results in significant increase in pneumoniapneumonia

• Interaction and role of Interaction and role of M. M. hyopneumoniae?hyopneumoniae?

• Role of vaccination?Role of vaccination?

• Mechanism is unknownMechanism is unknown

• Can bet immune system is involvedCan bet immune system is involved

ConclusionsConclusions

• M. hyopneumoniaeM. hyopneumoniae and PRRSV are both and PRRSV are both important factors in PRDCimportant factors in PRDC

• The pigs in our studies had no other The pigs in our studies had no other pathogenspathogens– these contribute to and interact with each these contribute to and interact with each

otherother

• These studies are aimed at beginning to These studies are aimed at beginning to understand the interaction between the understand the interaction between the various pathogensvarious pathogens

Conclusions (cont.)Conclusions (cont.)

• PCV 2 increasing in importance of disease PCV 2 increasing in importance of disease interactionsinteractions

• Other pathogens such as Other pathogens such as P. multocida P. multocida and and B. bronchiseptica B. bronchiseptica present add to the present add to the diseasedisease

• Diagnostics become very important on Diagnostics become very important on individual farm settings to implement the individual farm settings to implement the appropriate controlsappropriate controls

Conclusions (cont.)Conclusions (cont.)

• As our understanding of the pathogenesis As our understanding of the pathogenesis increases, appropriate intervention increases, appropriate intervention strategies can be developedstrategies can be developed– vaccines – very importantvaccines – very important

• new and currentnew and current

– antibioticsantibiotics– strategic timing of abovestrategic timing of above