Pathological Diagnosis of Mycoplasmosis in Swine

1
Pathological Diagnosis of Mycoplasmosis in Swine

• Swine Mycoplasma Pneumonia Workshop
• FDA / CVM
• March 6,7 of 2002
• Kansas City, MO
• Kent Schwartz

2
Swine Pneumonia Early Years

• Normal for pigs to cough / scratch
• Enzootic (Mycoplasma Pasteurella)
• Ascarid Migration
• 1918 H1N1 Swine Influenza
• Atrophic rhinitis (Bordetella and Pasteurella)
• Small farms / home remedies

3
(No Transcript)
4
Mechanization Trend to Confinement and Larger
Herds

• M hyo, SIV, ascarids, AR
• More science, agents, diagnostics
• PRV, Actinobacillus pleuropneumonia
• Pasteurella multocida with M hyo
• Age of therapeutics (antimicrobials)
• Vaccination products

5
(No Transcript)
6
Era of Altered Ecology/New Agents

• Segregated rearing / larger populations / Altered
  herd immunity / altered ecology
• M hyo, SIV, App remain
• Bacterial Opportunists Emerge
• Hemophilus parasuis, Streptococcus suis
• Actinobacillus suis, Salmonella sp. others
• New agents respiratory and systemic
• PRRSV, PCV, SIV H3N2, PRCV
• Porcine Respiratory Disease Complex (PRDC) is a
  multifactorial culmination

7
Immune Confusion

• Respiratory Tract mixing vessel for
• Systemic diseases (PRRSV, PCV, bacteria)
• Respiratory agents (SIV, bacteria)
• M hyo
• Herd immunity is variable for agents
• Sow herd stability influences maternal immunity
• Piglet infection status variable and sequential
• Immune status is variable
• Many permutations of agents involved
• Many permutations in sequence of infections and
  sequence may matter

8
M hyo remains Central and Primary

• Infection is common not easily eliminated
• Infection persists for months
• Alters mechanical clearance of debris
• Inflammation / immune-mediated damage
• Altered, nonproductive immune response
• Immunologically privileged site of infection so
  clearance is compromised
• Provides sites for opportunists
• Synergy with other lung pathogens

9
Clinical Disease M hyo alone

• Mild malaise
• No fever
• Cough nonproductive / chronic
• Moderate morbidity / no mortality
• Altered growth performance
• ADG
• Feed efficiency

10
Enzootic pneumoniaM hyo bacteria

• M hyo facilitates bacterial infections
• Cough, malaise and anorexia
• Moderate fevers 1030-1050
• Expiratory dyspnea / thump
• Variable morbidity and mortality
• Stunting, chronic pneumonia, death
• Strategic interventions (medication or
  vaccination) can influence outcome and/or
  subsequent disease severity

11
PRDC Enzootic pneumonia virus(M hyo
bacteria virus)

• Severe depression, high fever, anorexia
• Expiratory dyspnea (thump)
• Rapid loss of condition
• Medication less efficacious
• High morbidity and frequently high mortality
  (5-20)

12
Gross Pathology

• Bronchopneumonia
• Cranioventral, firm, exudate in airways
• Interstitial pneumonia
• Diffuse, mottled, lobular distribution
• Edema fluid in airways
• Both can occur simultaneously common in field
  cases of PRDC

13
Normal Lung Gross
14
Actinobacillus pleuropneumniae
15
Bronchogenic pneumoniaBacterial (B.
bronchiseptica)
16
Interstitial pneumonia(Viral, bacterial
septicemia)
17
M hyo mild and early
18
Early / mild M hyo.
19
SIV can be cranioventral
20
Lesion is not pathognomonic
21
Enzootic Mhyo P. multocida
22
PRDC Enzootic viral(M hyo P. multocida
PRRSV)
23
PRDC Mhyo P. multocida PRRSV
24
Enzootic Can resolve over time
25
Enzootic Resolution takes time
26
M hyo Gross Diagnosis

• Early 10 days-4 weeks
• Cranioventral, lobular, red, firmness
• Active 2-6 weeks
• Clearly demarcated, grayish, atelectasis
• Airways prominent with mucopus
• Resolution 5-20 weeks
• Gray fissures of atelectasis
• Distorted lobe structure of normal lung tissue
• A population will have animals at all stages of
  disease with variable severity

27
Histopathology Basics

• Bronchopneumonia
• Extends from small airways
• Bronchiolitis with exudate and debris
• Adjacent alveoli, interstitium
• Interstitial pneumonia
• extends from alveolar septae
• can involve small airways
• Both often present in chronic disease or in mixed
  infections.

28
Histopathology is Fallible

• Agents and agent combinations outnumber possible
  responses
• Chronic lesions are less specific
• Classic lesions only with single agents at some
  stages of disease
• Few lesions are pathognomonic or etiologically
  specific
• Lesions are compatible with.

29
M hyo Histopathological Diagnosis

• Early 10 days-4 weeks
• peribronchiolar lymphohistiocytic inflammation
  scattered neutrophils
• Active 2-12 weeks
• mucopus, atelectasis
• Resolution 5-20 weeks
• BALT hyperplasia
• A population will have animals at all stages of
  disease with variation in lesion severity

30
What else can look like M hyo ?

• Chronic persistence of antigen/agent
• Lymphoid hyperplasia / airway cuffs
• Subacute SIV Early M hyo
• Ascarid migration resolving
• Chronic bacterial pneumonia
• Chronic viral pneumonia
• It is often difficult to demonstrate organisms in
  chronic lesions

31
Mh IHC
32
M. hyopneumoniae IFA
33
M. hyopneumoniae Histopathology
34
M hyo BALT hyperplasia
35
Key Points Pathological Diagnosis

• Gross lesions are compatible with but not
  specific for M hyo
• Microscopic lesions are compatible with but are
  not specific for M hyo
• Sensitivity and Specificity of pathology??
• Most field cases are mixed infections
• M hyo, bacteria, viruses
• Time for resolution varies with
• Severity and extent of initial lesion
• Presence of concurrent pathogens

36
Etiologic diagnosis requires

• Demonstration of specific agent
• M hyo isolation is not routine
• Demonstration of specific antigen
• IHC, FAT, ELISA
• Demonstration of specific agent nucleic acid
• PCR and PCR based assays
• Serology confirms antibody but is NOT a
  definitive etiologic diagnosis

37
Diagnosis of Swine Pneumonia

• Research / Infection models
• controlled infection, controlled specimen
  collection, and standardized evaluations
• Predictable outcomes / valid measures
• Field Cases variability is uncontrolled
• Descriptive pathology has limitations
• Demonstrate agents specimen dependant
• age, stage, specimens, interventions
• Interpret results in the context of clinical
  signs, history and population dynamics

38
An accurate and useful field diagnosis uses all
available information

• Clinical signs, history, diagnostic records
• Production records
• Compatible gross lesions
• Compatible microscopic lesions
• Identify agents with appropriate tests
• Primary agents, secondary agents
• Define epidemiology in the population
• Serologic cross-sectional or longitudinal
• In population, infection and immunity status
  varies so need statistical sampling techniques

39
Mixed agents, duration, population variability
makes definitive diagnosis a challenge
40
Diagnostic profiles change over time
41
Summary M hyo in swine

• M hyo is common in swine populations
• M hyo alone is mild disease with cough,
  suppression of growth and feed efficiency
• M hyo duration of effect (3-20 weeks) creates
  opportunities for co-infections
• Not all are affected equally/simultaneously
• Enzootic pneumonia is M hyo bacteria
• PRDC is M hyo bacteria viruses

42
Summary M hyo in swine

• Takes time for lesions to develop / resolve
• Pathology is useful to describe severity
• Variability of lesion severity in populations
• Most field cases are mixed infections
• Field measures of current interventions
• Reduced prevalence of clinical pneumonia
• Reduced lesion prevalence and severity
• Reduced medication cost, treatments
• Less variation in growth rate
• Control of M hyo disease severity often does
  mitigate severity of other endemic diseases
• Infection models are useful to evaluate M hyo
  intervention strategies and disease interactions

43
(No Transcript)