Respiratory Pathogens (LA) Flashcards
What is the function of the ciliated respiratory epithelium?
To propel mucus up the airway, thereby removing particulate material
What are three bacterial species that have a tropism for ciliated epithelium of the respiratory tract?
- Bordetella
- Mycoplasma
- Chlamydia
Which five bacteria contribute to the clinical signs of bovine respiratory disease (BRD) or ‘shipping fever’?
- Mannheimia hemolytica
- Histophilus somni
- Mycoplasma bovis
- Pasteurella multocida
- Bibersteinia trehalosi
What are the clinical signs of BRD?
- Anorexia
- Depression
- Coughing
- Nasal discharge
- Fever
- Crackles in lungs
What samples should you collect to test for BRD on necropsy?
- Lungs
- Trachea and bronchus
- Heart
- Spleen
- Kidney
- Liver
What diagnostics should you use to test for BRD?
- Thoracic ultrasonography
- Culture and susceptibility
- PCR
- Necropsy
What are the characteristics of Mannheimia haemolytica?
- Gram-negative
- Facultative anaerobe
- Commensal bacteria of oropharyngeal and GI tract
What does M. haemolytica cause other than BRD?
Bronchopneumonia and septicemia
Which bacterial species predisposes the host to pneumonic pasteurellosis?
Mycoplasma
What are the virulence factors of M. haemolytica?
- Leukotoxin: Induces lysis of leukocytes and platelets → this causes tissue damage from proteolytic enzymes released from leukocytes
- Capsular polysaccharide (CPS): Prevents phagocytosis
- Lipopolysaccharide (LPS): Stimulates cytokine releases and microvascular necrosis → this induces edema, hemorrhage, and inflammation
What is the pathogenesis of M. haemolytica?
- Viral infections/environmental stressors lead to shift in the mucosal-commensal relationship leading to colonization of the organism
- Spread to other animals by inhalation of fomites or infective droplets
- Bacteria deposit in the mucous layer of the mucociliary apparatus
- Toxins lead to mucociliary dysfunction causing pneumonia
What lesions do we see with M. haemolytica?
- Hemorrhagic fibrinonecrotic bronchopneumonia
- Septicemia with fibrinous pleuritis, pericarditis, and peritonitis
What are the characteristics of Histophilus somni?
- Gram-negative
- Colonizes mucosal surfaces
True or False: Histophilus somni is the sole species of the genus Histophilus
True
What are the virulence factors of Histophilus somni?
Virulence is poorly defined. H. somni lacks a capsule, exotoxins, fimbriae, or surface structures that explain its virulence.
What is the pathogenesis of H. somni?
- Intracellular survival and replication in neutrophils, macrophages and monocytes
- LPS phase variation may enable evasion of the immune system
- Adheres to endothelial cells → induces cytotoxic changes, vasculitis and induction of apoptosis → formation of fibrinoid thrombi
What clinical signs does Histophilus somni cause in cattle?
- Pleuritis
- Myocarditis (and sudden death)
- Thrombotic meningoencephalitis (CNS signs)
What lesions do you see with H. somni?
- Fibrinous pleuritis, pericarditis, and bronchopneumonia
- Focal myocardial lesions
- Polyarthritis
- Fibrinous laryngitis
What laboratory diagnostics should you use to test for Histophilus somni?
- Necropsy
- Culture and susceptibility
- PCR
What are some post-mortem findings of H. somni?
- Multiple organs with evidence of thrombus and fibrinous inflammation
- Necrotic myocardial sequestrum (left papillary muscle)
- Thrombotic meningoencephalitits
What are some characteristics of Mycoplasma species?
- Lack a cell wall
- Slow growing
- Fastidious
- Host-specific!
Mycoplasma has a tropism for which two body systems?
- Respiratory
- Urogenital
Mycoplasma needs cilia - it wants to attach to the ciliated epithelium of trachea, bronchi, bronchioles
What are some virulence factors of Mycoplasma?
- Adhesins
- Hydrogen peroxide and reactive oxygen species (ROS)
- Biofilm formation
What is the pathogenesis of Mycoplasma?
Adherence to host cells → direct damage to ciliated epithelium → promotes neutrophil and mononuclear cellular response → ciliostasis → progresses to pneumonia
What lesions do you see with Mycoplasma?
- Bronchitis, bronchiolitis, pneumonia (in the ventral parts of the apical and cardiac lung lobe)
- Pleuropneumonia (fibrinonecrotic pneumonia, serofibrinous pleuritis, lesions may become sequestered in a fibrous capsule with viable bacteria)
What diagnostics should you do to test for Mycoplasma bovis?
PCR
Which three bacteria cause respiratory disease in small ruminants?
- Bibersteinia trehalosi
- Mycoplasma ovipneumoniae
- Corynebacterium pseudotuberculosis
Histophilus somni and Mannheimia hemolytica also contribute
What are some characteristics of Bibersteinia trehalosi?
- Gram-negative
- Commensal of the tonsils and nasopharynx
What are the virulence factors of Bibersteinia trehalosi?
- Leukotoxin: Induces lysis of leukocytes and platelets → this causes tissue damage from proteolytic enzymes released from leukocytes
- Capsular polysaccharide (CPS): prevents phagocytosis
- Lipopolysaccharide (LPS): stimulates cytokine releases and microvascular necrosis → this induces edema, hemorrhage and inflammation
Similar to M. haemolytica in cattle
What is the pathogenesis of Bibersteinia trehalosi?
Stressors → susceptible to respiratory infections → predisposes to secondary bacterial infections → once in the lungs (pneumonia) → systemic spread via blood to heart, liver, kidneys, spleen, joints, meninges
Similar to M. hemolytica in cattle
What general clinical signs does Bibersteinia trehalosi cause in small ruminants?
Bronchopneumonia and septicemia
Similar to M. hemolytica in cattle
What lesions do you see with Bibersteinia trehalosi?
- Fibrinous and ulcerative lesions of the oral cavity
- Suppurative bronchopneumonia
- Septicemia
What diagnostics should you do to test for Bibersteinia trehalosi?
- Culture and susceptibility
- PCR
- Necropsy
What are some predisposing factors of Mycoplasma ovipneumoniae?
- Other bacterial pneumonias (pasteurellosis) and viral infections
- Stress
What lesions do you see with Mycoplasma ovipneumoniae?
Suppurative bronchopneumonia
What diagnostics should you do to test for Mycoplasma ovipneumoniae?
- PCR
- Necropsy
What are some characteristics of Corynebacterium pseudotuberculosis?
- Gram-positive
- Facultative intracellular organism
Highly contagious, persists in the environment! Very hard to get rid of
What disease does Corynebacterium pseudotuberculosis cause in small ruminants?
Caseous lymphadenitis
What are some virulence factors for Corynebacterium pseudotuberculosis?
- Corynemycolic acids: Unique cell wall structure which may mediate intracellular survival
- Phospholipase D: Exotoxin, lethal to phagocytic cells, inhibits neutrophils, inactivates complement and increases vascular permeability
How is Corynebacterium pseudotuberculosis transmitted?
Direct contact with fomites
What is the pathogenesis of Corynebacterium pseudotuberculosis?
Contamination through penetrating or superficial wounds (shearing, castration, ear tags, other traumatic events) → bacteria reaches submucosa/subcutis → macrophages phagocytosis bacteria → transportation to lymph nodes → replication and inflammatory response → pyogranuloma formation and tissue destruction
What lesions do we see with Corynebacterium pseudotuberculosis?
- Pyogranulomatous abscesses of lymph nodes
- Systemic spread leads to abscesses in liver and lung
What is the classic lesion associated with caseous lymphadenitis in small ruminants?
Pyogranulomatous abscesses of lymph nodes caused by Corynebacterium pseudotuberculosis
Which bacterial species is associated with the clinical signs of pleuritis, myocarditis, and thrombotic meningoencephalitis in cattle?
Histophilus somni
Which bacterial agent causes hemorrhagic fibrinonecrotic bronchopneumonia in cattle?
Mannheimia hemolytica
Which bacterial agent causes fibrinonecrotic pneumonia, serofibrinous pleuritis, and bronchitis?
Mycoplasma bovis
Which three bacteria cause respiratory disease in swine?
- Actinobacillus pleuropneumoniae (APP)
- Bordetella bronchiseptica (atrophic rhinitis)
- Mycoplasma hyopneumoniae
What diagnostics should you do to test for Corynebacterium pseudotuberculosis?
- FNA of swelling areas
- Culture and susceptibility
- Necropsy
- Serology
What are some characteristics of Actinobacillus pleuropneumoniae?
- Gram-negative
- Fastidious
- Very important economically damaging disease
What are some virulence factors of Actinobacillus pleuropneumoniae?
- Fimbriae (adhesion and attachment)
- Apx toxins (affinity for alveolar epithelial cells, endothelial cells, RBCs, neutrophils and macrophages)
- Proteases (breakdown of host cell proteins)
What is the pathogenesis of Actinobacillus pleuropneumoniae?
Close contact exposure → colonization of tonsils and alveolar epithelium → phagocytosed by macrophages → toxin production → tissue damage (coagulative necrosis) → severe necrotizing vasculitis → septic shock (peracute death) and/or lung lesions
What lesions do you see with Actinobacillus pleuropneumoniae?
- Necro-hemorrhagic areas of consolidation with fibrinous pleuritis
- Hemorrhage and necrosis of the caudal dorsal lobes
- Interlobular edema
What diagnostics should you do to test for Actinobacillus pleuropneumoniae?
- Necropsy
- Culture and susceptibility
- Serology
What samples should you collect to test for Actinobacillus pleuropneumoniae?
- Lungs
- Brain
Which bacterial species is known for causing severe hemorrhages and necrosis in the caudal dorsal lobes of the lungs in swine?
Actinobacillus pleuropneumoniae
What are some characteristics of Bordetella bronchiseptica?
- Gram-negative
- Obligate aerobe
- Obligate pathogen (needs host to survive)
Which main disease does Bordetella bronchiseptica cause?
Atrophic rhinitis (complex of P. multocida Type A or D and B. bronchiseptica)
Extremely contagious
What are some virulence factors of Bordetella bronchiseptica?
- Fimbriae (attachment to host cell respiratory epithelium)
- Adenylate cyclase hemolysin (inhibits phagocytosis)
- Tracheal cytotoxin (damages and paralyzes ciliated tracheal epithelial cells)
- Increases mucous secretion, vasoconstriction of blood vessels
- Dermonecrotic toxin (inhibitory towards osteoblasts)
- LPS (causes influx of neutrophils and macrophages causing diphtheric membrane formation)
What is the pathogenesis of Bordetella bronchiseptica?
Pre-existing infection with B. bronchiseptica → colonization and proliferation of P. multocida → toxins produced by P. multocida (PM toxin) cause epithelial hypoplasia, atrophy of mucous glands and osteolysis → dermonecrotic toxin inhibits osteogenesis → atrophy of nasal turbinates and shrinking of snout
What lesions do you see with Bordetella bronchiseptica?
- Mild non-progressive lesions (Bordetella alone)
- Mild to severe turbinate atrophy +/- deviation of the nasal septum (Pasteurella and Bordetella combined)
What diagnostics should you do to test for Bordetella bronchiseptica?
- Culture and susceptibility (take a nasal swab)
- PCR
- Necropsy
Which three bacteria cause respiratory disease in poultry?
- Pasteurella multocida (fowl cholera)
- Avibacterium paragallinarum (infectious coryza)
- Mycoplasma gallisepticum (chronic respiratory disease)
What disease does Pasteurella multocida cause in chickens?
Fowl cholera
What disease does Avibacterium paragallinarum cause in chickens?
Infectious coryza
What are four clinical signs of poultry that indicate respiratory distress?
- Gasping
- Coughing
- Rales (lung crackles)
- Cyanosis
What are some characteristics of Pasteurella multocida?
- Gram-negative
- Facultative anaerobe
- Commensal of the mucous membranes, oropharynx, and GI tract
What are the virulence factors of Pasteurella multocida?
- PM toxin (cytotoxin)
- Polysaccharide capsule (prevents phagocytosis, resistance to complement, adherence)
Which main disease does Pasteurella multocida cause?
Fowl cholera
What are the two forms of fowl cholera?
Acute: Sudden onset, high morbidity and mortality (sudden death)
Chronic: Survivors of acute form or low virulence strains (asymptomatic, localized exudative infections and inflammation)
What lesions do we see with Pasteurella multocida?
Acute (Septicemia): Hemorrhages, hepatomegaly with focal necrosis, pharyngitis, airsacculitis, pneumonia, increase pericardial and peritoneal fluids
Chronic: Exudative infections (conjunctivitis, sinusitis, otitis media, meningitis), facial edema (swelling of face, wattles, sternal bursa, legs, joints)
How can we diagnose Pasteurella multocida?
- Culture and sensitivity (via tracheal swabs)
- Blood samples
What are some characteristics of Avibacterium paragallinarum?
- Gram-negative
Disease can be exacerbated by Mycoplasma or viral co-infections
What are the acute clinical signs of Avibacterium paragallinarum?
Focal necrosis, pharyngitis, airsacculitis, pneumonia, increased pericardial and peritoneal fluids.
What are the chronic clinical signs of Avibacterium paragallinarum?
Exudative infections (conjunctivitis, sinusitis, otitis media, meningitis), facial edema (swelling of face, wattles, sternal bursa, legs, joints).
How can we diagnose Pasteurella multocida?
Culture and sensitivity (via tracheal swabs) and blood samples.
How is Avibacterium paragallinarum transmitted?
Direct contact, airborne droplets, and contaminated drinking water.
Which main disease does Avibacterium paragallinarum cause?
Infectious coryza (acute respiratory disease in chickens).
What are some virulence factors of Avibacterium paragallinarum?
- Capsular polysaccharide (CPS) - mediates attachment to cilia of nasal mucosa.
- Hyaluronic acid - component of capsule helps to prevent phagocytosis.
- Lipopolysaccharide (LPS) - stimulates inflammatory response.
What are the two main forms of Avibacterium paragallinarum?
Mild/young chickens: Depression, serous nasal discharge, mild facial swelling.
Severe/older birds: Depression, diarrhea, decreased feed and water consumption, decreased growth, sneezing, serous/mucoid/suppurative nasal/ocular discharge, facial edema, swollen wattles, rales.
What main lesions do you see with Avibacterium paragallinarum?
Extreme swelling of infraorbital sinuses with edema, firm large swollen wattles, conjunctivitis.
What is an important differential diagnosis for Avibacterium paragallinarum?
Pasteurella multocida.
How can you diagnose Avibacterium paragallinarum?
Culture and susceptibility (swab the wattles and sinuses), submit entire bird (since the organism is very fastidious, this might be a good idea), PCR.
Name the three species of Mycoplasma that cause respiratory infections in cattle, sheep, pigs, and chickens.
Cattle: Mycoplasma bovis
Sheep: Mycoplasma ovipneumoniae
Pigs: Mycoplasma hyopneumoniae
Chickens: Mycoplasma gallisepticum.
Practice case:
A 2-year-old beef cow presents with sudden onset depression, fever, and difficulty breathing. Upon auscultation, crackles are heard in the lungs. The cow also has a nasal discharge. Upon necropsy, fibrinous pleuropneumonia with hemorrhagic areas of consolidation is observed. What is the most likely bacterial agent?
Mannheimia haemolytica.
Practice case:
A group of goats presents with abscesses in the lymph nodes, particularly around the head and neck region. Upon examination, the abscesses are found to be caseous in nature. What is the most likely bacterial agent?
Corynebacterium pseudotuberculosis.
Practice case:
A feedlot-raised steer presents with neurological signs such as head pressing and circling. Upon closer examination, the steer also exhibits signs of respiratory distress. Necropsy reveals thrombotic meningoencephalitis and fibrinous pleuritis. What is the most likely bacterial agent?
Histophilus somni.
Practice case:
A flock of sheep presents with respiratory distress, coughing, and nasal discharge. Upon necropsy, suppurative bronchopneumonia is observed. What is the most likely bacterial agent?
Mycoplasma ovipneumoniae.
Practice case:
A herd of sheep presents with sudden deaths and signs of respiratory distress in some individuals. Necropsy reveals fibrinous pleuritis and bronchopneumonia. What is the most likely bacterial agent?
Bibersteinia trehalosi.
There is no caseous lymphadenitis present so this is the next best guess
Practice case:
A herd of pigs presents with sudden deaths and respiratory distress. Necropsy reveals necro-hemorrhagic areas of consolidation in the lungs. What is the most likely bacterial agent?
Actinobacillus pleuropneumoniae.
