Transcript Histophilus somni: An important cause of fatal disease in

T. Allen 1, D. O’Toole 1, R. Hunter 2, L. Corbeil 3
University of Wyoming, Department of Veterinary Science
1.
2.
3.
778 Sybille Creek Road, Wheatland, WY 82072
Department of Pathology, University of California
 Gram-negative pleomorphic rod
 Bacterial pathogen in Bovine Respiratory Disease Complex
 Alone or concurrent with P. multocida and M. haemolytica
 Diseases associated with H. somni
 Thrombotic meningoencephalitis
 Laryngitis-tracheitis
 Abortion
 Other; synovitis; otitis; ophthalmitis;
 Myocarditis
 Not traditionally recognized in United States
 Canadian feedlots document the disease in sudden
death and myocarditis
 Inconsistent isolation from affected tissue
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Antibiotic use
Vaccination use
Moderately fastidious organism
Chronic infections
Autolysis/overgrowth
 Low BVD association
 Experimental reproduction unsuccessful
Document histophilosis-associated myocarditis in
Wyoming over a 3 month period (Nov ‘08-Jan ‘09)
1.
1.
Historically, this is when disease peaks
Obtain and characterize isolates from hearts and
establish bank of isolates
3. Develop hypothesis for basis of cardiac localization
4. Determine other, concurrent, causes of death
2.
 Referring veterinarian
 Two ranches
 Whole Heart
 Un-incised
 Lung
 Aseptic collection
 Urine*
 Serum*
* Urine collected from earlier samples,
Serum(pre or post-mortem) from later
samples
 Bacteriology
 Aseptic swabs or tissue
samples from heart and lung
 Histopathology
 10% neutral buffered
formalin
 Heart
 Interventricular septum
 Left ventricular papillary
muscle
 Right ventricular papillary
muscle
 Atria
 Lung
 Bacterial isolation
 Pinpoint colonies @ 24 hours
 Brown colonies @ 48 hours
 Yellow coloration when swabbed
 Growth Conditions
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Columbia Blood Agar
37⁰C
10% CO2
“Cold Feet”
 Does not survive moderate
freeze
 Banking Isolates
 Grown overnight on chocolate
slants, covered in BHI
 Frozen in acetone/dry ice bath
 Stored at -70⁰C
 Sectioned at 5µm thickness
 H. somni membrane
insoluble fraction specific
immunoglobulin
 Hematoxylin counterstain
 Transmission electron
microscopy
 Work done by Dr. L. Corbeil, UC-San Diego
 Bacterial Isolates
 Acute/Convalescent Serum
 Cardiac Strain
 Compare to lung, brain, fetal isolates
 Establish presence of IgbpA, DR1, and DR2
 Acute myocarditis
 Clinical signs 2 days
 Left ventricular papillary
 Note: Cranial PM less commonly
affected
 Chronic Myocarditis
 Suppurative
 Clinical signs 8 days
 Chronic Myocarditis
 Fibrotic
 Clinical signs 15 days
 Hemorrhagic valvular
endocarditis
 Ruptured chordae tendineae
 Common Findings
 Lung
 Purple
 Spongy
 No obvious pneumonia
 Edematous
Animal
Culture positive
1
2
3
4
5
6
7
Culture negative
8
9
10
Type of myocarditis
Cultured H somni
Clinical signs
Acute
Chronic
Acute
Acute
Acute
Acute
Acute
YES
YES
YES
YES
YES
YES
YES
2 days
Not reported
5 days
1 day
<1 day
<1 day
Found dead
Chronic
Subacute
Chronic
NO
NO
NO
15 days
Not reported
8 days
 H. somni isolated from 7 of 10 positive cases
 More often from acute myocarditis
 3 cases: concurrent isolation from lung
Animal
Culture positive
1
2
3
4
5
6
7
Culture negative
8
9
10
Type of myocarditis
H. somni IHC
H. somni IHC
Acute
Chronic
Acute
Acute
Acute
Acute
Acute
POSITIVE
POSITIVE
POSITIVE
POSITIVE
POSITIVE
POSITIVE
POSITIVE
Negative
Negative
POSITIVE
POSITIVE
Negative
Negative
POSITIVE
Chronic
Subacute
Chronic
POSITIVE
POSITIVE
POSITIVE
Negative
Negative
Negative
 IHC confirmed 7 bacterial cultures and three more
 Chronic myocarditis confirmed
 3 lung samples also IHC positive
 Bacterial emboli plug capillaries and veins
 Bacteria adherent to vessel walls
Animal
Culture positive
1
2
3
4
5
6
7
IgBP-A
DR1
DR2
Hemolysis
+
+
+
+
N/T
+
+
+
+
+
N/T
+
+
+
+
+
N/T
+
_
_
_
+
N/T
_
N/T
N/T
N/T
N/T
 Cardiac isolates positive for immunoglobulin
binding protein A, direct repeats 1 & 2
 1 isolate with hemolytic properties
 1 isolate still pending
 Similar to virulence patterns seen in isolates from
pneumonia, encephalitis and abortion
H. somni was an important cause of loss on two
Wyoming Ranches.
2. Diagnosis was established by clinical signs, gross
lesions, bacterial isolation, immunohistochemistry,
and electron microscopy
3. Aerobic isolation was less sensitive than
immunohistochemistry to confirm presence of H.
somni
4. Lesions involved left ventricular myocardium
predominately posterior papillary muscle
1.
Western blots established that virulence factors of H.
somni were present—there is no cardiac specific
strain of H. somni
6. There was limited evidence of antecedent
pneumonia to account for septicemia—the portal of
entry of H. somni was not determined
7. H. somni enters cardiac parenchyma by direct
destruction of endothelium—intracellular infection
of endothelium was not identified
5.