JPC SYSTEMIC PATHOLOGY

CARDIOVASCULAR SYSTEM

April 2022

C-B03 (NP)

 

SIGNALMENT (JPC #3103237): 6-year-old multiparous Holstein cow (Bos taurus)

 

HISTORY:  Four days after calving the cow developed watery stool that continued for 2 weeks, accompanied by weight loss and decrease in body condition. 20 days after calving it was unable to rise from sternal recumbency and was euthanized.

 

HISTOPATHOLOGIC DESCRIPTION: Heart: The endocardium is diffusely expanded up to 1mm by collagen and fibroblasts (fibrosis) with multifocal accumulation of basophilic, granular material (mineral) and mineralized collagen fibers, which multifocally extend into the subendocardial myocardium, separating and surrounding bundles of cardiac myocytes. Subendocardial myocytes are occasionally swollen with sarcoplasmic vacuolation and enlarged, rectangular nuclei (degeneration), or are rarely shrunken and hypereosinophilic with fragmented sarcoplasm, loss of cross striations and occasional mineralization (necrosis). Multifocally, myocytes are expanded by an intracytoplasmic, round to oval, up to 40um diameter, protozoal cyst with a 4um thick, eosinophilic capsule, containing numerous, up to 10um, basophilic, crescent-shaped bradyzoites.

 

MORPHOLOGIC DIAGNOSIS: 1. Heart: Endocardial mineralization and fibrosis, diffuse, marked, with myocardial degeneration, necrosis and mineralization, Holstein, bovine (Bos taurus).

2. Heart, myocardium: Sarcocysts, multifocal.

 

DISEASE NAME: Paratuberculosis or Johne’s disease

 

ETIOLOGIC DIAGNOSIS: Mycobacterial associated endocardial mineralization

 

CAUSE: Mycobacterium avium subspecies paratuberculosis (Map)

 

GENERAL DISCUSSION:

• Two main pathological forms of Johne’s disease are described: 
  • Paucibacillary form, inflammatory infiltrate composed of lymphocytes with some macrophages but few mycobacteria
  • Multibacillary form, mostly macrophages filled with numerous mycobacteria
• In sheep or goats with no clinical signs, there are focal granulomatous lesions in the intestinal lymphoid tissue
• There are no tests with high specificity and high sensitivity available for subclinically infected animals

 

PATHOGENESIS:

• Infection of newborn and young animals can be followed by a latent period that may last for years, with intermittent bacterial shedding
• Transmitted via feces, milk, semen, urine, and transplacentally
• Transmitted (via fecal-oral route) in the first months of life, but clinical disease only appears in animals older than one year (usually 2 to 5 years)
• Bacteria invade via tonsils, Peyer’s patches M cells, and enterocytes, mainly in the jejunum and ileocecal valve > disseminate to mucosal lamina propria and local lymph nodes
• After entering the intestine through Peyer’s patches the bacteria reaches the lymph nodes, escaping the initial local immune defenses in the gut, before inducing lesions in the intestine (in sheep and goat)
• Goat immune systems may control the bacterial multiplication resulting in regression and healing of lesions, or an uncontrolled bacterial multiplication leading to clinical disease
• Multibacillary lesions correspond to borderline lepromatous forms, associated with marked humoral peripheral responses
  • M2 macrophages predominate
• Paucibacillary lesions, show strong cellular immune responses, correspond to borderline tuberculoid forms
  • M1 macrophages predominate (high iNOS; low TNF-a)
• Focal intestinal granulomatous lesions have a high cellular immune response (tuberculoid)
• Cell-mediated immunity is thought to be essential in controlling the progression of infection
• Aortic wall mineralization occurs spontaneously

 

TYPICAL CLINICAL FINDINGS:

• Weight loss and cachexia
• Decreased milk production 
• Diarrhea
• Infertility

 

TYPICAL GROSS LESIONS:

• Thickening of the intestinal wall, granulomatous enteritis, lymphangitis, and lymphadenitis of regional lymph nodes
• Intestinal ulcers and strictures
• Crater-like lesions in the small intestine that occasionally coalesce
• Focal lesions are more common in lymph nodes in initial/latent forms of the disease

 

TYPICAL LIGHT MICROSCOPIC LESIONS:

• Intestine:
  • Diffuse granulomatous infiltrates; may be in jejunal Peyer’s patches and the patch at the ileocecal valve or severe diffuse lesions throughout the intestine
  • Granulomas or giant cells in intestinal villi and lymph nodes; multinucleated Langhans giant cells are common in cattle (not sheep/goat)
  • Peyer’s patches lymphoid depletion
  • Dilation of intestinal glands associated with infiltrates in the lamina propria, causing occlusion
  • Intestinal mucosal ulceration with transmural inflammation and serositis > may heal or perforate 
  • Granulomatous arteritis in small to medium-sized vessels in the submucosa (may require IHC to be observed)
  • Acid fast bacilli within macrophages and dilated intestinal lymphatics
  • Lymphocytic inflammation of submucosal nervous plexuses rarely observed
  • Loss of CD4+ T cells and an increased frequency of gamma–delta T cells in the ileum of cattle has been observed in multibacillary lesions
  • Lymphangiectasis is most common/severe in small ruminants
• Lymph nodes: 
  • Foci of necrosis and calcification in mesenteric lymph nodes
  • Granulomas in the ileal and jejunal lymph nodes
• Liver: Microscopic granulomas; liver biopsy is a useful diagnostic tool in sheep 
• Lung: Minimal lesions
• Vessels: Mineralization of the aortic wall 

 

ADDITIONAL DIAGNOSTIC TESTS:

• Bacterial culture and PCR (from blood, feces, milk, semen, urine, and tissues)

• MAP has 15-20 copies of the insertion sequence IS900 which differentiates it from M. avium subspecies avium

• Bacterial demonstration in tissue: IHC, acid-fast, and in situ hybridization (ISH); IHC and acid-fast demonstrate low numbers of bacteria in lesions
  • Labelling by MAP antibody is more efficient than Ziehl–Neelsen (ZN) staining for organism detection
  • Wall-deficient bacterial forms (like mycobacteria) are usually negative to ZN and difficult to culture, but can be demonstrated by in situ hybridization
• IHC:  Antibody to lysozyme is useful in immunolabelling macrophages or giant cells

 

COMPARATIVE PATHOLOGY:

• Fallow Deer: Focal, multifocal, and diffused forms (both multibacillary and paucibacillary) have been described
• Spontaneous disease occurs in ruminants, camelids, equids, and primates
• Natural infection occurs in lagomorphs, rodents, carnivores, and birds
• Experimentally induced in mice, rabbits, guinea pigs, hamsters, and macaques 

 

REFERENCES:

1. Balseiro A, Garcia Marin JF, Solano P, Garrido JM, Prieto JM. Histopathological classification of lesions observed in natural cases of paratuberculosis in free-ranging fallow deer (Dama dama). J Comp Pathol. 2008; 138: 180-188.
2. Boes KM, Durham AC. Bone Marrow, Blood Cells, and the Lymphoid/Lymphatic System. In: Zachary JF, eds. Pathologic Basis for Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022: 881-882.

 

1. Fernandez M, Benavides J, Castano P, et al. Macrophage subsets within granulomatous intestinal lesions in bovine paratuberculosis. Vet Pathol. 2017;54(1):82-93.
2. Gonzalez J, Geijo MV, Garcia-Pariente C, et. al. Histopathological classification of lesions associated with natural paratuberculosis infection in cattle. J Comp Path. 2005; 133: 184–196.
3. Krüger C, Köhler H, Liebler-Tenorio EM. Sequential development of lesions 3, 6, 9, and 12 months after experimental infection of goat kids with Mycobacterium avium subsp paratuberculosis. Vet Pathol. 2015; 52(2): 276-290.
4. Miller LM, Gal A. Cardiovascular system and lymphatic vessels. In: Zachary JF, ed. Pathologic Basis for Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:594-595.
5. Robinson WF, Robinson NA. Cardiovascular system. In: Maxie MG, ed. Jubb Kennedy and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:61.
6. Smith SL, Wilson PR, Collette MG, et al. Liver biopsy histopathology for diagnosis of Johne’s disease in sheep. Vet Pathol. 2014; 51(5):915-918.
7. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:194-197.

 

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