Joint Pathology Center
Veterinary Pathology Services
Wednesday Slide Conference
November 29th, 2017
CASE I: H12/1754 (JPC 4019375).
Signalment: 3.5-year-old, Aberdeen angus, Bos primigenius taurus, bovine.
History: Out of a group of 6 animals, one cow showed chronic, profuse diarrhea and severe, progressive emaciation. The bacteriologic investigation of the feces tested positive for acid-fast rods and negative for Salmonella. Because of the suspicion of paratuberculosis, the cow was euthanized and submitted for post-mortem investigation.
Gross Pathology: The animal was moderately emaciated. The muscle masses were reduced, and the ribs were easily palpated. Body fat depots were present. The mucosa of the small intestine, from the duodenum to the ileum was moderate to severe thickened, corrugated, nodular shaped and were light brown. The large intestine content was watery and brown, becoming slightly mucoid in the rectum. No lesions in the colonic mucosa were noted grossly. The mesenteric lymph nodes were moderately enlarged. The rumen pH was 6.5, and the fibers of the content were up to 15 cm long.
Hematology: (changed parameters)
Banded Neutrophils 0.54 109/l 0 - 0.2
Segmented Neutrophils 6.25 109/l 1.0 - 3.5
Lymphocytes 2.05 109/l 2.5 - 5.5
Monocytes 0.93 109/l 0 - 0.33
Eosinophils 0.00 109/l 0.3 - 1.5
Chemistry: (changed parameters)
Na 116 mmol/l 135 - 165
K 1.50 mmol/l 3.0 - 6.0
Cl 68 mmol/l 90 - 110
Urea 23.99 mmol/l 1.67 - 7.50
Creatinine 183 ?mol/l 88 - 133
Bilirubin 23.0 ?mol/l 0.85 - 8.6
ASAT (SGOT) 79 IU 117 - 234
GGT 67 IU 10 - 27
GLDH 46 IU 0 - 17
Serology Bovine viral diarrhea (during Swiss eradication program): negative.
Microscopic Description: Small intestine: The intestine is thickened and puts the mucosa in folds. About 90% of the lamina propria and the submucosa are diffusely infiltrated by large numbers of epitheloid macrophages, lymphocytes, plasma cells, eosinophils and fewer neutrophils with numerous multinucleated giant cells of the Langhans and foreign body type. The infiltration distorts and expands the lamina propria of villi. Multifocally, the crypts are moderate to severe extended, lined by an elongated and flattened epithelium. They contain accumulations of cellular debris, mucous and crystalline material (dystrophic calcification) (cryptitis). Crypt epithelium piles up with cells 3-5 deep and with a high nuclear to cytoplasmic ratio (hyperplasia). The lamina propria, the submucosa and the serosa are diffusely widened and pale (edema). The submucosal and serosal lymphatics are diffusely moderately to severely dilated and surrounded by lymphocytes, plasma cells and fewer macrophages. Rarely epitheloid macrophages and multinucleated giant cells plug the lumen of the lymphatics (lymphangitis).
Contributors Morphologic Diagnosis:
Small intestine: Granulomatous enteritis and lymphangitis with multinucleated giant cells, diffuse, severe, chronic.
Contributors Comment: Lesions extended from the duodenum to the colon. During necropsy we were impressed about the classic lesion, as it is rarely seen in our necropsy room. The classic histologic picture likewise was a treat. Ziehl-Neelson stained (ZN) many acid-fast rods within the macrophages. The cow had a mild histiocytic lymphadenitis of the mesenteric lymph nodes with ZN-positive rods as well. The diagnosis is paratuberculosis or Johne"s disease. Although other infections can be seen on top of mycobacteriosis (e.g. salmonellosis), further bacteriologic investigation was not done.
Johne"s disease (JD) or paratuberculosis, caused by Mycobacterium (M.) avium subsp. paratuberculosis (Map), causes chronic diarrhea in ruminants. As in our case, typical gross lesions are thickened mucosa, thrown into transverse rugae which will not disappear when the intestinal tract is stretched. Typical microscopic lesions were granulomatous enteritis of the small intestine and lymphadenitis of the draining lymph nodes.
The bacteria are taken up orally by young animals. Susceptibility to infection is greatest in the first 30 days of life. The incubation period of JD is protracted and clinical symptoms are usually detected in cattle 2-5 years-old. Chronic villous involvement leads to malabsorption, protein loss and profuse chronic diarrhea and severe emaciation. The pathogenesis of JD is best understood in cattle. It is assumed to be similar in other ruminants, except that in sheep and goats the enteric gross lesions are often milder. Map can be produced in pigs. Spontaneous disease occurs in a number of free-ranging and captive wild ruminants, camelids, rarely in equines and captive primates. Numerous species of wild mammals and several species of wild birds are naturally infected, though not necessarily diseased.1
Map has been suspected to play a role in Crohn"s disease (CD), a chronic inflammatory bowel disease in humans. Initial suggestion of Map involvement was based on the similarity of the clinical appearance of CD and JD. Map has been detected in multiple CD studies, but it is difficult to isolate Map from patients with CD. Genetically, over 30 Map genes have been identified in human disease, but no specific association has been shown so far.
JD is used as a bovine model of CD. Studies in cattle suggest the early immune response may be similar to the immune response to M. tuberculosis (Mtb) during the latent stage of infection. Map affords an opportunity to examine the immune response during the early and late stages of infection. These data would also provide insight into how mycobacterial pathogens could contribute to the pathogenesis of CD.2
JPC Diagnosis: Small intestine: Enteritis, granulomatous and lymphocytic, diffuse, marked with villar blunting, crypt abscessation and loss, and moderate lymphangitis, Aberdeen angus (Bos primigenius Taurus), bovine.
Conference Comment: Johnes disease in cattle, sheep, and goats is caused by Mycobacterium avium ssp. paratuberculosis (MAP) and induces granulomatous inflammation of the lepromatous (diffuse) type. The immune response is characterized by a Th2 type of adaptive immune response and appears microscopically as diffuse sheets of macrophages and multinucleated giant cells rather than distinct granulomas as would be expected with a Th1 response. Lesions are most common in the ileum, colon, and mesenteric lymph nodes. Bacteria, which are often numerous, can be identified within macrophages and extracellularly with acid-fast stains. Johnes disease causes injury to cells in three ways: (1) lysis of epithelial cells and extracellular matrix proteins that form cell junctional barriers in the small intestinal mucosa, (2) dysfunction of afferent lymphatic drainage in the small intestinal villi, and (3) lysis of monocyte-macrophage cells and other cells within the lamina propria of infected intestinal villi from chronic inflammatory mediators.3
Grossly, affected small intestinal walls are thickened with a cerebriform appearance and mesenteric lymph nodes are enlarged with coalescing areas of yellow-white caseous exudate which occasionally mineralizes. Lymphangitis is common resulting in thickened cords of lymphatic vessels coursing through the mesentery. Additionally, there is marked muscle loss and wasting with intermandibular edema (attributable to hypoproteinemia), fluid accumulation in body cavities, plaques of mineralization and fibrosis within the tunica intima of the thoracic aorta, and diffuse, watery diarrhea. Young animals are most susceptible, and are infected through ingestion of the bacterium which binds to receptors on the luminal surfaces of M (microfold) cells (which lack a mucous covering). Bacteria are then translocated across the cell into the underlying Peyers patches and subsequently phagocytosed by tissue macrophages. MAP requires iron for growth and secretes iron-chelating proteins known as exochelins, iron-reductases, and siderophores as virulence factors to acquire iron from ferritin stored in macrophages. Additionally, mycobacterium species can: (1) inhibit acidification of the phagosome, fusion of the phagosome and lysosome, and lysosomal enzyme activities through the production of peroxidases; (2) block injury from reactive oxygen and nitrogen intermediates; and (3) suppress macrophage activation by cytokines (IFN-?).3
There was apathetic debate amongst conference attendees regarding the use of granulomatous versus lymphoplasmacytic versus histiocytic to describe the inflammatory infiltrate in this case, a debate which has been oft-repeated over the years, especially when cases of Johnes disease are discussed. In this particular case, the presence of multinucleated giant cells and epithelioid macrophages suggest a granulomatous process, their presence however, was restricted to the submucosa and further out, especially around lymphatics. Lymphocytes, however, predominate in the lesion. Ultimately, the group decided that the presence of numerous epithelioid macrophages in the mucosa as well as the multinucleated macrophages warranted the use of granulomatous in this particular instance.
Institute of Animal Pathology, University of Berne
Länggassstrasse 122, Postfach 8466, CH-3001 Bern, Switzerland
1. Brown CC, Baker DC, Barker IK. Alimentary system. In Maxie MG, ed. Jubb, Kennedy, and Palmer"s Pathology of Domestic Animals. 5th ed. Vol. 2. Philadelphia, PA: Elsevier; 2007:222-225.
2. Davis WC, Madsen-Bouterse SA. Crohn"s disease and Mycobacterium avium subsp. paratatuberculosis: The need for a study is long overdue. Vet. Immunol. Immpathol. 2012;145:1-6.
3. Zachary JF. Mechanisms of microbial infections. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:162-163.