10-year-old, female, (Lama pacos) AlpacaThe animal was presented to the clinicians of the Institute of Farm Animals of the University of Zurich because of cachexia and weakness although it seemed to be eating normally. Clinical findings were intensified breathing, weakness and loss of gastrointestinal motility. The sonografic picture of the liver showed multifocal, echogenic, round to sickle-shaped unencapsulated structures of about 1 to 3 cm in diameter.

Gross Description:  

Firm, whitish nodules in size from 1 to 7 centimeters in diameter were found in the liver, lung, mediastinum, pleura, and omentum (Figs. 4-1, 4-2). In the cut surface some of the nodules showed fine whitish to grey beige spikes which were arranged in radial patterns (Fig. 4-3), other nodules showed centrally located homogenous grey beige caseous material with multifocal white gritty spots (Fig. 4-4).

Histopathologic Description:

Liver: Up to 70% of the parenchyma is replaced by multifocal to coalescing granulomas characterized by an amorphous, eosinophilic necrosis material surrounded by a smaller layer of elongated macrophages with light eosinophilic cytoplasm, a centrally located oval nucleus and indistinct cell boarders (epithelioid cells) and rarely of large cells with eosinophilic cytoplasm and numerous nuclei located in the periphery of the cell (multinucleated giant cells, Langhans-type) which are once again surrounded by a rim of lymphocytes, plasma cells, macrophages, fibroblasts embedded in a small amount of collagen fibers and to a lesser extend neutrophils (Fig. 4-5). Multifocally necrotic areas contain dark basophilic granular material (dystrophic calcification). The liver parenchyma is diffusely infiltrated with a moderate amount of lymphocytes and neutrophils.

Morphologic Diagnosis:  

Liver, granulomatous hepatitis, multifocal and coalescing, severe, chronic, with central caseous necrosis and myriads of acid-fast intrahistiocytic rod shaped bacteria (Fig. 4-6) (Mycobacteria kansasii)

Lab Results:  

Acid-fast stain (Ziehl- Neelson stain) revealed myriads of acid-fast bacteria in epithelioid macrophages and the PCR analysis resulted in Mycobacterium kansasii.


Mycobacterium kansasii

Contributor Comment:  

Mycobacterium kansasii is classified in Runions Group 1 and belongs to the nontuberculous mycobacteria (NTM); or mycobacteria other than tuberculosis (MOTT)). It is a saprophyte which is found in soil and water. M. kansasii is very heterogeneous as 5 well-defined different types (I-V) exist of which type I is frequently isolated from humans, type II from humans and the environment and III-V were present mostly in the environment and only rarely in humans sources.2 M. kansasii infection is described in cattle to cause lesions similar to bovine tuberculosis (BTB) although it seems to be exceedingly rare.5,6 In slaughtered cattle in Great Britain an incidence of 0.8% NTM was found and the majority of these belong to the M. avium complex.5 In Northern Ireland M. kansasii could be detected in 14 tissue specimens of 16,506 cattle, which demonstrates the rareness of the disease in cattle. Nevertheless, it is not known how many animals that are exposed to M. kansasii do not develop disease. It was also found that M. kansasii could be isolated from humans without disease.5 However, M. kansasii can cause pulmonary or disseminated disease in humans with an estimated 300 times higher incidence in HIV- patients.2 Experimental infection of healthy cattle failed to cause disease or pathologic changes but it did induce immune responses in TB tests.6 Since, some NTM and specifically M. kansasii do share some diagnostic antigens with Mycobacterium bovis complex bacteria 4, 5 there can be cross-reactions in traditional TB tests, which complicates the control and eradication of BTB.

JPC Diagnosis:  

Liver: Granulomas, multifocal to coalescing, with mild hepatocellular degeneration

Conference Comment:  

Mycobacteria are grampositive bacteria with high lipid content within their cell wall. This makes traditional gram staining largely ineffective, but mycobacteria do stain with carbol-fuschin and resist decoloration by inorganic acids giving them their acid-fast staining characteristic.3 Mycolic acid spacing within the bacterial cell wall is key to these bacteria being acid-fast.3 These same mycolic acids are hydrophobic accounting for the environmental hardiness and antimicrobial resistance of these troublesome bacteria.3 During the conference, Colonel Raymond questioned the participants about the classifications of mycobacteria and then the mechanistic basis of tuberculin skin testing. These bacteria cause a type IV hypersensitivity reaction, or delayed type hypersensitivity, as demonstrated by the tuberculin test. Histologically this manifests as aggregates of mononuclear cells around small veins and venules, or perivascular inflammation and cuffing.1 Important cytokines involved in delayed type hypersensitivity reactions include IL-12, IL-2, IFN-gamma, and TNF. IL- 12 is critical in propagating a Th1 response, IL-2 causes an autocrine and paracrine proliferation of T cells, and IFN-gamma is a potent macrophage activator.1 TNF is an important cytokine that acts on endothelial cells to cause vasodilation and facilitates the process of adhesion and extravasation of lymphocytes and monocytes.1


1. Abbas, Abul K: Disease of Immunity. In: Robins and Cotran Pathologic Basis of Diseases, ed. Kumar VK, Abbas AK, Fausto N, 7th ed., pp. 216-218. Elsevier, Philadelphia, Pennsylvania, 2005
2. Alcaide F, Richter I, Bernasconi C, Springer B, Hagenau C, Schulze-R+�-�bbecke R, Tortoli E, Martin R, B+�-�ttger EC, Telenti A: Heterogeneity and clonality among isolates of Mycobacterium kansasii: implications for epidemiological and pathogenicity studies. J Clin Microbiol 35(8):1959-64, 1997
3. Caswell JL, Williams KJ: Respiratory system. In: Jubb, Kennedy and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., pp. 632. Elsevier, Philadelphia, Pennsylvania, 2007
4. Huges MS, Ball NW, McCarroll J, Erskine M, Taylor MJ, Pollock JM, Skuce RA, Neill SD: Molecular analysis of mycobacteria other than the M. tuberculosis complex isolated from Northern Ireland cattle. Vet microbiol 108:101-112, 2005
5. Vordermeier HM, Brown J, Cockle OJ, Franken WPJ, Arend SM, Ottenhoff THM, Jahans K, Hewinson RG: Assessment of cross-reactivity between Mycobacterium bovis and M. kansasii ESAT-6 and CFP-10 at the T-cell epitope level. Clin Vaccine Immunol 14(9):1203-9, 2007
6. Waters WR, Palmer MV, Thacker TC, Payeur JB, Harris NB, Minion FC, Greenwald R, Esfandiari J, Andersen P, McNair J, Pollock JM, Lyashchenko KP: Immune responses do defined antigens of Mycobacterium bovis in cattle experimentally infected with Mycobacterium kansasii. Clin Vaccine Immunol 13:611-9, 2006

Click the slide to view.

4-1. Pleura

4-2. Liver

4-3. Liver

4-4. Lymph node

4-5. Liver

4-6. Liver

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