Signalment:  

9 year old, female, intact Kuhls black-eared marmoset (Callithrix kuhlii)Euthanized due to progressive lethargy with weight loss and diarrhea.

Gross Description:  

The animal was in markedly thin body condition at the time of death. The small and large intestines were distended with gas, and the contents were diffusely sparse, pasty and tan to slightly green. The intestinal wall varied segmentally from thin and flaccid to irregularly thickened and corrugated. The mesenteric and colonic lymph nodes were uniformly enlarged.

Histopathologic Description:

Pancreas: The lobular architecture of the exocrine pancreas is distorted by confluent deposits of mature collagenous connective tissue that separate, infiltrate and accentuate the preexistent lobular architecture and expand the periductal connective tissue stroma. There is diffuse atrophy of the exocrine secretory acini and many of the interlobular ducts are ectatic and contain one or more cross- and oblique sections of spirurid nematodes that measure up to 150 um in diameter. Intraductular spirurids are characterized by a 10-15 um thick cuticle with sharp spicules, polymyarian-coelomyarian somatic musculature, prominent lateral cords, each containing an excretory canal. The intestinal tract is composed of cuboidal to columnar uninucleated cells that are often finely vacuolated and exhibit a prominent eosinophilic brush border. Female nematodes have uteri containing thick-shelled, 50 um x 25 um, embryonated eggs and males display ductus deferens with intralumenal spermatozoa. Associated with the nematodes are intralumenal aggregates of eosinophils, macrophages and fewer neutrophils. Overall, the pancreatic lobules are composed of small groups of disorganized acini with lightly eosinophilic, vacuolated cytoplasm, abundant intralobular duct profiles and increased exocrine to endocrine tissue ratio (exocrine pancreatic atrophy) as well as low number of lymphocytes and plasma cells. Isolated pancreatic lobules have low to moderate numbers of interstitial and intralumenal neutrophils (not present in all sections).

Arterioles, pancreaticoduodenal ligament: The walls of arterioles are multifocally expanded by irregular plaques of mineralized to hyalinized connective tissue that efface the tunica media, interrupt the elastic lamina, elevate the endothelium and impinge on the vascular lumina (arteriosclerosis).

Duodenum: Multifocally throughout the mucosa, villi are blunted and fused, enterocytes are attenuated and crypts are lined by hyperplastic epithelial cells. Expanding the lamina propria in the villous tips and effacing multiple glands in the submucosa is a lightly eosinophilic, acellular matrix (amyloid) that is mildly infiltrated by low numbers of neutrophils and contains karyorrhectic debris. Moderate numbers of lymphocytes, plasma cells and neutrophils are scattered throughout the muscularis mucosa.

Morphologic Diagnosis:  

Pancreas:
1) Atrophy, acinar cell, chronic, severe with dissecting and periductular fibrosis, lymphoplasmacytic and eosinophilic infiltrates, ductular ectasia and intralumenal nematodes (morphology consistent with Spirurid spp.).
2) Pancreatitis, neutrophilic, subacute, mild (not present in all sections).

Duodenum:
1) Amyloidosis, mucosal and interstitial, multifocal, severe with villous blunting, atrophy and fusion, attenuation of enterocytes, crypt hyperplasia, gland loss.
2) Enteritis, lymphoplasmacytic to neutrophilic, chronic, generalized, mild.

Arterioles (mesenteric, not present in all sections):
Medial arteriosclerosis, hyaline-type, chronic, multifocal, mild with mineralization

Lab Results:  

Special stains:
Congo Red: Congophilic, birefringent (green under polarized light) material, consistent with amyloid, was abundant in the tips of duodenal villi and around Brunners glands. Amyloid deposits were also present in the liver, kidney and spleen.

Condition:  

Trichospirura leptostoma and duodenal amyloid

Contributor Comment:  

Nematodes in the pancreatic ducts were associated with lobular atrophy, periductular fibrosis and mild inflammation. The nematodes exhibit morphologic features consistent with Trichospirura leptostoma, a spirurid that inhabits the pancreatic duct of certain species of calltrichids (members of the New World primate family, Callitrichidae) including marmosets, tamarins, squirrel monkeys and owl monkeys.(1) Transmission occurs through ingestion of the intermediate host, the common cockroach. Trichospiruriasis is usually considered asymptomatic in marmosets; however, chronic wasting syndrome and exocrine pancreatic insufficiency have been associated with a heavy parasitic burden.(2) Morphologically, the severity of pancreatic lesions are associated with parasite load and progress from pancreatitis to pancreatic fibrosis with atrophy of exocrine pancreatic tissue and, rarely, to obstructive cholestasis. (1,3)

Unique histomorphological features of T. leptostoma include their location in interlobular pancreatic ducts, small cross-sectional diameter, long muscular esophagus, excretory pores in the lateral cords and primitive somatic musculature.(4) Based on the changes in the section presented, trichospiruriasis likely contributed to pancreatic insufficiency and secondary malnutrition.

A complicating disease in this animal that is also exceedingly common in captive calltrichids is chronic inflammatory bowel disease (IBD) characterized by diffuse, mucosal atrophy, lymphoplasmacytic inflammation and areas of mucosal ulceration. Typically, callitrichid IBD is most severe in the colon, but lesions were diffuse in this case and were complicated by intestinal amyloidosis. This condition is presently enigmatic, but multiple contributory factors have been implicated including various bacterial infections (Helicobacter sp., Campylobacter jejuni, and enteropathogenic Escherichia coli), immune dysfunction, genetic predisposition and stress.(5,6,7,8) Cotton top-tamarins (Saguinus oedipus) have been previously used as a primate model of colitis-associated colonic carcinogenesis because of the high propensity for spontaneous colitis that often progresses to adenocarcinomas in this species.(9)

Chronic systemic inflammation cause by the parasitic infestation and enterocolitis likely induced systemic AA amyloidosis due to elevated levels of the SAA amyloidogenic precursor molecule. In addition to the intestinal tract, amyloidosis was also present in the liver, spleen and kidneys. Ingestion of -�-�amyloid enhancing factors and hereditary predisposition have been implicated as contributory to the development of systemic AA amyloidosis in colonies of captive marmosets.(10)

JPC Diagnosis:  

1. Pancreas, exocrine tissue: Atrophy, diffuse, severe.
2. Pancreatic ducts: Numerous male and female adult spirurid nematodes with mild intraductal neutrophilic exudates.
3. Duodenum, mucosa: Amyloid, diffuse, moderate with marked villar blunting and fusion.
4. Mesentery, adipose tissue: Atrophy, diffuse, severe.
5. Large muscular artery: Mineralization, medial, mural, multifocal, marked.

Conference Comment:  

Although marmosets are popular as a laboratory primate species for a number of reasons, in captivity the animals are very susceptible to a condition which is not fully understood known as wasting marmoset syndrome (WMS). WMS is characterized by failure to thrive and generalized weakness which often progresses to death. Characteristics commonly associated with WMS are poor weight gain, weight loss, muscle atrophy, alopecia, diarrhea, and colitis. Histologic features include thin, atrophic intestinal mucosa and chronic lymphoplasmacytic enteritis usually in the distal jejunum and ileum. Other lesions include ulcerative typhlocolitis and bone fragility due to decreased intestinal vitamin D absorbtion. WMS is perhaps the most important and poorly understood disease syndrome of callitrichids(14,15,16).

The etiology of WMS is not known; however, malnutrition, alterations in intestinal microflora, parasitic infestations, and malabsorption have been suggested as the possible primary or contributing causes. Conference participants discussed several possible underlying etiologies, such as pancreatic spirurid infestation as in this case; bile duct fibrosis and obstruction by fluke migration; and immune-mediated enteropathic disease due to antibodies to gliadin, a glycoprotein found in wheat and other cereals, which is common in humans with celiac disease. In the moderators experience, pancreatic trichospirurids are often incidental and associated with no pathologic effects. Conference participants attributed the prominent fibrous connective tissue separating and surrounding exocrine pancreatic lobules as due to pancreatic atrophy from WMS and not fibrosis from the trichospirurids, and the loss of exocrine pancreatic zymogen granules as due to depletion(14,15,16).

The predominant clinical pathologic alterations in marmosets with WMS include mild macrocytic normochromic anemia, thrombocytosis, hypoproteinemia, hypoalbuminemia, and elevated alkaline phosphatase levels due to colonic inflammation. Most of these changes have been attributed to protein-calorie malnutrition and muscle wasting. Thrombocytosis in these marmosets probably represents a nonspecific response of the bone marrow to the chronic wasting and enteric inflammation. Thrombocytosis is mediated by cytokines released during chronic inflammation, and include thrombopoietin (TPO) and interleukin 6 (IL-6), which is commonly increased in inflammatory conditions(13).

References:

1. Toft JD: The pathoparasitology of the alimentary tract and pancreas of nonhuman primates: a review. Vet Pathol. Supplement 19:44-92, 1982.

2. Ludlage E and Mansfield K: Clinical care and diseases of the common marmoset (Callithrix jacchus). Comp Med 53:369-382, 2003.

3. Hawkins JV, Clapp NK, Carson RL, Henke MA, McCracken MD, Faulkner CT and Patton S: Diagnosis and treatment of Trichospirura leptostoma infection in common marmosets (Callithrix jacchus). Contemp Top Lab Anim Sci 36:52-55, 1997.

4. Smith WN and Chitwood MB: Trichospirura leptostoma gen. et sp. n. (Nematoda: Thelazioidea) from the Pancreatic Ducts of the White-Eared Marmoset Callithrix jacchus. J Parasitol 53:1270-1272, 1967.

5. Saunders KE, Shen Z, Dewhirst FE, Paster BJ, Dangler CA and Fox JG: Novel intestinal Helicobacter species isolated from cotton-top tamarins (Saguinus oedipus) with chronic colitis. Journal of Clinical Microbiology 37:146151, 1999.

6. Won YS, Vandamme P, Yoon JH, Park YH, Hyun BH, Kim HC, Itoh T, Tanioka Y, Choi YK: Helicobacter callitrichis sp. nov., a novel Helicobacter species isolated from the feces of the common marmoset (Callithrix jacchus). FEMS Microbiol Lett 271:239-244, 2007.

7. Wood JD, Peck OC, Tefend KS, Stonerook MJ, Caniano DA, Mutabagani KH, Lhot+�-�k S, Sharma HM: Evidence that colitis is initiated by environmental stress and sustained by fecal factors in the cotton-top tamarin (Saguinus oedipus). Dig Dis Sci 45:385-93, 2000.

8. Mansfield KG, Lin KC, Xia D, Newman JV, Schauer DB, MacKey J, Lackner AA, Carville A: Enteropathogenic Escherichia coli and ulcerative colitis in cotton-top tamarins (Saguinus oedipus) J Infect Dis 184:803807, 2001.

9. Kanneganti M, Mino-Kenudson M, Mizoguchi E: Animal Models of Colitis-Associated Carcinogenesis. J Biomed and Biotech 2011:Article ID 342637, 2011.

10. Ludlage E, Murphy CL, Davern SM, Solomon A, Weiss DT, Glenn-Smith D, Dworkin S, Mansfield KG: Systemic AA Amyloidosis in the Common Marmoset. Vet Pathol 42:117-124, 2005.

11. Lewis SM, Hotchkiss CE, Ullrey DE: Nutrition and Nutritional Diseases. In: The Laboratory Primate, ed. Wolfe-Coote S, p. 195 Elsevier Academic Press, London, UK, 2005.

12. April M, Keith JC: Cardiovascular and lymphoreticular systems. In: Nonhuman Primates in Biomedical Research: Diseases, ed. Bennett BT, Abee CR, Henrickson R, p. 256 Academic Press, San Diego, CA, 1998.

13. Logan AC, Khan KN. Clinical pathologic changes in two marmosets with wasting syndrome. Tox Pathol. 1996;24(6):707-9.

14. Gore MA, Brandes F, Kaup FJ, Lenzner R, Mothes T, Osman AA. Callitrichid nutrition and food sensitivity. J Med Primatol. 2001 Jun;30(3):179-84.

15. Sousa MB, Le+�-�o AC, Coutinho JF, de Oliveira Ramos AM. Histopathology findings in common marmosets (Callithrix jacchus Linnaeus, 1758) with chronic weight loss associated with bile tract obstruction by infestation with Platynosomum (Loos, 1907). Primates. 2008 Oct;49(4):283-7.

16. Schroeder C, Osman AA, Roggenbuck D, Mothes T. IgA-gliadin antibodies, IgA-containing circulating immune complexes, and IgA glomerular deposits in wasting marmoset syndrome. Nephrol Dial Transplant. 1999 Aug;14(8):1875-80.

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