JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
October 2021
D-P26

Signalment (JPC #2439475):  Two adult (6- and 10-year-old) male marmosets

HISTORY:  Both marmosets presented with weight loss and progressive weakness and were euthanized.

HISTOPATHOLOGICAL DESCRIPTION: Exocrine pancreas and duodenum:  Diffusely, effacing and replacing interlobular septa, peripancreatic fat, and perilobular acini and ducts are coalescing areas of lytic necrosis characterized by loss of cellular architecture with replacement by abundant eosinophilic cellular and karyorrhectic debris admixed with fibrin, edema, minimal hemorrhage, and moderate numbers of viable and degenerate neutrophils.  Areas of necrosis are bordered by moderate numbers of lymphocytes, eosinophils, and macrophages that occasionally are laden with cytoplasmic golden granular pigment (hemosiderin), fewer neutrophils, rare plasma cells, and variable amounts of fibrous connective tissue (fibrosis) that separates, surrounds and often replaces pancreatic acini.  Remaining pancreatic acini are either degenerate characterized by pale, vacuolated cytoplasm that lacks zymogen granules, or shrunken (atrophic).  Multifocally, there are increased numbers of small pancreatic ducts (tubular complexes) that are lined by hyperplastic epithelium and are often surrounded by fibrous connective tissue.  Ductular lumina are often ectatic and contain scant necrotic debris, few previously described inflammatory cells, and multiple cross and tangential sections of a 200um diameter adult spirurid nematode with a 5um thick, smooth cuticle, lateral cords, polymyarian-coelomyarian musculature, a pseudocoelom that contains granular eosinophilic fluid (spirurid), a tri-radiate esophagus, an intestinal tract lined by uninucleate cells with an indistinct brush border, and reproductive structures.  Previously described inflammatory cells and necrotic debris multifocally extend into and replace the outer longitudinal and, to a lesser extent, the inner circular layer of the duodenal tunica muscularis and serosa.   Adjacent tunica muscularis myocytes are vacuolated with swollen cytoplasm (degeneration).  The submucosa and remaining serosa of the duodenum are expanded by increased clear space and ectatic lymphatics (edema).

Lymph node, mesenteric:  Diffusely, subcapsular and medullary sinuses are expanded by macrophages that have foamy cytoplasm that occasionally contains golden pigment (hemosiderin), along with few eosinophils and edema.

MORPHOLOGIC DIAGNOSIS:

1. Exocrine pancreas:  Pancreatitis, necrotizing, lymphocytic, and eosinophilic, chronic, diffuse, moderate, with fibrosis, acinar degeneration, atrophy, and loss, tubular complexes, duct hyperplasia, necrotizing peripancreatic steatitis, and multiple intraductal adult spirurid nematodes, etiology consistent with Trichospirura leptostoma, marmoset, nonhuman primate.
2. Duodenum, tunica muscularis and serosa: Necrosis, focally extensive, with mild eosinophilic and lymphoplasmacytic inflammation and edema.
3. Lymph node, mesenteric: Sinus histiocytosis, diffuse, mild, with mild draining eosinophilia and edema.

ETIOLOGIC DIAGNOSIS:  Pancreatic trichospiruriasis

CAUSE:  Trichospirura leptostoma

GENERAL DISCUSSION:

• Order Spiruridae, Suborder Spirurina
• Found in pancreatic ducts of New World monkeys including marmosets, tamarins, squirrel monkeys, and owl monkeys

LIFE CYCLE:

• Embryonated eggs passed in feces > ingested by cockroach (intermediate host) > develops to infective L3 larvae > monkey eats infected cockroach > larvae migrate to pancreatic ducts and develop into adults > thick walled, oval, embryonated eggs passed through pancreatic ducts and eventually expelled in feces

TYPICAL CLINICAL FINDINGS:

• Usually no clinical signs
• May be associated with acute or chronic pancreatitis
• With chronic pancreatitis, can see weight loss despite good appetite and increased fecal volume

TYPICAL GROSS FINDINGS:

• Trichospirura is easily overlooked during necropsy examination; diagnosis requires histology or careful dissection with low magnification

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Tissue lesions:
  • Usually incidental with no lesions
  • Mild ductal inflammation, ectasia, epithelial attenuation
  • Chronic: Periductal fibrosis, chronic pancreatitis, parenchymal necrosis and atrophy, ductular proliferation
• T. leptostoma:
  • Males are smaller than females
  • Polymyarian-coelomyarian musculature
  • Lateral chords
  • Eosinophilic material within the pseudocoelom (characteristic spururid feature)
  • Esophagus divided into anterior muscular and posterior glandular areas with muscle fibers throughout
  • Uninucleate digestive tract
  • Extensive uteri usually filled with thick-shelled embryonated eggs, embryos with a large hook and several rows of spines on the head
  • Typical spirurid eggs are thick shelled and contain larvae

ADDITIONAL DIAGNOSIS:  

• Fecal examination

DIFFERENTIAL DIAGNOSIS:

• Molineus vexillarius, M. torulosus (D-P16): Trichostrongyle, infects duodenum and pyloric region of the stomach, occasionally the pancreas, chronic pancreatitis with eggs and worms within pancreatic ducts
• Filarid adults (Dipetalonema and Mansonella): Fibrinopurulent peritonitis with adhesions

COMPARATIVE PATHOLOGY:

• Pancreatitis is not common in animals except in dogs and cats
• Eurytrema pancreaticum: Pancreatic ductal fluke of ruminants
• Eurytrema procyonis: Pancreatic ductal fluke of carnivores
• Other flukes occasionally found in the pancreatic ducts are in the genera Dicrocoelium, Opisthorchis, and Metorchis
• Horses: Causes of pancreatitis include migrating strongyles, systemic adenovirus, encephalomyocarditis virus (Cardiovirus, Picornaviridae), foot and mouth virus (Aphthovirus, Picornaviridae), and coxsackievirus
• NHPs: Simian adenovirus-23 and 31 have both been implicated in severe necrotizing pancreatitis with prominent basophilic intranuclear inclusions within remaining acinar cells

REFERENCES:

1. Cosgrove GE, Humason G, Lushbaugh CC. Trichospirura leptostoma, a nematode of the pancreatic ducts of marmosets (Saguinus ). J Am Vet Med Assoc. 1970;157:696-698.
2. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 2006:34.
3. Jones TC, Hunt RD, King NW. Veterinary Pathology, 6th ed., Baltimore, MD: Williams and Wilkins; 1997:625,1107.
4. Matz-Rensing K, Lowenstine LJ. New World and Old Word Monkeys. In: Terio K, McAloose D, Leger J, eds. Pathology of Wildlife and Zoo Animals, San Diego, CA: Elsevier 2018:368.e10.
5. Strait K, Else JG, Eberhard ML. Parasitic diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T, eds. Nonhuman Primates in Biomedical Research: Diseases. Vol. 2. 2nd ed. San Diego, CA: Elsevier; 2012:237-238.
6. Toft JD. The pathoparasitology of the alimentary tract and pancreas of nonhuman primates: A review. Vet Pathol. 1982;19:44-92.

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