JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
September 2021
D-P14

 

 

Signalment (JPC #2317400):  Rhesus macaque (Macaca mulatta)

 

HISTORY:  This monkey had prominent gastric hyperplasia.

 

HISTOPATHOLOGIC DESCRIPTION:  Stomach:  Focally extensively, the mucosa of 50% of the section is thickened up to 4 mm, forming polypoid, frond-like projections characterized by deep, irregular, enlarged, tortuous gastric glands lined by hyperplastic mucous cells supported by a long fibrovascular stalk.  The gastric glands contain increased numbers of mucous cells which replace parietal cells (mucous neck cell metaplasia) and pile up to three cell layers thick with increased mitotic figures (mucous neck cell hyperplasia).  Multifocally gastric glands are characterized by one or more of the following changes: dilation and lining by low columnar to cuboidal epithelium; herniation into the submucosa; or luminal expansion by abundant eosinophilic cellular debris, degenerate inflammatory cells, sloughed epithelial cells, aggregates of oval, 30 X 50 um, thin-shelled, morulated eggs, and few cross sections of 150-500 um adult trichostrongyle nematodes.  These adult nematodes are characterized by evenly spaced, external, longitudinal cuticular ridges that flare prominently over the area of the lateral cords; platymyarian-meromyarian musculature; a pseudocoelom; an intestine lined by few multinucleate cells; and a reproductive tract (ovary containing immature ova or testes containing sperm).  Multifocally the lamina propria and submucosa are expanded by increased numbers of lymphocytes and plasma cells and fewer eosinophils.  There are multifocal areas of fibrosis within the deep lamina propria. Multifocally collagen fibers of the submucosa are separated by increased clear space (edema), and submucosal vessels are diffusely congested.

 

MORPHOLOGIC DIAGNOSIS:  Stomach:  Gastritis, proliferative, lymphoplasmacytic, and eosinophilic, chronic, focally extensive, moderate, with mucous neck cell metaplasia and hyperplasia and few adult trichostrongyle nematodes and many eggs, etiology consistent with Nochtia nochti, Rhesus monkey (Macaca mulatta), non-human primate.

 

ETIOLOGIC DIAGNOSIS:  Gastric nochtiasis

 

CAUSE:  Nochtia nochti

 

GENERAL DISCUSSION:

• nochti is a slender, bright red nematode that is found embedded in hyperplastic gastric nodules of rhesus, cynomolgus and stumptail macaques.
• Order Strongylida, superfamily Trichostrongylidae (threadworms)
• Females are 7.6 - 10 mm, and males are 5.7 - 6.5 mm in length.
• Trichostrongyloides mostly parasitize abomasum and proximal small intestine of ruminants causing diarrhea, ill-thrift, and death.

 

PATHOGENESIS:

• Proliferative lesions (gastric hypertrophy, hyperplasia, and polyps) are induced by burrowing larvae in monkeys.

 

LIFE CYCLE:

• Direct; fecal-oral transmission via ingestion of third stage larvae > larvae burrow into gastric mucosa at the junction of the fundus and pylorus > develop into adults > deposit eggs which embryonate within 12 hours, erode into the gastric lumen, and pass with feces > become infective third stage larvae within a week

 

TYPICAL CLINICAL FINDINGS:

• Usually no clinical signs.

 

TYPICAL GROSS FINDINGS:

• Single or multiple, hyperemic, sessile or pedunculated, cauliflower-like masses protruding from the pre-pyloric gastric mucosa

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Gastric lesions:
  • Marked hyperplasia of mucous neck cells that are tall-columnar and palisade along papillary projections
  • Mucous metaplasia of fundic or pyloric glands
  • Paucity of parietal cells
  • Adult worms and eggs are found deep at base of lesion
• N. nochti:
  • Free parasites are not found in the gastric lumen
  • Sixteen distinct, evenly spaced, longitudinal cuticular ridges flared near lateral cords
  • Pseudocoelom
  • Platymyarian - meromyarian musculature
  • Intestine is large and composed of few multinucleate cells
  • Reproductive tract (ovary or testis)
  • Eggs are thin-shelled, ellipsoidal, morulated (i.e., embryonated), and are 60-80 x 35-42 um

 

DIFFERENTIAL DIAGNOSIS:

• Trichostrongylids:
  • Molineus: Submucosal granulomatous inflammation and serosal nodules in the pyloric region and small intestine of New World monkeys; small, slender, pale red worms found on the mucosa
• Spirurids:
  • Physaloptera tumefaciens: More common in macaques than nochti; large nematodes resembling ascarids attached by the head to the mucosa with protrusion of the body into the gastric lumen; gastritis and gastric hyperplasia; cockroach intermediate host

 

COMPARATIVE PATHOLOGY:

• Trichostrongyloid gastritis/abomasitis in other species:
  • Cattle, goats, and horses: Trichostrongylus axei
  • Cattle: Ostertagia ostertagi (D-P13)
  • Sheep: Teladorsagia circumcincta
  • Sheep & goat: Trichostrongylus colubriformis, T. vitirnus, T. rugatus
  • Ruminants: Haemonchus
  • Swine: Hyostrongylus rubidus
  • Cats, felids, and swine: Ollulanus tricuspis

 

• Hypertrophic gastritis:
  • Horses – Draschia megastoma (D-P08, formerly Habronema megastoma) (focal, brood pouch), Habronema muscae, majus, and Trichostrongylus axei (diffuse gastric mucosal thickening)
  • Dogs – Chronic giant hypertrophic gastropathy (D-M03; Basenji, Beagle, Boxer, Bull terrier); unknown etiology

 

REFERENCES:

1. Bowman DD. Georgis Parasitology for Veterinarians. 9th ed. Philadelphia, PA: Elsevier Saunders; 2009:368-371.
2. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 2006:22-26.
3. Gelberg HB. Alimentary System and the Peritoneum, Omentum, Mesentery, and Peritoneal Cavity. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:363.
4. Rensing, KM, Lowenstine, LJ. New World and Old World Monkeys. In: Terio K, McAloose D, Leger J, eds. Pathology of Wildlife and Zoo Animals, San Diego, CA: Elsevier 2018:368.e9.
5. Strait K, Else JG, Eberhard ML. Parasitic diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardiff S, Morris T, eds. Nonhuman Primates in Biomedical Research Diseases. San Diego, CA: Academic Press; 2nd ed., 2012:234-235.
6. Uzal FA, Platter 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: 212.

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