JPC SYSTEMIC PATHOLOGY

DIGESTIVE SYSTEM

OCTOBER 2024

D-P25 (NP)

 

Signalment (JPC # 2188162): 21-month-old male Persian cat

 

HISTORY: This cat had a history of watery ocular discharge with intermittent periods of anorexia and vomiting.

 

HISTOPATHOLOGIC DESCRIPTION: Stomach, pylorus: Diffusely, the mucosa is thickened up to 2mm by hyperplastic mucosal epithelium that forms tortuous, convoluted glands often lined by abundant mucous neck cells that pile up to 5 cell layers thick and have frequent mitotic figures (mucous neck cell hyperplasia). Multifocally, pyloric glands are lost and replaced by fibrous connective tissue. Remaining pyloric glands are either tortuous and dilated with luminal sloughed epithelial cells and necrotic debris or are lined by basophilic cuboidal cells that pile up to 2-3 cell layers thick, have vesiculate nuclei, prominent nucleoli, and increased mitotic figures (regeneration). There are low to moderate numbers of lymphocytes, plasma cells, macrophages, and eosinophils within the lamina propria. There are numerous tangential and cross sections of adult nematodes within the gastric lumen, pits, and attenuated pyloric glands. These adult nematodes are 30 µm in diameter and have a 2 µm thick cuticle with numerous, evenly-spaced, longitudinal, cuticular ridges, platymyarian-meromyarian musculature, and a pseudocoelom containing a poorly discernible intestine and reproductive tract (trichostrongyles).

 

MORPHOLOGIC DIAGNOSIS: Stomach, pylorus: Gastritis, proliferative, chronic, diffuse, moderate, with fibrosis, mucous neck cell hyperplasia, and luminal and intraglandular trichostrongyle nematodes, Persian, feline.

 

ETIOLOGIC DIAGNOSIS: Gastric trichostrongyliasis

 

CAUSE: Ollulanus tricuspis

 

GENERAL DISCUSSION:

• A small, 1mm long, trichostrongyle nematode that inhabits the stomach of cats and swine, and is regionally common in some parts of the world
• Trichostrongyles: have platymyarian musculature, typically longitudinal cuticular ridges (evenly spaced or irregular, differences are used in speciation), and have characteristic strongylid intestinal tracts (large, lined by few multinucleated cells)

 

PATHOGENESIS:

 

LIFE CYCLE:

• Direct life cycle
• Entire life cycle can occur in one host
• Nematodes are viviparous (bear live larval young, in this case L3 larvae, not eggs), L3 larvae vomited à direct transmission via ingestion of L3 larvae à develop to adult within stomach

 

TYPICAL CLINICAL FINDINGS:

 

TYPICAL GROSS FINDINGS:

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Infection is associated with the following characteristic changes (characteristic even in the absence of identified nematodes): 
  • Increased lymphoid follicles deep in the gastric mucosa
  • Increased interstitial connective tissue in the mucosa which often separates gastric glands (fibrosis)
  • Numerous globule leukocytes in the gastric epithelium
  • Heavy infection may cause mucous metaplasia and hyperplasia of gastric glands with mucosa thrown up into hyperplastic folds
• Nematodes may be rare in histologic sections: 
  • Small, 1mm length, with numerous longitudinal cuticular ridges (synlophe) recognized as projections (cuticular ridges) on the surface of sectioned nematodes
  • Platymyarian-meromyarian musculature and strongylid intestine (large, with multinucleated cells) are often difficult to visualize in tissue sections 
  • Located beneath the mucus on the surface of the stomach or partly in gastric glands

 

ADDITIONAL DIAGNOSTIC TESTS:

• Requires examination of vomitus, stomach washes, or gastric mucosal scrapings; due to life cycle, organism is not usually detected on fecal examination and therefore may go undiagnosed
• Parasites (whole or partial) are not commonly observed on cytopathology; neutrophilic inflammation is often admixed with oropharyngeal flora and digesta

 

DIFFERENTIAL DIAGNOSIS:

Gastric nematodes of the cat:

• Ollulanus sp., Gnathostoma sp. (Spirurid), and Cylicospirura felineus (Spirurid) may cause gastritis in dogs and cats, but these are rare; found in submucosal nodules
• Gnathostoma spp. (Spirurid) have a copepod invertebrate as an intermediate host with variety of fish, amphibian, or reptiles as second intermediate or paratenic hosts; larva undergo migration through liver (resulting in fibrosis); adults found in groups of up to 10 in gastric mucosal nodules up to 5cm in diameter and open to gastric lumen
• Physaloptera spp.(Spirurid) are often thought of as gastric parasites because they are sometimes found in the stomach at necropsy/endoscopic exam, but they generally attach by anterior hooks to the proximal duodenal mucosa at the gastric valve; these occasionally cause vomiting, appear grossly similar to ascarids, and intermediate hosts are coprophagic beetles 
• Cylicospirura sp.: Gastric nematodes found uncommonly in the gastric lumen in domestic and wild felids; may also be associated with gastric nodules

 

COMPARATIVE PATHOLOGY:

Ollulanus tricuspis in other species:

Other trichostrongyles: 

• Ostertagia ostertagi in cattle (see D-P13)
• Ostertagia (now Teladorsagia) circumcincta in sheep and goats
• Molineus torulosus (see D-P16) and Nochtia nochti (see D-P14) in non-human primates
• Trichostrongylus axei in horses
• Trichostrongylus spp. - potential cause of anemia in poultry

 

REFERENCES:

1. Barnes HJ, Fletcher OJ. Chapter 1: Hemic System. In: Abdul-Aziz T, Fletcher OJ, Barns HJ, eds. Avian Histopathology. 4th ed. Madison, WI: Omnipress; 2016:5.
2. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology;1999:22-25.
3. Hostetter SJ. Chapter 7: Oral Cavity, Gastrointestinal Tract, and Associated Structures. In: Raskin RE, Meyer DJ, & Boes KM eds. Canine and Feline Cytopathology: A Color Atlas and Interpretation Guide. 4th ed. St. Louis, MO: Elsevier; 2022:302-303.
4. Spagnoli ST, Gelberg HB. Alimentary System and the Peritoneum, Omentum, Mesentery, and Peritoneal Cavity. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:435, 474, 480. 
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, Vol. 2. 2nd ed. Waltham, MA: Academic Press; 2012:233-235.
6. Terio KA, McAloose D, Mitchell E. Felidae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, England: Elsevier; 2018:278.
7. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: 54-55, 211.

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