JPC SYSTEMIC PATHOLOGY

DIGESTIVE SYSTEM

October 2024

D-P15

 

Signalment (JPC #3048313): A pigeon

 

HISTORY: None

 

HISTOPATHOLOGIC DESCRIPTION: Proventriculus: Multifocally, 50% of mucosal (compound tubular) glands are markedly dilated up to 3 x 2 mm, compressing adjacent atrophic glands (compression atrophy), and elevating the overlying mucosa. Affected glands are lined by attenuated epithelium and contain cross sections of plump adult female nematodes. These nematodes are up to 1.5mm in diameter, have a 3µm wrinkled cuticle, polymyarian-coelomyarian musculature, a pseudocoelom that contains abundant homogenous, brightly eosinophilic fluid, a tri-radiate esophagus, a digestive tract lined by many uninucleate cuboidal cells with a prominent brush border that contains abundant brown pigment, uteri containing numerous 25 x 50µm, oval, thick shelled, embryonated spirurid eggs, and variably sized ovaries with ova. Occasionally, embryonated eggs have visible polar filaments. Multifocally within the lamina propria, submucosa, muscularis, and serosa are several small aggregates of lymphocytes and rare heterophils. There is increased mucous production in the superficial mucosa. 

 

Heart; esophagus; ventriculus; great vessel; air sac; peripheral nerve; and lung: Essentially normal tissue.

 

MORPHOLOGIC DIAGNOSIS: Proventriculus: Glandular ectasia, multifocal, marked, with compression atrophy, intraglandular adult spirurid nematodes, and mild lymphocytic proventriculitis, pigeon (Columba livia), avian. 

 

ETIOLOGIC DIAGNOSIS: Proventricular tetrameriasis

 

CAUSE: Tetrameres sp. (T. americana or T. fissispina)

 

GENERAL DISCUSSION:

• Proventricular spirurid nematode affecting numerous aquatic birds, particularly Anseriformes, Ardeiformes, Gruiformes, and Charadriiformes, and less commonly affecting land birds such as Passerines and Galliformes.
• These parasites have marked sexual dimorphism; males are small, white, and filiform and either found with females in the mucosal glands or free in the lumen of the proventriculus; females are large, blood red, and either spherical (globular in tissue section ‑ Tetrameres) or coiled (lobate in tissue section ‑ Microtetrameres) in the mucosal glands

 

PATHOGENESIS:

• Tetrameres spp. invade proventricular glands, distending and filling the lumen
• Females suck blood and cause moderate to severe irritation/inflammation in the proventriculus of some avian hosts
• Necrosis and degeneration of proventricular mucosa, edema, leukocytosis, and extensive blood loss may occur
  1. With T. fissispina (in ducks), degeneration of glandular epithelium w/ edema and lymphoid cell infiltrate are characteristic 

 

LIFE CYCLE:

• Females live in the proventricular glands; males live free in the lumen or on the mucosal surface and enter the glands only temporarily to copulate
  1. Male and female nematodes are commonly found together in the lumen of the same proventricular gland
  2. Females are large and globular, while males are smaller and elongate – demonstrate extreme sexual dimorphism 
• Tetrameres require an intermediate host (water crustaceans or insects [grasshopper, earthworms, or cockroach])
• Embryonated eggs pass in feces > develop in intermediate host (grasshopper, cockroach) > eaten by a bird > infective larvae mature in the proventriculus

 

TYPICAL CLINICAL FINDINGS:

• Vary from no clinical signs to anemia, diarrhea, emaciation, and death depending on the severity of infection and susceptibility of the host species
• Tetrameres americana causes no signs in bobwhite quail but can cause death in pigeons

 

TYPICAL GROSS FINDINGS:

• Bright red female worms are embedded in the proventricular glands and can be observed through the wall of the unopened gland
• May develop thickening (due to mucosal hyperplasia) of the proventricular wall that can obliterate the proventricular lumen in some hosts

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Distension of glands by female nematodes with compression of adjacent tissue
• Mucosal hyperplasia with heavy infection
• T. americana is usually associated with mild inflammation, while T. fissispina produces degeneration, edema, and extensive leukocyte infiltration

• Nematode characteristics: Polymyarian/coelomyarian musculature; large stalked lateral cords; esophagus divided into anterior muscular and posterior glandular portions; large intestine lined by many uninucleate columnar to cuboidal cells with a prominent (long) microvillar border; distinguishing eosinophilic fluid in the pseudocoelom (feature of most Spirurids); and small, thick-shelled embryonated eggs with polar filaments (characteristic of Spirurids)

 

ADDITIONAL DIAGNOSTIC TESTS:

 

DIFFERENTIAL DIAGNOSIS: 

For nematodes in the proventriculus:

• Tetrameres sp.: Fat, spherical, blood-red worms in the wall of the proventriculus that distend the glands
• Microtetrameres sp.: Lobate, wide, coiled, blood red worms in the wall of the proventriculus (M. helix: Russian and North American crows and pigeons)
• Cyrnea sp.: Spirurids, but lack the marked sexual dimorphism of the Tetramitidae; nonpathogenic; do not suck blood; do not attach to mucosa or live in glands 
  • C. pileata: Bobwhite quail
  • C. colini: Various North American gallinaceous birds
• Dispharynx nasuta: Lives on the mucosa of the proventriculus, esophagus, and rarely the intestines of various species of pigeons, chickens, turkeys, and guinea fowl worldwide; can cause severe ulceration with chronic diffuse fibrosis; most severe in young birds and the main cause of grouse disease in the USA
• Echinuria uncinata: In the esophagus, proventriculus, gizzard, and small intestine of the duck, goose, and swan; penetrate deep into the mucosa forming large nodules with caseous centers, which can obstruct the passage of food
• Gongylonema ingluvicola: mucosa of the crop and sometimes the esophagus and proventriculus of chicken, turkey, partridge, pheasant, and quail; burrows in the mucosa, which appear as white convoluted tracks

 

COMPARATIVE PATHOLOGY:

Tetrameres spp.:

• Tetrameres americana: Chicken, quail, turkey, guinea fowl, pigeons, ducks, and geese; mainly in the USA and South Africa
• T. fissispina: Most common in ducks and geese; rare in pigeons, chickens, turkeys, and other birds; worldwide distribution
• T. crami: North American ducks
• T. pattersoni: Only in bobwhite quail 

 

s

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