JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1711212): Herring gull
HISTOPATHOLOGIC DESCRIPTION: Trachea: The mucosal epithelium is thickened up to five cell layers thick by disorganized epithelial cells that have enlarged, often vesiculate nuclei (hyperplasia) and increased numbers of goblet cells. Multifocally, overlying the epithelium is a thin layer of eosinophilic, finely fibrillar material (fibrin). Within the lumen, there are sloughed epithelial cells and multiple cross sections of adult nematodes that measure up to 500 um in diameter with a 1 um, smooth cuticle, a pseudocoelom lined by platymyarian-meromyarian musculature, an intestine lined by few multinucleated cells with a prominent brush border, and several sections of ovaries and uteri containing developing eggs. Diffusely, the subepithelial connective tissue is markedly expanded by moderate amounts of clear space (edema), moderate numbers of lymphocytes and plasma cells, fewer macrophages, heterophils, and low numbers of reactive fibroblasts.
Liver: Multifocally and randomly, there are few variably sized foci which contain pale, enlarged hepatocytes (degeneration) as well as eosinophilic material and basophilic karyorrhectic debris (necrosis) admixed with few to moderate numbers of macrophages, and heterophils and fewer lymphocytes.
Kidney: No significant lesions.
MORPHOLOGIC DIAGNOSIS: 1. Trachea: Tracheitis, proliferative, lymphoplasmacytic, diffuse, moderate, with goblet cell hyperplasia and intraluminal adult nematodes, etiology consistent with Syngamus trachea, herring gull (Larus argentatus), avian.
2. Liver: Hepatitis, pyogranulomatous necrosis, multifocal, random, mild.
ETIOLOGIC DIAGNOSIS: Tracheal syngamiasis
CAUSE: Syngamus trachea
SYNONYMS: Gapeworm, redworm, forked worm
- Class: Nematoda; Order: Strongylida; Superfamily: Strongyloidea; Family: Syngamidae; Genus: Syngamus
- Most common in young, flightless, free range birds (turkeys, pheasants, chickens, geese, guinea fowl, pea fowl, and quail with worldwide distribution)
- Characteristic lesions usually found in turkey/pheasants, less likely in chickens, and seldom if ever in guinea fowl; pheasants, turkey poults and young chickens are most susceptible
- Found in birds raised outdoors when access to infected intermediate hosts (e.g. earthworms) is available, especially after heavy rains bring them to the surface
- In fresh tissue, worms are frequently bright red due to the ingestion of host blood, and the male and female worms are permanently fused in copula, resulting in a "y"-shaped appearance; males are 2-6mm and females 5-20mm long
- Males burrow into the mucosal lining of the trachea acting as an anchor for the female
- In the trachea, the worms attach to the mucosa and feed on blood, with consequent catarrhal tracheitis and occasional secondary lobar pneumonia
- Deep embedment of the male within the wall of the trachea can result in the development of nodules
- Trachea becomes partially to completely occluded by worms and blood clots and causes subsequent gaping for air and death by suffocation
- Adult females lay eggs in the bird’s trachea that are coughed up, swallowed and passed out in the feces > Larvae may remain free or become encysted in transport hosts (earthworms,snails, slugs) and live for months to years in muscle > After ingestion by the bird (the definitive host), the larvae penetrate the wall of crop, esophagus or duodenum, migrate through the liver, enter the blood stream via the portal system, and are carried to the lungs > Adult worms migrate to the large bronchi and trachea where copulation takes place and eggs are laid
- Prepatent period: 17-20 days
- Direct transmission occurs by ingestion of the infective larvae or embryonated eggs
- Indirect transmission occurs when transport hosts such as earthworms, snails, slugs, flies and other arthropods ingest infective larvae
TYPICAL CLINICAL FINDINGS:
- Chiefly affects young birds; turkeys susceptible at all ages
- Dyspnea, coughing, asphyxia, and “gaping”
- Death results from asphyxiation or from progressive emaciation, anemia, and weakness caused by the parasites
TYPICAL GROSS FINDINGS:
- Tracheal lesions range from mild catarrhal and hemorrhagic tracheitis to severe ulcerative tracheitis with bronchitis and pneumonia
- In turkeys and larger birds, small white nodules may be found along the trachea and are considered to be presumptive evidence of previous infection
- Nodules are rare in chickens and guinea fowl
- Emaciation and pale carcass from anemia
- Worms are present in the distal trachea and are bright red with a characteristic “y” shape
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Males are up to 200 um and females up to 350 um in diameter with a pseudocoelom, 4-8um cuticle, platymyarian-meromyarian musculature and a prominent intestinal brush border lined by few multinucleate cells
- Thin shelled eggs measure 50 by 90 um, and have a thickened operculum at each pole
- Catarrhal and hemorrhagic tracheitis
- Possible lymphoid follicles in the trachea
- Verminous pneumonia in heavy infections
ADDITIONAL DIAGNOSTIC TESTS:
- In live birds, detection of double-operculated, 50 X 90 um strongyle eggs in coughed up mucus or on fecal flotation
- Cyathostoma bronchialis: Larger worm, less firmly united in copula; Eggs have an indistinct operculum; Found in the larynx, trachea, bronchi, and abdominal air sacs of ducks, geese and swans
- Associate bronchialis with water fowl and S. trachea with land birds though they can be found in either group
- Syngamus skrjabinomorpha: Similar grossly and histologically but only found in chickens and geese in Russia
- Various Mammomonogamus (formerly Syngamus) spp parasites have been reported in the larynx, nasal cavity, pharynx, middle ear, and bronchi of humans and other mammals
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- Wehr EE. Nematodes. In: Davis JW, ed. Infectious and Parasitic Diseases of Wild Birds. 1st ed. Ames, IA: Iowa State University Press; 1971:193-196.