JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1947594): A male gamebird
HISTORY: From a backyard flock in which all birds had a history of lameness
HISTOPATHOLOGIC DESCRIPTION: Lung: Multifocally expanding the interstitium of approximately 50% of the parabronchi and secondary bronchi, and extending into the adjacent pulmonary parenchyma are nodular to coalescing infiltrates consisting of moderate numbers of macrophages and fewer lymphocytes and plasma cells that are often admixed with intrahistiocytic and extracellular brown, granular, anisotropic material (mite pigment). Parabronchial lumina frequently contain cross and tangential sections of adult arthropods (mites) that are up to 400 um in diameter and are characterized by a thin yellow anisotropic chitinous exoskeleton, multiple jointed appendages, body cavity, and bands of striated muscle. Multifocally, fragments of degenerate mites and occasional small colonies of basophilic cocci are surrounded by granulomatous inflammation consisting of epitheloid macrophages, multinucleated giant cells (Langhan’s and foreign body type), fewer lymphocytes, plasma cells, small numbers of viable and degenerate heterophils, and occasional clusters of fibroblasts. Rarely, mesobronchi and secondary bronchi are lined by mildly hyperplastic epithelium and contain a moderate amount of intraluminal, granular to fibrillar, lightly eosinophilic material (fibrin) admixed with mild hemorrhage, low numbers of macrophages, sloughed epithelial cells, and sections of degenerate mites.
MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, granulomatous, multifocal, moderate, with parabronchial intraluminal arthropod parasites and colonies of cocci, gamebird, avian.
ETIOLOGIC DIAGNOSIS: Pulmonary acariasis
CAUSE: Cytodites nudus
CONDITION: Air sac mite infestation
- Parasite of the respiratory system of chickens, turkeys, pheasants, pigeons, canaries, parrots, and wild birds; other mite species infect the respiratory passages of other avians
- Called the air sac mite because of its usual habitat, but can be found occasionally in the bronchi, lungs, and pneumatic bone cavities of birds
- Nearly worldwide in distribution; described in a wide variety of avian hosts, but often overlooked at necropsy
- The mite is usually considered harmless but can cause peritonitis, pneumonia, and airway obstruction with heavy infestations; infected birds may be predisposed to avian tuberculosis
- Complete life cycle unknown; mites lay eggs in the lower air passages of the host > eggs are coughed up and swallowed > passed in the feces
TYPICAL CLINICAL FINDINGS:
- May be asymptomatic
- Coughing, emaciation, weakness, incoordination, death
TYPICAL GROSS FINDINGS:
- Small white motile specks on the transparent membranes of the air sacs
- Granulomatous pneumonia
- Peritonitis; occasionally present in abdominal cavity and visceral surfaces
- Obstruction; may be an accumulation of mucus in the trachea
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Characteristics of mite: 500‑600 um long and 300‑500 um wide, chitinous exoskeleton, jointed appendages, a reduced or vestigial body cavity (haemocoel), and striated muscle
- Histiocytic, lymphoplasmacytic, or granulomatous inflammation associated with the parasite
ADDITIONAL DIAGNOSTIC TESTS:
- Identification of mite: Very few setae (hair like projections of the cuticle), reduced gnathostoma (area containing head and mouthparts), minute chelicerae (pincer like appendages used in feeding)
DIFFERENTIAL DIAGNOSIS (Bird Lung Mites):
- Sternostoma tracheacolum – tracheal mite of canaries, Gouldian finches, and other passerines; cause mucosal epithelial necrosis, mucosal hyperplasia, and mixed inflammation
- Neonyssus spp. – usually non-pathogenic
- Rhinonyssus – usually non-pathogenic
- Laminosioptes cysticola (Fowl cyst mite/Subcutaneous mite) - Usually forms nodular subcuticular lesions; may also form nodules in the lungs of pigeons
- Speleognathus - starlings
- Pneumonyssus simicola – monkeys; pinhead or larger whitish foci throughout the lungs with soft or empty centers that contain mites and a black pigment
- Pneumonyssoides caninum – dogs infests nasal cavity and paranasal sinuses and sometimes causes sneezing and epistaxis
- Orthohalarachne attenuata, Halarachne sp. - pinnipeds
- Entonyssus sp., Entophionyssus sp.- snakes
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- Schmidt RE, Reavill DR, Phalen DN. Pathology of pet and aviary birds. 2nd ed. Ames, IA: Wiley; 2015:33, 39-41.