JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

September 2023

P-P19 (NP)

 

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 µm in diameter and are characterized by a thin yellow anisotropic chitinous exoskeleton, multiple jointed appendages, a 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 smooth muscle 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. Multifocally, there is increased clear space within the tunica adventitia of pulmonary arteries (edema) with mild endothelial cell hypertrophy.

 

MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, granulomatous, multifocal, moderate, with parabronchial intraluminal arthropods and few colonies of cocci, gamebird, avian.    

 

ETIOLOGIC DIAGNOSIS: Pulmonary acariasis

 

CAUSE: Cytodites nudus

 

CONDITION: Air sac mite infestation

 

GENERAL DISCUSSION: 

• 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 coelomitis, pneumonia, and airway obstruction with heavy infestations; infected birds may be predisposed to avian tuberculosis
• Part of the family suborder Astigmata

 

LIFE CYCLE:  

 

TYPICAL CLINICAL FINDINGS:

• May be asymptomatic 
• Coughing, dyspnea, emaciation, weakness, incoordination, death

 

TYPICAL GROSS FINDINGS:

• Small, white, motile specks on the transparent membranes of the air sacs
• Granulomatous pneumonia
• Air sacs may be thickened and cloudy
• Coelomitis; 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 µm long and 300‑500 µm 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:

 

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 spp. – 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 sp.- starlings

 

COMPARATIVE PATHOLOGY:   

Lung Mites:

• Pneumonyssus simicola (P-P18) – 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

 

REFERENCES:

1. Abdul-Aziz T, Fletcher OJ, Barnes HJ.  Avian histopathology.  4th ed.   Madison, WI: American Association of Avian Pathologists; 2016:199, 254-255.
2. Bowman DD. Georgi’s Parasitology for Veterinarians. 10th ed.  Philadelphia, PA: WB Saunders; 2014, 73.
3. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 1999:56-58.
4. Macwhirter P. Passeriformes. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian Medicine: Principles and Application. Lake Worth, FL: Wingers Publishing, Inc; 1994:1195.
5. McMullin PF. Parasitic diseases. In: Pattison M, McMullin PF, Bradbury JM, Alexander D, eds. Poultry Diseases. 6th ed. Philadelphia, PA: Elsevier Ltd; 2008:465-6.
6. McOrist S. Cytodites nudus infestation of chickens, Avian Pathology. 1983: 12:1: 151-155.
7. Schmidt RE, Reavill DR, Phalen DN.  Pathology of Pet and Aviary Birds.  2nd ed. Ames, IA: Wiley; 2015:33, 39-41.

 

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