JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

September 2023

P-P18

 

Signalment (JPC #1647279): 19-year-old male rhesus macaque.

 

HISTORY: Colony housed at a research institute; arthritic changes within both stifles; began declining clinically with cachexia, diarrhea, and dehydration prior to euthanasia; lung lesions on necropsy included 2-5mm diameter, slightly raised tan nodules in all lung lobes.

 

HISTOPATHOLOGIC DESCRIPTION: Lung: Multifocally affecting 20% of the section, bronchial and bronchiolar walls are transmurally and irregularly thickened or obscured by abundant lymphocytes, plasma cells, macrophages, eosinophils, and fewer neutrophils and multinucleated giant cells. Bronchial and bronchiolar lumens are often dilated and contain an exudate composed of macrophages, neutrophils, eosinophils, and cross and tangential sections of arthropods. Arthropods are 300-500 µm in diameter and characterized by a thin chitinized exoskeleton, jointed appendages, striated musculature, a body cavity (hemocoel), digestive tract, and reproductive organs. Many macrophages contain abundant intracytoplasmic golden-brown to black, finely granular, birefringent pigment (mite excrement). The peribronchial and peribronchiolar inflammatory cell aggregates multifocally form lymphoid follicles, variably compress or extend into adjacent alveolar tissue, and elevate the pleura. Affected bronchi and bronchioles exhibit moderate smooth muscle hypertrophy and occasional peribronchiolar fibrosis. In less affected lung, terminal airways and alveoli are multifocally dilated with occasional loss of alveolar septa.

 

MORPHOLOGIC DIAGNOSIS: Lung: Bronchitis and bronchiolitis, eosinophilic and granulomatous, multifocal, chronic, moderate, with bronchiectasis and bronchiolectasis, smooth muscle hypertrophy, and mites with mite pigment, macaque, primate. 

 

ETIOLOGIC DIAGNOSIS: Pulmonary pneumonyssiasis

 

CAUSE: Pneumonyssus simicola

 

GENERAL DISCUSSION:

• Pulmonary acariasis in Old World monkeys is caused by one of ten species of mites in the genus Pneumonyssus (family Halarachnidae)
• New World monkeys are relatively free of these parasites
• Pulmonary acariasis, most commonly caused by Pneumonyssus simicola, can be  found in the lungs of most wild caught rhesus macaques, and to a lesser extent in baboons

 

LIFE CYCLE:

• Possible routes of infection include inhalation of infected aerosols, ingestion during grooming, or through feces
• All stages of P. simicola (adults, eggs, larvae) can be found in the lungs
• Mites feed on host erythrocytes, lymph, and pulmonary epithelial cells and produce mite pigment containing hemoglobin, lipofuscin, silicates and other material

 

TYPICAL CLINICAL FINDINGS:

 

TYPICAL GROSS FINDINGS:

• Discrete, 1-7 mm, soft yellow-gray foci; flat to umbilicated; contain gelatinous material and 1 or more mites (“mite houses”); may be bullous or hemorrhagic
• Black mite pigment may be present in hilar lymph nodes and pulmonary lesions 
• +/- fibrous adhesions between pulmonary visceral and parietal pleura
• Sequelae: Pneumothorax, pulmonary arteritis, pleuritis, pericarditis

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Granulomatous bronchiolitis and peribronchiolitis with epithelial desquamation and intraluminal mites
• Alveolar emphysema and atelectasis; bronchiolar smooth muscle hypertrophy; interstitial fibrosis
• Arthropod characteristics: 300-500 µm in width; variably chitinized exoskeleton, mouth part, jointed appendages, striated musculature, a body cavity, digestive tract, reproductive structures, yolk material in yolk glands, developing eggs, and neural tissue
• Golden brown to black refractile mite pigment often within macrophages

 

ADDITIONAL DIAGNOSTIC TESTS:

 

DIFFERENTIAL DIAGNOSIS:

• Gross

• Mycobacterium spp.: Nodules usually more firm
• Coccidiodes spp.

 

COMPARATIVE PATHOLOGY:  Arthropods of the respiratory tract include:

• Pneumonyssoides sp. (mite): Nonhuman primates (NHP) – new world monkeys (NWM); similar to Pneumonyssiasis in old world monkeys (OWM)
• Pneumonyssus oudemansi (mite): NHP-OWM (chimpanzees and gorillas)
• Rhinophaga pongicola (mite): NHP-OWM (orangutans); nasal cavity and sinuses
• Pneumonyssoides caninum (mite): Dogs; nasal cavity and sinuses
• Entonyssus sp. and Entophionyssus sp.(mite): Snakes; trachea and lung
• Cytodites nudus (P-P19, mite): Air sac mite of poultry
• Sternostoma tracheacolum (mite): Blood sucking mite in finches and canaries; mites reside in the major airways, parabronchi, and air sacs and can be seen in the trachea and air sacs on necropsy
• Oestrus ovis (botfly): Sheep, rarely goats; nasal cavity and sinuses
• Linguatula serrata (pentastomid): Dogs and cats; nasal and paranasal sinuses

 

REFERENCES:

1. Gardiner CH, Poyton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 1999:56-58.
2. Lowenstine LJ, McManamon R, Terio KA. Apes. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 402.
3. Lowenstine LJ, Osborn KG. Respiratory system diseases of nonhuman primates. In: Abee C, Mansfield K, Tardif S, Morris T, eds. Nonhuman Primates in Biomedical Research: Diseases. London, UK: Academic Press; 2012:467-468.
4. Matz-Rensing K, Lowenstine LJ. New World and Old World Monkeys. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 366-368.
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. 2nd ed. Vol. 2. San Diego, CA: Academic Press; 2012:268-270.
6. Trupkiewicz J, Garner MM, Juan-Sallés C. Passiformes, Caprimulgiformes, Coraciiformes, Piciformes, Bucerotiformes, and Apodiformes. In:  Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier; 2018: 813.

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