JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1647279): An adult rhesus macaque
HISTORY: Wild-caught rhesus macaque
HISTOPATHOLOGIC DESCRIPTION: Lung: The walls of bronchioles are expanded and occasionally effaced by large numbers of infiltrating neutrophils, macrophages, eosinophils, fewer multinucleated giant cells, lymphocytes, and plasma cells which often extend into the adjacent parenchma. Multifocally bronchiolar epithelium is attenuated, absent, or occasionally hyperplastic, there is fibrosis and smooth muscle hyperplasia within bronchiole walls and peri-bronchiolar lymphoid tissue is hyperplastic. Occasionally there are few cross sections of adult arthropod parasites within the lumen or wall of bronchioles. Arthropods are approximately 300‑500 um in width, and contain a chitinized exoskeleton, jointed appendages, striated musculature, a body cavity, digestive tract, and neural tissue. Multifocally throughout the section there are aggregates of macrophages which contain intracytoplasmic golden-brown to black finely granular birefringent material (mite pigment). There is moderate perivascular fibrosis, smooth muscle hypertrophy, and perivascular edema. Within the surrounding alveoli are increased numbers of alveolar macrophages admixed with eosinophils, lymphocytes, plasma cells, fibrin, hemorrhage, and edema.
MORPHOLOGIC DIAGNOSIS: Lung: Bronchiolitis and bronchitis, pyogranulomatous and eosinophilic, chronic, multifocal, moderate, with fibrosis, smooth muscle hypertrophy, lymphoid hyperplasia, and bronchiolar and bronchial intraluminal arthropods with mite pigment, etiology consistent with Pneumonyssus simicola, rhesus macaque (Macaca mulatta), non-human primate.
ETIOLOGIC DIAGNOSIS: Pulmonary pneumonyssiasis
CAUSE: Pneumonyssus simicola
- Several species of mites in the genus Pneumonyssus (family Halarachnidae) are the cause of pulmonary acariasis in Old World monkeys; New World monkeys are relatively free of these parasites
- Pulmonary acariasis, most commonly caused by Pneumonyssus simicola, can be found in the lungs of mostly all wild caught rhesus macaques, and to a lesser extent in baboons
- Suggested lifecycle: male and female mites in the upper respiratory tract > fertilization > female migrates to the bronchioles > release prelarval mites > larvae mature in bronchioles > larvae migrate to the trachea > sneezing/coughing transmits larvae to a new host > larvae mature in the bronchial or tracheal mucosa
- All stages of simicola (adults, eggs, larvae) can be found in the lungs
- Mites feed on host erythrocytes, lymph, and pulmonary epithelial cells; mite pigment presumed to be from the metabolism of hemoglobin by the parasite
- Female mites and their metabolites (mite pigment) induce inflammation; larval mites are not typically associated with a host reaction
TYPICAL CLINICAL FINDINGS:
- Varies from none to coughing, sneezing, and dyspnea
TYPICAL GROSS FINDINGS:
- Discrete, 1-7 mm, yellow-gray cystic bullae which contain 1 or more mites (“mite houses”); tend to be nodular and subpleural
- Black 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
- Alveolar emphysema and atelectasis; bronchiolar smooth muscle hypertrophy; interstitial fibrosis
- Arthropod characteristics: 300-500 um 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:
- Tracheobronchiolar lavage
DIFFERENTIAL DIAGNOSIS: (gross differential)
- Aspiration pneumonia
COMPARATIVE PATHOLOGY: Arthropods of the respiratory tract include:
- Pneumonyssoides sp (mite): NHP-NWM, similar to Pneumonyssiasis in OWM
- Rhinophaga sp.(mite): NHP-OWM; nasal cavity and sinuses
- Pneumonyssoides caninum (mite): Dogs; nasal cavity and sinuses
- Entonyssus sp. and Entophionyssus sp.(mite): Snakes; trachea and lung
- Cytodites nudus (mite): Air sac mite of poultry
- Sternosoma tracheacolum (mite): Blood sucking mite in finches and canaries
- Oestrus ovis (botfly): Sheep, rarely goats; nasal cavity and sinuses
- Linguatula serrata (pentastomid): Dogs and cats; nasal and paranasal sinuses
- Bowman DD. Georgis Parasitology for Veterinarians. 9th ed. St Louis, MO: Saunders Elsevier; 2009:63.
- Gardiner CH, Poyton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 1999:56-58.
- 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.
- Purcell JE, Philipp MT. Parasitic Diseases of Nonhuman Primates: In Wolfe-Coote S, ed. The Laboratory Primate. San Diego, CA: Elsevier; 2005:589-590.
- Shirai N, Geoly FJ. Eosinophilic airway inflammation in a Cynomolgus monkey. Vet Pathol. 2010; 47(2): 318-321.
- 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.