JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1358025/Slide A): Tissue from a cat
HISTORY: Incidental finding in a cat with small white spots adjacent to bronchioles
HISTOPATHOLOGIC DESCRIPTION: Lung, two sections: Diffusely filling 70% of alveolar spaces are numerous nematode eggs, larvae and adults admixed with moderate numbers of alveolar macrophages, multinucleated macrophages, neutrophils, fewer eosinophils, scattered hemorrhage, and proteinaceous fluid, which extends into and fills bronchioles. The nematode eggs are 40-60µm, oval, thin walled, arranged in clusters and are either morulated or embryonated. Larvae are approximately 25 µm, composed of numerous nuclei, have lateral alae and have one tapered end that forms an eccentric tip. Adult nematodes have a 5µm cuticle, coelomyarian-polymyarian musculature, pseudocoelom, intestinal tract with birefringent yellow‑brown pigment and reproductive tract (ovaries). Multifocally alveolar septa are lined by hyperplastic pneumocytes (type II pneumocyte hyperplasia) and the smooth muscle surrounding terminal bronchioles is thickened (hypertrophy). Bronchiolar epithelium is hyperplastic, and surrounding larger blood vessels, bronchi and bronchioles are moderate numbers of lymphocytes and plasma cells. Multifocally the subpleural connective tissue contains low numbers of lymphocytes and plasma cells and the overlying mesothelium is reactive.
MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, histiocytic and neutrophilic, diffuse, moderate, with type II pneumocyte hyperplasia, smooth muscle hypertrophy, and large numbers of metastrongyle eggs, larvae and few adults, etiology consistent with Aelurostrongylus abstrusus, breed not specified, feline.
Sigmalment (JPC #3135343/Slide B): Five-month-old castrated male domestic-shorthaired cat.
HISTORY: This cat was found recumbent with shallow breathing and died shortly thereafter.
HISTOLOGIC DESCRIPTION: Lung: Multifocally, in a random and patchy distribution, alveoli contain variable numbers of eosinophils and foamy alveolar macrophages, admixed with fewer lymphocytes, plasma cells, fibrin, edema, and multinucleated giant cells which range from few to large aggregates and fill and expand alveolar lumina and alveolar septae. Focally, the lung is consolidated and alveolar lumina are expanded by multiple tangential cross sections of previously described nematode larvae and eggs. There is multifocal to coalescing thickening of alveolar septae and terminal bronchioles, up to five times normal, by hypertrophic smooth muscle. Throughout the section, the tunica media of pulmonary arterioles are markedly hypertrophic and the tunica adventitia is mildly expanded by clear space (edema). Diffusely bronchi and bronchioles contain small amounts exudate and there is moderate hyperplasia of goblet cells and bronchial submucosal glands. There is also mild diffuse subpleural edema.
MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, eosinophilic and granulomatous, chronic, multifocal to coalescing, moderate with diffuse marked smooth muscle hypertrophy of the alveolar septae, terminal bronchioles, and tunica media of pulmonary arterioles, and few nematode eggs and larvae, domestic short-haired, feline.
ETIOLOGY: Aelurostrongylus abstrusus
ETIOLOGIC DIAGNOSIS: Pulmonary aelurostrongyliasis
- abstrusus is the most common nematode parasite of cat lungs
- Usually found in rural, hunting cats that eat snails and slugs or in the proposed paratenic (transport) hosts, including rodents, birds, frogs, and lizards
- abstrusus is a member of the superfamily Metastrongyloidea, family Angiostrongyloidae
- Normally considered an incidental finding, but may be associated with anesthetic deaths
- Can cause chronic respiratory disease particularly when associated with a secondary bacterial infection
Oviparous female deposits eggs in the lung, primarily within bronchioles > first-stage larvae are coughed up and swallowed > passed in feces > larvae enter intermediate host (snail and slug) > 2 molts > paratenic host – (small mammal/bird) eats snail/slug > third-stage larvae encyst in tissues > cat eats intermediate or paratenic host > migrate from stomach to lungs via peritoneal and thoracic cavities > larvae appear in cat feces 5-6 weeks post infection
TYPICAL CLINICAL FINDINGS:
- Many cats are asymptomatic
- Moderate infections are manifested as coughing and anorexia
- Severe infections are manifested as dyspnea, coughing, polypnea and death
TYPICAL GROSS FINDINGS:
- Multifocal, amber, firm, subpleural nodules ranging from 1-10mm, that coalesce in severe cases
- Nodules contain eggs, larvae, fewer adults and exudate
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Bronchioles and alveoli contain eggs, adult, and larval parasites (Adults: 40-60 um, coelomyarian musculature, large multinucleated GI tract, accessory hypodermal cords; Larvae: 25 um, nucleated, lateral alae, tip of tail is eccentric to body)
- Adults are typically in the terminal and respiratory bronchioles
- Eggs and larvae are typically in alveoli
- Eosinophils and neutrophils are present early, but most lesions are dominated by macrophages and and multinucleated giant cells
- Catarrhal bronchiolitis, submucosal gland hyperplasia, granulomatous alveolitis, alveolar fibrosis
- Smooth muscle hypertrophy and hyperplasia of bronchioles and alveolar ducts
- Peribronchial, peribronchiolar and perivascular lymphocytic nodules
- Paragonimus kellicotti – lung trematode of mink, dogs and cats
- Toxoplasma gondii – necrotizing pneumonia with protozoal cysts
Lungworms in other species:
Dog - Filaroides hirthi; Crenosoma vulpis; Eucoleus aerophilis; Paragonimus kellicotti (fluke); Angiostrongylus vasorum and Dirofilaria immitis (found in pulmonary arteries)
Cat - Aelurostrongylus abstrusus; Eucoleus aerophilis
Ox - Dictyocaulus viviparous
Sheep and goats - Dictyocaulus filaria; Muellerius capillaries; Protostrongylus rufescens
Horse - Dictyocaulus arnfieldi
Pig - Metastrongylus apri; M. salmi; M. pudendotectus
Mustelis – Crenosoma sp.; Perostrongylus sp.; Filaroides hirthi; Skrjabingylus sp.
Wild felids – Aelurostrongylus abstrusus; Troglostrongylus brevio; Eucoleus aerophilis
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- Veronesi F, Traversa D, et al. Occurance of lungworms in European wildcats (Felis silvestris silvestris) of Central Italy. J Wildl Dis. 2016; 52(2):270-278.