September 2017



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




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






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


  1. Caswell JL, Williams KJ. The respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer"s Pathology of Domestic Animals. Vol. 2. 6th ed. Philadelphia, PA: Elsevier Saunders;2016:590-591.
  2. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissue. Washington, DC: Armed Forces Institute of Pathology; 1999:22-29.
  3. Kollias GV, Fernandez-Moran J. Mustelidae. In. In Miller ER, Fowler ME eds. Fowler’s Zoo and Wild Animal Medicine. Vol 8. St. Louis, MO: Elsevier; 2015:486.
  4. Lopez A, Martinson SA. The respiratory system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:551.
  5. Philbey AW, Krause S, Jefferies R. Verminous pneumonia and enteritis due to hyperinfection with Aelurostrongylus abstrusus in a kitten. J Comp Pathol. 2014; 150(4):357-360.
  6. 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.


Thornton 2017

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