Other parasites

Last author update: 1 September 2011
Last staff update: 26 March 2021

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PubMed search: cryptosporidium pulmonary, Dirofilaria immitis [title] pulmonary, echinococcal [title] cyst pulmonary, tropical pulmonary eosinophilia [title], Paragonimus kellicotti, Toxoplasma gondii [title] pulmonary

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Other parasites. website. Accessed May 19th, 2024.

Definition / general
  • Waterborne protozoal infection that mostly infects intestinal epithelium causing diarrhea or malabsorption
  • Often causes self limited illness in immunocompetent patients
  • In HIV / AIDS, may spread to hepatobiliary tree or airways


Microscopic (histologic) description
  • Characteristic spores on luminal epithelial cells
  • Mucosa with mild lymphocytic infiltrate

Cytology images

Images hosted on other servers:
Cryptosporidium in sputum

Cryptosporidium in sputum


Clinical features
  • Dog heartworm; may infect humans as secondary end stage host, particularly in southern coastal states in US
  • Adult worms die in right ventricle, embolize in pulmonary arterial circulation
  • Embolization of dead worms may be clinically silent or cause chest pain, fever, chills, hemoptysis or blood eosinophilia
  • Evokes necrotizing granulomatous response with vasculitis in lung tissue
  • Rarely see dead worms
  • Usually self limited in humans but may cause lung infarct
  • Usually diagnosed after resection of a nodule to exclude malignancy
  • Chest Xray: solitary peripheral pulmonary nodule or coin lesion (Int J Immunopathol Pharmacol 2010;23:345)

Case reports

Microscopic (histologic) description
  • Rounded infarct with coagulative necrosis, well demarcated from surrounding normal lung by epithelioid histiocytes and fibrous connective tissue
  • Focal calcifications and lymphoid aggregates
  • Necrotic nematode has homogenous cuticle without external ridges
  • Longitudinal muscle layer just internal to cuticle and internal cuticular ridges

Microscopic (histologic) images

Contributed by Dr. Vladimir Zaitsev
Pulmonary embolization Pulmonary embolization Pulmonary embolization Pulmonary embolization

Pulmonary embolization

Pulmonary embolization Pulmonary embolization Pulmonary embolization

Pulmonary embolization


Clinical features
  • Also called hydatid cyst
  • Humans become infected by eating food contaminated with tapeworm eggs, becoming intermediate hosts
  • Eggs from dog tapeworm Echinococcus granulosus or E. multilocularis where foxes are the most common definitive hosts; other species rarely cause hydatid diseae in humans
  • For E. granulosus, sheep are most important intermediate hosts; for E. multilocularis, rodents are most important intermediate hosts
  • E. granulosus is more common in humans and is most common cestode infection of the lung
  • Eggs hatch in duodenum and spread to liver, lung, bone or elsewhere
  • E. granulosus cysts are most common in liver, 5 - 15% occur in lung; pulmonary disease is often secondary to hepatic disease (World J Surg 2001;25:46)
  • Larvae lodge in capillaries and incite a mononuclear and eosinophilic inflammatory cell response
  • Many larvae die, some encyst
  • Pulmonary cysts may be asymptomatic or cause respiratory compromise by compressing airways or lung parenchyma; rarely complicated by Aspergilloma (Br J Radiol 2008;81:e279)
  • Cyst rupture may cause fatal anaphylactic shock or pneumonia with consequent development of numerous new cysts throughout lung

Case reports

Microscopic (histologic) description
  • Cysts gradually enlarge and years later may be several centimeters in diameter
  • Cyst is bilayered and surrounded by fibroblasts, mononuclear cells, eosinophils, multinucleated giant cells
  • Daughter cysts usually develop in large mother cyst
  • Daughter cysts develop as projections from a germinative layer and form brood capsules
  • Degenerating scolices of developing worms produce sediment so called "hydatid sand"

Microscopic (histologic) images

Contributed by Hanni Gulwani, M.B.B.S.

Various images

Cytology images

Images hosted on other servers:
2 cm lung nodule 2 cm lung nodule 2 cm lung nodule 2 cm lung nodule

2 cm lung nodule

BAL fluid - scolices

BAL fluid - scolices


Definition / general
  • Due to microfilaria of Wuchereria bancrofti or Brugia malayi, which circulate in pulmonary capillaries and cause an immediate type of eosinophilic hypersensitivity reaction
  • Patients have high levels of IgE and high titers of filarial antibodies
  • Adult worms not seen in lungs
  • Restricted to tropical regions
  • Tropical eosinophilia may occur from filaria in lymph nodes or spleen (Meyers-Kouwenaar syndrome)
  • Symptoms and signs: cough, typically nocturnal, dypsnea, chest tightness, wheezing, fevers, weight loss and eosinophilia

Microscopic (histologic) description
  • Rare microfilaria within pulmonary capillaries with marked eosinophilic infiltrate
  • Eosinophilic abscesses develop into granulomata

Clinical features
  • Freshwater trematode (lung fluke) found in North America that infects crayfish and crabs as intermediate hosts (MMWR Morb Mortal Wkly Rep 2010;59:1573)
  • Humans acquire infection by ingesting raw or undercooked infected shellfish; rarely contaminated seaweed or watercress
  • Larvae mature in gut and migrate through diaphragm to infect lungs
  • Most cases in Asia due to P. westermani; schistosomiasis may also involve the lung
  • May mimic lung tumor (Korean J Parasitol 2011;49:69)
  • May require serology to confirm diagnosis

Case reports

Microscopic (histologic) description
  • Necrotizing or non-necrotizing granulomas with giant cells containing eggs with operculum; also organizing pneumonia (Am J Surg Pathol 2011;35:707)
  • Variable vasculitis and pleuritis; also lymphocytes, plasma cells, eosinophils
  • Egg is birefringent

Cytology images

Images hosted on other servers:

Paragonimus egg

Various images

ova found in
lavage fluid


Definition / general
  • Associated with AIDS, immunosuppression including therapy and hematologic malignancy
  • May be transmitted in utero
  • Ubiquitous intracellular coccidian parasite that causes focal parenchymal necrosis, diffuse interstitial pneumonia
  • Cats are definitive hosts, humans are intermediate
  • Very high prevalence in France; in US, from 3% to 20% depending on geography, ethnic group
  • Humans acquire transmission from ingestion of material contaminated with cat feces or cysts contained in undercooked meat (pork, beef, mutton); infection may be acquired in utero
  • Most disease in CNS, eye and heart; pulmonary involvement is in 70% of disseminated cases
  • Pulmonary involvement is indicative of disseminated disease and risk of death from CNS disease or bronchopneumonia
  • May cause severe morbidity or death in affected neonates

Gross description
  • Lungs heavily congested, combined weight approximately 2000 grams

Microscopic (histologic) description
  • Organisms present in histiocytes, alveolar lining cells, endothelial cells and pseudocytes abundant in necrotic areas

Positive stains
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