17th February 2025

Parasitic respiratory infections

Overview of parasitic respiratory infections

Parasitic lung infections are rare in the UK and will mostly be encountered in the returning traveller and the immunosuppressed. Whilst there is a risk of direct infection and subsequent manifestation of disease, hypersensitivity reactions are generally the main presentation. 

The distribution of parasitic infections is likely to change with a changing global climate. 

Schistosomiasis

Schistosomiasis is a helminthic infection caused by one of five types of schistosome. The schistosomes are found in infested water and often use snails as a vector. Areas of particular incidence are East Asia, central Africa and, less commonly, the Mediterranean and Caribbean.

Pulmonary schistosomiasis is likely to present as wheeze, restrictive pulmonary compromise and chest X-ray infiltrates in the acute setting. It may be treated with praziquantel and is usually self-limiting.

Chronic infection may cause granulomatous reactions leading to pulmonary hypertension and pulmonary fibrosis.

Pulmonary hydatid disease

Pulmonary hydatid disease is caused by ingestion of parasitic eggs, with dogs, goats and sheep the most common vector for the adult worm. Hydatidosis is the most common parasitic lung disease globally.

Clinically, cough, haemoptysis and chest pain are the most common complaints. Cyst rupture may be reflected by an acute clinical deterioration and may cause anaphylaxis. 

Chest X-ray and CT may show calcified cysts, predominantly in the lower lobes.

The definitive treatment is surgery with excision of the cysts. Medical treatment with albendazole may be used for patients unfit for surgery but this may also precipitate cyst rupture.

Loffler’s syndrome

Loffler’s syndrome is a type of eosinophilic pneumonia whereby eosinophils migrate into the pulmonary tissue following transmission of parasitic larvae into the lung. The most common cause is the parasitic infection of Ascaris lumbricoides.

Its most distinguishing features are eosinophilia and parasites grown on sputum and stool culture, but this can be delayed.

Treatment is with antihelminthic agents such as albendazole. Steroids may help with the pulmonary hypersensitivity reactions.

Paragonimiasis

Paragonimiasis is caused by a trematode (fluke) found in East Asia, India, Central and South America and West Africa. The main risk factor is ingestion of undercooked seafood. Loffler’s syndrome is a possible complication, as are pleural effusions, haemoptysis and pneumothoraces.

Diagnosis is mainly via serology. Treatment is with praziquantel.

References

• Sarkar M, Pathania R, Jhobta A, Thakur B, Chopra R. Cystic pulmonary hydatidosis. Lung India. 2016;33(2):179
• T N, Marti H, Duhnsen S, G B. Pulmonary Schistosomiasis – Imaging Features. Journal of Radiology Case Reports [Internet]. 2010 Sep 1; 4(9):37–43 [accessed 23/08/22]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3303399/
• Chapman S. Oxford handbook of respiratory medicine. Oxford, United Kingdom: Oxford University Press; 2014