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Strongyloidiasis, hookworm, and other gut strongyloid nematodes 

Strongyloidiasis, hookworm, and other gut strongyloid nematodes

Chapter:
Strongyloidiasis, hookworm, and other gut strongyloid nematodes
Author(s):

Michael Brown

DOI:
10.1093/med/9780199204854.003.070904_update_001

August 28, 2014: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Strongyloides diagnosis—development of real-time PCR assays; treatment—two doses of ivermectin may be better than one.

Hookworm control programmes—systematic review published.

Hookworm treatment—single-dose mebendazole less effective than albendazole.

Soil-transmitted helminth treatment in schoolchildren—failure to achieve WHO’s 2010 target.

Hookworm vaccine—results of phase I studies.

Hookworm immune modulation—maternal helminth infections may reduce neonatal atopic disease.

Oesophagostomiasis—impact of mass treatment campaigns.

Updated on 31 May 2012. The previous version of this content can be found here.
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date: 24 April 2017

Strongyloides stercoralis and hookworms are common soil-transmitted nematodes in tropical and subtropical regions. After the organisms penetrate exposed skin, most infections are asymptomatic, but heavy infections can result in significant morbidity.

Strongyloidiasis

The roundworm S. stercoralis infects an estimated 30 million to 100 million people. Clinical manifestations include: (1) skin—often the only clinical manifestation, commonly in the form of larva currens, a serpiginous, pruritic, erythematous eruption at the site of migrating larvae; (2) lungs—cough and tracheal irritation; less commonly wheeze; patchy infiltrates on chest radiography with eosinophilia; (3) intestinal—epigastric pain and diarrhoea; (4) Strongyloides hyperinfection—occurs in patients who are immunosuppressed; severe diarrhoea is a common feature; mortality is high. Infection is persistent and may present decades after exposure. Diagnosis is usually by microscopy or culture of stool; serology is useful as a screening test. Treatment is typically with ivermectin or albendazole. Improved sanitation and appropriate footwear may reduce the acquisition of infection.

Hookworms

Hookworm infections, mainly caused by Ancylostoma duodenale and Necator americanus, affect more than 500 million people, predominantly in sub-Saharan Africa and Asia. Clinical manifestations include: (1) migratory/larval—ground itch (a pruritic, papular, and erythematous rash on the feet or hands); occasionally pneumonitis with eosinophilia; (2) intestinal—occasionally profuse watery diarrhoea, but most people are asymptomatic excepting for iron-deficiency anaemia (sometimes with haemoglobin <2 g/dl) in those with heavy infections, which are a particular problem in infants and pregnant women, in whom it affects pregnancy adversely. Diagnosis of acute infection is clinical and of chronic infection by discovering eggs in the stool by microscopy. A single dose of albendazole will reduce the worm load to levels below those likely to cause disease; complete eradication can be achieved with repeated doses.

Population-based control programmes, using single-dose antihelmintic therapies, aim to reduce anaemia and improve childhood growth and cognitive development in countries with high prevalence of soil-transmitted helminths. Integration with other helminth control programmes is most effective. Increasing attention is being paid to the effect of coinfection with hookworm on other diseases such as malaria, tuberculosis, HIV, and asthma.

Nonhuman hookworms

These cannot complete their life cycle in humans but are capable of causing significant morbidity, including: (1) cutaneous larva migrans—usually due to dog hookworms; presents as intensely pruritic lesions on exposed areas of the skin; diagnosis is clinical, although the worm may be visualized in skin biopsies; albendazole is effective; (2) Ancylostoma caninum-associated enteritis; (3) oesophagostomiasis; (4) trichostrongyliasis.

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