Intestinal helminths

Intestinal helminths are common in the developing world; current estimates suggest that one-third of the world's population is infected. Although most infections are light and asymptomatic, they are a significant cause of morbidity in heavily infected individuals. Hookworms cause iron-deficiency anaemia, malnutrition results from heavy Ascaris infections, and dysentery and rectal prolapse are seen in children heavily infected with Trichuris. Disseminated strongyloidiasis may be a fatal outcome of immunosupression in infected patients. Even moderate infections may have profound effects on pregnancy outcome, growth and cognitive function, and worldwide and national policies are focusing on the relative public health priority of helminth eradication. The availability of safe and effective antihelminthic drugs, particularly single-dose albendazole, make mass treatment of communities in endemic regions the primary control strategy for reducing the burden of disease caused by these organisms. Other manifestations of helminthic infection include epilepsy as a result of neurocysticercosis, respiratory symptoms from the migratory phase of recent hookworm or Ascaris infection, and dermatological consequences such as larva currens from Strongyloides stercoralis and cutaneous larva migrans. Pruritus ani caused by Enterobius infection is common in temperature countries. The immune response induced by helminthic infection may subvert responses to other pathogens such as HIV, tuberculosis and malaria. Related mechanisms by which helminths might suppress the immune response have been suggested as contributing factors in the increasing prevalence of atopy and asthma in more industrialized regions of the world where the prevalence of helminths has been declining.