24. Helminth Infections: Soil–Transmitted Helminth Infections and Schistosomiasis


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Richard Lord, www.rlordphoto.com

People living in poverty in developing countries often suffer from helminth infections, which more often physically impair their hosts than kill them. While soil–transmitted helminths (STHs) and schistosomiasis together account for 150,000 deaths annually, the global prevalence of infection is close to 3 billion. STHs?commonly roundworms, whipworms, and hookworms?exacerbate iron deficiency anemia, particularly among children, women of reproductive age, and pregnant women. Schistosomiasis?also caused by parasites?can lead to complications such as bladder ulcers and renal failure. Risk factors include involvement in agricultural pursuits, poor sanitation and lack of clean water, and proximity to warm, wet environments.

Beyond their health effects, helminth infections can thwart educational advancement and hinder economic development. The severe anemia triggered by helminth infections can cause faltering growth, decreased physical fitness, and behavior–related problems in children; neonatal prematurity, reduced birth weight, and poor lactation in mothers; and chronic urinary and kidney problems among adults. Disability, pain, and undernutrition reduce the contributions individuals can make to their communities.

Of the three major interventions aimed at helminth infections?antihelminthic drug treatment, improved sanitation, and health education?the first, deworming, stands out as the most cost–effective. Regular deworming helps reduce malnutrition and improves motor and language development in very young children; has a positive effect on nutritional status, physical fitness, growth, and language development in school–age children; and improves maternal hemoglobin as well as birth weight and child survival. The advantage of periodic deworming lies in its simplicity: only one tablet per individual, which can be administered by persons without medical training, is required. Until new approaches become available, whether a hookworm vaccine or improved sanitation infrastructures, antihelminthic therapy for school–age children remains the most practical way to control helminth infections in the developing world.