Ascariasis and hookworm.

Ascariasis and hookworm (ancylostomiasis) remain the most common intestinal nematodes in the world with significant economic, social, and medical impact. An understanding of the transmission and pathogenesis of ascariasis and hookworm are necessary to recognize their clinical manifestations and to manage the pulmonary sequelae of infection. Transmission occurs predominantly in the tropics and rural areas where there is suboptimal sanitation, personal hygiene, and education regarding these parasites. Ascariasis generally occurs through hand-to-mouth ingestion of agricultural products or food contaminated with parasite eggs. Hookworm is transmitted through larval penetration of the skin. Larval pulmonary migration generally is asymptomatic. However, symptomatic pulmonary disease may occur with fever, cough, chest pain, hemoptysis, dyspnea, and wheezing due to (1) Loffler's syndrome, (2) the effects of larval tissue migration, (3) airway reactivity or bronchospasm, (4) infectious bacterial complications from parasitic migration and associated aspiration, and rarely (5) chronic eosinophilic pneumonia, transdiaphragmatic penetration, or symptoms of upper airway obstruction. Clinical evaluation shows pulmonary opacities on chest radiograph, peripheral blood eosinophilia, and larvae in respiratory or gastric secretions. Symptomatic treatment may be necessary with bronchodilators and systemic steroids or antibiotics for bacterial complications. The drug of choice is mebendazole (Vermox) 100 mg twice a day for 3 days. Alternatives include a single dose of pyrantel pamoate (Antiminth) 11 mg/kg (maximum dose, 1 g) or albendazole (Zentel) 400 mg orally once. Invermectin (Mectizan) is available through the World Health Organization, and, in the United States, through the manufacturer on a compassionate-use basis. Ivermectin is as effective as currently available drugs against Ascaris but shows only partial efficacy against hookworms, which infest humans. Preventive measures, improvement of sanitary facilities, education, and school screening may be important in the endemic areas to control these parasitic infections.