Infestation with the Strongyloides stercorals worm, 2 mm long, which occurs frequently in the tropics. About 35 million people are affected. Only the females live in the small intestine, where they lay their eggs. The larvae hatch in the body and are excreted with the faeces, then develop into infectious larvae in the ground. These larvae can penetrate into man via the skin, after which they pass through the blood and lungs to the intestine, where they develop into adult worms in 17 days. In cases of massive infestation the intestinal wall can be seriously damaged: stomach pain, nausea and constipation, alternating with diarrhoea and slimy faeces, are the consequence. The skin is sometimes itchy and covered with red patches. Coughing and mild fever are also possible, but usually the infestation passes unnoticed. Worm cure treatment is effective. The best way of avoiding infestation is by avoiding contact with contaminated ground.