Title. This wormy world: consequences, co-infections and the challenge of field-based study designs

Summary. Helminth parasites remain highly prevalent worldwide. In particular, the soil-transmitted helminths (STHs) (including the large roundworm Ascaris lumbricoides, the whipworm Trichuris trichiura and two species of hookworm) are now listed among 17 neglected tropical diseases that are described as poverty-promoting conditions. STHs contribute to insidious morbidity, including growth retardation and effects on cognitive development, particularly in growing children and women of reproductive age. Large-scale deworming programmes are being rolled out worldwide, however, there is an urgent need to understand how such control may alter pattern and process in STH infection. Furthermore, the growing perception that infection with STHs have an effect on the host immune response, with consequences for concurrent important infectious diseases, such as malaria, renewed interest in the consequences of early infection with worms in the context of the hygiene hypothesis and the modulatory consequences for development of allergies, all greatly enhance the public heath significance of such parasites. We still urgently require high quality empirical parasitological data from humans under field conditions in order to understand the impact of such infections, the implications of co-infection and the consequences of large scale control programmes.