Worm infections in free-range layers are increasingly causing health problem in the poultry industry. Despite this, there are knowledge gaps about how worms are detected in living laying hens and on methods for how they can be controlled in modern free-range housing systems. The objectives of the project are to; i) develop a new molecular tool with which one can distinguish eggs from Ascaridia and Heterakis, and ii) evaluate a method of targeted treatment during production conditions which so far has only been tested on a smaller scale. All in all, the idea is to investigate whether it is possible to suppress the spread of infection and thereby prevent severe re-infection by beginning the deworming at an early stage of the infection cycle. We also intend to evaluate the results of a monitoring program initiated by the Swedish Egg Association in 2009. The results of the proposed research program will thus form the basis and be able to be implemented in the extension service to farmers.