 During the Second World War Mer served in the British Forces with the rank of colonel and was malaria adviser to Middle East Command.After the war he joined the staff of the new school of medicine and became chief malaria adviser to the Ministry of Health in Israel, of which he was acting director in 1956 and 1957.As malaria was brought under control Professor Mer investigated the control of other insects, particularly the horse-fly, and the Rosh Pinna research station undertook the testing of insecticides and the training of scientists.