The book meant for the undergraduate level Zoology students of all leading universities across the country focuses on disease-causing organisms that affect human physiology. The latest facts and figures pertaining to the recent advancements are furnished in the book. Every effort has been made by the author to cover all the aspects of the age-old conflict between the parasites and the hosts. The procedures of laboratory detection, normal values of the clinical parameters and the treatment of the tropical diseases are also discussed with minute details.