This book is meant for all who have an interest in knowing the epidemiology so as to institute preventive measures in maintaining the good health and efficient production. In this context, this book was designed to support epidemiology, which ought to be more directly relevant to the prevention, control or investigation of some common intestinal/haemo protozoan, and rickettsial diseases affecting the economy of livestock especially in the tropics. It also briefs pathogenesis, clinical signs in animals and man, prophylaxis in with reference to vaccination and current vaccines practiced. There are many books and publications available detailing the protozoan diseases however, this book will, I believe, be useful as a guide for the students for better understanding of the life cycle being depicted in attracting flow diagrams and epidemiology under separate heading, of the commonly encountered protozoan diseases.