This book proves the importance of field expertise complemented by molecular analysis. The author has laid the basis for a vaccine in Zambia based on the infection and treatment method using local strains. This approach was funded by the Belgian Development Cooperation and has been very successful and is still applied today. Now he is working as a senior scientist at the Institute of Tropical Medicine in Antwerp, Belgium. The book discusses various basic aspects of parasite diversity and compares diversity in T. parva with Plasmodium, a related protozoan parasite. Zambia is an interesting case study as it is at the edge of the vector¹s ecological distribution range and has a recent history of T. parva introduction. Moreover there has been a restricted vaccine trial in Southern Province with the Muguga cocktail, consisting of strains from Kenya. The molecular analysis describes the influence of the vaccine trial on the field populations as T. parva field isolates from before and after the vaccine trial are compared. The same analysis is repeated in Eastern Province where a vaccine based on local strains has been used and isolates from before the vaccination are compared.