For many years following its discovery in Brazil by Carlos Chagas (1909), American human trypanosomiasis or Chagas' disease was considered, like African trypanosomiasis or sleeping sickness, to be a disease of the tropics. Trypanosoma cruzi, the haematozoön causing Chagas' disease, is now known to range in the Western Hemisphere from 41° Latitude South (Mazza, 1936, in Triatoma infestans from Patagones, province of Buenos Aires, Argentina) to 38° Latitude North (Dias, 1938, in bats, Antrozous pallidus pacificus, from Pinole, California, U. S. A.). The wide distribution of reservoir animals and insect vectors is largely responsible for the spread of this human disease. Brumpt (1939) records over 550 human cases from South and Central America and Mexico. Yorke (1937) gives an excellent review of the disease in man.
The trypanosome of bats which is morphologically identical with T. cruzi has a high degree of host specificity for bats.