Experimental Studies on Chagas' Disease in Panama

Abstract
Summary 1. Five cases of Chagas' disease have been found in children in Panama during the past ten months. 2. Rabbits, guinea pigs and white rats were inoculated and became positive with heavy infections from one of these human cases. This strain was sucessfully transferred to a monkey, guinea pigs, white rats, white mice and bats. 3. A young dog naturally infected with trypanosomes that appear to be identical with those found in the human cases was discovered at the home of the first human case. 4. Guinea pigs, white rats and white mice were infected through inoculation of blood from a naturally infected dog. This strain was carried on to other guinea pigs and a bat. 5. Twenty-eight armadillos, Dasypus novemcinctus fenestratus Peters were examined and six, or 21.4 per cent, were found to be infected with a trypanosome that we believe to be T. cruzi. 6. Eighty-one opossums, Didelphis marsupialis etensis Allen, were examined and twenty or 24.6 per cent were found infected with what was apparently T. cruzi. 7. A squirrel, kept as a pet in the house where two cases of Chagas' disease lived proved to be infected with a trypanosome identical with T. cruzi. This was the second occasion in which a pet, in the same household with one of the five human cases, was found positive for trypanosomes. 8. Bats infected with a trypanosome believed to be T. cruzi were found in Panama. A total of 161 of these flying mammals was examined and 30, or 18.6 per cent proved to be infected. Those found positive represented 5 species. 9. The trypanosome of the bats was readily transmitted to dogs, guinea pigs, white rats and white mice. 10. Ninety specimens of Triatoma geniculata were collected in the Chilibrillo Caves. This completes a record of infected Triatoma, infected bats and an infected opossum found in the same chamber of these caves. 11. The feces of 55.5 per cent of the bugs proved to contain trypanosomes. 12. Twenty-six guinea pigs were each inoculated with a macerated Triatoma and 21, or 80.8 per cent, became positive. 13. Seven guinea pigs became infected through Triatoma geniculata feeding upon them. It was not determined whether these infections were caused through the bites of the bugs or through infection with their feces. 14. The incubation period of the experimentally infected animals varied from three to twenty-eight days. 15. The degree of the infection in the experimentally infected animals varied considerably. One guinea pig had a peak peripheral infection of more than 1600 trypanosomes in a thick blood film. 16. The persistence of infectivity has extended in 1 guinea pig for more than two hundred and seventy-eight days. 17. Although all our laboratory animals could be infected with this trypanosome the guinea pig seemed to be the most satisfactory for experimental purposes. The adult animals proved so susceptible to infection that no very young ones were used. 18. The trypanosomes soon disappear from the peripheral blood of the human cases. Infected animals have lived for a considerable number of days since the beginning of their infection and in some of them trypanosomes have been found for many days. 19. Leishmania forms of the trypanosome have been found in the hearts of some animals but others fail to show them. 20. Our experience indicates that this trypanosome does not possess a high degree of virulence. However, we cannot read what the future holds in store in the way of remote serious sequelae. 1

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