American trypanosomiasis in British Honduras. VI. A natural infection with Trypanosoma (Schizotrypanum) cruzi in the opossum Didelphis marsupialis (Marsupialia, Didelphoidea), and experimental investigations of different wild-animal species as possible reservoirs for the parasite

ABSTRACT

The occurrence is described of a natural infection with Trypanosoma (Schizotrypanum) cruzi in the common opossum, Didelphis marsupialis, captured in El Cayo District, British Honduras. The identity of the parasite was established from histological sections if the heart muscle, which showed pseudocysts filled with leishmania forms. Seven species of wild animal were experimentally infected with T. cruzi. Rats of the species Heteromys desmarestianus, Ototylomys philotis, Tylomys nudicaudus and Oryzomys sp. were all highly susceptible to the parasite and developed a fatal illness. It ie concluded that these species are unlikely to act as natural reservoirs for T. cruzi, but that they may prove useful in further experimental studies on the parasite and for the passage of strains. A rat of the species Nyctomys sumichrasti showed a high resistance to the infection; only scanty intracellular forms of T. cruzi were found in heart-muscle smears, and chagastic pseudocysts were present in small numbers in histological sections of the heart muscle. Results similar to those obtained with the Nyctomys rat were observed in a coati (Nasua narica), which also showed a high resistance to the challenge . No intracellular forms of T. cruzi were found in the heart muscle, but they were present in small numbers in the liver and spleen; they were morphologically identical to those seen in the heart muscle smears from the Nyctomys rat. No infection developed in two young grey foxes (Urocyon cinereo-argenteus) when challenged with a highly virulent strain of T. cruzi. It is concluded that these animals are unlikely to act as natural reservoirs for the parasite in British Honduras. It is believed that, although experimental inoculation of wild animals with T. cruzi may be prejudiced by their possible previous contact with the parasite, the results may give some indication of the nature of possible reservoir-hosts. (AU)