Abstract Chagas disease is caused by the parasite Trypanosoma cruzi and it is transmitted to humans by the triatomine bug Rhodnius prolixus . The main insect vector in the Andean countries presents sylvatic and domestic cycles involving humans, insects and reservoirs (e.g small mammals). It is commonly assumed that vectorial transmission is the main route for parasite spread between hosts. Recent studies have reported high percentages (21-80%) of infected opossums ( Didelphis marsupialis ) in the sylvatic cycle, raising the question of whether such a high proportion of infected could be only maintained by vectorial transmission, a seemingly inefficient pathway. To address this question, we formulated a mathematical model that describes the sylvatic transmission dynamics considering vectors and hosts and parametrized with field data. Our results show that vectorial transmission it is not sufficient to explain such high percentages of infected host-mammals reported in the literature. Here we propose oral transmission as an alternate route of transmission that may increase the number of infected individuals found in field studies.