Detection of leishmanial activity in nature by means of sentinel animals

In order to assess the usefulness of the sentinel-animal study method for field investigations on cutaneous leishmaniasis in tropical forested areas, several series of laboratory animals were exposed to the bite of sandflies in the forest of 2 distinct geographical regions of Panama. The golden hamster, Mesocricetus auratus, the cotton rat, Sigmodon hispidus, and the domestic dog, Canis familiaris were used in these investigations. A high proportion of sentinel rodents died during the exposure period, especially in the first trials. From animals that completed their exposure period, 1 of 5 dogs, and 1 of 52 hamsters proved to be infected. All 29 cotton rats simultaneously exposed were negative. The use of sentinel animals seems a promising method to investigate leishmanial activity in nature. Nevertheless, to obtain final results requires the expenditure of considerable time for the exposure period and the post-exposure observations of the sentinels in the laboratory. A knowledge of the local sandfly species composition and their feeding habits is a prerequisite in every area under study. Further comparisons with newer techniques are needed to determine the best single or combination of methods for the detection of natural leishmaniasis. Cotton rats challenge inoculated with Leishmania braziliensis were readily infected, showing the importance of this rodent for studies on experimental cutaneous leishmaniasis.