Abstract
Trypanosoma rangeli is a non-pathogenic protozoan parasite that infects mammals, including humans, in Chagas disease-endemic areas of South and Central America. The parasite is transmitted to a mammalian host when an infected triatomine injects metacyclic trypomastigotes into the host′s skin during a bloodmeal. Infected mammals behave as parasite reservoirs for several months and despite intensive research, some major aspects of T. rangeli-vertebrate interactions are still poorly understood. In particular, many questions still remain unanswered, e.g. parasite survival and development inside vertebrates, as no parasite multiplication sites have yet been identified. The present study used an insect bite transmission strategy to investigate whether the vector inoculation spot in the skin behave as a parasite-replication site. Histological data from the skin identified extracellular parasites in the dermis and hypodermis of infected mice in the first 24 hours post-infection, as well as the presence of inflammatory infiltrates in a period of up to 7 days. However, qPCR analyses demonstrated that T. rangeli is eliminated from the skin after 7 days of infection despite being still consistently found on circulating blood and secondary lymphoid tissues for up to 30 days post-infection. Interestingly, significant numbers of parasites were found in the spleen and mesenteric lymph nodes of infected mice during different periods of infection and steady basal numbers of flagellates are maintained in the host′s bloodstream, which might behave as a transmission source to insect vectors. The presence of parasites in the spleen was confirmed by fluorescent photomicrography of free and cell-associated T. rangeli forms. Altogether our results suggest that this organ could possibly behave as a T. rangeli maintenance hotspot in vertebrates.
Highlights
Trypanosoma rangeli and Trypanosoma cruzi are the two species of trypanosomes that infect humans in the Americas [1]
Trypanosoma rangeli development inside vertebrates is a highly controversial field of study, since there is no evidence of parasite multiplication in host tissues
Evaluation of infected mice for a period of 30 days demonstrated that a stable basal amount of parasites was detected in circulating blood, an increased amount of T. rangeli DNA was found in mesenteric lymph nodes and spleen
Summary
Trypanosoma rangeli and Trypanosoma cruzi are the two species of trypanosomes that infect humans in the Americas [1]. T. rangeli transmission has been reported for triatomines feeding on long-term chronically infected mice showing up to 12 months of infection [13,14,15], suggesting that the parasite must undergo replication to establish a systemic infection in mammalian hosts. Sub-cutaneous or intradermal inoculation of parasite-cultured forms have been used as infection strategy in most studies aimed to find T. rangeli in vertebrates hosts [9,14,16,17]. Such approaches do not essentially reflect vector-born natural ways of transmission and possibly create an infection-establishment bias
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