What is it about?

Leishmania braziliensis causes a neglected tropical disease that may result in face disfiguring lesions and other severe outcomes to human beings in Latin America. This parasite is also often capable of resisting the major treatment options. For these reasons, there has been intense research for finding biomarkers in this parasite’s genetic content that could help predict if an infected person would be of greater chance of severe disease or treatment failure, during diagnosis. However, the identification of consistent diagnostic genetic markers requires a deeper understanding of how genes propagate through generations of individuals within this parasite’s natural populations. Would the parasite’s off-springs inherit the entire genomes of single parents with little changes as the result of clonal reproduction, or would the off-springs’ genomes consist in mixes of parental genomes produced as the result of sexual reproduction, as happens among human beings, for example? In this study, we revisited this previously addressed but still open and very relevant question. We carried out this task by exploring two small segments of DNA (called loci) present on two different chromosomes of L. braziliensis. The parasites that were employed in the study were drawn from cases of human leishmaniasis occurred in Northeast Brazil. We used these parasites and the two loci mentioned above to test several genetic parameters that helped us better profile how often genes are exchanged within that population of L. braziliensis.

Featured Image

Why is it important?

To revisit this previously addressed but still open and very relevant question, we explored the above-mentioned small segments of DNA (called loci), one on chromosome 24, the other on chromosome 28 of L. braziliensis. We also employed two samples of parasites isolated from lesions of human patients diagnosed with leishmaniasis during two four-year periods of time that occurred approximately 10 years apart. We sequenced the DNA of those two loci in each parasite of the two samples. Then, we evaluated the status of several population genetics parameters among them. Based on our findings to that region in Brazil, we concluded that L. braziliensis can maintain populations that are genetically stable for several years in foci of human leishmaniasis. But, most importantly, we also concluded that the individuals that make these populations are capable of robust exchange of their genetic contents, possibly as the result of events of sexual reproduction. Our findings helped validate observations of two previous experimental studies and one populational study on this subject, and further extended our understanding about the structure of populations of L. braziliensis that are involved in human disease.


Our findings indicate that diagnostic biomarkers of leishmaniasis features, like treatment response or disease severity, need to be genetically encoded within L. braziliensis genomes near the genes that cause such infection phenotypes. Otherwise, these markers may not be capable of consistently maintaining their predictive ability, and thus their usefulness, for a long period of time in the natural foci of human disease.

Albert Schriefer

Read the Original

This page is a summary of: Leishmania braziliensis causing human disease in Northeast Brazil presents loci with genotypes in long-term equilibrium, PLoS Neglected Tropical Diseases, June 2022, PLOS, DOI: 10.1371/journal.pntd.0010390.
You can read the full text:



The following have contributed to this page