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Unique Parasite Strain Causes Atypical Leishmaniasis Cases in Brazil

A recent study of patients with atypical cutaneous leishmaniasis (ACL) in northeast Brazil has shown that these cases are caused by distinct strains of Leishmania braziliensis. Luiz Henrique Guimarães, from the Federal University of Bahia, Salvador, Brazil, and colleagues, published the results of their study online in PLOS Neglected Tropical Diseases.
Leishmaniasis is a parasitic disease found in parts of the tropics and subtropics, as well as in southern Europe. It is caused by the protozoan organism Leishmania braziliensis, which is transmitted by the bites of phlebotomine sand flies.

“ACL found in Northeast Brazil is caused by distinct genotypes of [Leishmania (Viannia]) braziliensis and presents a cytokine profile that departs from that in classical CL [localized cutaneous leishmaniasis] patients,” the authors wrote. “We think that differences in antigenic contents among parasites may be in part responsible for the variation in cytokine responses and possibly immunopathology between CL and ACL.”
In the New World, Leishmania (Viannia) braziliensis is the main species of the organism that causes American tegumentary leishmaniasis (ATL), of which four main forms occur in Brazil: CL, mucosal leishmaniasis (ML), disseminated leishmaniasis (DL), and diffuse cutaneous leishmaniasis (DCL).
However, according to the authors, cases of atypical cutaneous leishmaniasis (ACL) have been increasingly reported in northeast Brazil that typically do not fit into any of the four categories of ATL. Previously, scientists have suspected that these atypical cases occurred in patients with underlying predisposing conditions, such as immunosuppression, chronic disease, or pregnancy. However, most patients with ACL do not have such underlying conditions.
With this in mind, the researchers conducted a study to better understand the differences between ACL and ATL. They collected clinical data, as well as samples of blood and skin, in order to examine the genetics of the parasite infecting each patient and the patients’ immune responses to the disease.

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