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Unique Parasite Strain Causes Atypical Leishmaniasis Cases in Brazil

The results of the study showed that ACL involves genetically distinct L. braziliensis strains that seem to cause increased inflammatory responses in infected patients. Patients with ACL had significantly more lesions, especially above the waist, than those with CL had. The clinical course of ACL also lasted longer than CL did, and was more likely to be resistant to antimony-based treatment, which is the front-line treatment used in Brazil for leishmaniasis. The researchers found that, although almost 100% of initially refractory CL patients respond favourably to two courses of antimony therapy, more than 60% of those with ACL failed two courses of treatment.
They showed that cases of ACL in the northeast of Brazil are caused by a genetically distinct strain of L. braziliensis—the parasites that infected 62.5% of patients with ACL—had genetic variations seen only in these organisms that caused ACL, and not in those that caused CL. Levels of inflammatory cytokines in peripheral blood mononuclear cells also differed between patients with ACL and those with CL—patients with ACL had lower IFN-γ and higher IL-10 levels.
The authors suggested that this difference may favor parasite growth, and may also help to explain the exacerbated pathogenesis of ACL as well as its high rate of therapeutic failure.
"Precise identification of ACL is important because it usually does not readily respond to drugs commonly used to treat leishmaniasis in Brazil, but readily responds to other treatment options available," the authors concluded.
“These findings may contribute to our understanding of the pathogenesis of ACL, and ultimately to a more logical approach to management of this and other unusual forms of ATL.”

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.
Feature Picture Source: Dr. Martin D. Hicklin / Centers for Disease Control and Prevention
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