Scientists in Switzerland as well as at Washington University in St. Louis have identified a virus infecting the Leishmania parasite which appears to increase the pathogenicity of the parasite. This is hypothesized to explain the severe mucocutaneous Leishmaniasis in which the parasite causes the erosion of the soft tissues around the nose and mouth. Using tests of mice and hamsters, they determined that only some strains of Leishmania caused the mucocutaneous form of the disease. The researchers determined that this difference in pathogenicity was related to the TLR3 sensor proteins in macrophages which are infected by the parasite, though the mechanism was not known. An interuption of the RNAi interference pathway in the parasite by the virus was thought to be a major player. This research suggests that it may be possible to use antivirals to decrease the pathogenicity of leishmaniasis in cases of the disease.