Cryotherapy of cutaneous leishmaniasis caused by Leishmania major in BALB/c mice: A comparative experimental study.

Background & objectives: Leishmania parasites are sensitive to very low temperature. Cryotherapy is considered as an alternative to the existing pentavalent antimonials, for local treatment of cutaneous leishmaniasis (CL). Normally, liquid nitrogen (N2 ) at a temperature of -196 °C, is used in cryotherapy of CL, but it's efficacy is not consistent. Recently, few studies have also reported the use of carbon dioxide (CO2 ) slush at -78.5 °C in CL cryotherapy. This study was aimed to evaluate the effectiveness of N2 vs CO2 cryotherapy for CL treatment in mice. Methods: In total, 21 BALB/c mice were infected with Leishmania major strain [MRHO/IR/74/ER]. Samples were divided into three groups based on the intervention provided-Solid CO2 cryotherapy, liquid N2 cryotherapy and control group; with seven mice randomly assigned to each group. Control group received no intervention, and in the other two groups cryotherapy was used every two weeks for maximum of three months. Follow up examinations were scheduled at the time of cryotherapy, during which the size of each lesion was measured. For three mice in each study group, the spleen parasite DNA load was quantified using real-time PCR.

Results: After treatment, the liquid N2 cryotherapy showed significant reduction in size of the lesions (p = 0.029) as compared to the solid CO2 cryotherapy and control group. Also, Leishmania DNA load in spleen was significantly lower in the mice receiving liquid N2 cryotherapy (p <0.001).

Interpretation & conclusion: Liquid N2 cryotherapy is superior to CO2 cryotherapy, and it can be an effective method for controlling L. major infection. Further investigations are essential to find optimal number of treatment sessions and time intervals.