Clinical characteristics of the disease in humans
Cutaneous leishmaniasis is the milder form of leishmaniasis and usually leads to formation of skin lesions or nodules around the exposed bite sites such as face, neck, or limbs [8, 24].
Lesions can heal spontaneously in few months, or in some extreme cases, it can take few years to resolve [8]. Although CL is self-curing and nonlife-threatening, accumulation of CL often leads to disfigured formations on skin. Lesion number can vary between 1 and 20, and upon healing, distinct scars are left on the skin. Various treatment methods are used in order to speed up the healing process for CL.Depending on the disease forms observed clinically such as uncomplicated form, chronic recurrent form, and diffuse form, there are four causative pathogens in the Old World and five causative pathogens in the New World [18]. L. major, L. tropica, L. infantum, and L. aethiopica are the pathogens of Old World, whereas L. L. mexicana, L. L. amazonensis, L. V braziliensis, L. Vguyanensis, and L. Vpanamensis are the pathogens of New World in the case of CL [18].
VL also known as kala-azar is the fatal form of leishmaniasis with a mortality rate of 75-95%. Macrophages affected by the parasite spread the infection throughout the body, and patients develop pancytopenia and immunosuppression [6, 43, 44]. VL is often discussed together with HIV as they both affect immune system heavily making patients susceptible to other infections. Incubation period is between 2 weeks and 2 years. Liver- and spleen-related problems are common in patients with VL.
Parasite spreading around the initial bite site using the lymphatic way and infecting the nose or mouth mucosa leads to ML (Figure 1) [45]. Immune system reacting to parasite at the tip of the nose effects airway walls causing lumen obstruction which is related to necrosis of the cartilage in the nose. Unlike CL, ML is not a self-healing disease and can cause permanent skin problems. Destruction of the tip of the nose is a severe condition that may affect patients in their social life. Breathing problems are common result of ML in patients due to the blocked airways [46].
Another form of the disease, post kala-azar dermal leishmaniasis is a complication of VL in which patients cured of VL develops nodular, macular, or maculopapular rash on skin as a result of immune suppression following VL. It is mainly observed in Sudan and India where majority of the VL cases progress into post kala-azar dermal leishmaniasis [47].
7.