Cutaneous Leishmaniasis (CL) and mucosal (LM) are infectious diseases that affect the skin and mucous membranes. They are caused by protozoa of the genus Leishmania and transmitted to animals and humans by vectors of the Psychodidae fly family. Its distribution is worldwide and about 1.5 million new cases are estimated to occur each year.
CL and ML are caused by different species of protozoa of the genus Leishmania, which worldwide comprises about 22 species pathogenic to humans. In the Americas, human infection occurs by 15 species, which are grouped in the subgenera Leishmania and Viannia. In the American region, the three most important species of the subgenus Leishmania are: L. (L.) mexicana, L. (L.) amazonensis and L. (L.) venezuelensis. The subgenus Viannia has four main species: L. (V.) braziliensis, L. (V.) panamensis, L. (V.) peruviana and L. (V.) guyanensis. Species are morphologically indistinguishable, but can be differentiated by enzyme-linked analysis, molecular methods, or monoclonal antibodies.
Source of Infection
Leishmania infections that cause CL and ML are found in various species of wild, synanthropic and domestic animals. Several species of rodents, marsupials and edentates have been recorded as natural hosts and potential wildlife reservoirs.
In the Americas, leishmaniasis is predominantly transmitted by the bite of infected sandflies of the genus Lutzomyia. There are about 53 species of sandflies involved in the transmission.
Signs and Symptoms
The incubation period in humans is 2-3 months on average, but may have shorter (2 weeks) or longer (two years) incubation periods.
People with CL have one or more skin lesions and sores can change in size and appearance over time. Skin lesions may begin as a papule (or bump) that evolves to a rounded, painless nodule, which gradually increases in size and ulcerates. Ulcers initially are covered by a scab or crust; once the scab falls off, the typical sore has a clean pink background with granular-appearing rounded tissue, and painless high indurated (scalloped) edges. Sometimes ulcers can become infected with other microbial agents (e.g. bacteria).
When the disease involves the lobe of the ear, cutaneous lesion can cause painful, abnormal enlargement of the ear. This type of transmission was initially termed “chiclero's ulcer” because it was very common among "chicleros" (gum collectors) and agricultural workers in the Yucatan Peninsula, Mexico.
The mucosa of the nasal septum is the most commonly affected site in mucosal lesions, which can progress to perforation of the septum. The process may extend to the palate and pharynx causing palate dysfunction, difficulty in swallowing and speaking, aspiration and severe disfigurement.
Clinical: Consideration should be given to people from endemic areas with signs and symptoms suggestive of LC and LM.
Laboratory: Tissue specimens can be examined for presence of the parasite. Samples may be smear or culture material obtained from the wound. Since it is not always possible to visualize or isolate the parasite, the clinical diagnosis may be supplemented by specific histological or immunological tests.
Prevention and Control
No vaccines are available to prevent infection.
For the human population: Recommended measures for personal protection are aimed at reducing contact with vectors, in particular: avoid outdoor activities from dusk to dawn; use of mosquito nets; use of protective clothing and insect repellent; and leaving at least 400 meters of distance from the edge of the woods or areas of dense vegetation when constructing housing.
For vectors: Environmental management techniques should be implemented such as keeping backyards and patios tidy and with minimal vegetation, to make the household environment less favorable for the adult and immature stages of the vector.
The most commonly used drugs in the treatment of cutaneous and mucosal leishmaniasis are pentavalent antimonials, in two different formulations: antimonate N-methylglucamine and sodium stibogluconate. Drugs such as pentamidine isethionate, miltefosine, amphotericin B and liposomal amphotericin B are other therapeutic options.
However, no single drug completely eliminates the parasite. Treatment includes disease management of the patient, the reduction of the parasite’s burden on the body and the resolution of skin or mucosal lesions by the monitored use of the appropriate medicines. The severity of adverse effects associated with systemic drugs treatment has led to the acceptance of local treatment (intralesional administration of meglumine anitmoniate or thermotherapy) for localized cutaneous leishmaniasis.
To set priorities for the use of therapeutic alternatives, the following aspects should be considered:
- Evidence of efficacy and safety of local and systemic treatments in each of the countries of the Region
- Operational conditions to ensure efficient distribution and product management
- Registration and availability of the product in the country
- Tracking capability for detecting long-term complications
- Cultural issues on the acceptability of specific therapeutic modalities
Mucosal leishmaniasis: loss of structure and disappearance of nasal septum causing severe impairment to function of the nose.
Credits: J Soto, FUNDERMA, Bolivia.