A protozoa, there are numerous species depending on where it was acquired. There is old world predominantly L. donovani and New World, of which there are TNTC.
New World: All over C. and S. America. Spread by the sand fly. Coming North with global heating (PubMed). In the US dogs are the likely resourvoir of L. infantum , esp hounds.
There was a case of Leishmania donovani in North Dakota in a child that had never been out the state (PubMed). Poor kid. A life in North Dakota.
Cutaneous: a large, ragged, dry ulcer at the site of the bite, 2 weeks to 2 months after the bite. With L. braziliensis, the mucous membranes can be involved to cause destruction of the nose, face etc.
Kala-azar or visceral disease: fever, weight loss, hepatosplenomegaly, anemia, and leukopenia. It can be a major problem in AIDS patients. It sounds like a Ricardo Montalban character who fights Kirk.
The ins and outs of Leishmania are too complicated for this guide; the few cases I have treated have always been with the help of the CDC.
Liposomal Amphotericin B (10 or 20 mg/kg single dose is probably the preferred treatment for visceral disease and should cure 95% (PubMed,PubMed)), ketoconazole 400 - 600 mg qd and itraconazole have activity against some Leishmania.
With cutaneous disease, pentoxifylline 400 mg po tid for 30 days (PubMed) increases healing and decreases relapse and in one small study (PubMed) rimiquimod 7.5% cream administered topically every other day for 20 days, intravenous meglumine antimoniate 20 mg/kg per day every day for 20 days was superior to either agent alone.
For cutaneous L. major topical paromomycin-gentamicin or paromomycin alone daily for 20 days ((15% paromomycin–0.5% gentamicin cream) or paromomycin alone (15% paromomycin cream)) are effective (PubMed).
Heat is also effective for cutaneous Leishmania major (Plos).
If you suspect a case, call the CDC. They are extremely helpful, will aid in getting the ulcer cultured and help guide therapy. Invaluable.