Leishmaniasis is a
vector-borne disease that is transmitted by sandflies and caused by
obligate intracellular protozoa of the genus Leishmania. Human
infection is caused by about 21 of 30 species that infect mammals.
These include the L. donovani complex with 3 species (L.
donovani, L. infantum, and L. chagasi); the L.
mexicana complex with 3 main species (L. mexicana, L.
amazonensis, and L. venezuelensis); L. tropica; L.
major; L. aethiopica; and the subgenus Viannia with 4
main species (L. (V.) braziliensis, L. (V.) guyanensis,
L. (V.) panamensis, and L. (V.) peruviana). The different
species are morphologically indistinguishable, but they can be
differentiated by isoenzyme analysis, molecular methods, or monoclonal
transmitted by the bite of female phlebotomine sandflies. The sandflies
inject the infective stage, promastigotes, during blood meals
Promastigotes that reach the puncture wound are phagocytized by
transform into amastigotes
Amastigotes multiply in infected cells and affect different tissues,
depending in part on the Leishmania species
This originates the clinical manifestations of leishmaniasis. Sandflies
become infected during blood meals on an infected host when they ingest
macrophages infected with amastigotes (
In the sandfly's midgut, the parasites differentiate into promastigotes
which multiply and migrate to the proboscis
found in parts of about 88 countries. Approximately 350 million people
live in these areas. Most of the affected countries are in the tropics
and subtropics. The settings in which leishmaniasis is found range from
rain forests in Central and South America to deserts in West Asia. More
than 90 percent of the world's cases of visceral leishmaniasis are in
India, Bangladesh, Nepal, Sudan, and Brazil.
found in Mexico, Central America, and South America—from northern
Argentina to southern Texas (not in Uruguay, Chile, or Canada), southern
Europe (leishmaniasis is not common in travelers to southern Europe),
Asia (not Southeast Asia), the Middle East, and Africa (particularly
East and North Africa, with some cases elsewhere).
infections can result in 2 main forms of disease, cutaneous
leishmaniasis and visceral leishmaniasis (kala-azar). The factors
determining the form of disease include leishmanial species, geographic
location, and immune response of the host. Cutaneous leishmaniasis is
characterized by one or more cutaneous lesions on areas where sandflies
have fed. Persons who have cutaneous leishmaniasis have one or more
sores on their skin. The sores can change in size and appearance over
time. They often end up looking somewhat like a volcano, with a raised
edge and central crater. A scab covers some sores. The sores can be
painless or painful. Some people have swollen glands near the sores
(for example, in the armpit if the sores are on the arm or hand).
Persons who have
visceral leishmaniasis usually have fever, weight loss, and an enlarged
spleen and liver (usually the spleen is bigger than the liver). Some
patients have swollen glands. Certain blood tests are abnormal. For
example, patients usually have low blood counts, including a low red
blood cell count (anemia), low white blood cell count, and low platelet
count. Some patients develop post kala-azar dermal leishmaniasis.
Visceral leishmaniasis is becoming an important opportunistic infection
in areas where it coexists with HIV.
Giemsa-stained slides of the relevant tissue is still the technique most
commonly used to detect the parasite.
Isolation of the
organism in culture (using for example the diphasic NNN medium) or in
experimental animals (hamsters) constitutes another method of
parasitilogic confirmation of the diagnosis, and in addition can provide
material for further investigations (e.g., isoenzyme analysis).
Antibody detection can prove useful in visceral leishmaniasis but is of
limited value in cutaneous disease, where most patients do not develop a
significant antibody response. In addition, cross reactivity can occur
with Trypanosoma cruzi, a fact to consider when investigating
Leishmania antibody response in patients who have been in Central or
South America. Other diagnostic techniques exist that allow parasite
detection and/or species identification using biochemical (isoenzymes),
immunologic (immunoassays), and molecular (PCR) approaches. Such
techniques, however, are not readily available in general diagnostic
consult CDC to obtain information on how to treat leishmaniasis.