Leishmaniasis is a disease caused by protozoan parasites that belong to the
genus Leishmania and is transmitted by the bite of certain species of sand fly.
Most forms of the disease are transmissible only from animals (zoonosis), but
some can be spread between humans. Human infection is caused by about 21
of 30 species that infect mammals.
Cutaneous leishmaniasis is the most common form of leishmaniasis. Visceral
leishmaniasis is a severe form in which the parasites have migrated to the vital
organs.
The most important species of Leishmania is L. donovani causes visceral
leishmaniasis (Kala-azar, black disease, dumdum fever).
Amastigote (leishmanial form) is oval and
measures 2-5 microns by 1 - 3 microns,
whereas
the
leptomonad
(Leishmania
promastigotes) measures 14 - 20 microns by
1.5
-
4
microns,
trypanosomes.
a
similar
size
to
Leishmania promastigotes. This is the form that lives in the sandfly and is
injected into humans or animals. Notice the flagella. Spindle-shaped cells with a
single flagellum that endows them with motility. This form of the parasite can be
easily cultured in tissue culture medium
Leishmania amastigote. This is the form that lives in the human. Notice the
lack of flagella. The amastigotes are smaller, oval-shaped cells that have
only a residual flagellum and lack motility.

Leishmaniasis can be transmitted in many tropical and sub-tropical
countries, and is found in parts of about 88 countries. Approximately
350 million people live in these areas.

The settings in which leishmaniasis is found range from rainforests in
Central and South America to deserts in West Asia and the Middle
East. It affects as many as 12 million people worldwide, with 1.5–2
million new cases each year.

The visceral form of leishmaniasis has an estimated incidence of
500,000 new cases and 60,000 deaths each year. More than 90
percent of the world's cases of visceral leishmaniasis are in India,
Bangladesh, Nepal, Sudan, and Brazil.
The organism is transmitted by the bite of several species of bloodfeeding sand flies (Phlebotomus) which carry the promastigote in the
anterior gut and pharynx. The parasites gain access to mononuclear
phagocytes where they transform into amastigotes and divide until the
infected cell ruptures. The released organisms infect other cells. The
sandfly acquires the organisms during the blood meal; the amastigotes
transform into flagellate promastigotes and multiply in the gut until the
anterior gut and pharynx are packed. Dogs and rodents are common
reservoirs.
Phlebotomus (sandfly)
The symptoms of leishmaniasis are skin sores which erupt
weeks to months after the person affected is bitten by sand
flies. Other consequences, which can become manifest
anywhere from a few months to years after infection,
include fever, damage to the spleen and liver, and
anaemia.
In the medical field, leishmaniasis is one of the famous
causes of a markedly enlarged spleen, which may become
larger even than the liver.
Leishmaniasis may be divided into the following
types:
 Cutaneous
leishmaniasis
 Mucocutaneous
 Visceral
leishmaniasis
leishmaniasis

Cutaneous leishmaniasis – the most common form which
causes a sore at the bite site, which heals in a few
months to a year, leaving an unpleasant looking scar.

Mucocutaneous leishmaniasis – commences with skin
ulcers
which
spread
causing
tissue
damage
to
(particularly) nose and mouth.

Visceral leishmaniasis – the most serious form and
potentially fatal if untreated.
Cutaneous leishmaniasis ulcer
Visceral leishmaniasis or
"Kala-azar" is caused by
infection with Leishmania
donovani.
Parasiteinfected cells can
be found in spleen, liver,
lymph glands, intestinal
mucosa and bone marrow.
This can result in a very
enlarged liver and spleen.
Leishmaniasis is diagnosed in the haematology laboratory by direct
visualization of the amastigotes (Leishman-Donovan bodies).
Buffy-coat preparations of peripheral blood or aspirates from marrow,
spleen, lymph nodes or skin lesions should be spread on a slide to
make a thin smear, and stained with Leishman's or Giemsa's stain
(pH 7.2) for 20 minutes.
Amastigotes are seen with monocytes or, less commonly in neutrophil
in peripheral blood and in macrophages in aspirates.
Sodium stibogluconate (Pentostam) is the drug of choice.
Pentamidine isethionate is used as an alternative.
Control measures involve vector control and avoidance.
Immunization has not been effective.
Amphotericin (AmBisome) is now the treatment of
choice; its failure in some cases to treat visceral
leishmaniasis (Leishmania donovani) has been reported in
Sudan, but this may be related to host factors such as coinfection with HIV or tuberculosis rather than parasite
resistance.
Miltefosine (Impavido) is a new drug for visceral and
cutaneous leishmaniasis