Fact Sheet N° 116
Revised May 2000
THE LEISHMANIASES AND LEISHMANIA/HIV
Transmitted by the bite of the infected female
phlebotomine sandfly, the leishmaniases are a globally widespread
group of parasitic diseases. The sandfly vector is usually
infected with one species of flagellate protozoa belonging to the
About 30 species of sandflies can become
infected when taking a blood meal from a reservoir host. Hosts are
infected humans, wild animals, such as rodents, and domestic
animals, such as dogs. Most leishmaniases are zoonotic
(transmitted to humans from animals), and humans become infected
only when accidentally exposed to the natural transmission cycle.
However, in the anthroponotic forms (those transmitted from human
to human through the sandfly vector), humans are the sole
Leishmaniasis presents itself in humans in four
different forms with a broad range of clinical manifestations. All
forms can have devastating consequences.
Visceral leishmaniasis (VL),
also known as kala azar, is the most severe form of the
disease, which, if untreated, has a mortality rate of almost 100%.
It is characterized by irregular bouts of fever, substantial
weight loss, swelling of the spleen and liver, and anaemia.
Mucocutaneous leishmaniasis (MCL),
or espundia, produces lesions which can lead to extensive
and disfiguring destruction of mucous membranes of the nose, mouth
and throat cavities.
Cutaneous leishmaniasis (CL)
can produce large numbers of skin ulcers—as many as 200 in some
cases—on the exposed parts of the body, such as the face, arms
and legs, causing serious disability and leaving the patient
permanently scarred. Diffuse cutaneous leishmaniasis (DCL) never
heals spontaneously and tends to relapse after treatment. The
cutaneous forms of leishmaniasis are the most common and represent
50-75% of all new cases.
- Since 1993, regions that are Leishmania-endemic have
expanded significantly, accompanied by a sharp increase in the
number of recorded cases of the disease.
- The geographic spread is due to factors related mostly to
development. These include massive rural-urban migration and
agro-industrial projects that bring non-immune urban dwellers
into endemic rural areas. Man-made projects with environmental
impact, like dams, irrigation systems and wells, as well as
deforestation, also contribute to the spread of leishmaniasis.
- AIDS and other immunosuppressive conditions increase the
risk of Leishmania-infected people developing visceral
illness. In certain areas of the world the risk of
co-infection with HIV is rising due to epidemiological
The leishmaniases are now endemic in 88 countries on five
continents—Africa, Asia, Europe, North America and South
America—with a total of 350 million people at risk.
- It is believed that worldwide 12 million people are affected
by leishmaniasis; this figure includes cases with overt
disease and those with no apparent symptoms. Of the 1.5-2
million new cases of leishmaniasis estimated to occur
annually, only 600 000 are officially declared.
- Of the 500 000 new cases of VL which occur annually, 90% are
in five countries: Bangladesh, Brazil, India, Nepal and Sudan.
- 90% of all cases of MCL occur in Bolivia, Brazil and Peru.
- 90% of all cases of CL occur in Afghanistan, Brazil, Iran,
Peru, Saudi Arabia and Syria, with 1-1.5 million new cases
reported annually worldwide.
- The geographical distribution of leishmaniasis is limited
by the distribution of the sandfly, its susceptibility to
cold climates, its tendency to take blood from humans or
animals only and its capacity to support the internal
development of specific species of Leishmania.
co-infection is emerging as an extremely serious, new disease and
it is increasingly frequent. There are important clinical,
diagnostic, chemotherapeutic, epidemiological and economic
implications of this trend.
- Although people are often bitten by sandflies infected with Leishmania
protozoa, most do not develop the disease. However, among
persons who are immunosuppressed (e.g. as a result of advanced
HIV infections, immunosuppressive treatment for organ
transplants, haematological malignancy, auto-immune diseases),
cases quickly evolve to a full clinical presentation of severe
- AIDS and VL are locked in a vicious circle of mutual
reinforcement. On the one hand, VL quickly accelerates the
onset of AIDS (with opportunistic diseases such as
tuberculosis or pneumonia) and shortens the life expectancy of
HIV-infected people. On the other hand, HIV spurs the spread
of VL. AIDS increases the risk of VL by 100-1000 times in
This duo of diseases produces cumulative
deficiency of the immune response since Leishmania parasites
and HIV destroy the same cells, exponentially increasing disease
severity and consequences. VL is considered a major contributor
to a fatal outcome in co-infected patients. Lately, however, use
of tritherapy, where it is available, has improved the prognosis
for Leishmania/HIV cases.
- Leishmaniasis can be transmitted directly person to person
through the sharing of needles, as is often the case among
intravenous drug users. This group is the main population at
risk for co-infection.
Areas of Co-infection
Cases of Leishmania/HIV
co-infections are being reported more frequently in various parts
of the world. It is anticipated that the number of Leishmania/HIV
co-infections will continue to rise in the coming years and there
are indications that cases are no longer restricted to endemic
The overlapping geographical distribution of VL
and AIDS is increasing due to two main factors: the spread of the
AIDS pandemic in suburban and rural areas of the world, and the
simultaneous spread of VL from rural to suburban areas.
- Leishmania/HIV co-infections are considered a real
threat, especially in south-western Europe. Of the first 1 700
cases of co-infection which have been reported to the World
Health Organization (WHO) from 33 countries worldwide up to
1998, 1 440 cases were from the region: Spain (835); Italy
(229); France (259); and Portugal (117). Of 965 cases
retrospectively analyzed, 83.2% were males, 85.7% were young
adults (20-40 years old) and 71.1% were intravenous drug
- Most co-infections in the Americas are reported in Brazil,
where the incidence of AIDS has risen from 0.8 cases per 100
000 inhabitants in 1986 to 10.5 cases per 100 000 inhabitants
in 1997. As HIV transmission has spread into rural areas, VL
has simultaneously become more urbanized—especially in
north-eastern Brazil—increasing the risk of overlapping
- The number of cases of Leishmania/HIV co-infection is
expected to rise in Africa owing to the simultaneous spread of
the two infectious diseases and their increasingly overlapping
geographical distribution, complicated by mass migration,
displacement, civil unrest, and war.
In general, the reported cases of Leishmania/HIV
co-infection in Africa are a very modest estimation and would
substantially increase if active surveillance were implemented
throughout the continent. Ethiopia has a well-organized system
of detection, management and reporting of co-infection. Kenya
and Sudan began surveillance in 1998 and Morocco has also
established a surveillance centre.
In East Africa, cases of Leishmania/HIV
co-infections have been reported in Djibouti (10), Ethiopia
(74), Kenya (15), Malawi (1) and Sudan (3). West Africa has no
official surveillance system yet, but several cases have been
reported: Cameroon (1), Guinea Bissau (1), Mali (4) and
Senegal (2). In North Africa, cases have been reported in Algeria
(20) and Morocco (4). *
co-infections impose specific difficulties in terms of diagnosis
The usual clinical features (fever, weight loss, liver and spleen
enlargement, inflammation of the lymph nodes) are not always
present. The clinical diagnosis can also be made difficult
by associated diseases such as cryptosporidium, disseminated
cryptococcosis, cytomegalovirus infection or mycobacterial
- The serological diagnosis is falsely negative in 42.6% of
co-infected patients. HIV-positive patients have difficulty in
producing antibodies against new infectious agents, especially
at a late stage or during relapses. Consequently, there is a
need to use two or more serological tests and antigens freshly
prepared in the laboratory to increase sensitivity.
- Although multiple localizations are frequent (blood, skin,
digestive tract, lungs, central nervous system), parasitological
diagnosis can be difficult and has to be repeated to orient
the treatment. Bone marrow aspirate (BMA) remains the safest
and most sensitive technique, but spleen aspirate and liver
biopsy are also used. When BMA cannot be performed, the search
for Leishmania can be conducted in peripheral blood
- Treatment for co-infected patients is aimed at clinical and
parasitological cures and prevention of relapses.
Unfortunately, in such patients treatment failure, relapses
due to drug resistance and drug toxicity are very common. In
south-western Europe, follow-up studies using pentavalent
antimonials, the same first-line drug used to treat classic
leishmaniasis, show a positive response in 83% of cases.
However, 52% of patients relapse within a period of one month
to three years, with the number of relapses ranging from one
The main alternative drugs include
pentamidine, amphotericin B and amphotericin B encapsulated in
liposomes. This encapsulation reduces the occurrence of
side-effects, but relapses still occur and the drug remains
co-infections can lead to epidemiological changes which modify
the traditional patterns of zoonotic VL. Co-infected patients
harbour a high number of Leishmania in their blood so
there is also a risk of them becoming reservoirs of the disease
(that is, infective for the sandfly vector) as in anthroponotic
foci in Bangladesh, India, Nepal and East Africa. Consequently,
there is an increased risk of future epidemics.
- Experimentally, sandflies can be infected through a blood
meal containing a very small quantity of blood from
co-infected patients. The quantity may be less than the
content of a needle. As 71.1% of co-infected patients in
south-western Europe are intravenous drug users,
transmission of Leishmania has occurred through the
sharing of syringes in this population group.
The World Health Organization Response
Because of the anticipated substantial increase
in Leishmania/HIV co-infections, they are among the
priorities for WHO's Department of Communicable Disease
Surveillance and Response (CSR).
- In 1996, WHO established an initial surveillance system,
comprised of 14 institutions in 10 countries. A standardized
Case Report Form was elaborated and endorsed by the members of
the network, and a Central International Registry was set up
within WHO to centralize, process and disseminate information
- In 1998, a new WHO/Joint United Nations Programme on
HIV/AIDS (UNAIDS) initiative was launched which helped
strengthen the surveillance network; it has been expanded to
include 28 institutions, especially in East Africa and the
Indian subcontinent (India, Nepal). All member institutions
of the network report to WHO on an annual basis. A
computerized Geographic Information System (GIS) is used to
map and monitor co-infections in a way that permits easy
visualization and analysis of epidemiological data.
The evolution of Leishmania/HIV
co-infection is being closely monitored by extending the
geographic coverage of the surveillance network and by improving
case reporting. WHO encourages active medical surveillance,
especially in south-western Europe, of intravenous drug users,
the main population at risk. Finally, because case notification
of leishmaniasis is compulsory in only 40 of the 88 endemic
countries, WHO strongly suggests the remaining 48 endemic
countries follow suit.
from countries without surveillance systems are based upon random reports
only. To properly assess the scale of the problem, there is an urgent need
for more accurate information based on specific studies
For further information, please contact the
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or Dr Philippe Desjeux, Tel.: +41 22 791 3870/3186; Fax: +41 22
791 4878; E-mail: email@example.com
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