80	 Trends in Parasitology, January 2020, Vol. 36, No. 1	 © Published by Elsevier Ltd.		 https://doi.org/10.1016/j.pt.2019.10.006
Trends in Parasitology | Parasite of the Month
Leishmania infantum
Tiago D. Serafim,1,*
Eva Iniguez,1
and Fabiano Oliveira1,*
1
Vector Molecular Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA
*Correspondence:
loliveira@niaid.nih.gov,
tiago.donatelliserafim@nih.gov
Trends in Parasitology
Trends in Parasitology
KEY FACTS:
L. infantum was introduced into the New
World during Portuguese and Spanish
colonization; it was formerly named
Leishmania chagasi.
The primary hosts are humans and
canids. Domestic dogs are the main
parasite reservoir. Wild hares serve as
sylvatic reservoirs in southern Europe. It
is controversial whether humans act as
reservoirs.
The main vectors are: Lutzomyia longipalpis
in Brazil; Phlebotomus perniciosus in Spain,
Portugal, and Italy; and Phlebotomus ariasi
in France and Portugal.
During a blood meal, parasites are
inoculated into the host skin together
with sand fly gut microbiota and salivary
proteins, as well as Leishmania-derived
proteophosphoglycans and exosomes.
Multiple blood meals (also uninfected) are
critical for successful sand fly infection and
parasite development to the infective stage.
Genetic markers are associated with drug
resistance.
The genome consists of 36 chromosomes,
~32 Mb.
DISEASE FACTS:
Disease is caused by amastigote forms of
the parasite living in macrophages.
It mainly affects children under 10 years of
age and immunocompromised adults.
The most severe cases occur in South
America.
Symptoms include persistent fever and
hepatosplenomegaly. Cutaneous lesions are
an uncommon manifestation of infection.
Poor nutritional status is associated with
disease progression.
TAXONOMY AND CLASSIFICATION:
KINGDOM: Protozoa
PHYLUM: Euglenozoa
CLASS: Kinetoplastea
ORDER: Kinetoplastida
FAMILY: Trypanosomatidae
GENUS: Leishmania
SUBGENUS: Leishmania
SPECIES: L. infantum
Leishmania infantum is the etiological agent of visceral leishmaniasis (VL) in South America,
the Mediterranean basin, and West and Central Asia. It can also cause cutaneous lesions,
particularly in the Mediterranean. The most affected country, Brazil, reported 4297 VL cases
in 2017. L. infantum is transmitted by female phlebotomine sand flies during successive blood
meals. After being picked up by the insect vector during a bite on a reservoir host, the parasites
become extracellular and undergo a series of morphological changes culminating in the rise
of the metacyclic infective stage, which is then inoculated into the host skin during a blood meal.
Metacyclic parasites will infect multi- and mononuclear cells in the host and become intracellular
amastigotes. Parasite visceralization results in impaired function of the liver, spleen, and bone
marrow with fatal consequences in many cases. To date, no human vaccine is available, and
therapeutic drugs, some with severe side effects, are used to achieve a clinical curative response.
Trends in Parasitology, January 2020, Vol. 36, No. 1    © Published by Elsevier Ltd.           https://doi.org/10.1016/j.pt.2019.10.006       81
Trends in Parasitology | Parasite of the Month
Acknowledgments
We would like to thank Ryan Kissinger from the Research Technology Branch (RTB), National Institute of Allergy and Infectious Diseases (NIAID), for illustration support; Elizabeth
Fischer from RTB for electron microscopy support; Owen Schwartz, Biological Imaging Facility, NIAID, for taking the infected macrophage picture; Selma Jeronimo from the
Federal University of Rio Grande do Norte, for providing patient image; Jesus G. Valenzuela from Vector Molecular Biology Section, Laboratory of Malaria and Vector Research,
NIAID for critical reading of the manuscript. T.D.S, E.I., and F.O. were supported by the Intramural Research Program of the National Institutes of Health (NIH), National Institute
of Allergy and Infectious Diseases.
Resources
www.who.int/leishmaniasis/en/
www.cdc.gov/parasites/leishmaniasis/
www.paho.org/hq/index.php?option=com_topics&view=article&id=29&Itemid=40754&lang=en
www.dndi.org/diseases-projects/leishmaniasis/
https://tritrypdb.org/tritrypdb/
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