Leishmaniasis remains a major public health problem worldwide and is
classified as Category I by the TDR/WHO, mainly due to the absence of control. Many
experimental models like rodents, dogs and monkeys have been developed, each with
specific features, in order to characterize the immune response to
Leishmania species, but none reproduces the pathology observed in
human disease. Conflicting data may arise in part because different parasite strains
or species are being examined, different tissue targets (mice footpad, ear, or base
of tail) are being infected, and different numbers (“low” 1×102 and “high”
1×106) of metacyclic promastigotes have been inoculated. Recently, new
approaches have been proposed to provide more meaningful data regarding the host
response and pathogenesis that parallels human disease. The use of sand fly saliva
and low numbers of parasites in experimental infections has led to mimic natural
transmission and find new molecules and immune mechanisms which should be considered
when designing vaccines and control strategies. Moreover, the use of wild rodents as
experimental models has been proposed as a good alternative for studying the
host-pathogen relationships and for testing candidate vaccines. To date, using
natural reservoirs to study Leishmania infection has been
challenging because immunologic reagents for use in wild rodents are lacking. This
review discusses the principal immunological findings against
Leishmania infection in different animal models highlighting the
importance of using experimental conditions similar to natural transmission and
reservoir species as experimental models to study the immunopathology of the
disease.
American cutaneous leishmaniasis (ACL) is a major public health problem caused by
vector-borne protozoan intracellular parasites from the genus Leishmania, subgenera
Viannia and Leishmania. Asymptomatic infection is the most common outcome after
Leishmania inoculation. There is incomplete knowledge of the biological processes
explaining the absence of signs or symptoms in most cases while other cases present a
variety of clinical findings. Most studies of asymptomatic infection have been
conducted in areas of endemic visceral leishmaniasis. In contrast, asymptomatic ACL
infection has been neglected. This review is focused on the following: (1)
epidemiological studies supporting the existence of asymptomatic ACL infection and
(2) immunological studies conducted to understand the mechanisms responsible for
controlling the parasite and avoiding tissue damage.
Localized cutaneous leishmaniasis (LCL) is endemic in Mexico, mainly in the states of Campeche and Quintana Roo, hyperendemic areas of Leishmania (Leishmania) mexicana transmission. In this report, epidemiological features of Leishmania infections in the municipality of Tinum, Yucatan State, Mexico are presented. Nine cases of LCL were diagnosed in 2015. Patients were men between 30 and 74 years of age, without a history of living or traveling to endemic areas (Quintana Roo or Campeche). Due to asymptomatic infection is the most common outcome after Leishmania inoculation, between November 2017 to June 2018, 47 men working in the forest were tested by Montenegro skin test (MST). Thirteen of them (27.6%) were identified MST positive, in absence of either lesion or typical scar, and evidence of exposure to vector. Findings in Tinum, Yucatan, supported the presence of specific environmental conditions that seem to favor Leishmania transmission in this region. Thus, active surveillance for the detection of new cases in the municipality of Tinum as well as the eco-epidemiological characterization to identify all the transmission components (parasite, vector, and reservoir species) are urgently needed.
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