Viable Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers.

Asymptomatic infection (the absence or inapparent signs and symptoms) has been observed in many endemic areas of leishmaniasis, however, little is known about the parasitological and immunological factors associated with this type of infection. This study aimed to identify the in vitro expression of IFN-γ in asymptomatic carriers of viable Leishmania parasites. Asymptomatic infection was identified using the Montenegro skin test in an at-risk population from Yucatan, Mexico. Parasite viability was evinced in the blood by 7SL RNA transcripts amplification. The expression of mRNA IFN-γ was analyzed in peripheral blood mononuclear cells stimulated with soluble Leishmania antigen, using RT-qPCR. Parasite viability was observed in 33.3 % (5/15) of asymptomatic subjects. No differences were found in the expression of IFN-γ between asymptomatic and healthy subjects, and no correlation was found between the presence of viable parasites and the expression of IFN-γ. This study demonstrates the persistence of Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers from Mexico.

Viable Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers

ABSTRACT Asymptomatic infection (the absence or inapparent signs and symptoms) has been observed in many endemic areas of leishmaniasis, however, little is known about the parasitological and immunological factors associated with this type of infection. This study aimed to identify the in vitro expression of IFN-γ in asymptomatic carriers of viable Leishmania parasites. Asymptomatic infection was identified using the Montenegro skin test in an at-risk population from Yucatan, Mexico. Parasite viability was evinced in the blood by 7SL RNA transcripts amplification. The expression of mRNA IFN-γ was analyzed in peripheral blood mononuclear cells stimulated with soluble Leishmania antigen, using RT-qPCR. Parasite viability was observed in 33.3 % (5/15) of asymptomatic subjects. No differences were found in the expression of IFN-γ between asymptomatic and healthy subjects, and no correlation was found between the presence of viable parasites and the expression of IFN-γ. This study demonstrates the persistence of Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers from Mexico.

Molecular Detection of Leishmania (Leishmania) mexicana in Sandflies from the State of Yucatan, Mexico.

Background: Leishmaniases are a group of vector-borne zoonotic diseases of public health relevance within the tropical and subtropical regions of the world. The state of Yucatan is a vulnerable and receptive area to localized cutaneous leishmaniasis (LCL) due to its proximity to the high-transmission endemic states of Campeche and Quintana Roo. Autochthonous cases of LCL caused by Leishmania (Leishmania) mexicana have been documented in the state, showing a geographical expansion of the disease. Materials and Methods: Using CO2-supplemented Centers for Disease Control and Prevention light traps and Shannon traps, we captured anthropophilic sandflies in the surroundings of a locality with recent records of autochthonous cases of LCL. Sandflies carrying Leishmania DNA were evidenced using PCR. Results: A total of 140 Phlebotominae (Diptera: Psychodidae) females of four species were captured: Lutzomyia (Tricholateralis) cruciata (Coquillett), Psathyromyia (Psathyromyia) shannoni (Dyar), Lutzomyia (Lutzomyia) longipalpis (Lutz and Neiva), and Dampfomyia (Coromyia) deleoni (Fairchild and Hertig). Molecular results showed that 6.1% (95% confidence interval [CI] = 2.3-12.9%) of Lu. cruciata and 43.8% (95% CI = 19.8-70.1%) of Pa. shannoni showed evidence of carrying L. (L.) mexicana DNA. Conclusion: We provide evidence of anthropophilic sandflies carrying L. mexicana DNA in a municipality with recorded autochthonous cases of LCL caused by this parasite species in the state of Yucatan, suggesting the emergence of new focus of LCL in Mexico.

Report of autochthonous cases of localized cutaneous leishmaniasis caused by Leishmania (Leishmania) mexicana in vulnerable, susceptible areas of Southeastern Mexico.

Localized cutaneous leishmaniasis (LCL) is an endemic disease in several Mexican States with the main endemic areas located in the South-Southeast region of the country, where 90% of Leishmania (Leishmania) mexicana cases are registered. The Southeast region is located in the Yucatan Peninsula, including Campeche, Quintana Roo and Yucatan States. Campeche and Quintana Roo register more than 60% of the cases in the country each year, while in Yucatan the reports are of imported cases due to residents traveling to endemic areas. However, since 2015, autochthonous cases have been diagnosed by health authorities in municipalities with no previous transmission records. We aimed to identify Leishmania parasite species involved in autochthonous cases by means of the PCR technique. The present study included 13 autochthonous cases of LCL with clinical and parasitological diagnoses during 2018 and 2019 by health authorities, without specific identification of the causal agent. Tissue samples were taken by scraping the margins of active lesions and then they were spotted onto an FTATM Elute Microcard. Next, DNA was eluted and used for PCR amplification of specific Leishmania genus and L. (L.) mexicana species-specific fragments. Molecular analysis showed evidence that L. (L.) mexicana was the causal agent of LCL in 12 of the 13 patients; in one patient, PCR was not performed due to the patient's refusal to participate in the study. Identifying Leishmania species that cause LCL is necessary to define efficient treatment schemes and control strategies for the disease in vulnerable and susceptible areas of the Yucatan State's municipalities.

Report of autochthonous cases of localized cutaneous leishmaniasis caused by Leishmania (Leishmania) mexicana in vulnerable, susceptible areas of Southeastern Mexico

ABSTRACT Localized cutaneous leishmaniasis (LCL) is an endemic disease in several Mexican States with the main endemic areas located in the South-Southeast region of the country, where 90% of Leishmania (Leishmania) mexicana cases are registered. The Southeast region is located in the Yucatan Peninsula, including Campeche, Quintana Roo and Yucatan States. Campeche and Quintana Roo register more than 60% of the cases in the country each year, while in Yucatan the reports are of imported cases due to residents traveling to endemic areas. However, since 2015, autochthonous cases have been diagnosed by health authorities in municipalities with no previous transmission records. We aimed to identify Leishmania parasite species involved in autochthonous cases by means of the PCR technique. The present study included 13 autochthonous cases of LCL with clinical and parasitological diagnoses during 2018 and 2019 by health authorities, without specific identification of the causal agent. Tissue samples were taken by scraping the margins of active lesions and then they were spotted onto an FTATM Elute Microcard. Next, DNA was eluted and used for PCR amplification of specific Leishmania genus and L. (L.) mexicana species-specific fragments. Molecular analysis showed evidence that L. (L.) mexicana was the causal agent of LCL in 12 of the 13 patients; in one patient, PCR was not performed due to the patient's refusal to participate in the study. Identifying Leishmania species that cause LCL is necessary to define efficient treatment schemes and control strategies for the disease in vulnerable and susceptible areas of the Yucatan State's municipalities.

Preliminary epidemiological findings of Leishmania infection in the municipality of Tinum, Yucatan State, Mexico.

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.