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.

Morphology variation of Lutzomyia cruciata eggs (Diptera: Psychodidae: Phlebotominae) in southern Mexico.

The sand fly Lutzomyia cruciata has been associated with the transmission of Leishmania mexicana to humans in Mexico. This species has a wide distribution in Mexico occupying different microhabitats and environments. In this work comparisons of the egg exochorion of Lu. cruciata from different physiographic areas are presented. Study sites are from different states of southern Mexico. Exochorion analysis was carried out using scanning electron microscopy (SEM). Results show differences in the exochorionic pattern among samples from Veracruz (AVER), Yucatán (HOYU) and Chiapas (TACH). The morphotype "Chiapas" has a polygonal crest pattern, the morphotype "Veracruz" shows parallel and longitudinal crests with some or few connections, and the morphotype "Yucatán" has weak connections between crest ridges. These morphological differences could be the result of local adaptations or evidence of divergence within the nominal unit Lutzomyia cruciata.

The immature stages of Micropygomyia (Coquillettimyia) chiapanensis (Dampf) (Diptera: Psychodidae, Phlebotominae).

The egg exochorion, larval instars and pupa of the phlebotomine sand fly Micropygomyia (Coquillettimyia) chiapanensis (Dampf) are described and illustrated based on specimens collected in the locality of Farallón, municipality of Actopan, Veracruz, Mexico. Morphology of fourth instar larval mouthparts, particularly the incisor lobe and molar lobe shape of mandible, could be important for species identification of immature Phlebotominae. In this work is compared the pupal chaetotaxy of Mi. chiapanensis with other species previously described. The fourth instar larva of Mi. chiapanensis is compared with other species of this genus, the most important differentiating characters being the size, shape and position of the abdominal dorsal internal seta.