Asymptomatic infection with American cutaneous leishmaniasis: epidemiological and immunological studies

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.

The histopathology of cutaneous leishmaniasis due to Leishmania (Leishmania) mexicana in the Yucatan peninsula, Mexico

La Leishmaniosis Cutánea Localizada (LCL) mejor conocida como "úlcera del chiclero" en el sureste de México fue descrita por SEIDELIN en 1912. Desde entonces la región selvática de la península de Yucatán ha sido identificada como un área endémica de LCL. En el presente estudio se analizaron 73 biopsias de lesiones de casos de LCL causados por Leishmania (Leishmania) mexicana con el fin de: 1) examinar la respuesta a nivel tisular; y 2) relacionar las manifestaciones de esta respuesta con ciertas características de la presentación clínica. Con base en la clasificación histopatológica de Magalhães el patrón histopatológico más frecuente se caracterizó por la presencia de granuloma desorganizado y ausencia de necrosis (43.83%). Otro hallazgo importante a señalar fue la presencia de parásito en 50/73 (68.5%) de las biopsias estudiadas. Respecto a las posibles relaciones significativas hubo una relación directa entre el tamaño de la lesión y el tiempo de evolución (rs = 0.3079, p = 0.03); una correlación inversa entre el tamaño de la lesión y la abundancia de promastigostes (rs = -0.2467, p = 0.03). Con base en la complejidad de los hallazgos clínicos e histopatológicos, consideramos necesario estudiar la respuesta inmune mediada por células relacionada con los cambios histopatológicos, así como el papel de los factores genéticos.

Seasonal transmission of Leishmania (Leishmania) mexicana in the state of Campeche, Yucatan Peninsula, Mexico

In the Yucatan Peninsula, Mexico, localized cutaneous leishmaniasis (LCL) caused by Leishmania (Leishmania) mexicana is a typical wild zoonosis restricted to the forest, and humans are only accidentally involved. The transmission of L. (L.) mexicana has been related to the patient's occupation: chicleros(gum collectors) and agricultural workers. The objective of this study was to document L. (L.) mexicana seasonally of transmission in endemic areas of LCL in the state of Campeche, Yucatan Peninsula, Mexico. The timing of incidence of LCL in humans during 1993-1994, as well as the rate and time of infection in rodents and sand flies between February 1993 and March 1995 were analyzed. Rodents and sand flies were found infected between November and March, when men carried out their field activities and are exposed. Based on results analyzed, it is concluded that L. (L.) mexicana in the endemic area of LCL in the state of Campeche, Yucatan Peninsula, Mexico, presents a seasonal transmission restricted to the months of November to March. The knowledge of the timing of the transmission cycle in an endemic area of leishmaniasis is very important because intervention measures on the high-risk focus and population might be restricted.

Clinical picture of cutaneous leishmaniases due to Leishmania (Leishmania) mexicana in the Yucatan peninsula, Mexico

Localized cutaneous leishmaniasis (LCL), known as "chiclero's ulcer" in southeast Mexico, was described by Seidelin in 1912. Since then, the sylvatic region of the Yucatan peninsula has been identified as an endemic focus of LCL. The purpose of the present work was to describe the clinical picture of LCL caused by Leishmania (Leishmania) mexicana in the Yucatan peninsula. A total of 136 cases of LCL, based on isolation and characterization of L. (L.) mexicana by isoenzymes and/or monoclonal antibodies, were selected. Some variability of clinical features regarding number, type, size, form, location and time of evolution of the lesions was observed. The most frequently observed presentation was a single, ulcerated, rounded small lesion, located on the ear, with an evolution time of less than three months, with neither cutaneous metastases nor lymphatic nor mucosal involvement. This picture corresponds to previous studies carried out in the same endemic area where an organism of the L. mexicana complex has been incriminated as a major aetiological agent of classical "chiclero's ulcer", confirming that in the Yucatan peninsula LCL due to L. (L.) mexicana when located on the pinna of the ear is a remarkable characteristic

Retention of Leishmania (Leishmania) mexicana in naturally infected rodents from the State of Campeche, Mexico

In the State of Campeche, Mexico, zoonotic cutaneous leishmaniasis is mainly due to Leishmania (L.) mexicana. The parasite population is maintained in a mammalian species, a reservoir in which the ideal course of infection should be long and relatively nonpathogenic. The objective of the present study was to document the retention of L. (L.) mexicana in 29 naturally infected rodents. These cricetids lived in captivity for up to two years and were tested monthly for the presence of the parasite, by cultures of needle aspirates from the base of the tail. Peromyscus yucatanicus and Ototylomys phyllotis were incriminated as the primary reservoir hosts. The finding that the multiplication of parasites in P. yucatanicus might be triggered by temperature, suggests that this animal would be a good choice for further research on L. (L.) mexicana.

Obtención de cultivo axénico de amastigotes de tres cepas de Leishmania (Leishmania) mexicana a partir de promastigotes aislados de pacientes con leishmaniasis cutánea localizada en México / Obtention of axenic cultivation of amastigotes of the three strains of Leishmania (Leishmania) mexicana using promastigotes isolated from patients with cutaneous leishmaniasis in Mexico

Introducción. La Leishmaniasis Cutánea Localizada, en la Península de Yucatán, es causada predominantemente por Leishmania (L.) mexicana. Las especies de Leishmania son parásitos intracelulares obligados dimórficos. Los promastigotes, formas flageladas y móviles, se replican y diferencian en el intestino del insecto vector. Los mastigotes, formas intracelulares inmóviles, viven dentro del fagolisosoma del macrófago huésped. Los amastigotes son más difíciles de obtener, debido a que se requieren ser aislados de tejidos y/o cultivos en líneas celulares de macrófagos. La alternativa es el cultivo axénico de formas de amastigotes. Material y métodos. El presente estudio describe la obtención de formas de amastigotes de tres cepas de Leishmania (L.) mexicana, (M/HOM/MX/94/VMC/663,M/HOM/MX/94/JM/758,M/HOM/MX/MX/95LPD/787), mediante la variación del pH y la temperatura de incubación en el medio de cultivo de Grace. Resultados. Los resultados mostraron un comportamiento diferente en cada cepa, determinado por la densidad celular y el porcentaje relativo de transformación. Los promastigotes de cada cepa se transformaron en más del 80 por ciento a formas de amastigotes al segundo día de incubación a pH 5.5 y temperatura de 35ºC. Por otro lado, la variación del pH, de 7.2 a 5.5 a 25ºC, permitió la transformación de promastigotes en metacíclicos. Conclusiones. La variación del pH y la temperatura de incubación permitió obtener las tres etapas de transformación del parásito (promastigotes, metacíclicos y amastigotes), los cuales podrán emplearse en futuros estudios bioquímicos e inmunológicos

A two years study on vectors of cutaneous leishmaniasis: evidence for sylvatic transmission cycle in the state of Campeche, Mexico

Vectors of cutaneous leishmaniasis in the State of Campeche were studied in relation to the transmission cycle of Leishmania (Le.) mexicana. To determine how transmission of leishmaniasis occurs, we collected phlebotomine sand flies for two years. In the first year (October 1990 to November 1991) the collections were made with CDC light traps, Shannon traps and direct captures at natural shelters around the village (<200m) of La Libertad. In the second year (February 1993 to January 1994) the catches were perfomed at 8 km southeast of La Libertad in the forest. Female sand flies were examined for Leishmania. During the first year, 347 sand flies of nine species were collected, most of which were Lutzomyia deleoni (61.3 per cent). When all nine species were considered, more females than males were captured. Low densities of anthropophillic species of sand flies around the village indicated that sylvatic transmission was taking place. For the second year, 1484 sand flies of 16 species were caught. The most common were L. olmeca olmeca (21.7 per cent), L. cruciata (19.2 per cent) and L. ovallesi (14.1 per cent). Similarly, more females were caught than males. Thirty-five females of five species were found infected with flagellates believed to be Leishmania sp. The highest infection rate was found in L. olmeca olmeca (7.1 per cent) followed by L. cruciata (4.5 per cent) and L. ovallesi (1.1 per cent). These data plus other evidence on the epidemiology of human cases and results from reservoir studies are discussed in relation to the sylvatic transmission cycle.

Population dynamics and biting rhythm of the anthropophilic sandfly Lutzomyia cruciata (Diptera: Psychodidae) in Southeast, Mexico

Flebotomo atraidos por cebo humano fueron conectados en un foco de leishmaniais cutanea localizada en el estado de Campeche, Mexico. Colectas fueron llevadas a cabo mensalmente de Febrero 1994 a Enero de 1995 entre las 18:00 a 22:00 h. Lutzomyia cruciata fue la unica especie capturada. El mayor pico plobacional fue encontrado en Marzo con picos similares en Febrero, Diciembre 1994 y Enero 1995. La tasa maxima de picadura de Lu. cruciata estuvo compreendida entre 18:00 e 19:00 h Las hembras hambientes de Lu. cruciata, fueron directamente relacionadas con niveles de humedad relativa entre 88 a 100 por cento. Bajas y altas temperaturas tuvieron un efecto negativo sobre la actividad de Lu. cruciata. Se discute el posible papel de Lu. criciata como vector de leishmaniasis en el estado de Campeche, Mexico