The increase in the promastigotes population of Leishmania pifanoi in Lutzomyia youngi experimentally infected and kept on 50% sacarose under constant conditions of temperature and humidity is described. Two stages in the differentation and growth of the parasites are recognised between two and twenty-four hours after meals. The pleomorphic differentiation of the amastigotes in short promastigotes which multiply by binary division for 60 hours, when the rupture of the peritrophic membrane occurs, takes place within 48 hours. The second stage occurs between 72 and 96 hours when some of the parasites migrate to the esophagic valve and the rest of the free parasites are excreted in fecal drops as large, active promastigotes. The first drops excreted react positively to glucose or contain crystals of urate. The excess promastigotes of the second stage of development are eliminated in the last excretions and react positively to the Hemoscreen and Biuret tests for total proteins as also for glucose and account for 82% of the of drops excreted. The excretion of parasites by Lu. youngi is a normal stage in the growth of L. pifanoi into a vector.

Se describe el desarrollo poblacional promastigótico de Leishmania pifanoi en Lutzomyia youngi experimentalmente infectada y mantenida con sacarosa al 50% bajo condiciones constantes de temperatura y humedad. Se reconocen dos etapas para la diferenciación y el crecimiento de los parásitos entre las dos y ciento veinte horas postprandiales. Hasta 48 horas tiene lugar la diferenciación pleomórfica de amastigotos en promastigotos cortos, que se multiplican por división binaria hasta las 60 horas, cuando ocurre la ruptura de la membrana peritrófica. La segunda etapa tiene lugar entre las 72 y 96 horas cuando algunos parásitos migran hacia la válvula esofágica y los demás parásitos libres son excretados en gotitas fecales como promastigotos grandes y activos. Las primeras gotitas excretadas dan reacción positiva a glucosa o contienen cristales de urato. El exceso de promastigotos de la segunda fase de desarrollo es eliminado en las últimas excretas que dan reacción positiva con las pruebas Hemoscreen y Biuret para proteínas totales y también para glucosa, y constituyen el 82% del total de gotas excretadas. La excreción de parásitos por Lu. youngi es fase normal del desarrollo de L. pifanoi en un vector.

The increase in the promastigotes population of Leishmania pifanoi in Lutzomyia youngi experimentally infected and kept on 50% sacarose under constant conditions of temperature and humidity is described. Two stages in the differentation and growth of the parasites are recognised between two and twenty-four hours after meals. The pleomorphic differentiation of the amastigotes in short promastigotes which multiply by binary division for 60 hours, when the rupture of the peritrophic membrane occurs, takes place within 48 hours. The second stage occurs between 72 and 96 hours when some of the parasites migrate to the esophagic valve and the rest of the free parasites are excreted in fecal drops as large, active promastigotes. The first drops excreted react positively to glucose or contain crystals of urate. The excess promastigotes of the second stage of development are eliminated in the last excretions and react positively to the Hemoscreen and Biuret tests for total proteins as also for glucose and account for 82% of the of drops excreted. The excretion of parasites by Lu. youngi is a normal stage in the growth of L. pifanoi into a vector.

Se describe el desarrollo poblacional promastigótico de Leishmania pifanoi en Lutzomyia youngi experimentalmente infectada y mantenida con sacarosa al 50% bajo condiciones constantes de temperatura y humedad. Se reconocen dos etapas para la diferenciación y el crecimiento de los parásitos entre las dos y ciento veinte horas postprandiales. Hasta 48 horas tiene lugar la diferenciación pleomórfica de amastigotos en promastigotos cortos, que se multiplican por división binaria hasta las 60 horas, cuando ocurre la ruptura de la membrana peritrófica. La segunda etapa tiene lugar entre las 72 y 96 horas cuando algunos parásitos migran hacia la válvula esofágica y los demás parásitos libres son excretados en gotitas fecales como promastigotos grandes y activos. Las primeras gotitas excretadas dan reacción positiva a glucosa o contienen cristales de urato. El exceso de promastigotos de la segunda fase de desarrollo es eliminado en las últimas excretas que dan reacción positiva con las pruebas Hemoscreen y Biuret para proteínas totales y también para glucosa, y constituyen el 82% del total de gotas excretadas. La excreción de parásitos por Lu. youngi es fase normal del desarrollo de L. pifanoi en un vector.

Two lots of 20 young male guinea pigs were inoculated subcutaneously in the tarsi with 10 (elevated to fourth potency) amastigotes of Leishmania braziliensis or L. b. guyanensis to study the susceptibility of this Neotropical hystricomorph rodent the autochthonous parasites. Almost 50% of the animals showed lesions in the inoculation site and had parazitations that were infective to hamsters, as shown by inoculating homogenates of the dermal lesion, of the spleen, of the liver, and of the nasal mucosa into hamsters at 20, 40, 60 and 120 days after inoculation of the guinea pig. Smears of the above organs showed the presence of amastigotes. Parasites inoculated into the tarsi were detected early in the skin, spleen, and liver of the guinea pig host. Blood cultures made by cardiopuncture on sacrifice of the guinea pigs were uniformly negative. The nasal mucosa of nearly all animals positive in the skin or viscera was invaded early by the parasites, although with grater frequency between 60 and 120 days post-inoculation. The use of this model for the study of mucocutaneous parasitism by L. brasiliensis is discussed, together with the phenomena of parasitism at a distance from the inoculation site, the temperature of the body regions affected, and the possible genetic influence on susceptibility of the guinea pig to L. brasiliensis.