RESUMEN
The life cycle of Leishmania panamensis in Phlebotomus papatasi was studied to characterize barriers limiting parasite colonization, differentiation, migration, and attachment in an unnatural sand fly host. The insects were fed a suspension of L. panamensis-infected macrophages and human erythrocytes, and were examined up to 16 days post-infection by light and electron microscopy. Histologic examination of 401 flies showed the peritrophic membrane to be the first important barrier to parasite establishment in the gut lumen. In most flies, parasites were unable to escape from the closed peritrophic sac, which was either excreted or retained intact in the midgut. After five days, only 31% of the flies were infected; attached parasites colonized the pylorus-ileum and/or colon regions of the hindgut. Anterior migration into the cardia region of the midgut occurred in less than 1% of infected flies; no parasites colonized the foregut. In the bloodmeal and residual bloodmeal, five morphologic forms developed from ingested amastigotes: stumpy, spatulate, elongate, short nectomonad promastigotes, and paramastigotes. Abnormal retention of amastigotes in macrophages and delayed development of promastigote stages was observed. The primary form attached in the hindgut was a pear-shaped haptomonad promastigote. Differentiation of L. panamensis in Ph. papatasi appeared to be similar to that described in natural hosts, except that metacyclic infective forms were not observed, and some forms developed in unusual locations. Phlebotomus papatasi was a partly refractory biological host for L. panamensis. The peritrophic membrane adversely affected the infection rate; rare anterior migration and a lack of metacyclic promastigotes may preclude transmission by bite.
Asunto(s)
Leishmania braziliensis/crecimiento & desarrollo , Phlebotomus/parasitología , Animales , Interacciones Huésped-Parásitos , Insectos Vectores/parasitología , Intestinos/parasitología , Intestinos/ultraestructura , Leishmania braziliensis/fisiología , Leishmania braziliensis/ultraestructura , Phlebotomus/ultraestructura , Píloro/parasitología , Píloro/ultraestructura , Especificidad de la EspecieRESUMEN
Five new phlebotomus fever virus serotypes (Bunyaviridae: Phlebovirus) are described. These viruses, designated Ambe, Ixcanal, Mariquita, Armero, and Durania, were isolated from sand flies (Diptera: Psychodidae) collected in Brazil, Colombia, and Guatemala. Two of the agents were recovered from pools of male sand flies. The new viruses are antigenically related to other members of the phlebotomus fever serogroup by immunofluorescence, but are distinct from the other 39 members of this serogroup by plaque reduction neutralization test.
Asunto(s)
Bunyaviridae/clasificación , Phlebovirus/clasificación , Psychodidae/microbiología , Animales , Animales Recién Nacidos , Antígenos Virales/análisis , Brasil , Colombia , Femenino , Técnica del Anticuerpo Fluorescente , Guatemala , Humanos , Masculino , Ratones , Pruebas de Neutralización , Phlebovirus/inmunología , Serotipificación , Clima Tropical , Células VeroRESUMEN
The development of Leishmania (Viannia) panamensis in a natural sand fly host, Lutzomyia gomezi, was studied by light and transmission electron microscopy. New aspects of peripylarian parasite behavior and morphology in the sand fly gut, early bloodmeal stages, and ultrastructural development in the anterior gut were documented. Eight distinct morphological forms were observed in the life cycle of the parasite within the insect. In the bloodmeal, amastigotes (1) transformed into stumpy promastigotes (2) which rapidly multiplied, resulting in spatulate-shaped nectomonad promastigotes (3) and elongate nectomonad promastigotes (4). These latter forms migrated primarily into the hindgut, where both were observed attached (=haptomonad phase) to the cuticular intima by hemidesmosomes within extremely shortened flagella. Spatulate haptomonad promastigotes predominated, colonizing the entire length of the hindgut, with the greatest density at 2 disjunct sites: the pylorus/ileum and the anterior rectum/rectal sac. Paramastigotes and dividing flagellates were rare. Some parasites migrated directly to the cardia/stomodeal valve region without a hindgut phase; however, major movement anteriorly was from the hindgut beginning at 6 days postinfection. In the cardia lumen, dividing short Type A promastigotes (5) predominated, intermixed with short Type B promastigotes with longer flagella (6). Paramastigotes (7) were free-swimming in the lumen as well as attached to the stomodeal valve. The primary colonizers of the valve were pear-shaped haptomonad promastigotes (8), with flagella of variable lengths and multi-segmented hemidesmosomal attachment points to the intima. Promastigotes and paramastigotes colonized the esophagus-pharynx region and attached to the foregut lining by flagellar hemidesmosomes. Both forms may represent infective stages of L. (V.) panamensis; however, no parasites were detected in the cibarium or proboscis. L. (V.) panamensis appeared well-adapted to the gut of Lu. gomezi, multiplying extensively at 2 sites, changing morphological form, and adhering to host surfaces by variously modified flagellar hemidesmosomes.
Asunto(s)
Insectos Vectores/parasitología , Leishmania braziliensis/crecimiento & desarrollo , Leishmania/crecimiento & desarrollo , Psychodidae/parasitología , Animales , Cardias/parasitología , Desmosomas/ultraestructura , Sistema Digestivo/parasitología , Flagelos/ultraestructura , Interacciones Huésped-Parásitos , Leishmania braziliensis/ultraestructura , Microscopía ElectrónicaRESUMEN
Five isolations of the Alagoas serotype of vesicular stomatitis virus (Rhabdoviridae: Vesiculovirus) were made from naturally infected phlebotomine sand flies (Lutzomyia spp.) collected in Colombia. These are the first isolations of Alagoas virus from an arthropod. Replication of the virus occurred in laboratory-reared sand flies (Lutzomyia longipalpis) after inoculation. Bite and transovarial transmission of the virus was also demonstrated in experimentally infected sand flies. Alagoas virus neutralizing antibodies were found in sera of humans and animals living near the insect collection site; antibody rates among human residents of two nearby towns were 63% and 83%, respectively. Results of comparative serologic studies demonstrated that Alagoas virus is closely related antigenically to Indiana, Cocal, and Maraba viruses and that these four agents form a complex within the vesicular stomatitis virus serogroup. The antigenic similarity among these four viruses makes their differentiation difficult; it also raises doubts about the accuracy of current laboratory methods used for identifying isolates in this serogroup. A discussion follows on the significance of human antibodies to these agents and on the role of sand flies in their ecology.
Asunto(s)
Psychodidae/microbiología , Virus de la Estomatitis Vesicular Indiana/aislamiento & purificación , Virosis/epidemiología , Animales , Anticuerpos Antivirales/análisis , Antígenos Virales/inmunología , Colombia , Femenino , Humanos , Masculino , Pruebas de Neutralización , Serotipificación , Estomatitis/epidemiología , Estomatitis/veterinaria , Virus de la Estomatitis Vesicular Indiana/clasificación , Virus de la Estomatitis Vesicular Indiana/crecimiento & desarrollo , Virus de la Estomatitis Vesicular Indiana/inmunología , Virosis/veterinariaRESUMEN
The life cycle of Leishmania mexicana mexicana in the gut of the sand fly, Lutzomyia abonnenci, was studied by light and electron microscopy. Development was suprapylarian with initial establishment of parasites in the bloodmeal (posterior midgut), and anterior migration of parasites to the cardia/stomodeal valve region beginning at 2.5 days post-infection. Flagellates were first observed in the esophagus at 3.5 days, in the posterior armature region of the pharynx at 5 days, and in the anterior pharynx at 7 days; but they were not detected in the cibarium or proboscis. Infection of the pylorus region of the hindgut and of the Malpighian tubules was also commonly observed. Three different morphological forms of L. m. mexicana developed in the gut: nectomonad promastigotes, short promastigotes, and paramastigotes. Nectomonads occurred primarily in the abdominal midgut after bloodmeal digestion, where they were oriented in longitudinal masses in the lumen, or interdigitated with epithelial microvilli via the flagellum. Short promastigotes found in the cardia/stomodeal valve region are described for the first time. These forms were smaller than nectomonads, showed an amplification of the kinetoplast, apposition of kinetoplast and nucleus, and were embedded in a gel-like matrix. To maintain position in the cardia, parasites commonly inserted the flagellum deep into microvilli or cytoplasm of the epithelium; adherence to the cuticular intima of the stomodeal valve was by flagellar modification and formation of hemidesmosome plaques. Paramastigotes occurred in the esophagus, were sometimes degenerated in appearance, and were attached via flagellar hemidesmosomes. Paramastigotes observed in the lumen of the pharynx were commonly degenerated and were not attached to the intima. L. m. mexicana was able to colonize the various gut habitats of Lu. abonnenci by a number of adaptations; this sand fly appears to be a suitable biological host for the parasite.
Asunto(s)
Leishmania mexicana/fisiología , Psychodidae/parasitología , Animales , Sistema Digestivo/ultraestructura , Femenino , Interacciones Huésped-Parásitos , Ratones , Ratones Endogámicos BALB C , Microscopía Electrónica , Psychodidae/ultraestructuraRESUMEN
Six isolates of a new phlebotomus fever serogroup virus, designated Arboledas virus, were obtained from sand flies (Lutzomyia spp.) collected in northeastern Colombia. One of the isolates was made from a pool of male sand flies. By immunofluorescence, Arboledas virus is related to Caimito and Pacui viruses; by neutralization test, it is distinct. Arboledas virus neutralizing antibodies were found in the sera of opossums (Didelphis marsupialis) and humans living in the study area. D. marsupialis inoculated with the virus developed a viremia of four days' duration, and sand flies (Lutzomyia gomezi) feeding on a viremic opossum were readily infected. Transovarial transmission of Arboledas virus was also demonstrated in experimentally infected Lu. gomezi. Results of the above laboratory studies suggest that Arboledas virus is maintained in nature by two mechanisms: vertical (transovarial) transmission in the insect vector, and an alternating marsupial-sand fly cycle. The implications of this complex maintenance cycle for other phleboviruses are discussed.
Asunto(s)
Bunyaviridae/aislamiento & purificación , Insectos Vectores/microbiología , Phlebovirus/aislamiento & purificación , Psychodidae/microbiología , Animales , Antígenos Virales/análisis , Colombia , Femenino , Humanos , Zarigüeyas/microbiología , Fiebre por Flebótomos/microbiología , Fiebre por Flebótomos/transmisión , Phlebovirus/inmunología , Phlebovirus/fisiologíaRESUMEN
Previously described monoclonal antibodies IX-IF9-D8, IX-2H7-E10 and IX-5H9-C1 recognize promastigote stage-specific determinants present on externally exposed membrane proteins of axenically cultured Leishmania mexicana amazonensis. In the present study, these antigens were demonstrated by indirect immunofluorescence to be present on promastigotes found in the gut lumen of infected Lutzoymia longipalpis. The presence of these antigens on promastigotes found in infected sandflies suggests that the same antigens should be relevant for protective immunity studies and for species identification of Leishmania encountered in epidemiological studies.