Prevalencia de la infección por Leishmania spp. en un área periurbana de Altagracia de Orituco, estado Guárico, Venezuela / Prevalence of infection with Leishmania spp. in a suburban area of Altagracia de Orituco, Guarico State, Venezuela

Leishmania infantum es el agente etiológico de la leishmaniasis visceral (LV). Sin embargo, tanto en el Viejo Mundo como en el Nuevo Mundo(América Central), este protozoario ha sido involucrado en casos de leishmaniasis cutánea atípica (LCA). Evidencias clínicas, parasitológicas, moleculares y entomológicas han demostrado que una situación similar está ocurriendo en un área periurbana de Altagracia de Orituco (Guárico, Venezuela). Con la finalidad de contribuir al entendimiento de este nuevo escenario epidemiológico, se realizó un estudio transversal en el cual se determinó la reactividad a la prueba de leishmanina [Leishmanin skin test (LST)] y la seroprevalencia a antígenos crudos de Leishmania spp. y al antígeno específico rK39 mediante la prueba de ELISA en una muestra de ocho casos de LCA detectados en el periodo 1997-2000, en sus cohabitantes (n=15) y en una muestra de 233 de la comunidad igualmente expuestas a riesgo. La dermoprevalencia resultó ser de 31,6% (67/212). El 28,8% (67/233) resultó positivo a la prueba de ELISA usando promastigotas de L. infantum (=L. chagasi) y 13,3% (31/233) poseían anticuerpos anti-L. braziliensis. Así mismo, la prueba de ELISA usando el antígeno rK39 resultó positiva en uno de los ocho casos estudiados y en dos de sus cohabitantes; así como también en 13,7% (32/233) de los individuos residentes en la comunidad. Los resultados obtenidos indican la circulación de especies del subgénero Leishmania y del subgénero Viannia en el área en estudio y que la presencia de anticuerpos anti-Leishmania en general se encontró asociada a la edad y al tiempo de residencia en la zona

Leishmania infantum is the etiological agent of the visceral leishmaniasis (VL). However, in the OldWorld as well in the New World (Central America), thisprotozo an has also been involved in cases of atypicalcutaneous leishmaniasis (ACL). Clinical, molecularand entomological evidences have demonstrated thata similar situation is happening in a peri-urban areaof Altagracia de Orituco (Guárico state, Venezuela). With the purpose of contributing to the understandingof such an epidemiological scenario, a cross-sectionalstudy was carryed out using the leishmanin skin test(LST) and screening for the seroprevalence to crudeantigens of Leishmania spp. and rK39 by means ofthe ELISA test in cases of ACL reported in the period1997-2000 (n=8), among their co-inhabitants (n=15) and in a randomly selected sample of 233 people. Thedermoprevalence was 31.6% (67/212); 28.8% (67/233)were positive to the ELISA test using promastigotes of L. infantum (= L. chagasi) and 13.3% (31/233) hadantibodies anti-L. braziliensis. In addition, the test of ELISA using the antigen rK39 was positive in oneout of the eight cases studied and in two out of theirco-inhabitants; as well as in 13.7% (32/233) of theinhabitants of the community. The results obtained inthis epidemiological study indicate the circulation of species of the sub-genus Leishmania as well as of thesubgenus Viannia. The presence of antibodies anti-Leishmania in general was associated to the age andthe time of residence in the zone

Cultivation and molecular identification of Ehrlichia canis and Ehrlichia chaffeensis from a naturally co-infected dog in Venezuela.

BACKGROUND: Diagnosis of canine ehrlichiosis in Venezuela is normally performed by examination of buffy coat smears (BCS). Characteristic inclusion bodies are frequently observed in leukocytes and platelets from dogs with clinical signs of the disease. OBJECTIVE: The purpose of this study was to investigate the co-infection of a dog with Ehrlichia canis and E hrlichia chaffeensis using microbiological and molecular techniques. METHODS: Primary cultures of monocytes from a dog showing signs of ehrlichiosis were performed. Ehrlichial inclusions in blood cells were demonstrated by BCS and in cultured cell smears with direct immunofluorescence and Dip Quick staining. Nested PCR analysis was performed with DNA from blood samples and cultures, using primers specific for E. canis and E. chaffeensis. The amplified DNA fragments were sequenced to confirm the specificity of the amplifications. RESULTS: The BCS of the naturally infected dog contained intracellular morulae. Ehrlichial inclusions were observed 9 days after inoculation of the primary cultures. After 3 passages with monocytes from a healthy dog, 65% of infected cells, and cells with >60 morulae were observed. A healthy female German Shepherd dog, seronegative for E. canis and E. chaffeensis antigens and without contact to ticks, was inoculated with an infected culture. The animal developed signs of canine monocytic ehrlichiosis and became seropositive. Nested PCR results and sequencing of amplified DNA fragments demonstrated the simultaneous presence of E. canis and E. chaffeensis in both dogs. CONCLUSIONS: This is the first report of E. chaffeensis in dogs in South America. This organism was previously identified in dogs by PCR only in the United States.

Effect of antimalarial drugs on plasmodia cell-free protein synthesis.

A cell-free system from Plasmodium falciparum able to translate endogenous mRNA was used to determine the effect of artemisinin, chloroquine and primaquine on the protein synthesis mechanism of the parasite. The antimalarial drugs did not inhibit the incorporation of [3H] methionine into parasite proteins even at concentrations higher than the ones found to strongly inhibit the parasite growth. Results clearly indicate that these compounds do not have a direct effect on protein synthesis activity of P. falciparum coded by endogenous mRNA.

Feeding behavior of Lutzomyia pseudolongipalpis (Diptera: Psychodidae), a putative vector of visceral leishmaniasis in Venezuela.

Lutzomyia pseudolongipalpis Arrivillaga & Feliciangeli is the first new sand fly species in the L. longipalpis species complex that has been formally described since it was separated by genetic as well as by morphological characters. It is the putative vector of the American visceral leishmaniasis in La Rinconada, Curarigua, a restricted focus in central western Venezuela. We investigated the feeding behavior of this species. The blood meals from 210 of 429 (48.9%) engorged females caught by CDC light traps were identified by a dot enzyme-linked immuno-absorbent assay using antisera against humans and common domestic animals. We propose a new index, the host selectivity index, which is the number of sand flies fed on a given host relative to the available biomass of that host, as an indicator of the feeding behavior of this phlebotomine sand fly. The host selectivity index is compared with the forage ratio, which is the percentage of sand flies fed on a given host by the percentage which that host represented in the total census of available animals and humans. The most attractive animal for L. pseudolongipalpis in Curarigua was the dog, whereas humans were shown to be relatively unattractive. However, not only selectivity or biomass, but also the accessibility to this host may have influenced these results. The low population density of dogs and the low accessibility of L. pseudolongipalpis to humans in relation to domestic animals might help to explain the sporadic transmission of visceral leishmaniasis in this focus.

Effect of Antimalarial Drugs on Plasmodia Cell-Free Protein Synthesis

A cell-free system from Plasmodium falciparum able to translate endogenous mRNA was used to determine the effect of artemisinin, chloroquine and primaquine on the protein synthesis mechanism of the parasite. The antimalarial drugs did not inhibit the incorporation of [³H] methionine into parasite proteins even at concentrations higher than the ones found to strongly inhibit the parasite growth. Results clearly indicate that these compounds do not have a direct effect on protein synthesis activity of P. falciparum coded by endogenous mRNA

An in vitro system from Plasmodium falciparum active in endogenous mRNA translation

An in vitro translation system has been prepared from Plasmodium falciparum by saponin lysis of infected-erythrocytes to free parasites which were homogeneized with glass beads, centrifuged to obtain a S-30 fraction followed by Sephadex G-25 gel filtration. This treatment produced a system with very low contamination of host proteins (<1). The system, optimized for Mg2+ and K+, translates endogenous mRNA and is active for 80 min which suggests that their protein factors and mRNA are quite stable.