SUMMARYDuring the earlier stages of visceral leishmaniasis transmission in Posadas City, Misiones, both the night activity and attraction to humans of Lutzomyia longipalpis were assessed, in order to provide preliminary recommendations. The impact of peridomestic deltamethrin spraying performed by local officials was also evaluated. Although Lu. longipalpis were found in traps located over a dog the entire night, 90% of the females were captured from 20.30h to 1.30h, and only landed on a human when he was at a distance of 1.5 m from the dog. Peridomestic spraying of deltamethrin (25 mg/m 2 ) reduced the sand fly capture up to seven days post-intervention without dispersion in the border of the sprayed areas. These results support the recommendations about time-space focus of the protection measures: first half of the night, in the backyard, with pets and domestic animals kept at least 5 m from humans. The deltamethrin as it was used did not seem very effective in this scenario; neither did the eventual use of bed nets, at least in adults, due to the place/hour of sand fly higher activity. This study strengthens the need for a multidisciplinary approach to develop prevention strategies based both on biological and anthropological studies.
Abstract. Dogs are the principal reservoir hosts of zoonotic visceral leishmaniasis (VL) but current serological methods are not sensitive enough to detect all subclinically infected animals, which is crucial to VL control programs. Polymerase chain reaction (PCR) methods have greater sensitivity but require expensive equipment and trained personnel, impairing its implementation in endemic areas. We developed a diagnostic test that uses isothermal recombinase polymerase amplification (RPA) to detect Leishmania infantum. This method was coupled with lateral flow (LF) reading with the naked eye to be adapted as a point-of-care test. The L. infantum RPA-LF had an analytical sensitivity similar to real time-PCR, detecting DNA of 0.1 parasites spiked in dog blood, which was equivalent to 40 parasites/mL. There was no cross amplification with dog or human DNA or with Leishmania braziliensis, Leishmania amazonensis, or Trypanosoma cruzi. The test also amplified Leishmania donovani strains (N = 7). In a group of clinically normal dogs (N = 30), RPA-LF detected more subclinical infections than rK39 strip test, a standard serological method (50% versus 13.3% positivity, respectively; P = 0.005). Also, RPA-LF detected L. infantum in noninvasive mucosal samples of dogs with a sensitivity comparable to blood samples. This novel molecular test may have a positive impact in leishmaniasis control programs.
<p><strong>Introducción.</strong> La leishmaniasis visceral es una enfermedad desatendida de alta letalidad que requiere profundizar los estudios locales para un diseño de estrategias de control efectivo. En América se verificó la urbanización de su transmisión, teniendo como reservorio principal al perro doméstico, donde condiciones socio-económicas, representaciones y prácticas de grupos domésticos (GD) jugarían un rol estratégico poco conocido para su endemicidad. <strong>Objetivo.</strong> Analizar representaciones y prácticas de prevención y afrontamiento de leishmaniasis visceral en humanos (LVh) y caninos (LVc) y factores socio-económicos de riesgo.</p><p><strong>Materiales y métodos.</strong> Estudio transversal de casos y controles. Caso: GD, con al menos un integrante con antecedentes de LVh notificado por Ministerio de Salud Pública. Control: GD sin integrantes con antecedentes de LVh. A partir de información primaria, se caracterizó demográfica y socialmente la población, la calidad de su vivienda y se construyó un ranking de conocimientos y actitudes frente a la LV, se describieron prácticas asociadas a riesgo y presencia de LVc.</p><p><strong>Resultados.</strong> Mala calidad de la vivienda (p≤0,001), personas del GD fuera vivienda después 18 hs (razón de momios, RM=4,5; IC 95%<sub>:</sub> 1,69-12,18), la reproducción sin control racial de perros (RM=15,7; IC 95%: 3,91-63,2) y con LVc en el domicilio (RM=120,3; IC 95%: 18,51-728,3) se asocian positivamente o incrementan el riesgo de contraer LVh.</p><p><strong>Conclusión.</strong> Se observa una determinación social de riesgo asociada a pobreza estructural, que aumentan la probabilidad de contacto humano-vector por mala calidad de vivienda y hacinamiento. El factor de riesgo más importante para la LVh fue la tenencia de perros con LVc en el domicilio.</p>
Abstract. Direct observation of Leishmania parasites in tissue aspirates has shown low sensitivity for the detection of canine visceral leishmaniasis (VL). Therefore in the last quarter century immunoenzymatic tests have been developed to improve diagnosis. The purpose of this study was to develop a fast recombinant K28 antigen, naked-eye qualitative enzyme-linked immunosorbent assay (VL Ql-ELISA) and a quantitative version (VL Qt-ELISA), and to display it in a kit format, whose cutoff value (0.156) was selected as the most adequate one to differentiate reactive from nonreactive samples. Considering 167 cases and 300 controls, sensitivity was 91% for both assays and specificity was 100% and 98.7% in Ql-ELISA and Qt-ELISA, respectively. Positive predictive values were 100% and 97.4% for Ql-ELISA and Qt-ELISA, respectively, and negative predictive values were 95.2% for both ELISAs. Reagent stability, reliability studies, including periodic repetitions and retest of samples, cutoff selection, and comparison of rK28 ELISAs with rK39 immunochromatographic test, were the international criteria that supported the quality in both kits. The performance of both ELISA kits in this work confirmed their validity and emphasized their usefulness for low-to-medium complexity laboratories.
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