Studies on sandflies (Diptera: Psychodidae) of the Parque Estadual do Turvo, RS, Brazil, and their role in Leishmania transmission

Abstract

SUMMARY OF THESIS* SILVA, Onilda Santos da - Studies on sandflies (Diptera: Psychodidae) of the Parque Estadual do Turvo, RGS, Brazil, and their role in Leishmaniatransmission. Tubingen, Germany, 2000. (Thesis presented to Department of Medical Entomology, Hygiene Institute of the Eberhard-Karls-University, to obtain a Doctor Degree in Biological Sciences). STUDIES ON SANDFLIES (DIPTERA: PSYCHODIDAE) OF THE PARQUE ESTADUAL DO TURVO, RS,BRAZIL, AND THEIR ROLE IN Leishmania TRANSMISSION To identify the local sandfly fauna of the Parque Estadual do Turvo,and estimate their role in Leishmania transmission in the Park’s marginalforest zone (27°10' - 27°20' S and 53°40' - 54°10' W), sandflies werecollected during three summer seasons (Nov 1996 to Feb 1997, Nov1997 to Jan 1998 and Nov 1998 to Jan 1999). Domicile sites sampledby aspirator were the indoor and outdoor surfaces of the walls of thehouse. Peridomicile sites were a chicken pen and cattle shelter. The forestsite was sampled by a Shannon trap 3 km west of the lodge.Polymerase chain reaction (PCR) probes were applied to 2,270females to identify natural infection by Leishmania (Viannia), thecausative agent of ACL.A total of 5,244 specimens were collected comprising 12 Lutzomyiaand 2 Brumptomyia species. The species belonged to Lu. migonei, Lu.pessoai, Lu. lanei, Lu. misionensis, Lu. neivai, Lu. shannoni, Lu.monticola, Lu. fischeri, Lu. bianchigalatiae, Lu. schreiberi, Lu.correalimai, Lu. alphabetica, B. pintoi and B. nitzulescui. All threesurveys revealed that Lu. migonei and Lu. pessoai predominate in thedomicile and peridomicile areas, while Lu. misionensis was the mostnumerous species in the forest.Naturally infected females were only found during the first survey.From 920 females examined Leishmania (V.) infections were detectedby kDNA amplification in two Lu. pessoai females from the domicilearea and one Lu. misionensis female from the forest area. Lu. misionensishas never been found before carrying a natural infection of Leishmania(V.).While identifying the sandflies it was noticed that one male hadblood in the alimentary canal. By careful examination of 1,743 malescollected, 62 were found to have blood in the gut (55 Lu. migonei, 5 Lu.pessoai, 1 Lu. fischeri and 1 B. pintoi). The presence of mammalianerythrocytes was confirmed by examining the gut by Giemsa-stainedsmears. All blood-fed males were caught in the peridomicile area.To obtain more information about the mechanism of blood feedingin males, the mouthparts of both males and females of Lu. migonei werecompared by scanning electron microscopy and light microscope.Mandibles are posses in both sexes but in males they are reduced and incontrast to females no teeth were observed. As in females, the laciniae inmales are highly sclerotised, but the number of lateral teeth are reducedand retrorse teeth are absent. Only females present teeth at the tip of thehypopharynx while in males they are substituted by spicula. Except forthe length from the junction with the hypopharynx to the tip, that isshorter in males than in females, the labrum is similar in both sexes interms of form and sensilla. On the labrum of males sensilla could bedetected, similar to the apical sensilla of females which might play arole in the identification of blood. However, further studies should identifyif the function of these sensilla in males Lu. migonei , are homologous tothose in females.Because of the epidemiological importance of Lu. migonei on Le.(V.) braziliensis transmission, studies were conducted to investigate DNApolymorphism in samples originating from three areas of Brazil (SaoPaulo, Turvo park and Santa Maria, RGS), and one sample reared inlaboratory, originating from Venezuela. The sudies were conducted usingrandom-amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). From ten decamer primers tested, only three were able todiscriminate between the samples. In the Brazilian samples, only constantfragments were obtained when compared with Venezuelan samples. Thisdifferentiation among the samples could be associated with geographicaldistribution or be may due to particular adaptive strategies related to thebiology of these species.