Entomological Studies in Itaúna, Brazil, an Area With Visceral Leishmaniasis Transmission: Fauna Survey, Natural Leishmania Infection, and Molecular Characterization of the Species Circulating in Phlebotomine Sand Flies (Diptera: Psychodidae)

Abstract

Among neglected tropical diseases, visceral leishmaniasis (VL) shows great relevance in global terms and is a serious public health concern due to the possibility of severe and lethal forms in humans. In this study, we evaluate entomological factors such as diversity and abundance of phlebotomine sand flies (Diptera:Psychodidae) and the Leishmania species circulating in these species in possible association with VL transmission in the Brazilian town Itaúna. The entomological collections were performed during three consecutive nights, always in the third week of each month, within a period of 12 mo. A total of 1,786 sand fly specimens were collected, from which 20% were collected inside houses. The influence of three local climatic variables (temperature, rainfall, relative humidity) on the population sizes of these insects was evaluated. Temperature was the most influential factor, with a significant positive correlation with the local population size of phlebotomine sand flies collected per month. Lutzomyia longipalpis (Lutz & Neiva, 1912) was the predominant species in the study area. Leishmania DNA was detected in nine out of 133 pools of sand fly females, using nested/PCR, which resulted in a minimal natural infection rate of 2.91%. DNA from Leishmania infantum Nicolle, 1908 (Kinetoplastida: Trypanosomatida), was detected in Evandromyia cortelezzii (Bréthes, 1923), Ev. evandroi (Costa, Lima & Antunes, 1936), Ev. lenti (Mangabeira, 1938), and Ev. termitophila (Martins, Falcão & Silva, 1964), besides Lu. longipalpis. Our study indicates favorable conditions for VL spreading in Itaúna due to the presence of Lu. longipalpis and Le. infantum-infected phlebotomine sand flies.

Canine visceral leishmaniasis in area with recent Leishmania transmission: prevalence, diagnosis, and molecular identification of the infecting species

“…Although our study was restricted to selected neighborhoods, it was possible to confirm favorable conditions for the spread of human VL in Itaúna, such as the concomitant or close presence of a high population of L. longipalpis, L. infantum-infected L. longipalpis, or L. infantum-infected dogs 11 . In a recent ecological study on phlebotomine sand flies 45 , the predominance of L. longipalpis among flies captured in Itaúna was confirmed.…”

“…DNA sequencing was performed using the BigDye ® Terminator v3.1 Cycle kit and an ABI 3730 automated DNA sequencing platform (Applied Biosytems) of Instituto René Rachou. Sequencing conditions are described elsewhere 11 . The consensus nucleotide sequence for each sample was aligned and compared to L. braziliensis (M80292.1), L. amazonensis (M80293.1), and L. infantum (M81430.1); the sequences were deposited in the GenBank ® database.…”

“…Numbers of human VL cases since the first report in 2007 were kindly provided by the Municipal Health Department of Itaúna with respective georeferenced coordinates. L. longipalpis and Leishmania-infected L. longipalpis data were also represented to provide a panorama of VL concerning parasites, vectors, and domestic reservoirs 11 . The R software package was used for map locations 19 .…”

“…CVL prevalence per neighborhood was distributed into ranges as follows: < 50, 50-99, ≧ 100 ( Figure 2). In an attempt to paint a more complete scenario of urban VL in the city, collection sites of L. longipalpis specimens and Leishmania-infected L. longipalpis (April 2015 to March 2016) 11 , as well as all human VL cases reported since 2007, are also shown in the figure.…”

“…In the last few years, however, public health officials from the local Zoonoses Control Center (ZCC) noticed an increase in the number of CVL-positive dogs submitted for serological testing by owners concerned about their dog’s health, termed ‘spontaneous owner’s demand’ (SOD). In a previous study we evaluated parasite-vector relationships through a phlebotomine sand fly survey in Itaúna 11 , due to the lack of local epidemiological data regarding the parasite-vector-reservoir triad involved in the VL transmission cycle. In the present study, we focused on the domestic reservoir, aiming to: a) perform a canine census survey in selected neighborhoods of Itaúna; b) determine the prevalence of CVL in selected neighborhoods using current serological diagnostic tests; c) confirm the presence of Leishmania in seropositive dogs using parasitological and molecular-based methods; and d) identify the infecting Leishmania species in seropositive dogs.…”