Epidemiological survey of Lutzomyia longipalpis infected by Leishmania infantum in an endemic area of Brazil

Abstract

The objective of this study was to perform an epidemiological survey to determine the areas at risk of visceral leishmaniasis through the detection and quantification of natural infection by Leishmania infantum in Lutzomyia longipalpis. The sandflies were captured between February 2009 and January 2010, at 21 sites in four regions of the Fortaleza municipality. Samples were screened for the presence of Leishmania DNA by Real Time PCR (qPCR), amplification of kDNA minicircle sequence. Out of the 123 pools of analyzed sandflies, 45 were positive for L.infantum, and the minimum infection rate was 3.7%. In the north, south, east and west regions, the pool screen assay predicted sand-fly infection prevalence of 3.4%, 4.7%, 4.9% and 8.4%, respectively. The parasite load ranged from 2.45 ± 0.96 to 2,820,246 ± 106,072. No statistical differences were found with respect to the frequency of sand-fly infection between the regions (P=0.3014), seasons (P = 0.3906) or trap locations (P = 0.8486). Statistical differences were found with respect to the frequency of sand-fly infection between the two seasons only in the west region (P=0.0152). The qPCR was able to detect and quantify L. infantum in L. longipalpis, therefore succeeding in identifying the areas of greatest risk of VL transmission.Keywords: Leishmania infantum, Lutzomyia longipalpis, minimum infection rate, qPCR. ResumoO objetivo foi realizar um estudo epidemiológico para determinar as áreas de risco de transmissão de leishmaniose visceral pela detecção e quantificação de infecções naturais por Leishmania infantum em Lutzomyia longipalpis. As coletas foram realizadas entre fevereiro de 2009 e janeiro de 2010 em 21 locais, distribuídos em quatro regiões do município de Fortaleza. As amostras foram testadas quanto à presença de DNA de Leishmania por PCR em tempo real (qPCR). Dos 123 pools de flebotomíneos investigados, 45 foram positivos para L. infantum, e a taxa de infecção mínima foi de 3,7%. Nas regiões Norte, Sul, Leste e Oeste, a prevalência de flebotomíneos infectados foi de 3,4%, 4,7%, 4,9% e 8,4%, respectivamente. A carga de parasitas nos pools variou de 2,45 ± 0,96 a 2.820.246 ± 106.072. Não foram observadas diferenças significativas na frequência de flebotomíneos infectados entre as regiões (P = 0,3014), estação do ano (P = 0,3906) ou localização da armadilha (P = 0,8486). Foram observadas diferenças significativas na frequência de flebotomíneos somente na região oeste durante a estação chuvosa (P = 0,0152). A qPCR foi capaz de detectar e quantificar L. infantum em L. longipalpis, identificando as áreas de maior risco de transmissão de leishmaniose visceral.Palavras-chave: Leishmania infantum, Lutzomyia longipalpis, taxa de infecção mínima, qPCR.

Multiplex qPCR assay to determine Leishmania infantum load in Lutzomyia longipalpis sandfly samples

“…None of the qPCR assay standardizations present in the literature have evaluated small L. longipalpis samples such as an individual midgut (Ranasinghe et al, 2008; Bezerra‐Vasconcelos et al, 2011; Cunha et al, 2014). Several studies detecting Leishmania parasites in sandfly samples have used an extra reaction promoting the usage of more sample material, which is scarce in cases where DNA has been extracted from only one sandfly (Rodrigues et al, 2016; de Sousa Ferreira et al, 2018). For a multiplex reaction approach, some studies have used sandfly constitutive genes such as cacophony, periodicity and also VATP (Rodrigues et al, 2014; Araujo‐Pereira et al, 2020).…”

Contribution to the Knowledgment of Feeding Habbits of Lutzomyia (Lutzomyia) Longipalpis (Lutz & Neiva, 1912) in Association to Natural Infection by Leishmania (Leishmania) Infantum Chagasi (Cunha & Chagas, 1937)

“…When parasite load analyses are performed on phlebotomines, one should consider the possibility that parasitic load may be different in each infected female, and the level of individual infection may interfere with the total pool load. Thus, if a sample showed a high parasitic load, this may be due to one or more infected phlebotomines [64]. In Camaçari (Salvador) was performed a compared study in diferents periods of captures from L. longipalpis, the results of parasite load was low and did not vary regardless of the season, despite the number of collected sand ies [65].…”

Visceral Leishmaniasis and Natural Infection Rates of Leishmania in Lutzomyia longipalpis in Latin America

“…However, molecular methods have the dis-advantage of not being able to distinguish between viable and dead parasites [81]. To access the genetic material of the parasite, DNA/RNA is extracted generally using a pool of about 10 female phlebotomine sandflies [82,83].…”

“…longipalpis) responsible for VL [82,[89][90][91]. Besides that, qPCR combines the identification of genetic material with the quantification of parasites present in the phlebotomine, which is important for VL transmission and the establishment of infection [83].…”