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Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

ABSTRACT: Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longipalpis population and to elucidate the influence of bioclimatic factors on the monthly fluctuations of this vector. HP light traps were monthly set in the intradomicile and peridomicile of residences located in the central and beachfront areas of Camaçari, a VL endemic area. The sand fly collection was conducted in two periods: i) period 1-between December 2011 and November 2012 and ii) period 2-August 2014 and July 2015. Sand fly species were identified and detection of L. infantum infection by qPCR was performed in pools of female Lu. longipalpis. For the first time, the parasite load of positive pools was correlated with the number of Lu. longipalpis captured per month in both periods. Correlation analyses between the monthly fluctuation of the sand fly population and bioclimatic indices of the municipality in both collection periods were also performed. In both evaluated periods, more than 98% of the collected sand flies were Lu. longipalpis, confirming the predominance of this species in the region. It was captured mostly in the beachfront area in all months evaluated (99%). For the period 1, Leishmania DNA was detected in 81% of tested pools representing a minimal infection rate of 9.6%. In the period 2, 40% of the pools were positive with a minimal infection rate of 10.2%. Infected sand flies were only detected in the beachfront area in both periods. The parasite load was low and did not vary in the evaluated months despite the number of collected sand flies. No correlation was observed for climatic factors in both areas of Camaçari. These findings emphasize the high risk of Leishmania transmission in Camaçari regardless of the season and that other factors, aside from bioclimatic elements, are influencing the sand fly population monthly fluctuation.

SUBMITTER: Mota TF

PROVIDER: S-EPMC6730935 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

Mota Tiago Feitosa TF de Sousa Orlando Marcos Farias OMF Silva Yuri de Jesus YJ Borja Lairton Souza LS Leite Bruna Martins Macedo BMM Solcà Manuela da Silva MDS de Melo Djalma Alves DA Brodskyn Claudia Ida CI Dias Edelberto Santos ES Veras Patrícia Sampaio Tavares PST Fraga Deborah Bittencourt Mothé DBM

PLoS neglected tropical diseases 20190826 8

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longi ...[more]

PMID: 31449534

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Project description:Leishmania is transmitted by female sand flies and deposited together with saliva, which contains a vast repertoire of pharmacologically active molecules that contribute to the establishment of the infection. The exposure to vector saliva induces an immune response against its components that can be used as a marker of exposure to the vector. Performing large-scale serological studies to detect vector exposure has been limited by the difficulty in obtaining sand fly saliva. Here, we validate the use of two sand fly salivary recombinant proteins as markers for vector exposure.ELISA was used to screen human sera, collected in an area endemic for visceral leishmaniasis, against the salivary gland sonicate (SGS) or two recombinant proteins (rLJM11 and rLJM17) from Lutzomyia longipalpis saliva. Antibody levels before and after SGS seroconversion (n = 26) were compared using the Wilcoxon signed rank paired test. Human sera from an area endemic for VL which recognize Lu. longipalpis saliva in ELISA also recognize a combination of rLJM17 and rLJM11. We then extended the analysis to include 40 sera from individuals who were seropositive and 40 seronegative to Lu. longipalpis SGS. Each recombinant protein was able to detect anti-saliva seroconversion, whereas the two proteins combined increased the detection significantly. Additionally, we evaluated the specificity of the anti-Lu. longipalpis response by testing 40 sera positive to Lutzomyia intermedia SGS, and very limited (2/40) cross-reactivity was observed. Receiver-operator characteristics (ROC) curve analysis was used to identify the effectiveness of these proteins for the prediction of anti-SGS positivity. These ROC curves evidenced the superior performance of rLJM17+rLJM11. Predicted threshold levels were confirmed for rLJM17+rLJM11 using a large panel of 1,077 serum samples.Our results show the possibility of substituting Lu. longipalpis SGS for two recombinant proteins, LJM17 and LJM11, in order to probe for vector exposure in individuals residing in endemic areas.

Project description:BACKGROUND:Visceral leishmaniasis (VL) is an infectious disease with a variety of clinical signs. The main form of parasite transmission to humans and other mammalian hosts is through the bite of infected arthropod females with Lutzomyia longipalpis serving as the main vector in the Americas. Dogs are the main urban domestic reservoirs of the parasite and the main source of vector infection due to their high prevalence in endemic areas and the large number of parasites in the skin of infected animals. Although miltefosine has been used in Europe since 2002 for treatment of VL infected dogs, in the Americas the treatment of dogs has not been recommended. Therefore, this study aimed to evaluate efficacy of miltefosine observing a reduction of clinical signs in infected dogs and the infectiveness to the vector by Leishmania (L.) infantum. METHODS:To our knowledge, this is the first controlled study using qPCR and xenodiagnosis to evaluate the efficacy of miltefosine (Milteforan®, Virbac) as a single treatment in Brazil. Thirty-five adult dogs with canine visceral leishmaniasis (CVL), confirmed by clinical and laboratory tests, were included in this study. They received miltefosine at a dose of 2 mg/kg every 24 h for 28 days. The dogs were observed over a three-month period, during which clinical evaluations based on a scoring system were conducted at pre-established times. Parasite load was assessed by cytology and real-time polymerase chain reaction (qPCR). Transmissibility to the vector was evaluated by xenodiagnosis. RESULTS:At the end of the period, the following were observed: (i) the remission of clinical signs with a reduction in clinical scores for 94.2% of the animals; (ii) a statistically significant reduction (98.7%) in parasitic load by qPCR; and (iii) a reduction in infectivity to sand flies. After treatment, 74.2% of the animals remained or had become non-infectious. CONCLUSIONS:Our study indicates that the use of miltefosine administered orally for 4 weeks contributes to a clinical improvement and reduction in infectivity of dogs to L. infantum.

Dataset Information

Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

Publications

Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

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