Phleboviruses detection in Phlebotomus perniciosus from a human leishmaniasis focus in South-West Madrid region, Spain

Cluster Analysis of Factors Associated with Leishmaniasis in Peru

OBJECTIVE

To analyze the factors associated with leishmaniasis in Peru, according to the cluster classification in the period 2017-2021.

METHODS

Quantitative approach, with an ecological, descriptive correlational, and cross-sectional design. The population was from the geographical region of Peru, where a total of 26,956 cases of leishmaniasis were registered by the Peruvian Ministry of Health from 2017 to 2021. Spearman's Rho statistic was used to analyze the variables that are most associated with the cases of leishmaniasis reported per year, and, in addition, the multivariate technique of cluster analysis was applied.

RESULTS

Annual rainfall and areas with humid forest (climatic factors) and mortality from transmissible diseases (health factor) are directly associated with reported cases of leishmaniasis. Households with basic access to infrastructure, drinking water, drainage, and electric lighting; illiteracy, regional social progress, and unsatisfied basic needs (social factors); and percentage of urban population (demographic factor) are inversely and significantly associated with cases of leishmaniasis.

CONCLUSIONS

Climatic and environmental factors contribute to the multiplication of the leishmaniasis disease vector. The incidence of leishmaniasis adds up to the mortality rates for transmissible diseases in Peru. As living conditions improve, the incidence of this pathology decreases.

The Role of the Leishmania infantum Infected Dogs as a Potential Reservoir Host for Toscana Virus in a Zoonotic Visceral Leishmaniasis Focus of Northern Tunisia

The role of dogs as reservoir hosts for Toscana virus (TOSV) remains undetermined. This study investigated TOSV and Leishmania infantum infections in one healthy and three infected dogs with Leishmania (A, B, C) following natural exposition to sandfly bites in a focus of zoonotic visceral leishmaniasis (ZVL) located in Northern Tunisia from June to October 2020. At the end of the exposition period, infected and healthy dogs were examined for TOSV and L. infantum infections by xenodiagnosis using a colony of Phlebotomus perniciosus. Pools of freshly engorged P. perniciosus at days 0 and those at days 7 post-feeding were screened for TOSV and L. infantum by nested PCR in the polymerase gene and kinetoplast minicircle DNA, respectively. In the exposure site, P. pernicious is the most abundant sandfly species. The infection rates of sandflies with TOSV and L. infantum were 0.10 and 0.05%, respectively. Leishmania infantum DNA and TOSV RNA were detected in P. perniciosus females fed on dog B and C, respectively. The isolation of TOSV in Vero cells was achieved from two pools containing P. perniciosus fed on dog C. No pathogens were detected in P. perniciosus females fed on dog A and on control dog. We report for the first time the reservoir competence of dog with ZVL in the transmission of TOSV to sandfly vectors in natural settings, in addition to its role as a main reservoir host of L. infantum.

High rates of antibodies against Toscana and Sicilian phleboviruses in common quail Coturnix coturnix birds

Introduction

Birds are involved natural cycle of a number of vector-borne viruses in both rural and urban areas. Toscana (TOSV) and Sicilian (SFSV) phleboviruses are sandfly-borne viruses in the genus Phlebovirus that can cause diseases in human. However, there is limited information on the role of the birds in sandfly-borne phleboviruses natural cycle and reservoirs ofthese viruses remain unknown.

Methods

In this study, we analyzed Common Quail (Coturnix coturnix) sera from Spain to identify the seroprevalence of these two phleboviruses. We tested respectively, 106 and 110 quail serum against TOSV and SFSV from 2018, 2019, and 2021 from two locations in northern Spain with using virus neutralization test.

Results

We identified high neutralizing antibody rates for SFSV (45.45%) and TOSV (42.45%) with yearly fluctuation.

Discussion

This is the first identification of SFSV and TOSV neutralizing antibodies in wild birds. High seroprevalence rates of TOSV and SFSV in quail birds raises the question whether birds have a role as amplifying hosts in the natural cycle of phleboviruses.

Phlebotomine sand flies (Diptera, Psychodidae) from Spain: an updated checklist and extended distributions

Phlebotomine sand flies (Diptera: Psychodidae) are the natural vectors of Leishmania spp. (Kinetoplastida: Trypanosomatidae) and phleboviruses (Bunyavirales: Phenuiviridae). In Spain, these vectors appear to be increasing their geographical distribution and have serious repercussions on public and veterinary health, encouraging studies of sand flies and their associated pathogens. An up-to-date and easily accessible compendium of current and historical data on their presence and detailed distribution is a crucial step towards the development and implementation of appropriate preventive strategies. A checklist on the presence and distribution of sand flies in Spain is compiled from data extracted from a comprehensive review of scientific literature published between 1909 and 2021 and our new records on the presence of sand flies specimens collected under the entomological surveillance of bluetongue vectors from the Spanish Ministry of Agriculture, Fishery and Food (MAPA) during the period 2004-2021. In total, 13 Spanish species of sand flies (two of them with controversial status) belonging to two genera and six subgenera are presented in this updated checklist, including new distribution data for seven species, among which several stand out as confirmed or suspected vectors of Leishmaniainfantum: Phlebotomusariasi, Ph.langeroni, Ph.mascittii, and Ph.perniciosus.

Density assessment and reporting for Phlebotomus perniciosus and other sand fly species in periurban residential estates in Spain

Green periurban residential areas in Mediterranean countries have flourished in the last decades and become foci for leishmaniasis. To remedy the absence of information on vector ecology in these environments, we examined phlebotomine sand fly distribution in 29 sites in Murcia City over a 3-year period, including the plots of 20 detached houses and nine non-urbanized sites nearby. We collected 5,066 specimens from five species using "sticky" interception and light attraction traps. The relative frequency of the main Leishmania infantum vector Phlebotomus perniciosus in these traps was 32% and 63%, respectively. Sand fly density was widely variable spatially and temporally and greatest in non-urbanized sites, particularly in caves and abandoned buildings close to domestic animal holdings. Phlebotomus perniciosus density in house plots was positively correlated with those in non-urbanized sites, greatest in larger properties with extensive vegetation and non-permanently lived, but not associated to dog presence or a history of canine leishmaniasis. Within house plots, sand fly density was highest in traps closest to walls. Furthermore, the study provides a guideline for insect density assessment and reporting and is envisioned as a building block towards the development of a pan-European database for robust investigation of environmental determinants of sand fly distribution.

Phlebovirus-associated diseases transmitted by phlebotominae in Spain: Are we at risk?

The genera Phlebovirus transmitted by Diptera belonging to the Psychodidae family are a cause of self-limited febrile syndrome in the Mediterranean basin in summer and autumn. Toscana virus can also cause meningitis and meningoencephalitis. In Spain, Toscana, Granada, Naples, Sicily, Arbia and Arrabida-like viruses have been detected. The almost widespread distribution of Phlebotomus genus vectors, and especially Phlebotomus perniciosus, in which several of these viruses have been detected, makes it very likely that there will be regular human infections in our country, with this risk considered moderate for Toscana virus and low for the other ones, in areas with the highest vector activity. Most of the infections would be undiagnosed, while only Toscana virus would have a greater impact due to the potential severity of the illness.

Clinically Important Phleboviruses and Their Detection in Human Samples

The detection of phleboviruses (family: Phenuiviridae) in human samples is challenged by the overall diversity and genetic complexity of clinically relevant strains, their predominantly nondescript clinical associations, and a related lack of awareness among some clinicians and laboratorians. Here, we seek to inform the detection of human phlebovirus infections by providing a brief introduction to clinically relevant phleboviruses, as well as key targets and approaches for their detection. Given the diversity of pathogens within the genus, this report focuses on diagnostic attributes that are generally shared among these agents and should be used as a complement to, rather than a replacement of, more detailed discussions on the detection of phleboviruses at the individual virus level.

Real-time RT-PCR assay to detect Granada virus and the related Massilia and Arrabida phleboviruses

BACKGROUND

Granada virus belongs to the genus Phlebovirus within the Naples serocomplex and was detected for the first time in sand flies from Spain in 2003. Seroprevalence studies have revealed that Granada virus may infect humans with most cases being asymptomatic. Moreover, recent studies in vector samples revealed that the related Massilia and Arrabida phleboviruses could be also circulating in Spain. The objective of this study was to develop and assess a new sensitive real-time RT-PCR assay for Granada virus diagnosis able to detect the related phleboviruses Massilia and Arrabida.

METHODS

Two specific primers and one unique probe to detect Granada, Massilia and Arrabida viruses, without differentiating between them, were designed targeting the conserved L-segment of their genome. Sensitivity was assessed using 10-fold serial dilutions of quantified in vitro DNA samples. Specificity was evaluated by testing different genomic RNA extracted from other representative phleboviruses. The new assay was used for virus detection in sand flies collected in 2012 from the Balearic Archipelago, a touristic hotspot in the Mediterranean.

RESULTS

The real-time RT-PCR assay exhibited a sensitivity per reaction of 19 copies for Granada and Arrabida, and 16 copies for Massilia. No other related phleboviruses were detected. From the 37 pools of sand fly samples studied from four different Balearic Islands, we detected one positive in the island of Cabrera.

CONCLUSIONS

To our knowledge, the method described here is the first real-time RT-PCR designed to detect Granada virus and the related Massilia and Arrabida phleboviruses. The study demonstrated that this is a rapid, robust and reliable assay for the accurate diagnosis of human infections as well as for virus surveillance in vectors.

Phlebovirus-associated diseases transmitted by phlebotominae in Spain: Are we at risk?

The genera Phlebovirus transmitted by Diptera belonging to the Psychodidae family are a cause of self-limited febrile syndrome in the Mediterranean basin in summer and autumn. Toscana virus can also cause meningitis and meningoencephalitis. In Spain, Toscana, Granada, Naples, Sicily, Arbia and Arrabida-like viruses have been detected. The almost widespread distribution of Phlebotomus genus vectors, and especially Phlebotomus perniciosus, in which several of these viruses have been detected, makes it very likely that there will be regular human infections in our country, with this risk considered moderate for Toscana virus and low for the other ones, in areas with the highest vector activity. Most of the infections would be undiagnosed, while only Toscana virus would have a greater impact due to the potential severity of the illness.

Phlebotomine sand flies in Southwest Germany: an update with records in new locations

Background

Vector-borne diseases (VBD) are of growing global importance. Sand flies are potential vectors for phleboviruses (family Phenuiviridae) including Toscana virus (TOSV), Sicilian virus, Sandfly fever, Naples virus, and Leishmania parasites in Europe. To date, only two phlebotomine species have been recorded for Germany: Phlebotomus perniciosus and Phlebotomus mascittii. This study updates the distribution and abundance of the two occurring species.

Methods

An entomological field study was carried out during 2015–2018 to assess the abundance of sand flies in Southwest Germany within the federal states Baden-Wuerttemberg (BW) and Rhineland-Palatinate (RLP). A total of 176 collection sites were examined using CDC light traps.

Results

A total of 149 individuals of P. mascittii were collected. During 2015–2018, P. mascittii was found at all sites known positive from previous studies and was detected at 15 additional sites previously unknown for the presence of sand flies. Although the environment has changed considerably in 30 years, no significant difference in sand fly dynamics and distribution was found. Phlebotomus perniciosus has only been trapped once since 2001.

Conclusions

This study showed that sand flies occur in different areas in Southern Germany where they had not been recorded previously. Therefore, it can be assumed that they are more widespread than expected. In addition, sand flies could be found over several years at the same trapping sites, indicating population stability. This supports the need for continued surveillance of possible vector populations and urgent clarification of the vector competence of P. mascittii.

Co-circulation of Toscana virus and Leishmania infantum in a focus of zoonotic visceral leishmaniasis from Central Tunisia

In the Mediterranean basin, sand flies are vectors of Leishmania parasites and phleboviruses affecting humans and animals. In this study, we aimed to investigate phlebovirus and Leishmania parasites circulating in a focus of zoonotic visceral leishmaniasis (ZVL) located in a highly irrigated area within the arid Central Tunisia, known mainly to be endemic for zoonotic cutaenous leishmaniasis (ZCL) caused Leishmania major and transmitted by Phlebotomus papatasi. Sand flies were collected using CDC light traps in the village of Saddaguia, an emergent focus of ZVL located in Central Tunisia during September-October 2014, 2015, and 2016. Pools of live female sand flies were screened for phleboviruses and Leishmania by nested PCR in the polymerase gene and kinetoplast minicircle DNA, respectively. Dead sand flies were identified morphologically to species level. Sand flies of the subgenus Larroussius mainly Phlebotomus perfiliewi, Phlebotomus perniciosus, and Phlebotomus longicuspis were predominant in this ZVL focus compared to P. papatasi. A total of 1932, 1740, and 444 sand flies were tested in 2014, 2015 and 2016, respectively. Pathogen screening performed on 4116 sand flies distributed in 148 pools revealed the presence of Leishmania infantum and Toscana virus. The minimum infection rates of sand flies with TOSV in 2014, 2015, and 2016 were 0.05%, 011%, and 0.22%, respectively. The minimum infection rates of sand flies with L. infantum in 2014, 2015, and 2016 were 0.25%, 012%, and 0.79%, respectively. No L. major was detected during the 3-years investigation in this ZVL focus. Our results showed clearly the endemic co-circulation of TOSV and L. infantum in this emergent ZVL focus. However, no co-infection of TOSV and L. infantum was detected in any of the sand fly pools investigated during the three years period. TOSV was isolated from positive pools in 2015. Phylogenetic analysis showed that the Tunisian strains of TOSV belonged to the sublineage A. Based on the present findings, our results provided strong evidence that TOSV and L. infantum are transmitted by the same predominant sand fly species of the subgenus Larroussius, and subsequently, humans and dogs could be co-infected through co-infected or successive infected bites. Our results showed clearly that the development of irrigation in arid areas contributed significantly to the establishment of stable transmission cycles of L. infantum and TOSV and subsequently to the emergence of a ZVL focus within this arid bio-geographical area characterized by the presence of multiple foci of ZCL located outside the study site. Thus, more studies are needed to better understand the impact of RNA viruses shared by vectors and reservoir hosts of L. infantum on the development of zoonotic visceral leishmaniasis.

Broader Geographical Distribution of Toscana Virus in the Mediterranean Region Suggests the Existence of Larger Varieties of Sand Fly Vectors

Toscana virus (TOSV) is endemic in the Mediterranean basin, where it is transmitted by sand flies. TOSV can infect humans and cause febrile illness as well as neuroinvasive infections affecting the central and peripheral nervous systems. Although TOSV is a significant human pathogen, it remains neglected and there are consequently many gaps of knowledge. Recent seroepidemiology studies and case reports showed that TOSV’s geographic distribution is much wider than was assumed a decade ago. The apparent extension of the TOSV circulation area raises the question of the sandfly species that are able to transmit the virus in natural conditions. Phlebotomus (Ph.)perniciosus and Ph. perfiliewi were historically identified as competent species. Recent results suggest that other species of sand flies could be competent for TOSV maintenance and transmission. Here we organize current knowledge in entomology, epidemiology, and virology supporting the possible existence of additional phlebotomine species such as Ph. longicuspis, Ph. sergenti, Ph. tobbi, Ph. neglectus, and Sergentomyia minuta in TOSV maintenance. We also highlight some of the knowledge gaps to be addressed in future studies.

The small non-coding RNA response to virus infection in the Leishmania vector Lutzomyia longipalpis

Sandflies are well known vectors for Leishmania but also transmit a number of arthropod-borne viruses (arboviruses). Few studies have addressed the interaction between sandflies and arboviruses. RNA interference (RNAi) mechanisms utilize small non-coding RNAs to regulate different aspects of host-pathogen interactions. The small interfering RNA (siRNA) pathway is a broad antiviral mechanism in insects. In addition, at least in mosquitoes, another RNAi mechanism mediated by PIWI interacting RNAs (piRNAs) is activated by viral infection. Finally, endogenous microRNAs (miRNA) may also regulate host immune responses. Here, we analyzed the small non-coding RNA response to Vesicular stomatitis virus (VSV) infection in the sandfly Lutzoymia longipalpis. We detected abundant production of virus-derived siRNAs after VSV infection in adult sandflies. However, there was no production of virus-derived piRNAs and only mild changes in the expression of vector miRNAs in response to infection. We also observed abundant production of virus-derived siRNAs against two other viruses in Lutzomyia Lulo cells. Together, our results suggest that the siRNA but not the piRNA pathway mediates an antiviral response in sandflies. In agreement with this hypothesis, pre-treatment of cells with dsRNA against VSV was able to inhibit viral replication while knock-down of the central siRNA component, Argonaute-2, led to increased virus levels. Our work begins to elucidate the role of RNAi mechanisms in the interaction between L. longipalpis and viruses and should also open the way for studies with other sandfly-borne pathogens.

Sandflies are important insect vectors that transmit many species of Leishmania, bacteria and viruses. We know very little about how this insect vector responds to viral infection. RNA interference (RNAi) utilizes small non-coding RNAs to regulate different aspects of animal physiology, including immune responses. Small interfering RNAs (siRNAs) mediate a major antiviral response in insects. Virus-derived PIWI-interacting RNAs (piRNAs) can also be generated during infection, at least in some insects. Finally, endogenous microRNAs (miRNA) can regulate the host response to infection. Here we show that virus infection triggers activation of the siRNA pathway but not production of piRNAs in the sandfly Lutzomyia longipalpis. Furthermore, activation or inhibition of the siRNA pathway had a direct effect on viral replication. We also show that virus infection caused mild changes to the expression of endogenous miRNAs. Our work describes for the first time a model to study virus infection in sandflies and highlights the importance of the siRNA pathway for the control of virus infection in L. longipalpis. The framework described here can be used to explore other aspects of the vector-pathogen interactions.

Practical Guidelines for Studies on Sandfly-Borne Phleboviruses: Part II: Important Points to Consider for Fieldwork and Subsequent Virological Screening

In this series of review articles entitled "Practical guidelines for studies on sandfly-borne phleboviruses," the important points to be considered at the prefieldwork stage were addressed in part I, including parameters to be taken into account to define the geographic area for sand fly trapping and how to organize field collections. Here in part II, the following points have been addressed: (1) factors influencing the efficacy of trapping and the different types of traps with their respective advantages and drawbacks, (2) how to process the trapped sand flies in the field, and (3) how to process the sand flies in the virology laboratory. These chapters provide the necessary information for adopting the most appropriate procedures depending on the requirements of the study. In addition, practical information gathered through years of experience of translational projects is included to help newcomers to fieldwork studies.