Detection of Leishmania infantum and a Novel Phlebovirus (Balkan Virus) from Sand Flies in Albania

Neutralization-based seroprevalence of Toscana virus and sandfly fever Sicilian virus in dogs in the Republic of Kosovo

BACKGROUND

Phlebotomine sand flies are the key vectors for phleboviruses (order Hareavirales and family Phenuiviridae), of which some are associated with febrile diseases and nervous system infections. In the Mediterranean Basin, Toscana virus (TOSV; Phlebovirus toscanaense) and sandfly fever Sicilian viruses (SFSV; Phlebovirus siciliaense) are important human pathogens, and their endemicity has been known for decades, particularly in the Balkan countries. While the circulation of both viruses is highly evident among humans and livestock in the Central Balkan country Kosovo, data from companion animals are scarce; however, it might help to further assess the distribution of both viruses in the country.

METHODS

Sera of dogs from all seven districts of Kosovo were screened for TOSV and SFSV antibodies by seroneutralization assays.

RESULTS

Altogether, 45 of 288 (15.6%) samples showed anti-Phlebovirus antibodies, of which 36 (12.5%) were against TOSV, 11 (3.8%) were against SFSV, and 2 (0.7%) were positive for antibodies against both viruses.

CONCLUSIONS

Phlebovirus seroprevalence was observed in all seven districts of the country, generally being higher for TOSV compared with SFSV. Our study presents the first assessment of neutralization-based seroprevalence of two medically important phleboviruses among dogs in the Republic of Kosovo. Although healthy dogs are unsusceptible to Phlebovirus infection, dogs with leishmaniasis can be potential amplifying hosts. Given the high number of stray dogs, frequent uncontrolled spreading of phleboviruses in dogs, and potential spillover in populated regions of the country, these findings should be taken into consideration.

Comprehensive evaluation of nucleic acid amplification methods widely used for generic detection of sandfly-borne phleboviruses

Sandfly-borne phleboviruses (SBPs), which cause sandfly fever, aseptic meningitis, encephalitis, and meningoencephalitis, are emerging pathogens of major public health concern. Virus nucleic acid testing is essential for SBP diagnosis, especially in the early stages of infection, and for the discovery of novel SBPs. The efficacy of utilizing generic primers that target conserved nucleotide sequences for the detection of both known and novel SBPs has not been extensively evaluated. We aimed to compare and evaluate the performance of five generic primer sets, widely used to detect S- and L-segments of arthropod-borne phleboviruses and designed as singleplex (n = 3) and nested (n = 2) formats, including both well-known and recently characterized 15 Old World virus strains. Furthermore, we performed in silico analysis to assess the detection capabilities of these generic primer sets. The initial evaluation of previously published generic primer sets for SBP detection yielded two singleplex primer sets with the potential to be adapted for use in real-time or high-throughput detection settings. Studies are ongoing to develop and further optimize a preliminary assay and test various hosts and vectors to assess their capacity to detect known and novel viruses.

IMPORTANCE

Virus nucleic acid testing is the primary diagnostic method, particularly in the early stages of illness. Virus-specific or syndromic tests are widely used for this purpose. The use of generic primers has had a considerable impact on the discovery, identification, and detection of Old World sandfly-borne phleboviruses (OWSBP). The study is significant because it is the first to carry out a comparative evaluation of all published OWSBP generic primer sets.

First Detection and Molecular Analysis of Leishmania infantum DNA in Sand Flies of Kosovo

Phlebotomine sand flies (Diptera: Psychodidae) are the principal vectors of phleboviruses and Leishmania spp., the causative agents of leishmaniases. The Mediterranean sand fly fauna is diverse, and leishmaniasis, mainly caused by Leishmania infantum, is endemic in the Balkan countries. Despite recent entomological surveys, only some districts of Kosovo have been sampled for sand flies, with no proof/confirmation of L. infantum. This study aimed to gain further insights into the species composition of natural sand fly populations in previously unsampled districts and areas in Kosovo without reports of leishmaniasis and to detect Leishmania DNA in sand flies. A sand fly survey was conducted in 2022 in all seven districts of Kosovo. Collected females were screened for Leishmania DNA by PCR. Positive samples were sequenced and subjected to maximum likelihood analysis with reference sequences for further molecular characterization. The trapping activities at 114 different localities resulted in 3272 caught specimens, comprising seven sand fly species of two genera, namely Phlebotomus neglectus, Ph. perfiliewi, Ph. tobbi, Ph. papatasi, Ph. simici, Ph. balcanicus and Sergentomyia minuta. Leishmania infantum DNA was detected in three individual sand flies of Ph. neglectus and Ph. perfiliewi. This study provides the most extensive sand fly survey in Kosovo and reports the first record of L. infantum DNA in sand flies, indicating autochthonous circulation of L. infantum.

The estimated distribution of autochthonous leishmaniasis by Leishmania infantum in Europe in 2005-2020

BACKGROUND

This study describes the spatial and temporal distribution between 2005 and 2020 of human and animal leishmaniasis by Leishmania infantum in European countries reporting autochthonous cases, and highlights potential activities to improve disease control.

METHODOLOGY/PRINCIPAL FINDINGS

It was based on a review of the scientific literature and data reported by the World Health Organization (WHO), the World Organization for Animal Health (WOAH) and the Ministries of Health, including hospital discharges in some countries. Autochthonous infections were reported in the scientific literature from 22 countries, including 13 and 21 countries reporting human and animal infections, respectively. In contrast, only 17 countries reported autochthonous human leishmaniasis cases to the WHO and 8 countries animal infections to the WOAH. The number of WOAH reported cases were 4,203, comprising 4,183 canine cases and 20 cases in wildlife. Of 8,367 WHO reported human cases, 69% were visceral leishmaniasis cases-of which 94% were autochthonous-and 31% cutaneous leishmaniasis cases-of which 53% were imported and mostly in France. The resulting cumulative incidence per 100,000 population of visceral leishmaniasis between 2005-2020, was highest in Albania (2.15 cases), followed by Montenegro, Malta, Greece, Spain and North Macedonia (0.53-0.42), Italy (0.16), Portugal (0.09) and lower in other endemic countries (0.07-0.002). However, according to hospital discharges, the estimated human leishmaniasis incidence was 0.70 in Italy and visceral leishmaniasis incidences were 0.67 in Spain and 0.41 in Portugal.

CONCLUSIONS/SIGNIFICANCE

Overall, there was no evidence of widespread increased incidence of autochthonous human leishmaniasis by L. infantum in European countries. Visceral leishmaniasis incidence followed a decreasing trend in Albania, Italy and Portugal, and peaked in Greece in 2013, 2014 and 2017, and in Spain in 2006-2007 and 2011-2013. Animal and human cutaneous leishmaniasis remain highly underreported. In humans, hospital discharge databases provide the most accurate information on visceral leishmaniasis and may be a valuable indirect source of information to identify hotspots of animal leishmaniasis. Integrated leishmaniasis surveillance and reporting following the One Health approach, needs to be enhanced in order to improve disease control.

Endoplasmic Stress Affects the Coinfection of Leishmania Amazonensis and the Phlebovirus (Bunyaviridae) Icoaraci

Viral coinfections can modulate the severity of parasitic diseases, such as human cutaneous leishmaniasis. Leishmania parasites infect thousands of people worldwide and cause from single cutaneous self-healing lesions to massive mucosal destructive lesions. The transmission to vertebrates requires the bite of Phlebotomine sandflies, which can also transmit Phlebovirus. We have demonstrated that Leishmania infection requires and triggers the Endoplasmic stress (ER stress) response in infected macrophages. In the present paper, we tested the hypothesis that ER stress is increased and required for the aggravation of Leishmania infection due to coinfection with Phlebovirus. We demonstrated that Phlebovirus Icoaraci induces the ER stress program in macrophages mediated by the branches IRE/XBP1 and PERK/ATF4. The coinfection with L. amazonensis potentiates and sustains the ER stress, and the inhibition of IRE1α or PERK results in poor viral replication and decreased parasite load in macrophages. Importantly, we observed an increase in viral replication during the coinfection with Leishmania. Our results demonstrated the role of ER stress branches IRE1/XBP1 and PERK/ATF4 in the synergic effect on the Leishmania increased load during Phlebovirus coinfection and suggests that Leishmania infection can also increase the replication of Phlebovirus in macrophages.

Sandfly Fever Viruses Attenuate the Type I Interferon Response by Targeting the Phosphorylation of JAK-STAT Components

Sandfly fever viruses are emerging Phleboviruses typically causing mild febrile illness. Some strains, however, can cause severe and occasionally fatal neuro-invasive disease. Like most viruses, Phleboviruses have devised various strategies to inhibit the type I interferon (IFN) response to support a productive infection. Still, most of the strategies identified so far focus on inhibiting the sensing arm of the IFN response. In contrast, the effect of sandfly virus infection on signaling from the IFN receptor is less characterized. Therefore, we tested the effect of sandfly fever virus Naples (SFNV) and Sicily (SFSV) infection on IFN signaling. We found that infection with either of these viruses inhibits signaling from the IFN receptor by inhibiting STAT1 phosphorylation and nuclear localization. We show that the viral nonstructural protein NSs mediates these effects, but only NSs from SFNV was found to interact with STAT1 directly. Thus, we tested the upstream IFN signaling components and found that Janus kinase 1 (Jak1) phosphorylation is also impaired by infection.

Furthermore, the NSs proteins from both viruses directly interacted with Jak1. Last, we show that IFN inhibition by SFNV and SFSV is most likely downstream of the IFN receptor at the Jak1 level. Overall, our results reveal the multiple strategies used by these related viruses to overcome host defenses.

Phlebotomine sand flies (Diptera: Psychodidae) of the Maghreb region: A systematic review of distribution, morphology, and role in the transmission of the pathogens

BACKGROUND

Phlebotomine sand flies (Diptera: Psychodidae) are important vectors of various human and animal pathogens such as Bartonella bacilliformis, Phlebovirus, and parasitic protozoa of the genus Leishmania, causative agent of leishmaniases that account among most significant vector-borne diseases. The Maghreb countries Mauritania, Morocco, Algeria, Tunisia, and Libya occupy a vast area of North Africa and belong to most affected regions by these diseases. Locally varying climatic and ecological conditions support diverse sand fly fauna that includes many proven or suspected vectors. The aim of this review is to summarize often fragmented information and to provide an updated list of sand fly species of the Maghreb region with illustration of species-specific morphological features and maps of their reported distribution.

MATERIALS AND METHODS

The literature search focused on scholar databases to review information on the sand fly species distribution and their role in the disease transmissions in Mauritania, Morocco, Algeria, Tunisia, and Libya, surveying sources from the period between 1900 and 2020. Reported distribution of each species was collated using Google Earth, and distribution maps were drawn using ArcGIS software. Morphological illustrations were compiled from various published sources.

RESULTS AND CONCLUSIONS

In total, 32 species of the genera Phlebotomus (Ph.) and Sergentomyia (Se.) were reported in the Maghreb region (15 from Libya, 18 from Tunisia, 23 from Morocco, 24 from Algeria, and 9 from Mauritania). Phlebotomus mariae and Se. africana subsp. asiatica were recorded only in Morocco, Ph. mascitti, Se. hirtus, and Se. tiberiadis only in Algeria, whereas Ph. duboscqi, Se. dubia, Se. africana africana, Se. lesleyae, Se. magna, and Se. freetownensis were reported only from Mauritania. Our review has updated and summarized the geographic distribution of 26 species reported so far in Morocco, Algeria, Tunisia, and Libya, excluding Mauritania from a detailed analysis due to the unavailability of accurate distribution data. In addition, morphological differences important for species identification are summarized with particular attention to closely related species such as Ph. papatasi and Ph. bergeroti, Ph. chabaudi, and Ph. riouxi, and Se. christophersi and Se. clydei.

NSs of the mildly virulent sandfly fever Sicilian virus is unable to inhibit interferon signaling and upregulation of interferon-stimulated genes

Phleboviruses (order Bunyavirales, family Phenuiviridae) are globally emerging arboviruses with a wide spectrum of virulence. Sandfly fever Sicilian virus (SFSV) is one of the most ubiquitous members of the genus Phlebovirus and associated with a self-limited, incapacitating febrile disease in travellers and military troops. The phleboviral NSs protein is an established virulence factor, acting as antagonist of the antiviral interferon (IFN) system. Consistently, we previously reported that SFSV NSs targets the induction of IFN mRNA synthesis by specifically binding to the DNA-binding domain of the IFN transcription factor IRF3. Here, we further characterized the effect of SFSV and its NSs towards IFN induction, and evaluated its potential to affect the downstream IFN-stimulated signalling and the subsequent transactivation of antiviral interferon-stimulated genes (ISGs). We found that SFSV dampened, but did not entirely abolish type I and type III IFN induction. Furthermore, SFSV NSs did not affect IFN signalling, resulting in substantial ISG expression in infected cells. Hence, although SFSV targets IRF3 to reduce IFN induction, it is not capable of entirely disarming the IFN system in the presence of high basal IRF3 and/or IRF7 levels, and we speculate that this significantly contributes to its low level of virulence.

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.

Leishmania spp. seropositivity in Austrian soldiers returning from the Kosovo

Leishmaniasis is a severe vector-borne disease with two main clinical forms, visceral leishmaniasis and cutaneous leishmaniasis. Both forms of leishmaniasis are also endemic in Mediterranean countries including the Balkan region from where mainly visceral leishmaniasis is reported. Austrian soldiers returning from Kosovo were screened for anti-Leishmania antibodies to assess the risk of infection during operations. Anti-Leishmania antibodies were detected in more than 20% of the soldiers investigated, which indicates a considerable risk of infection during missions in this area and thus suggests the application of protective measures.

Detection of a Novel Phlebovirus (Drin Virus) from Sand Flies in Albania

Phlebotomine sand flies are generalist vectors with significant implications for public health. They are able to transmit phleboviruses that cause sand fly fever, headaches, or meningitis in humans. Albania is a country in Southeast Europe with a typical Mediterranean climate which provides convenient conditions for the presence of sand flies. Hence, the circulation of phleboviruses, such as the Toscana and Balkan viruses, has been recently described in the country. We followed a virus discovery approach on sand fly samples collected in 2015 and 2016 in seven regions of Albania, with the aim to investigate and characterize potentially circulating phleboviruses in phlebotomine sand flies. A presumed novel phlebovirus was detected in a pool consisting of 24 Phlebotomus neglectus males. The virus was provisionally named the Drin virus after a river near the locality of Kukës, where the infected sand flies were trapped. Genetic and phylogenetic analysis revealed that the Drin virus is closely related to the Corfou (CFUV) virus, isolated in the 1980s from Phlebotomus major sand flies on the eponymous island of Greece, and may also be involved in human infections because of its similarity to the sand fly fever Sicilian virus. The latter justifies further studies to specifically address this concern. Together with recent findings, this study confirms that Albania and the Balkan peninsula are hot spots for phleboviruses.

Real-time PCR applications for diagnosis of leishmaniasis

Leishmaniasis is a vector-borne disease caused by many Leishmania species, which can infect both humans and other mammals. Leishmaniasis is a complex disease, with heterogeneous clinical manifestations ranging from asymptomatic infections to lesions at cutaneous sites (cutaneous leishmaniasis), mucosal sites (mucocutaneous leishmaniasis) or in visceral organs (visceral leishmaniasis), depending on the species and host characteristics. Often, symptoms are inconclusive and leishmaniasis can be confused with other co-endemic diseases. Moreover, co-infections (mainly with HIV in humans) can produce atypical clinical presentations. A correct diagnosis is crucial to apply the appropriate treatment and the use of molecular techniques in diagnosis of leishmaniasis has become increasingly relevant due to their remarkable sensitivity, specificity and possible application to a variety of clinical samples. Among them, real-time PCR (qPCR)-based approaches have become increasingly popular in the last years not only for detection and quantification of Leishmania species but also for species identification. However, despite qPCR-based methods having proven to be very effective in the diagnosis of leishmaniasis, a standardized method does not exist. This review summarizes the qPCR-based methods in the diagnosis of leishmaniasis focusing on the recent developments and applications in this field.

High Rates of Neutralizing Antibodies to Toscana and Sandfly Fever Sicilian Viruses in Livestock, Kosovo

Toscana and sandfly fever Sicilian viruses (TOSV and SFSV, respectively), both transmitted by sand flies, are prominent human pathogens in the Old World. Of 1,086 serum samples collected from cattle and sheep during 2013 in various regions of Kosovo (Balkan Peninsula), 4.7% and 53.4% had neutralizing antibodies against TOSV and SFSV, respectively.

Direct evidence for an expanded circulation area of the recently identified Balkan virus (Sandfly fever Naples virus species) in several countries of the Balkan archipelago

Background

Recently, Balkan virus (BALKV, family Phenuiviridae, genus Phlebovirus) was discovered in sand flies collected in Albania and genetically characterised as a member of the Sandfly fever Naples species complex. To gain knowledge concerning the geographical area where exposure to BALKV exists, entomological surveys were conducted in 2014 and 2015, in Croatia, Bosnia and Herzegovina (BH), Kosovo, Republic of Macedonia and Serbia.

Results

A total of 2830 sand flies were trapped during 2014 and 2015 campaigns, and organised as 263 pools. BALKV RNA was detected in four pools from Croatia and in one pool from BH. Phylogenetic relationships were examined using sequences in the S and L RNA segments. Study of the diversity between BALKV sequences from Albania, Croatia and BH showed that Albanian sequences were the most divergent (9–11% [NP]) from the others and that Croatian and BH sequences were grouped (0.9–5.4% [NP]; 0.7–5% [L]). The sand fly infection rate of BALKV was 0.26% in BH and 0.27% in Croatia. Identification of the species content of pools using cox1 and cytb partial regions showed that the five BALKV positive pools contained Phlebotomus neglectus DNA; in four pools, P neglectus was the unique species, whereas P. tobbi DNA was also detected in one pool.

Conclusions

We report here (i) the first direct evidence that the Balkan virus initially described in coastal Albania has a much wider dissemination area than originally believed, (ii) two real-time RT-PCR assays that may be useful for further screening of patients presenting with fever of unknown origin that may be caused by Balkan virus infection, (iii) entomological results suggesting that Balkan virus is likely transmitted by Phlebotomus neglectus, and possibly other sand fly species of the subgenus Larroussius. So far, BALKV has been detected only in sand flies. Whether BALKV can cause disease in humans is unknown and remains to be investigated.

Of phlebotomines (sandflies) and viruses: a comprehensive perspective on a complex situation

Old World sandfly-borne phleboviruses are classified into three serological complexes: Sandfly fever Sicilian, Sandfly fever Naples and Salehabad. Human pathogens (febrile illness ['sandfly fever'], neuroinvasive infections) belong to the two first complexes. The increasing number of newly discovered sandfly-borne phleboviruses raises concerns about their medical and veterinary importance. They occupy a wide geographic area from Mediterranean basin to North Africa and the Middle East to the central Asia. At least nine species of sandflies can transmit these viruses. Recent results suggest that sandfly vectors are not as specific for viruses as initially believed. Recent seroprevalence studies demonstrate that humans and domestic animals are heavily exposed. Specific molecular diagnostic methods must be developed and implemented in clinical microbiology laboratories.

Surveillance of Arthropod-Borne Viruses and Their Vectors in the Mediterranean and Black Sea Regions Within the MediLabSecure Network

PURPOSE OF REVIEW

Arboviruses, viruses transmitted by arthropods such as mosquitoes, ticks, sandflies, and fleas are a significant threat to public health because of their epidemic and zoonotic potential. The geographical distribution of mosquito-borne diseases such as West Nile (WN), Rift Valley fever (RVF), Dengue, Chikungunya, and Zika has expanded over the last decades. Countries of the Mediterranean and Black Sea regions are not spared. Outbreaks of WN are repeatedly reported in the Mediterranean basin. Human cases of RVF were reported at the southern borders of the Maghreb region. For this reason, establishing the basis for the research to understand the potential for the future emergence of these and other arboviruses and their expansion into new geographic areas became a public health priority. In this context, the European network "MediLabSecure" gathering laboratories in 19 non-EU countries from the Mediterranean and Black Sea regions seeks to improve the surveillance (of animals, humans, and vectors) by reinforcing capacity building and harmonizing national surveillance systems to address this important human and veterinary health issue. The aim of this review is to give an exhaustive overview of arboviruses and their vectors in the region.

RECENT FINDINGS

The data presented underline the importance of surveillance in the implementation of more adapted control strategies to combat vector-borne diseases. Partner laboratories within the MediLabSecure network present a wide range of infrastructures and have benefited from different training programs.

SUMMARY

Although reporting of arboviral presence is not carried out in a systematic manner, the expansion of the area where arboviruses are present cannot be disputed. This reinforces the need for increasing surveillance capacity building in this region to prevent future emergences.