Entomological study in an anthroponotic cutaneous leishmaniasis focus in Morocco: Fauna survey, Leishmania infection screening, molecular characterization and MALDI-TOF MS protein profiling of relevant Phlebotomus species

Entomological, parasitological and molecular investigations in a new focus of cutaneous leishmaniasis in Youssoufia region, Morocco

BACKGROUND AND AIMS

Leishmaniasis is a neglected tropical infection caused by Leishmania parasite that affect human and animal. In Morocco, the cutaneous leishmaniasis has spread substantially to the new areas. The surveillance limited to active foci may underestimate the occurrence of cutaneous leishmaniasis (CL). This study aims to investigate the local transmission of CL in rural districts of Youssoufia province, central Morocco, as a potential focus of CL.

METHODS

For this purpose, parasitological, molecular and entomological investigations were carried out in this area. Data collection concerns potential vectors and human cases. Thus, 402 patients were examined for suspected leishmaniasis lesions in three localities of the province of Youssoufia. In these same localities, 983 sand flies were collected by CDC light traps and sticky paper during one-night per month during 6 months. These sand flies were all identified morphologically using the Moroccan identification key.

RESULTS

The results showed that among the 25 skin lesions detected in a population of 402 individuals, 18 were confirmed by kDNA nested PCR as CL positive patients, of which only 25% were positive by direct examination. Leishmania tropica and Leishmania major were identified as causative agents of CL in the study area. Direct parasitological examination showed a low sensitivity (27.78%), especially for L. major, although its specificity was evaluated at 100%. Regarding entomological results, both genera of the Moroccan sand fly were collected in the study area: Genus/Phlebotomus (75.28%) and Sergentomyia (24.72%). Phlebotomus (P) papatasi, the proven vector of L. major, was the most abundant species (33.98%), followed by Paralongicollum sergenti (22.58%), the confirmed vector of L. tropica; while Sergentomyia (S) minuta, P. longicuspis, S. fallax and P. kazeruni were collected with, respectively, 17.60%, 16.99%, 7.12% and 1.73%.

CONCLUSION

This study constitutes the first report of CL in the study areas, as well as the coexistence of L. tropica and L. major in these rural localities. Local transmission of CL is highly probable, as indicated by the prevalence of the two proven vectors of L. major and L. tropica. To control the spread of this disease, our results suggest the use of highly sensitive molecular methods to detect CL cases in potential leishmaniasis foci, which will improve surveillance.

Investigating the role of Sterol C24-Methyl transferase mutation on drug resistance in leishmaniasis and identifying potential inhibitors

Leishmaniasis is a fatal disease caused by the leishmania parasite. For the survival of the leishmania parasite, Sterol C24-Methyl Transferase (SMT) is essential which is an enzyme of the ergosterol pathway. SMT protein mutation is responsible for Amphotericin-B drug resistance in Leishmania, which is the main treatment for visceral leishmaniasis. Amphotericin-B resistance is caused by three mutated residues V131I, V321I and F72C. The underlying mechanisms and structural changes in SMT enzymes responsible for resistance due to mutation are still not well understood. In the current study, the potential mechanism of resistance due to these mutations and the structure variation of wild and mutant SMT proteins were investigated through molecular dynamics simulations and molecular docking analysis. The results showed that AmB established strong bonding interaction with wild SMT as compare to mutants SMT. The binding energy calculation showed that binding energy of AmB with mutants SMT increases as compare to the wild SMT. Further structural based virtual screening was carried out to design potential inhibitors for the mutant SMT. On the basis of structural-based virtual screening four inhibitors (SANC01057, SANC00882, SANC00414, SANC01047) were computationally identified as potential mutant SMT (F72C) inhibitors. This work provides valuable information for improved management of drug resistant Leishmaniasis.Communicated by Ramaswamy H. Sarma.

A Review of Historical Phlebotominae Taxonomy (Diptera: Psychodidae)

Psychodidae is a group constituted by ca. 3400 species distributed in six existing and one extinct subfamily. Among them, Phlebotominae is of relevant medical and veterinary interest as vectors of pathogens, such as viruses, bacteria, and trypanosomatides, to vertebrates. The taxonomy of Phlebotominae, begun in 1786, received a great boost at the beginning of the twentieth century, when some of its species began to be implicated as vectors of leishmaniasis agents. Currently, the group consists of 1060 species/subspecies described for both hemispheres. Its taxonomy and systematics have been largely based on the morphological characters of adults in view of the limited number of species known in their immature forms, as well as by molecular approaches. This review focuses on the evolution of the phlebotomine systematics, with information regarding when the descriptions of the sand fly species/subspecies occurred, where their type localities are, the number of authors involved in their descriptions, and the researchers who have most contributed to the description of these taxa and their respective institutions. The morphological characters of adult forms used in the taxonomy of groups, in an evolutionary approach, and the current state of knowledge based on immature forms is also presented.

MALDI-TOF MS Limits for the Identification of Mediterranean Sandflies of the Subgenus Larroussius, with a Special Focus on the Phlebotomus perniciosus Complex

Leishmania infantum is the agent of visceral leishmaniasis in the Mediterranean basin. It is transmitted by sandflies of the subgenus Larroussius. Although Phlebotomus perniciosus is the most important vector in this area, an atypical Ph. perniciosus easily confused with Ph. longicuspis has been observed in North Africa. MALDI-TOF MS, an important tool for vector identification, has recently been applied for the identification of sandflies. Spectral databases presented in the literature, however, include only a limited number of Larroussius species. Our objective was to create an in-house database to identify Mediterranean sandflies and to evaluate the ability of MALDI-TOF MS to discriminate close species or atypical forms within the Larroussius subgenus. Field-caught specimens (n = 94) were identified morphologically as typical Ph. perniciosus (PN; n = 55), atypical Ph. perniciosus (PNA; n = 9), Ph. longicuspis (n = 9), Ph. ariasi (n = 9), Ph. mascittii (n = 3), Ph. neglectus (n = 5), Ph. perfiliewi (n = 1), Ph. similis (n = 9) and Ph. papatasi (n = 2). Identifications were confirmed by sequencing of the mtDNA CytB region and sixteen specimens were included in the in-house database. Blind assessment on 73 specimens (representing 1073 good quality spectra) showed a good agreement (98.5%) between MALDI-TOF MS and molecular identification. Discrepancies concerned confusions between Ph. perfiliewi and Ph. perniciosus. Hierarchical clustering did not allow classification of PN and PNA. The use of machine learning, however, allowed discernment between PN and PNA and between the lcus and lcx haplotypes of Ph. longicuspis (accuracy: 0.8938 with partial-least-square regression and random forest models). MALDI-TOF MS is a promising tool for the rapid and accurate identification of field-caught sandflies. The use of machine learning could allow to discriminate similar species.

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.

Transmission patterns of Leishmania tropica around the Mediterranean basin: Could Morocco be impacted by a zoonotic spillover?

Cutaneous leishmaniasis (CL) due to Leishmania tropica is a neglected tropical disease characterized by a wide geographical distribution in the Mediterranean basin and is endemic in several of its countries. In addition, the vector Phlebotomus sergenti is abundantly present all around the basin. Its transmission cycle is still subject to debate. In some countries, the presence of an animal reservoir has been confirmed. In Morocco, CL due to L. tropica has risen since the 1980s and has spread widely to become the most abundant form of leishmaniasis in the territory. However, the anthroponotic transmission is so far the only recognized mode, despite recordings of L. tropica infection in animal hosts. In this review article, we assess the situation of CL due to L. tropica in the Mediterranean basin with a focus on Morocco and gather knowledge about any potential zoonotic transmission in the country. A concomitant zoonotic transmission could explain the persistence of the disease in areas where human protective measures combined with vector management did not help reduce the disease burden.

Cutaneous leishmaniasis (CL) due to Leishmania tropica is a neglected tropical disease still considered to be anthroponotic in Morocco despite evidence of zoonotic transmission in other endemic countries of the Mediterranean basin. Its high incidence in the country makes it necessary to investigate whether or not a potential concomitant zoonotic transmission exists alongside the anthroponotic one. Moreover, several reports of natural animal infection have been noted in the country. In this paper, we review how CL due to L. tropica is present around the Mediterranean basin, with a particular focus on the Moroccan foci, and try to unveil the existence of a zoonotic transmission in the area. A deep understanding of the transmission patterns of L. tropica in the region is necessary for the implementation of effective control measures and a better assessment of the disease burden. In addition, the complexity of this neglected disease requires more fundamental and applied research to unveil potential factors involved in its spread.

Intra and peridomiciliary comparison of density, sex ratio and gonotrophic stage of Phlebotomus sergenti in an active anthroponotic cutaneous leishmaniasis focus in Morocco

Cutaneous leishmaniasis due to Leishmania tropica represents a major public health problem due to its ability to spread into non-endemic areas by means of its vectors, and the associated dramatic psychosocial impact. The objective of this work was to compare the intra and extradomiciliary density, sex ratio and gonotrophic stage of sand flies from a recent active focus in Morocco. This field study is based on the need to optimize the effectiveness of control programs. Two different capture methods, CDC light traps and sticky traps, were used at two different times of the year, corresponding with the peaks of sand fly abundance. 7,815 sand flies were captured and classified into 13 species belonging to genera Sergentomyia (50.8%) and Phlebotomus (49.2%). Phlebotomus sergenti was the most abundant and frequent species of the genus Phlebotomus both inside (49.3%) and outside houses (52.1%) and it showed the highest density in extradomiciliary captures in June. The proportion of blood-fed females was similar indoors and outdoors (21.5% and 26.3%, respectively). Females in the three gonotrophic stages were found in 26% houses and this was significantly associated with some factors related to housing conditions. Therefore, P. sergenti seems well adapted to both indoors and outdoors biotopes where these females coexist with males. These findings suggest that the adoption of additional measures could benefit the strategy of the Moroccan health authorities, currently consisting of indoor insecticide spraying, given that transmission may also occur outdoors.