Modeling Spatial Distribution of Sergentomyia minuta (Diptera: Psychodidae) and Its Potential Implication in Leishmaniasis Transmission in Morocco

Effect of high-volume insecticide spraying on sand fly vectors in household gardens in Spain

This study investigated the efficacy of high-volume spraying with the adulticide α-cypermethrin alone and in combination with the larvicide diflubenzuron on the density of sand flies in gardens of three detached households in periurban areas in southeast Spain. Treatments were applied four times between June and August 2016, and four nearby sites, two households and two non-urbanized sites, were untreated controls. The number of sand flies collected between May and October 2016 using sticky interception and light attraction traps, was 4446 specimens. Species identified morphologically included Sergentomyia minuta (n = 2101; 48%), Phlebotomus perniciosus (n = 1922; 44%), Phlebotomus papatasi (n = 173; 4%), Phlebotomus sergenti (n = 161; 4%) and Phlebotomus ariasi (n = 36; 1%). Sand flies were detected in both treated and untreated sites. The proportion of positive sticky traps and the median (range) density of sand flies in positive traps were 61% traps and 7 (2-172) sand flies/m2 /day in untreated sites, and 43% traps and 4 (1-56) sand flies/m2 /day in treated sites (p < 0.05). Similarly, for light traps, it was 96% traps and 30 (3-168) flies/trap/day, and 83% traps and 3 (1-12) sand flies/trap/day, respectively (p < 0.05). However, sand fly density followed a comparable seasonal pattern in untreated and treated sites and did not consistently decrease following insecticide applications. These results were confirmed with mixed negative binomial modelling of sand fly density adjusted for time since application, month, environmental setting and site. The limited efficacy of the treatments, added to their cost, the impact of insecticides on non-target organisms and human health, and the risk of development of insecticide resistance, should dissuade similar outdoor applications to control sand fly vector populations in residential areas.

Taxonomic and Ecological Interaction of Leishmaniasis Vectors (Diptera: Psychodidae) in Sefrou Province (Middle Atlas Morocco)

An entomological survey was carried out in the locality of Aichoune to conduct a study on sand flies, species composition, and monthly relative abundance. This study is essential for the implementation of integrated vector management control. Insects collection was carried out twice a month from January 2013 to December 2014 by means of adhesive and CDC-type light traps. A total of 5441 sand flies were collected with the predominance of males (a sex ratio = 1.89). The sampled specimens consist of seven species divided into two genera: Phlebotomus (99.55%) and Sergentomyia (0.44%). Phlebotomus sergenti was the dominant species with an average annual proportion of 47.38%, followed by P. perniciosus (37.32%), P. longicuspis (8,56%), P. papatasi (6.23%), and P. ariasi (0.05%). The genus Sergentomyia was less common (0.44%). S.minuta was represented only by 0.36% and S. fallax by 0.07%. The species dynamics showed a unimodal evolution for P. sergenti and P. papatasi. They were active from May to October. P. perniciosus presents a trimodal trend showing the most relevant peak in August. The highest number of specimens was collected in June, when the temperature reaches an annual average value of 25.5°C. The obtained results will help us better understand the leishmaniasis transmission dynamics in the Aichoune locality and will contribute to the design of a surveillance strategy.

Climate Change Influences on the Potential Distribution of the Sand Fly Phlebotomus sergenti, Vector of Leishmania tropica in Morocco

BACKGROUND

Leishmaniases are a vector-borne disease, re-emerging in several regions of the world posing a burden on public health. As other vector-borne diseases, climate change is a crucial factor affecting the evolution of leishmaniasis. In Morocco, anthroponotic cutaneous leishmaniasis (ACL) is widespread geographically as many foci across the country, mainly in central Morocco. The objective of this study is to evaluate the potential impacts of climate change on the distribution of ACL due to Leishmania tropica, and its corresponding vector Phlebotomus sergenti in Morocco.

METHODS

Using Ecological Niche Modeling (ENM) tool, the estimated geographical range shift of L. tropica and P. sergenti by 2050 was projected under two Representative's Concentration's Pathways (RCPs) to be 2.6 and RCP 8.5 respectively. P. sergenti records were obtained from field collections of the laboratory team and previously published entomological observations, while, epidemiological data for L. tropica were obtained from Moroccan Ministry of Health reports.

RESULTS

Our models under present-day conditions indicated a probable expansion for L. tropica as well as for its vector in Morocco, P. sergenti. It showed a concentrated distribution in the west-central and northern area of Morocco. Future predictions anticipate expansion into areas not identified as suitable for P. sergenti under present conditions, particularly in northern and southeastern areas of Morocco. L. tropica is also expected to have high expansion in southern areas for the next 30 years in Morocco.

CONCLUSION

This indicates that L. tropica and P. sergenti will continue to find suitable climate conditions in the future. A higher abundance of P. sergenti may indeed result in a higher transmission risk of ACL. This information is essential in developing a control plan for ACL in Morocco. However, future investigations on L. tropica reservoirs are needed to confirm our predictions.

Leishmania spp. in Squamata reptiles from the Mediterranean basin

Leishmania tarentolae is a non-pathogenic trypanosomatid species isolated from geckoes in the Mediterranean basin. In Italy, L. tarentolae and Leishmania infantum occur in sympatry in areas where canine leishmaniosis (CanL) is endemic. Here, we investigated the prevalence and distribution of L. tarentolae in reptilian hosts, and the presence of L. infantum in these hosts in southern Italy. From April 2020 to April 2021, lizards and snakes were captured in urban, peri-urban sites, natural parks and dog shelters. Blood was individually sampled and assessed for the presence of Leishmania spp. by cytology and/or molecular biology. Captured lizards were euthanized and their tissues/organs were tested by duplex real-time-PCR for the detection of L. infantum and L. tarentolae and the positive ones were amplified by conventional PCR to confirm the species identification by sequencing. Samples were also screened by real-time-PCR for L. infantum kDNA minicircle. Of the 259 collected Squamata reptiles, 34 (13.1%) specimens scored positive for Leishmania spp., with a prevalence of 10% for L. tarentolae (n = 26) and of 3.1% for L. infantum (n = 8). Positive lizards were mostly Podarcis siculus (n = 26) from dog shelters, with six specimens positive for L. infantum. In addition, L. tarentolae was detected in one Podarcis filfolensis lizard, and in five T. mauritanica geckos (with one gecko and P. filfolensis lizard showing amastigote-like forms in thrombocytes), whereas L. infantum was detected in one T. mauritanica, and one Hemidactylus turcicus. Saurian reptiles living in CanL endemic areas of the Mediterranean basin may be exposed to both L. tarentolae and L. infantum indicating a sympatric circulation of these species in different vertebrate hosts. Moreover, this study represents the first molecular evidence of L. infantum infection in European reptiles. This article is protected by copyright. All rights reserved.

Detection of Leishmania tarentolae in lizards, sand flies and dogs in southern Italy, where Leishmania infantum is endemic: hindrances and opportunities

Background

Leishmania tarentolae is a protozoan isolated from geckoes (Tarentola annularis, Tarentola mauritanica), which is considered non-pathogenic and is transmitted by herpetophilic Sergentomyia spp. sand flies. This species occurs in sympatry with Leishmania infantum in areas where canine leishmaniasis is endemic. In the present study, we investigated the circulation of L. tarentolae and L. infantum in sand flies, dogs and lizards in a dog shelter in southern Italy, where canine leishmaniasis by L. infantum is endemic.

Methods

Sheltered dogs (n = 100) negative for Leishmania spp. (March 2020) were screened by immunofluorescence antibody test (IFAT) using promastigotes of both species at two time points (June 2020 and March 2021). Whole blood from dogs, tissues of Podarcis siculus lizards (n = 28) and sand flies (n = 2306) were also sampled and tested by a duplex real-time PCR (dqPCR). Host blood meal was assessed in sand flies by PCR.

Results

Overall, 16 dogs became positive for L. infantum and/or L. tarentolae by IFAT at one or both sampling periods. One canine blood sample was positive for L. infantum, whilst two for L. tarentolae by dqPCR. At the cytology of lizard blood, Leishmania spp. amastigote-like forms were detected in erythrocytes. Twenty-two tissue samples, mostly lung (21.4%), scored molecularly positive for L. tarentolae, corresponding to 10 lizards (i.e., 35.7%). Of the female Sergentomyia minuta sampled (n = 1252), 158 scored positive for L. tarentolae, four for L. infantum, and one co-infected. Two Phlebotomus perniciosus (out of 29 females) were positive for L. tarentolae. Engorged S. minuta (n = 10) fed on humans, and one P. perniciosus, positive for L. tarentolae, on lagomorphs.

Conclusions

Dogs and lacertid lizards (Podarcis siculus) were herein found for the first time infected by L. tarentolae. The detection of both L. tarentolae and L. infantum in S. minuta and P. perniciosus suggests their sympatric circulation, with a potential overlap in vertebrate hosts. The interactions between L. tarentolae and L. infantum should be further investigated in both vectors and vertebrate hosts to understand the potential implications for the diagnosis and control of canine leishmaniasis in endemic areas.

Graphical abstract

Diversity of Necrophagous Flies (Diptera: Calliphoridae, Mesembrinellidae, and Sarcophagidae) in Anthropogenic and Preserved Environments of Five Different Phytophysiognomies in Northeastern Brazil

The present study investigated the potential association between the richness and abundance of species of the dipteran families Calliphoridae, Mesembrinellidae, and Sarcophagidae in anthropogenic and preserved environments of five phytophysiognomies (Cerrado, Amazon forest, Palm forest, marshland, and mangrove) that occur throughout the state of Maranhão, in northeastern Brazil. We sampled 90 sites (45 preserved and 45 anthropogenic areas) where we collected 26,036 specimens: 15,023 calliphorids (11 species), 231 mesembrinellids (one species), and 10,772 sarcophagids (52 species). Four environmental factors, canopy openness, temperature, leaf litter depth, and vegetation height, contributed most to the separation of preserved and anthropogenic sites in all five phytophysiognomies. Leaf litter depth was positively associated with the species richness of the calliphorids and mesembrinellids (C+ M group), while tree/shrub density, vegetation height, and temperature were associated negatively with the richness of the sarcophagids. Tree/shrub density and vegetation height were also associated negatively with abundance in both C+M and sarcophagid species. Overall, then, the structural characteristics of the environment affected the species richness and abundance, and deforestation may favor certain synanthropic species, leading to a decrease in the richness and abundance of the species that are adapted to preserved environments.