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

Abstract

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.

Keywords: Canine leishmaniasis; IFAT; Leishmania infantum; Leishmania tarentolae; Reptiles; Sergentomyia minuta; Zoonosis; dqPCR.

Fig. 1

Dog shelter characteristics, and sand fly and lizard capture in a canine leishmaniasis-endemic area. a Lizard near the dog households (red arrow). b Sticky trap placement on the surrounding muretti a secco. c Lizard near the sticky traps (red arrow). d Podarcis siculus lizard

Fig. 2

IFAT and cultured promastigotes of Leishmania infantum and Leishmania tarentolae. a IFAT using as antigen promastigotes of L. infantum (zymodeme MON-1). b IFAT using as antigen promastigotes of L. tarentolae (strain RTAR/IT/81/ISS21-G.6c). c Cultured promastigotes of L. infantum (zymodeme MON-1). d Promastigotes of L. tarentolae (strain RTAR/IT/81/ISS21-G.6c)

Fig. 3

Leishmania tarentolae forms in blood from Podarcis siculus lizard. a Amastigote-like forms associated to erythrocyte (red arrow). b Promastigote-like form (red arrow). Scale bar 10 µm

Fig. 4

Phylogenetic tree based on Leishmania ITS1 sequences inferred using the maximum likelihood method based on the Kimura 2-parameter model. Bootstrap values (> 50%) are shown near the nodes. Trypanosoma brucei is used as outgroups. Scale bar indicates nucleotide substitution per site. Leishmania spp. sequenced in this study are in bold. Silhouettes represent human, dog, lizard, Sergentomyia minuta sand fly and cultured promastigotes of Leishmania infantum and Leishmania tarentolae