Leishmania (Leishmania) infantum and Leishmania (Sauroleishmania) tarentolae in outdoor cats and report of infection in feline-derived peripheral blood mononuclear cells.

Background: Feline leishmaniosis (FeL) is mainly caused by Leishmania infantum in the Mediterranean Basin. In Italy, in the same epidemiological context where canine leishmaniosis (CanL) is hyperendemic, a nonpathogenic species, Leishmania tarentolae, may also occur in sympatry, infecting reptiles, dogs, and humans. Thus, this study aimed to assess L. tarentolae infection in outdoor cats along with its co-occurrence with L. infantum and to evaluate risk factors. In addition, the persistence of L. tarentolae in feline-derived peripheral blood mononuclear cells (PBMCs) was herein evaluated in vitro.

Methods: Outdoor colony or stray cats were screened for Leishmania spp. by immunofluorescence antibody test (IFAT) using promastigotes of both L. infantum and L. tarentolae. Whole blood and buffy coat were tested by a real-time polymerase chain reaction (qPCR) and duplex real-time PCR (dqPCR), and positive samples sequenced following an ITS1 conventional PCR (cPCR). Feline-derived PMBCs were subsequently infected with promastigotes of L. tarentolae to assess the persistence of amastigotes. Viral infections caused by feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) were molecularly addressed in all enrolled cats. Statistical analysis was performed to evaluate the possible association between Leishmania spp. infection and FIV/FeLV infection by using a multivariate logistic regression model following an initial LASSO-penalized logistic regression.

Results: Overall, 42 out of 194 cats (21.6%) were serologically or molecularly positive for Leishmania spp. In particular, 26 (13.4%) cats were seropositive for L. infantum and/or L. tarentolae by IFAT, with 16 (8.2%) animals positive for both species. Molecularly, 14 out of 194 cats (7.2%) were positive for L. infantum by qPCR, whereas five (2.6%) were positive for L. tarentolae by dqPCR. Cat PBMCs were successfully infected with L. tarentolae, and the infection persisted for at least 72 h. Overall, 38 out of the 194 screened cats (19.6%) were infected by FIV and/or FeLV, of which 12 were serologically or molecularly positive for Leishmania spp., with one cat positive for L. tarentolae DNA, and five for L. infantum DNA. Multivariate screening identified municipality (OR 2.206; P = 0.031; 95% CI 1.077-4.516) as a risk factor for Leishmania spp. infection, while the association between Leishmania spp. and FIV infection was not significant (OR 2.359; P = 0.08, 95% CI 0.901-6.179).

Conclusions: Colony or stray cats were herein found for the first time infected by L. tarentolae, in areas where L. infantum is endemic. Cross-reactivity using IFAT test may pose a diagnostic hindrance also in FeL. The infection with this saurian-associated Leishmania in cats was further confirmed through the persistence of this Leishmania in cat PBMCs. Further studies are needed to fully unravel the complex interactions between both species of Leishmania and the implication of the sympatric occurrence of both species in the diagnosis and control of leishmaniosis.