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.

Temperature is a common climatic descriptor of lachryphagous activity period in Phortica variegata (Diptera: Drosophilidae) from multiple geographical locations.

BACKGROUND: The drosophilid Phortica variegata is known as vector of Thelazia callipaeda, the oriental eyeworm native to Asia that has become an emergent zoonotic agent in several European regions. Unlike almost all other arthropod vectors of pathogens, only P. variegata males feed of lachrymal secretions of animals, ingesting first-stage larvae (L1) of the worm living in the orbital cavities of the host, and allowing with the same behaviour the introduction of infective L3. Despite the increased detection of T. callipaeda in many European countries, information about the length of the lachryphagous activity period of P. variegata and a deep knowledge of the environmental and climatic variables involved are still limited. METHODS: We herein present the results of a multicentre study involving five sites from four different countries (Italy, Spain, UK and USA) where canine thelaziosis is endemic and/or where it has already been ascertained the presence of P. variegata. Field data have been obtained on a fortnightly basis from mid-April to the end of November 2018 from a contemporary standardized sampling (same sampling effort and time of collection in all sites) of lachryphagous flies collected around the eyes of a human bait using an entomological net. These data have been associated to data collection of local climatic variables (day length, temperature, wind speed, barometric pressure and relative humidity). RESULTS: Overall, a total of 4862 P. variegata flies (4637 males and 224 females) were collected, with high differences in densities among the different sampling sites. Significant positive correlations were found between P. variegata male density and temperature and wind speed, while negative correlations were observed for barometric pressure and relative humidity. However, the above significant differences are confirmed in each sampling site separately only for the temperature. CONCLUSIONS: This multicentre study highlights that temperature is the major common environmental driver in describing the lachryphagous activity of P. variegata in Europe and USA and, therefore, the transmission risk of thelaziosis.

Comparative efficacy of afoxolaner and ivermectin in dogs naturally infested with Rhipicephalus sanguineus sensu lato: A clinical field study conducted in Thailand.

Afoxolaner is a novel insecticidal and acaricidal of the isoxazoline family, which is used in veterinary practice to control infestation of dogs by fleas, ticks, and mites (NexGard, Boehringer Ingelheim). Ivermectin is an avermectin administered at microdoses to prevent infection of dogs with Dirofilaria immitis and is used off-label to control Rhipicephalus sanguineus infestation of dogs in numerous countries, including Thailand. Here we conducted two trials to assess the efficacy of afoxolaner for treating natural R. sanguineus sensu lato (s.l.) infestations of dogs residing in the Chiang Mai area of Thailand. The first trial compared the efficacies of afoxolaner and ivermectin in dogs infested with <500 ticks. A randomized, investigator-blinded, controlled study was conducted of 16 dogs, allocated into the groups as follows: afoxolaner (2.7-6.9 mg/kg, PO, group 1; n = 8), ivermectin (300 µg/kg, SC, group 2; n = 5), untreated (group 3; n = 3). Tick counts and drug administration were performed on days 0, 28, and 56. Mean numbers of ticks on day 0 in groups 1, 2, and 3 were not significantly different (225, 169, and 123, respectively; p = .36). The mean number of ticks (%efficacy to control) in groups 1, 2 and 3 on day 28 were 7 (97.05%), 230 (2.95%), and 237, respectively; on day 56 were 4 (96.11%), 93 (9.71%), and 103, respectively; and on day 84 were 1 (98.65%), 44 (40.54%), and 74, respectively. The efficacy of afoxolaner was >96%, whereas the efficacy of ivermectin was significantly lower compared with that of afoxolaner (p < .05) and never achieved the 90% efficacy threshold claimed by registration agencies. The second trial assessed the efficacy of afoxolaner for treating dogs with heavy tick infestations (>500 ticks/dog), including four dogs from two households. The dogs were treated monthly with Afoxolaner. The mean values of the numbers of ticks on dogs in the 2 households were not significantly different (913 and 800 on day 0, p = .18). The numbers of ticks significantly decreased thereafter, and the efficacy of afoxolaner was >99% on days 28, 56, and 84. Adverse reactions were not observed in either trial. In conclusion, this study confirms the efficacy of afoxolaner against adult R. sanguineus s.l. that naturally infests dogs that inhabit Thailand.