First detection of Leishmania infantum in dogs and wild-caught Culicoides oxystoma in Hainan Province, Southern China

Abstract Background Leishmaniases are neglected parasitic diseases expanding globally. In China, Leishmania infantum , endemic in the west, has reemerged and spread to the central part of the country, raising concerns about further potential expansion. Given limited data from southern China, this study investigated the presence of Leishmania spp. infection in dogs and potential vectors in Haikou, Hainan, China’s southernmost Province. Methods Blood, conjunctival swabs, and lymph node aspirates were collected from 52 dogs at two shelters, where an entomological survey using CDC light traps was also performed. Leishmania DNA was amplified by kDNA and ITS1 PCR. A commercial rapid test (SNAP® Leish 4Dx®; IDEXX, USA) and immunofluorescence antibody test (IFAT) were used to detect antibodies against L. infantum . Insects were morphologically and molecularly identified, and tested for Leishmania by ITS1 PCR and sequencing. Phylogenetic relationships were inferred using Maximum likelihood and neighbour-joining trees constructed in MEGA X. Results Overall, 4 of 52 samples (7.7%) were serologically (n = 3) or molecularly (n = 1, conjunctival swab by kDNA PCR) positive for Leishmania species. Two dogs were SNAP® positive, with one showing generalized lymphadenomegaly, and one was IFAT positive (1:160). No sand flies and 1568 Culicoides were captured. Leishmania DNA sequences (10 L. infantum , 1 L. tarentolae ) were detected in 11/224 non-engorged female Culicoides oxystoma and clustered within their corresponding phylogenetic clades. Conclusions This study provides the first evidence of L. infantum infection in dogs and biting midges from Hainan Province. Ongoing surveillance of competent vectors and dogs in this region is advocated.