Thelaziosis in central Italy. Molecular detection of a variant haplotype in a human case and epidemiological aspects

Thelazia callipaeda is an emerging zoonotic nematode responsible for ocular infection in Europe, transmitted by lachryphagous drosophilid flies of the genus Phortica. In this study, we updated the epidemiological picture of thelaziosis in Italy analysing parasites collected from a human case, in the vector Phortica variegata, and in a single naturally infected definitive host (dog), all from the same geographical area, the Latium region, central Italy. Median joining network and phylogenetic analyses based on the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of T. callipaeda revealed a novel variant haplotype, named Haplotype 22, for the nematode from the human patient, distinct from the common Haplotype 1, detected for the nematodes from the infected dog and the positive specimens of P. variegata flies. The discovery of the new circulating haplotype variant, besides the dominant Haplotype 1, the so far only known haplotype in Europe, expands the knowledge on the genetic polymorphism of T. callipaeda. The results obtained support the hypothesis that the European population of T. callipaeda, despite its lower level of polymorphism, is genetically differentiated from that occurring in Asia, as previously suggested. These findings highlight the importance of the parasite’s monitoring in Europe, after its first detection in the late 1990s, possibly adopting a One Health approach. The zoonotic role of T. callipaeda, transmitted by Phortica spp. in urban settings of Italy as here demonstrated, evidences the need for increasing medical awareness.