Phortica oldenbergi (Diptera: Drosophilidae): A new potential vector of the zoonotic Thelazia callipaeda eyeworm

Thelazia callipaeda is a zoonotic nematode parasitizing the eyes of many hosts species, primarily dogs. To date Phortica variegata and Phortica okadai are the only known vectors of this nematode in Europe and China, respectively. In this study we investigated the role played by a third species, Phortica oldenbergi, as vector of T. callipaeda in Europe. Drosophilid flies of this species were collected in central Italy and maintained in laboratory. One hundred forty P. oldenbergi were experimentally infected with T. callipaeda L1 recovered from field collected gravid females belonging to haplotype 1, which is that detected in several countries in Europe. Seventy-four (i.e., 60 females and 14 males) specimens died at 5 days post infection (d.p.i.) (±1) and scored negative for T. callipaeda larvae at the dissection. Sixty-six (i.e., 46 females and 20 males) P. oldenbergi survived and were dissected at 21 d.p.i. From those, T. callipaeda L3 were detected in the proboscis of two females (3.0%). Overall, at the molecular analysis, 11.4% (n = 16/140; 13 females and 3 males) scored positive for the presence of T. callipaeda DNA. Data herein reported brings further insights on the biology of T. callipaeda by adding P. oldenbergi as a new potential intermediate host under experimental conditions. The role of this drosophilid in the transmission cycle of T. callipaeda needs to be confirmed under natural conditions.