Field survey on Phortica variegata and the high infection rate of Thelazia callipaeda in Lazio and Basilicata regions

INTRODUCTION. The eyeworm Thelazia callipaeda (Spirurida, Thelaziidae) parasitizes the conjunctival sac and the nictitating membranes of domestic and wild carnivores, rabbits and humans. The fruit fly Phortica variegata (Diptera, Drosophilidae) is until now the only proven vector of this eyeworm species responsible for canine thelaziosis, due to the lacryphagous behaviour of male insects. Despite thelaziosis is undoubtedly an emerging zoonotic disease in Europe, the peculiar ecology of P. variegata associated to wild areas dominated by the presence of Turkey oak tree (Quercus cerris) seems to limit its local distribution to scarcely populated areas where the major reservoirs are domestic and stray dogs (Otranto et al., 2006, Med Vet Entomol 20:358-64). MATERIALS AND METHODS. Sampling of flies was performed during September 2017 in two field sites: Oliveto Lucano (MT, Basilicata), an area known to be highly endemic for T. callipaeda, and Manziana (RM, Lazio), where data on this nematode in dogs and on its vector are unavailable. Flies were collected with a net: i) using a fruit bait, a white cloth bag containing fermented sliced fruit laced to the north side of an oak tree about 1m from the undergrowth; ii) using a human bait, waiting for the arrival of flies around the collector’s face. The specimens were brought to laboratory, morphologically identified as P. variegata (Bächli et al., 2005, Fauna Entomologica Scandinava, 39:1-362) and molecularly analysed for T. callipaeda presence by conventional PCR (Otranto et al., 2005, Parasitology 131:847–855). RESULTS AND CONCLUSIONS. Overall, a total of 172 P. variegata specimens were collected in both sites (Manziana: 74 males, 6 females; Oliveto Lucano: 91 males, 1 female). T. callipaeda positive specimens were found in both sites, Oliveto Lucano and Manziana (5.5% and 6.8% of males, respectively), suggesting high levels of transmission of this eyeworm by P. variegata males also in the latter area. Contrarily to the sampling site of Oliveto Lucano, that is an almost uninhabited wild area about 5 km far from the village, the sampling site in Manziana is a protected area enclosed into an urbanized context highly frequented by both humans and dogs. Then the epidemiological consequences of the zoonotic transmission potential of T. callipaeda in urbanized areas of Central Italy such as Manziana are not negligible and need to be carefully taken into account.