BACKGROUND: Five species of the Phortica genus (Diptera: Drosophilidae) are known in Europe and the Middle East. Among these, Phortica variegata and Phortica okadai are better known for their role as vectors of the zoonotic eyeworm Thelazia callipaeda. Other species, such as Phortica semivirgo and Phortica oldenbergi, have been studied less. Given the paucity of data about these Phortica spp. vectors, we explored the population dynamics and ecology of Phortica spp. in an area highly endemic for T. callipeada (Manziana, Rome, Central Italy). METHODS: Phortica spp. flies were collected over a 3-year period (2018-2020) during their active season (April-October) with a sweep net while hovering around fermenting fruits or a human operator acting as baits. Collected flies were morphologically identified and tested for a T. callipeada infection and for the presence of Wolbachia, by polymerase chain reaction (PCR). Population dynamics of species collected was associated to environmental drivers through generalized additive models. RESULTS: Of the 5564 flies collected, 90.8% were P. variegata, 9.1% were P. oldenbergi, 0.05% were P. semivirgo, and one specimen was P. okadai. Only P. variegata scored molecularly infected with T. callipeada throughout the 3-year sampling period (1.8%). Phortica oldenbergi, observed consistently during the entire sampling period, exhibited a marked preference for fruit traps, contrasting with the lachryphagous activity of P. variegata. Analysis of environmental drivers of P. oldenbergi and P. variegata population dynamics indicated temperature, wind speed, and pressure as significant factors. In addition, Wolbachia pipientis endosymbiont was detected in P. oldenbergi and P. okadai. CONCLUSIONS: For the first time, this study analysed several ecological aspects of Phortica species coexisting in a T. callipeada endemic area, highlighting different behaviors in the same environment and their vectorial role. Notably, this is also the first report of the presence of P. oldenbergi in Italy and P. okadai in Europe, underscoring the importance of extensive sampling for detecting potential vectors and alien species with direct implications for vector-borne disease epidemiology.

Boehringer Ingelheim Animal Health Lyon France

ClinVet International Ltd Bloemfontein South Africa

Czech Entomological Society Prague Czech Republic

Department of Veterinary Clinical Sciences City University of Hong Kong Kowloon Tong Hong Kong China

Dipartimento di Biologia Ambientale Sapienza Università di Roma Rome Italy

Dipartimento di Malattie Infettive Istituto Superiore di Sanità Rome Italy

Dipartimento di Medicina Veterinaria Università degli Studi di Bari Valenzano Bari Italy

Dipartimento di Sanità Pubblica e Malattie Infettive Sapienza Università di Roma Rome Italy

See more in PubMed

Global Biodiversity Information Facility (GBIF) [Internet]. [cited 2024 Jun 9]. Available from: https://www.gbif.org/.

Jin Y, Liu Z, Wei J, Wen Y, He N, Tang L, et al. A first report of Thelazia callipaeda infection in Phortica okadai and wildlife in national nature reserves in China. Parasit Vectors. 2021;14:13. PubMed PMC

Máca J, Otranto D. Drosophilidae feeding on animals and the inherent mystery of their parasitism. Parasit Vectors. 2014;7:1–8. 10.1186/s13071-014-0516-4. PubMed PMC

Otranto D, Lia RP, Cantacessi C, Testini G, Troccoli A, Shen JL, et al. Nematode biology and larval development of Thelazia callipaeda (Spirurida, Thelaziidae) in the drosophilid intermediate host in Europe and China. Parasitology. 2005;131:847. PubMed

Bojan G, Vanja BS, Aleksandra P, Milica K, Neda B, Duško Ć. First report of eyeworm infection by Thelazia callipaeda in gray wolf (Canis lupus) from Serbia. Parasitol Res. 2019;118:3549–53. PubMed

Deak G, Ionică AM, Mihalca AD. First report of Thelazia callipaeda Railliet & Henry, 1910 in a zoo lion (Panthera leo) (Linnaeus, 1758) from Romania. Vet Res Commun. 2023;47:2173–7. PubMed

Nájera F, De Lucas-Veguillas J, Vela Á, López-Fernández M, Martínez-Martínez P, Mata-Huete M, et al. First report of Thelazia callipaeda in a free-ranging Iberian wolf (Canis lupus signatus) from Spain. Parasitol Res. 2020;119:2347–50. PubMed

Otranto D, Brianti E, Cantacessi C, Lia RP, Máca J. The zoophilic fruitfly Phortica variegata : morphology, ecology and biological niche. Med Vet Entomol. 2006;20:358–64. PubMed

Otranto D, Cantacessi C, Testini G, Lia RP. Phortica variegata as an intermediate host of Thelazia callipaeda under natural conditions: evidence for pathogen transmission by a male arthropod vector. Int J Parasitol. 2006;36:1167–73. PubMed

Otranto D, Cantacessi C, Mallia E, Lia RP. First report of Thelazia callipaeda (Spirurida, Thelaziidae) in wolves in Italy. J Wildl Dis. 2007;43:508–11. PubMed

Otranto D, Dantas-Torres F, Mallia E, DiGeronimo PM, Brianti E, Testini G, et al. Thelazia callipaeda (Spirurida, Thelaziidae) in wild animals: report of new host species and ecological implications. Vet Parasitol. 2009;166:262–7. PubMed

Otranto D, Dutto M. Human Thelaziasis, Europe. Emerg Infect Dis. 2008;14:647–9. PubMed PMC

Papadopoulos E, Komnenou A, Karamanlidis AA, Bezerra-Santos MA, Otranto D. Zoonotic Thelazia callipaeda eyeworm in brown bears (Ursus arctos ): a new host record in Europe. Transbound Emerg Dis. 2022;69:235–9. PubMed

Paradžik MT, Samardžić K, Živičnjak T, Martinković F, Janjetović Ž, Miletić-Medved M. Thelazia callipaeda—first human case of thelaziosis in Croatia. Wien Klin Wochenschr. 2016;128:221–3. PubMed

Kitajima A, Tokiwa T, Doi K, Kotani K, Otsubo H, Kamei C, et al. New host record of Thelazia callipaeda (Nematoda: Spirurida) with a notably wide host range and shared zoonotic lineage in Japan. Parasitol Int. 2024;102913. PubMed

Do Vale B, Lopes AP, Da Conceição FM, Silvestre M, Cardoso L, Coelho AC. Thelaziosis due to Thelazia callipaeda in Europe in the 21st century—a review. Vet Parasitol. 2019;275:108957. PubMed

Martínez-Sánchez MI, Bolívar-de-Miguel G, Cuadros-González J, González JMR. Ocular thelaziosis: a case report of an emerging zoonosis. Am J Ophthalmol Case Rep. 2021;22:101045. PubMed PMC

Otranto D, Mendoza-Roldan JA, Dantas-Torres F. Thelazia callipaeda. 2021 [cited 2024 Jul 16]; Available from: https://www.arca.fiocruz.br/handle/icict/50732. PubMed

Manoj RR, White H, Young R, Brown CE, Wilcox R, Otranto D, et al. Emergence of Thelaziosis Caused by Thelazia callipaeda in Dogs and Cats, United States. Emerg Infect Dis. 2024;30:591. PubMed PMC

Bezerra-Santos MA, Bernardini I, Lia RP, Mendoza-Roldan JA, Beugnet F, Pombi M, et al. Phortica oldenbergi (Diptera: Drosophilidae): a new potential vector of the zoonotic Thelazia callipaeda eyeworm. Acta Trop. 2022;233:106565. PubMed

Otranto D, Iatta R, Lia RP, Cavalera MA, Màca J, Pombi M, et al. Competence of Phortica variegata from the United States as an intermediate host of the Thelazia callipaeda eyeworm. Am J Trop Med Hyg. 2018;98:1175. PubMed PMC

Lutovinovas E, Ivinskis P, Rimšait J. Phortica semivirgo (Máca, 1977)—new to the fauna of Lithuania (Diptera: Drosophilidae). Bull Lithuanian Entomol Soc. 2020;4: 109-113

Unterköfler MS, Dengg P, Niederbacher M, Lindorfer S, Eberle A, Huck A, et al. Occurrence of Thelazia callipaeda and its vector Phortica variegata in Austria and South Tyrol, Italy, and a global comparison by phylogenetic network analysis. Parasit Vectors. 2023;16:294. PubMed PMC

Bächli G, Vilela CR, Escher SA, Saura A. The Drosophilidae (Diptera) of Fennoscandia and Denmark. [Internet]. Brill Academic Publishers; 2004 [cited 2024 Jan 12]. Available from: https://www.cabdirect.org/cabdirect/abstract/20053205535.

Máca J. Revision of Palaearctic species of Amiota subge nus Photica (Diptera, Drosophilidae). Acta Entomol Bohemoslov. 1977;74:115–30.

Carles-Tolrá M, Páez AV. Nuevos datos dipterológicos del Parque Natural de los Alcornocales (Cádiz, España) (Insecta, Diptera). Boletín de la Sociedad Entomologica Aragonesa (S.E.A.), no 47 (2010):369–371. 2010.

Bernardini I, Poggi C, Manzi S, Bezerra-Santos MA, Beugnet F, Fourie J, et al. Laboratory breeding of two Phortica species (Diptera: Drosophilidae), vectors of the zoonotic eyeworm Thelazia callipaeda. Parasit Vectors. 2022;15:200. PubMed PMC

Otranto D, Cantacessi C, Lia RP, Kadow ICG, Purayil SK, Dantas-Torres F, et al. First laboratory culture of Phortica variegata (Diptera, Steganinae), a vector of Thelazia callipaeda. J Vector Ecol. 2012;37:458–61. PubMed

González MA, Bravo-Barriga D, Alarcón-Elbal PM, Álvarez-Calero JM, Quero C, Ferraguti M, et al. Development of Novel Management Tools for Phortica variegata (Diptera: Drosophilidae), Vector of the Oriental Eyeworm, Thelazia callipaeda (Spirurida: Thelaziidae). Europe J Med Entomol. 2022;59:328–36. PubMed PMC

Pombi M, Marino V, Jaenike J, Graham-Brown J, Bernardini I, Lia RP, et al. Temperature is a common climatic descriptor of lachryphagous activity period in Phortica variegata (Diptera: Drosophilidae) from multiple geographical locations. Parasit Vectors. 2020;13:89. PubMed PMC

Arme TM, Lia RP, Annoscia G, Casalino E, Pombi M, Otranto D. Survival of Phortica variegata experimentally and naturally infected with Thelazia callipaeda. Med Vet Entomol. 2020;34:201–6. PubMed

Bächli G, Weber D. Taufliegen oder Kleine Fruchtfliegen (Insecta, Diptera, Drosophilidae) aus Höhlen des Grossherzogtums Luxemburg. Ferrantia. 2013;69:349–53.

Beschovsky VL. Representatives of Diptera-Brachycera in the caves of Bulgaria. Académie Bulg Sci Bull L’Institut Zool Mus. 1972;35:23–9.

Casiraghi M, Bain O, Guerrero R, Martin C, Pocacqua V, Gardner SL, et al. Mapping the presence of Wolbachia pipientis on the phylogeny of filarial nematodes: evidence for symbiont loss during evolution. Int J Parasitol. 2004;34:191–203. PubMed

Manoj RRS, Latrofa MS, Epis S, Otranto D. Wolbachia: endosymbiont of onchocercid nematodes and their vectors. Parasit Vectors. 2021;14:245. PubMed PMC

Máca J. Amiota Loew (Diptera: Drosophilidae, Steganinae). Biologica (Santiago). 2003;47:247–74.

Lunt DH, Zhang D-X, Szymura JM, Hewltt OM. The insect cytochrome oxidase I gene: evolutionary patterns and conserved primers for phylogenetic studies. Insect Mol Biol. 1996;5:153–65. PubMed

Technelysium Pty Ltd. Chromas version 2.6.6 [Internet]. 2024 [cited 2024 Jun 9]. Available from: https://technelysium.com.au/wp/chromas/.

Tamura K, Stecher G, Kumar S. MEGA11: molecular evolutionary genetics analysis version 11. Mol Biol Evol. 2021;38:3022–7. PubMed PMC

BLAST: Basic Local Alignment Search Tool [Internet]. [cited 2024 Jun 9]. Available from: https://blast.ncbi.nlm.nih.gov/Blast.cgi.

Casiraghi M, Anderson TJC, Bandi C, Bazzocchi C, Genchi C. A phylogenetic analysis of filarial nematodes: comparison with the phylogeny of Wolbachia endosymbionts. Parasitology. 2001;122:93–103. PubMed

Zhou W, Rousset F, O’Neill S. Phylogeny and PCR–based classification of Wolbachia strains using wsp gene sequences. Proc R Soc Lond B Biol Sci. 1998;265:509–15. PubMed PMC

R Development Core Team. R: A language and enviroment for statistical computing. Vienna: R Foundation for Statistical Computing; 2023. https://www.R-project.org/.

Coretta S. tidygam: Tidy prediction and plotting of Generalised Additive Models. R Package Version 02 0. 2023;

Wood SN. Inference and computation with generalized additive models and their extensions. TEST. 2020;29:307–39.

Checklist [Internet]. LifeWatch Italy. [cited 2024 Jul 8]. Available from: https://www.lifewatchitaly.eu/en/initiatives/checklist-fauna-italia-en/checklist/.

Roggero C, Schaffner F, Bächli G, Mathis A, Schnyder M. Survey of Phortica drosophilid flies within and outside of a recently identified transmission area of the eye worm Thelazia callipaeda in Switzerland. Vet Parasitol. 2010;171:58–67. PubMed

Bächli G, Schatzmann E, Haring E. On some population parameters of drosophilids in Switzerland (Diptera, Drosophilidae). 2008 [cited 2024 Jan 12]; Available from: https://www.zora.uzh.ch/id/eprint/14220.

Toda MJ. Vertical Microdistribution of Drosophilidae (Diptera) within various Forests in Hokkaido.: I. Natural Broad-Leaved Forest. Jpn J Ecol. 1977;27:207–14.

Morgado ACT, do Vale B, Ribeiro P, Coutinho T, Santos-Silva S, de Sousa Moreira A, et al. First report of human Thelazia callipaeda infection in Portugal. Acta Trop. 2022;231:106436. PubMed

McCabe EA, Unfried LN, Teets NM. Survival and nutritional requirements for overwintering Drosophila suzukii (Diptera: Drosophilidae) in Kentucky. Environ Entomol. 2023;52:1071–81. PubMed

Marino V, Gálvez R, Colella V, Sarquis J, Checa R, Montoya A, et al. Detection of Thelazia callipaeda in Phortica variegata and spread of canine thelaziosis to new areas in Spain. Parasit Vectors. 2018;11:195. PubMed PMC

Jones LE, Grimaldi DA. Revision of the Nearctic species of the genus Amiota Loew (Diptera: Drosophilidae). Bull Am Mus Nat Hist. 2022;458:1–177.

Ito F, Awasaki T. Comparative analysis of temperature preference behavior and effects of temperature on daily behavior in 11 Drosophila species. Sci Rep. 2022;12:12692. PubMed PMC

Sanaei E, Charlat S, Engelstädter J. Wolbachia host shifts: routes, mechanisms, constraints and evolutionary consequences. Biol Rev. 2021;96:433–53. PubMed

Ote M, Yamamoto D. Impact of Wolbachia infection on Drosophila female germline stem cells. Curr Opin Insect Sci. 2020;37:8–15. PubMed