The zoophilic fruitfly Phortica variegata: morphology, ecology and biological niche

Abstract

Flies belonging to the subfamily Steganinae (Drosophilidae) display unusual zoophilic feeding habits at the adult and/or larval stage. Phortica variegata (Fallén) feeds on tears or eye liquid around the eyes of humans and carnivores. When feeding it is a potential vector of Thelazia callipaeda (Railliet and Henry) eyeworms. Adult and larval stages of this fly may be easily confused with other species belonging to the same genus, and little is known on the biology and ecology of P. variegata. In April-November 2005, a total of 969 P. variegata were collected in an area with a high prevalence of canine thelaziosis. The number of flies collected weekly was then related to climatic and environmental parameters (e.g. temperature, relative humidity and total rainfall) recorded daily at the collection site. The highest number of Phortica were collected during July-August. The sex ratio (number of males : females) rose from approximately 0.5 during May-July, to approximately 3.0 in August and 181 during September-October. Distributional data, representing 242 sites at which P. variegata has been collected in Europe, were analysed using a desktop implementation of the genetic algorithm for rule-set prediction (GARP) to model ecological requirements across Europe, as well as in Italy. P. variegata is shown to be mainly active at 20-25 degrees C and 50-75% RH. The ecological niche model suggests with a high degree of confidence that large areas of Europe are likely to represent suitable habitat for this species, mostly concentrated in central Europe. The results reported here contribute basic knowledge on the ecology and geographical distribution of P. variegata flies, which will be fundamental to gaining a better understanding of their role as vectors of human and animal pathogens.

Emergence of canine ocular thelaziosis caused by Thelazia callipaeda in southern Switzerland

“…The presence of a potential vector, the zoophilic fruitfly P. variegata, which is a known vector and intermediate host of T. callipaeda in southern Italy, has been reported in southern and central Ticino (http://www.taxodros.unizh.ch/, compiled by G. Bächli). This territory is also predicted to be a suitable habitat for P. variegata flies based on a predictive geoclimatic model (Otranto et al, 2006a). Additionally, a dog population of approximately 20'000 in the study area and an overall prevalence of 5.3% suggest that more than a thousand dogs could be infected and contribute to the expansion of thelaziosis.…”

“…An ecological niche model suggested that the climate of large areas of Europe could be suitable habitats for this vector (Otranto et al, 2006a) and thus are potentially endemic for T.…”

Development of a PCR‐RFLP assay to identify Drosophila melanogaster among field‐collected larvae

“…The misidentified D. suzukii and D. busckii larvae belonged to a Diptera species of the Drosophilidae family, genus Phortica according to sequencing results. This genus was reported in France according to previous survey (Otranto, Brianti, Cantacessi, Lia, & Máca, 2006), but not in the Rhone‐Alpes region (Withers & Allemand, 2012). …”

Serbia: Another endemic region for canine ocular thelaziosis

“…Infection is endemic in dogs. It occurs during the most intensive vector activity in the warm period of the year (19). T. callipaeda firststage larvae (L 1 ) can be found in the lachrymal secretions of dogs in summer (June-July), when infections of intermediate hosts occur.…”

“…Although humans are competent hosts, they usually act as accidental final hosts, in whom the third-stage larvae can grow into adults, but without epidemiologic effects on parasite transmission (7). All cases of thelaziosis in humans were reported during summer, in the period of the most intensive vector activity (19,21). The occurrence of thelaziosis and allergic (pollen-induced) conjunctivitis in humans in spring and summer may affect the validity of the etiological diagnosis of this disease.…”