Development of Novel Management Tools for Phortica variegata (Diptera: Drosophilidae), Vector of the Oriental Eyeworm, Thelazia callipaeda (Spirurida: Thelaziidae), in Europe

Lachryphagous males of Phortica variegata (Fallén, 1823) are gaining increasing attention in Europe, as they act as vectors of the nematode Thelazia callipaeda Railliet & Henry, 1910, causal agent of thelaziosis, an emergent zoonotic disease. Currently, there are no effective control strategies against the vector, and surveillance and monitoring rely on time-consuming and nonselective sampling methods. Our aim was to improve the knowledge about the population dynamics and the chemical ecology of the species. A total of 5,726 P. variegata flies (96.4% males and 3.6% females, mostly gravid) were collected in field experiments during June–September of 2020 in an oak forest in northern Spain. Our results indicate that 1) by means of sweep netting a significantly higher number of captures were found both around the collector´s body and in the air than at ground level; 2) a positive relationship was detected between the abundance of Phortica flies and temperature, with two significant peaks of abundance at 24 and 33°C; 3) the blend of red wine and cider vinegar was the most attractive bait; 4) yellow traps captured fewer flies compared to black and transparent traps; and 5) a significant reduction toward vinegar and wine was detected in presence of the phenolic monoterpenoid carvacrol. In addition, all the males (n = 690) analyzed by both molecular detection and dissection resulted negative for the presence of T. callipaeda larvae. Overall, these findings provide a better understanding of the vector in terms of monitoring and management strategies.

Efficacy of fipronil/(S)-methoprene/eprinomectin/praziquantel (Broadline®) against Thelazia callipaeda in naturally infected cats

Background The present clinical field trial was conducted to assess the efficacy of a broad-spectrum parasiticide spot-on formulation containing eprinomectin (Broadline®) against Thelazia callipaeda eyeworm in naturally infected cats. Methods Fifteen privately owned cats harboring at least one live adult T. callipaeda were included in the study. Cats were randomly allocated to an untreated control group of seven cats or to a Broadline®-treated group of eight cats. Cats were treated on Day 0; ocular examinations were performed at inclusion and on Days 7 and 14; eyeworms were recovered and counted on Day 14. The primary efficacy assessment was based on group comparison of number of T. callipaeda on Day 14. Results Seven days after treatment, six of eight treated cats were negative for eyeworm infection per visual examination, and on Day 14 no eyeworms were found in the treated cats while the seven untreated cats were still infected (geometric mean: 1.97). All cats had inflammatory ocular signs at inclusion; on Day 14, five of eight treated cats had recovered while all untreated control cats were still symptomatic. All collected parasites were confirmed to be T. callipaeda by morphology and molecular characterization. Conclusions A single treatment with Broadline® provided 100% efficacy against feline thelaziosis and improved related ocular inflammation signs. Graphical abstract

Feline thelaziosis (Thelazia callipaeda) in Spain: state-of-the-art and first prophylactic trial in cats

Objectives Thelaziosis caused by the nematode Thelazia callipaeda (Spirurida, Thelaziidae) affects the eyes of domestic and wild carnivores, lagomorphs and even humans. The role of cats in spreading thelaziosis remains unclear. The present study assesses the current status of feline T callipaeda infection in Spain and presents the results of the first prophylactic trial conducted in this species. Methods We retrospectively analysed the occurrence of feline thelaziosis (study 1), examined its prevalence based on cross-sectional sampling of endemic areas (study 2), and assessed the therapeutic/prophylactic benefits of a spot-on (moxidectin) and therapeutic efficacy of an eye drop (ivermectin) formulation (study 3). Results In study 1, 69 Thelazia-infected cats were examined. Autochthonous cases were detected in 18/26 municipalities surveyed in Spain, which corresponds to 88.4% (n = 61/69) of the total number of cases. In study 2, 74 cats (20 from La Vera region and 54 from Orense province) were examined from 2011 to 2013. Ten of these cats (13.5%) were infected with T callipaeda. The infection prevalence was 40% (n = 8/20) in La Vera and 3.7% (n = 2/54) in Orense. The therapeutic efficacy of ivermectin was assessed over a summer (2011) in 12 cats, while that of moxidectin was examined over a 17-month period in seven cats. Four of these seven cats were subsequently included in an all-year-round prophylaxis trial. Treatment efficacy ranged from 91.7% (ivermectin) on day 28 after treatment to 100% (moxidectin) on day 14. Moxidectin prevented reinfections in cats. Conclusions and relevance Our data confirm the endemic status of T callipaeda infection in Spain, revealing its high prevalence in cats living in known endemic areas. Moxidectin was effective in treating and preventing infection. We strongly recommend the inclusion of thelaziosis in the differential diagnosis of pets and humans presenting with ocular manifestations, along with adequate preventive measures.

Okuläre Thelaziose bei einem Hund in Deutschland – ein autochthoner Fall?

Zusammenfassung Thelazia callipaeda, ein von Phortica spp. (Fruchtfliegen) übertragener Nematode, verursacht bei Hunden, Katzen, Hasenartigen und Menschen eine milde bis schwere Konjunktivitis und Keratitis. Er war aufgrund seines Vorkommens lange Zeit als orientalischer Augenwurm bekannt, ist aber inzwischen in vielen süd- und osteuropäischen Ländern endemisch und breitet sich zunehmend in Europa aus. Bei einer aufgrund von therapieresistenter Konjunktivitis überwiesenen Hündin wurden bei der ophthalmologischen Untersuchung 3 adulte Augenwürmer im Konjunktivalsack und auf der bulbären Seite der Nickhaut des linken Auges gefunden. Diese ließen sich mittels morphologischer Merkmale und molekulargenetischer Techniken als T. callipaeda identifizieren und stellten die Ursache für unilateralen Blepharospasmus, hyperämische Konjunktiven und Epiphora dar. Die Therapie erfolgte durch Absammeln der Würmer und Applikation von Moxidectin/Imidacloprid als Spot-on-Präparat (Advocate®, Bayer). Sämtliche klinischen Symptome verschwanden innerhalb 1 Woche nach Therapiebeginn. In Deutschland ist die okuläre Thelaziose immer noch eine selten auftretende Erkrankung. Bei den meisten Patienten handelt es sich um Hunde und Katzen, die entweder aus dem Ausland importiert wurden oder sich auf Auslandsreisen infiziert haben. Die hier vorgestellte Hündin wurde dagegen in Deutschland geboren und hatte außer 1 Woche Auslandsaufenthalt in den Niederlanden, 15 Monate vor Beginn der Symptome, Deutschland nie verlassen. Aufgrund der Präpatenz von T. callipaeda handelt es sich daher höchstwahrscheinlich um eine autochthone Infektion.