Abstract
BackgroundMale fruitflies Phortica variegata (Drosophilidae, Steganinae) are the intermediate host of the zoonotic nematode Thelazia callipaeda (Spirurida, Thelaziidae). More than 10 years ago, when T. callipaeda was confined to remote regions of southern Italy, ecological niche models were used to predict the potential distribution of P. variegata across Europe and the likely risk of the nematode spreading through infected dogs travelling to/from endemic regions. As predicted, over the last 10 years T. callipaeda has spread rapidly across Europe. Recently, we identified the potential for its introduction to the UK through infected dogs travelling to/from endemic regions of mainland Europe.MethodsHere updated information is used to re-evaluate the model-predicted European, and specifically, UK distribution to determine the likelihood of T. callipaeda becoming established. Additionally, the UK distribution of P. variegata was further investigated through snapshot fly trapping at model-predicted locations.ResultsEcological niche modelling using Genetic Algorithm for Rule-set Prediction (GARP) analysis suggests a European range similar to that described previously, with some indication of potential spread further eastward. Finer scale UK mapping suggested that P. variegata presence was limited mostly to southern England, but highlighted regions where P. variegata has not been documented previously. The arbitrary fly trapping identified activity of P. variegata at two locations where the species has been found previously late in the season. No specimens were collected at model-predicted locations, although habitat suitable for the species was identified.ConclusionsGARP-model prediction of P. variegata distribution suggests presence of suitable conditions in previously undocumented regions of the UK and Europe and highlight the possibility for further spread of T. callipaeda across Europe, including the UK. Further work to validate the P. variegata UK model with field data will help improve its accuracy in predicting suitable areas, whilst surveillance of sylvatic definitive host species in such locations is advised to monitor for evidence of autochthonous T. callipaeda transmission.
Highlights
Male fruitflies Phortica variegata (Drosophilidae, Steganinae) are the intermediate host of the zoonotic nematode Thelazia callipaeda (Spirurida, Thelaziidae)
T. callipaeda appears to have spread rapidly through Europe: since 2003 the list of endemic countries has expanded from Italy [3], where autochthonous transmission was first recorded in Europe, to include France, Switzerland, Germany, Spain, Portugal, Bosnia and Herzegovina, Croatia, Romania, Bulgaria, Hungary, Greece, Slovakia and Serbia [4,5,6,7,8,9,10,11,12,13,14,15]
The European distribution predicted by the Genetic Algorithm for Rule-set Prediction (GARP) model (Fig. 1a) indicated that large areas are suitable for the development of P. variegata, with the geographic range extended further east compared to that published by Otranto et al [23]
Summary
Male fruitflies Phortica variegata (Drosophilidae, Steganinae) are the intermediate host of the zoonotic nematode Thelazia callipaeda (Spirurida, Thelaziidae). Thelazia callipaeda (Spirurida: Thelaziidae) is a vector borne, zoonotic nematode of animal and public health importance capable of infecting a range of host species, including dogs and cats, foxes, wolves, rabbits and humans [1]. DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene performed on specimens collected from several different host species across Europe has demonstrated presence of a single haplotype (h1). This suggests spread of T. callipaeda in Europe has occurred from a single introduction event and/or that this haplotype (h1) is well adapted for survival and transmission in Europe [18]
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