This study represents the first report of the dog louse fly, H. longipennis, acting as a potential intermediate host of the recently identified species of canine filarial nematode Acanthocheilonema sp.? nov.. Both conventional parasitological and molecular methods provide evidence of biological involvement between H. longipennis and this parasite in northern India. Despite careful examination of different anatomical regions of the flies during dissection, only infective larvae were observed; this is similar to the findings of Nelson  who also failed to find other developmental stages of larvae of A. dracunculoides except for a single second stage larva found in the abdominal cavity. Nelson suggested that the absence of other developmental stages may have been due to the prolonged feeding interval of the fly, which could allow larvae to become fully infective before re-feeding on the host a few days later. Hafez and Hilali  however demonstrated that the fly could only withstand starvation for 12 to 36 hours before dying and that feeding occurs more regularly than this. It is reported that the developmental period from L1 to infective larvae for A. reconditum in fleas and A. dracunculoides in ticks is approximately seven days and thirteen days, respectively [16, 27]. The development of Acanthocheilonema sp.? nov. within its hippoboscid host therefore requires further investigation. Despite the fact that we have demonstrated a potential intermediate host-parasite relationship between H. longipennis and Acanthocheilonema sp.? nov., determination of the vector competence for any blood-feeding arthropod should be based on the demonstration of its capability of transmitting the parasite to a receptive host during blood feeding using experimental trials [15, 27], and this remains to be performed.
The precise identification of this nematode remains unclear. A proper morphological comparison of the third-stage larvae, microfilaria and recovery and comparison of adult worms with those of the other filarial nematodes of dogs in addition to the molecular phylogenetics would be required in order to comply with the establishment criteria listed in Article 7 to 11 of the Code of Zoological Nomenclature, which would allow official classification of this Acanthocheiloma sp. nov.? found in dogs.
Species of Hippobosca do not normally travel long distances but they are strong fliers and will actively fly between hosts within a group . When on the host, H. longipennis moves swiftly between hairs and is very difficult to catch (authors' personal observation). It is known that on average the female leaves the host for larviposition (on the soil, in crevices or in cracks of tree barks) about 8 times throughout her lifetime, on each occasion she returns to the host to feed and start another larval maturation cycle . Hafez and Hilali  stated that the amount of complete blood meal ingested by H. longipennis varies from 1.5 to 4.5 mg with a feeding duration of 3 to 13 minutes and meals are taken at least every 6 hours. This information highlights the significance of this fly as important blood sucking ectoparasite, hence increasing the opportunity for it to be an effective disseminator of blood parasites among dogs.
The subfamilies Lipopteninae, and Ornithomyiinae are known biological vectors for Trypanosoma and Haemoproteus of birds, sheep and goat . The subfamily Hippoboscinae has been documented only as a vector for A. dracunculoides in dogs . More recently, over 70% of Hippobosca equina were positive for Bartonella DNA , but further investigation is needed to clarify biological or mechanical involvement of the fly as a vector for this pathogen. To the authors' knowledge, there are no other reports exploring the role of the genus Hippobosca as a vector/intermediate host for any other pathogen. Indeed, it is surprising how little information is known about the capability of the subfamily Hippoboscinae as vectors of pathogens. Further investigations are crucial to reduce this knowledge gap.
Despite being commonly encountered in semi-arid regions of Africa and Asia, there is no peer-reviewed information available on the efficacy of ectoparasitic drugs against H. longipennis on dogs. Staff at several zoos in United States applied methoxychlor, malathion and carbaryl-sulfur dust formulations to the animals and their surroundings to control and eradicate H. longipennis infestations [7, 8]. In addition to its role as an intermediate host for canine filariae, our findings have also confirmed earlier reports that C. yasguri mites are phoretic on H. longipennis [30, 31] and that the fly may play an important role in mechanically disseminating this mite among dogs. The fly's potential to cause heavy infections of dogs with accompanying anaemia and/or skin lesions, signals a need for further studies to determine the efficacy of currently available insecticides against H. longipennis.
With respect to the public health significance of this epifaunistic ectoparasite, it is known that humans are occasionally bitten by flies from the family Hippoboscidae , but it is of note that the authors did not receive any bites from H. longipennis during the collection process. Apart from mechanical irritation and injury, the fly may also facilitate the zoonotic transmission of C. yasguri . It has also been hypothesised that H. longipennis may act as a mechanical vector for Leishmania spp. in areas where the parasite is endemic in dogs . Furthermore, H. equina (forest fly) and Lipoptena cervi (deer ked), other blood-sucking species belonging to the family Hippoboscidae, have been reported feeding on  and causing anaphylactic reactions in humans in Finland  and Hungary  and this may also be a possibility with H. longipennis. In summary, to date, this fly appears to have minimal public health significance, but further investigation is needed to verify this.