Endemic Hippobosca equina (Diptera, Hippoboscidae) Louse Fly Infestation of Cattle During Summer Grazing in the Alps of Austria.

PURPOSE: Although Hippobosca equina is considered widespread in the Palearctic region, it appears to have been a rare louse fly species in most parts of central Europe for decades, currently occurring in larger numbers only in a few geographical locations and rarely parasitizing livestock. This paper reports on the monitoring of cattle infested with H. equina during summer grazing in the Salzburg Alps, Austria. METHODS: During two consecutive grazing seasons, each lasting from about mid-May to mid-September, cattle were inspected in intervals of approximately two to three weeks to estimate prevalence and intensity of infestation with H. equina. Due to animal husbandry practices, the number of cattle on pasture fluctuated, so that between 31 and 57 animals were examined per occasion in 2016 and 2017. RESULTS: Infestation of the cattle with H. equina began shortly after pasture turnout and was present throughout the mountain grazing season. The infestation pattern of H. equina on the animals was broadly similar in both years, with prevalence and intensity reaching maximum values in August and then declining significantly until the end of September. The individual H. equina burden was low (range, 1 to 8), and at the peak of infestation, approximately one-third of the cattle were infested and harbored an average of 2.8 louse flies. According to the statements of the farmers and the observations made during the inspection of the animals, the cattle seemed to be accustomed to the exposure to H. equina, and the existing low infestation apparently caused little or no discomfort. CONCLUSION: This is the first report indicating the presence of an apparently stable local breeding population of H. equina in central Europe, which is primarily maintained on cattle. H. equina appears to be a summer species, producing one generation per year.