Epidemiological data on canine and human dirofilariosis in the Rostov Region (Southern Russia) are presented. Prevalence of Dirofilaria spp. infections in 795 autochthonous dogs, assessed by the Knott test, was 20.25%. The highest prevalence was found in Novocherkassk (38.3%) and Rostov-on-Don (18.5%), while prevalences were lower in other points of the region. Prevalence of D. repens was 44.7%, prevalence of D. immitis was 30.3%, and coinfections were observed in 25.0% of the dog population. A case finding study carried out during 9 years (2000–2009) revealed 131 cases of human dirofilariosis in the Rostov Region, 129 of subcutaneous dirofilariosis and 2 of pulmonary dirofilariosis. Seroprevalence among 317 healthy blood donors from the Rostov Region was 10.4%, while seroprevalence in policemen living in Rostov city and working in training dogs was 19%. These data show high infection rates of Dirofilaria spp. in both human and dog populations of Rostov, probably because of the existence of favorable conditions for the transmission in this region.

Having studied the timing of a horseflies daily activity, it is possible to effectively and purposefully apply protective measures during their massive parasitism. The gnus complex consists of mosquitoes (Culicidae), horseflies (Tabanidae), midges (Simuliidae) and biting midges (Ceratopogonidae). The factors that determine the high abundance of midges are favorable climatic conditions for their reproduction and existence in combination with an abundance of breeding biotopes (reservoirs and swamp formations) and habitat of adults (tree, shrub or tall herbaceous vegetation), as well as the presence of a sufficient number of warm-blooded animals is a source of blood saturation. Horseflies (Diptera, Tabanidae) are widespread in almost all climatic zones of our country. The article examines their daily activity in the Tyumen region during the summer period of 2017. At the beginning of the season (the first decade of June) the flight of the adult horseflies continues from 09:00 a.m. to 09:00 p.m., the maximum flight is observed at 02:00-05: 00 p.m., the total duration is 10-12 hours. In the second and third decades of June-July flight begins at 05:00-06:00 a.m., and ends at 09:00-10:00 p.m., maximum - at 02:00-04:00 p.m., the total duration of the daily activity of horseflies is 15-17 hours. In late July-early August, flights start at 06:00-08: 00 a.m., end at 07:00-08:00 p.m., mass flights - at 11: 00-12:00 a.m. and reach a maximum at 12:00-02:00 p.m., total duration – 13-15 hours.