[Invasion of Dermanyssus gallinae (De Geer, 1778) in poultry farms in the Toruń region].

The studies were conducted in three big fully automaticised egg-laying farms within the boundaries of Toruń Voivodship, where Dermanyssus gallinae (DE GEER 1778) was present. The increased invasion of the parasite on one of the farms resulted in the presence of all clinical symptoms of dermanyssosis. A considerable decrease in the body weight, anaemia and organism exhaustion were observed. A growth in the hens' death rate from 1% (when they were not contaminated) to 4% was observed. There was also a decrease in egg-laying, particularly in its top phase. When breeding farms are not contaminated, egg-laying amounts normally to 91-93%, whereas in the contaminated farm the percentage lowered to 80-82%. The hens' death rate, a decrease in the egg production as well as a fall in the productive cycle by two months resulted in economical losses suffered by the farm owner. Having excluded the treatment costs, the sum amounted to c. 36,000 PLN in a single production cycle. To fight the parasite effectively, cleansing frequency, desinfecting with Wirkon and Pollena Jod K or caustic soda, and disinsectization with Neguvon and Alfasep 10WP were increased.