EN
The data were collected on the basis of the findings of diagnostic examinations performed by 22 veterinary laboratories in Poland in 1980—1988. In that period of time the morbidity and sporadic mortalities of carp fry due to Dactylogyrus were observed only in 10—89 ponds (1.2—7.0% of 1200 carp fry ponds existing in Poland), whereas the asymptomatic carrier state took place in 286—841 ponds (24— 70%). In the same time the morbidity and sporadic mortalities of carp fry caused by Gyrodactylus were noted in 5—34 ponds (0.4 to 2.8%) and the asymptomatic carrier state in 85—266 ponds (7.0—22%). The date indicate that the asymptomatic prevalence of Dactylogyrus infections are very frequent in fish farms in Poland, however, the economical losses provoked by dactylogyrosis are rather slight. The Gyrodactylus infections represent still smaller economical problem than dactylogyrosis. It is probable that this favourable epdzootical situation is the result of preventive methods applied in breeding ponds being under the control of many veterinary laboratories and the common use of phosphoorganic compounds in the control of dactylogyrosis and gyrodactylosis.