Causative agent of the crayfish plague: Aphanomyces astaci Schikora, 1906

Abstract

Riječni rakovi važan su element slatkovodnih ekosustava. U posljednjih 200 godina došlo je do drastičnog smanjenja brojnosti autohtonih vrsta riječnih rakova na području Europe. Kao jedan od ključnih uzroka tog smanjenja navodi se izbijanje epidemija račje kuge uzrokovane patogenom Aphanomyces astaci. Infektivne čestice ove bolesti sekundarne su zoospore koje se stvaraju na krajevima hifa ovog obligatnog parazita. Osim riječnih rakova, kao vektori širenja ovog patogena opisane su i druge vrste rakova. Postoji pet opisanih sojeva A. astaci, od kojih su za dva opisani podtipovi. Smatra se da sojevi potječu iz dva vala unosa alohtonih sjevernoameričkih vrsta riječnih rakova na područje Europe. Opaženo je više oblika horizontalnog prijenosa A. astaci, poput prijenosa ribama, pticama i antropogenim djelovanjem (ribolovna oprema, brodovi i trgovina kućnim ljubimcima). Na Balkanu su pronađene latentno zaražene populacije, za koje se smatra da su zaražene u prva dva vala širenja ovog patogena. Razlike podtipova unutar sojeva A. astaci, kao i njihov utjecaj na ekosustave u kojima se nalaze, još su nedovoljno istraženi. Također su potrebna dodatna istraživanja metoda suzbijanja zaraze ovim patogenom kako bi se umanjio utjecaj A. astaci na europske autohtone vrste riječnih rakova.Crayfish represent an important element of freshwater ecosystems. However, there has been a drastic decrease in the number of autochthonous species of crayfish in Europe over the past 200 years. Epidemic outbreaks of crayfish plague caused by the pathogen Aphanomyces astaci have been reported as one of the main causes of this decrease in abundance. The infective units of the disease are secondary zoospores produced at hypha ends of this obligatory parasite. Apart from crayfish, other crustacean species have also been identified as pathogen’s hosts and carriers. There are five described genotype groups, two of which have multiple subtypes. It is considered that the all of the strains originate from two waves of introduction of North American crayfish species into Europe. Multiple types of horizontal transmission of A. astaci have been observed, such as by fish, birds and anthropogenic activities (fishing equipment, ships and pet trade). Latent infections have been discovered in the Balkan region, which are considered to have been caused by the strains introduced by the first two phases /waves. Subtype differences within the different strains of A. astaci and their effect on ecosystems in which they are present are still inadequately studied. Furthermore, additional research of infection control methods of this pathogen is required to reduce the impact of A. astaci on European freshwater crayfish and ecosystems in general