Aphanomyces astaciPsI-genotype isolates from different Finnish signal crayfish stocks show variation in their virulence but still kill fast

Abstract

Key-words:crayfish plague, noble crayfish, potent killer, Psorospermium haeckeliWe detected significant virulence differences among five tested (PsI-Puujärvi, PsI-Pyhäjärvi, PsI-Kukkia, PsI-Saimaa I and PsI-Saimaa II) PsI-genotype crayfish plague (Aphanomyces astaci) isolates against lake Mikitänjärvi noble crayfish population. The crayfish were inoculated with a dose of 300 m·L −1 A. astaci spores in ambient water under experimental conditions. Mortalities started from four to seven days after inoculation, depending on the PsI-genotype isolate. In all the experimentally infected groups it took no more than three days for all the crayfish to die after the first mortality. The PsI-Puujärvi isolate proved to be the most virulent strain, while PsI-Kukkia was the least virulent. The average day of death for these experimental groups was fifth and ninth day, respectively. We did not discover correlation between the average day of death and gender or level of additional Psorospermium haeckeli infestation. Our results show that there are, from the practical point of view, minor virulence differences among PsI-genotype A. astaci isolates, and that all the tested five isolates are highly virulent. The present results emphasize the necessity to prevent all further spread of highly virulent strains of A. astaci to aid and shelter successful conservations attempts of the native European crayfishes.

The signal crayfish is vulnerable to both the As and the PsI-isolates of the crayfish plague

“…None of the crayfish were infested by P. haeckeli. The experimental system consisted of individual interconnected 2 L tanks with a recirculating filtered (Jussila et al, 2011a) Lake Kallavesi water with a flow that ensured full turnover of the 2 L tanks every hour (Jussila et al, 2013a).…”

“…Thörnqvist and Söderhäll, 1995) and also anecdotal evidence from wild populations (e.g. Jussila et al, 2013aJussila et al, , 2013bJussila et al, , 2013c indicating that the crayfish plague could have caused increased mortality among the wild signal crayfish stocks. These warnings have been largely ignored and the original assumption of the signal crayfish being able to resist the crayfish plague infection has been repeatedly brought up (Kirjavainen and Westman, 1999;Westman et al, 1999: Nylund andWestman, 2000).…”

Practical disinfection chemicals for fishing and crayfishing gear against crayfish plague transfer

“…This would exhaust the oxidising potential of the PAA based solution and thus it could be disposed of safely. As the prevention of the accidental spread of the crayfish plague in fishing and crayfishing gear is of utmost importance (Oidtmann et al, 2002;Kouba et al, 2012;Jussila et al, 2013aJussila et al, , 2013b, we summarise that certain peracetic acid (PAA) based solutions would be suitable for the disinfection of the fishing and crayfishing gear. The benefit of PAA based solution as a disinfectant is that the breakdown compounds are rather harmless to the environment and humans, too, thus increasing work safety.…”

“…The virulence of the most common A. astaci isolates in Europe has been shown to be high and variable (Makkonen, 2013;Filipova et al, 2013;Jussila et al, 2013a) emphasising the need for the prevention of the spread of this disease. The European water courses are plentiful with most of them having an easy access.…”

Experimental evaluation of the potential for crayfish plague transmission through the digestive system of warm‐blooded predators

“…Several pathways of the pathogen dispersal have been identified: (a) infected hosts; (b) spore‐contaminated water and items that have been in recent contact with such water; and (c) animals that have been in contact with water containing spores or animals that have been feeding on infected crayfish (Oidtmann, Heitz, Rogers, & Hoffmann, ; Svoboda et al, ). The last pathway might be facilitated by the fact that infected crayfish are progressively paralysed, lose their limbs and show abnormal behaviour such as daytime activity (Jussila, Kokko, Kortet, & Makkonen, ; Makkonen, Kokko, Vainikka, Kortet, & Jussila, ; Oidtmann et al, ), which makes them an easy prey.…”