Department of Biology, University of Eastern Finland, Kuopio Campus, P.O. Box 1627, 70211 Kuopio, Finland.
Norwegian Veterinary Institute, P.O. Box 750, Sentrum, 0106 Oslo, Norway; Microbial Evolution Research Group (MERG), Department of Biology, University of Oslo, Pb 1066, Blindern, 0316 Oslo, Norway.
Vet Microbiol. 2013 Mar 23;162(2-4):750-755. doi: 10.1016/j.vetmic.2012.09.027. Epub 2012 Oct 3.
Aphanomyces astaci sporulation is crucial for the spreading potential of this disease agent. For the first time, we are reporting timing and quantity of A. astaci spores released from noble crayfish (Astacus astacus) suffering from crayfish plague under practical aquatic conditions. We infected nine noble crayfish with A. astaci PsI-genotype and maintained them in individual 8L tanks. Spores (zoospores and cysts) were quantified from water samples (3 × 1 mL) taken every 12h over 10 d using A. astaci specific qPCR. A clear sporulation trend was found, together with a high individual spore estimate variation. The median spore counts from two days before death to 12h post mortem were from 500 to ~2000 spores L(-1). A significant sporulation increase occurred after 24h post mortem (12,000 spores L(-1)) and reached a peak after two days (~65,000 spores L(-1)) before declining to or below pre mortem levels from the fourth day. The single most sporulating crayfish released from ~75,000 to ~400,000 spores L(-1) during the mass sporulating period, yielding a maximum estimate of ~3,200,000 spores released from a single crayfish if we assume homogeneous spore distribution. The results confirm a mass A. astaci spore release from moribund and recently dead infected noble crayfish, with a sporulation peak one to three days post mortem. The acute crayfish mortality only three days after zoospore exposure confirm the lethal potential of the PsI-genotype. The powerful sporulation potential observed here may be one of the key virulence factors of this genotype.
阿氏阿斯塔藻的孢子形成对于这种疾病的传播潜力至关重要。我们首次报告了在实际水生条件下，患有螯虾瘟的高贵螯虾（Astacus astacus）释放的阿氏阿斯塔藻孢子的时间和数量。我们用 A. astaci PsI- 基因型感染了 9 只高贵螯虾，并将它们分别放在 8L 的单个水箱中饲养。用 A. astaci 特异性 qPCR 从水样（3×1mL）中定量检测（12h 采集一次），共采集 10d。发现了一个明显的孢子形成趋势，同时个体孢子估计值的变化也很大。从死亡前两天到死后 12h 的孢子中位数计数为 500-2000 个孢子/L。死后 24h 后，孢子大量形成（约 12000 个孢子/L），两天后达到峰值（约 65000 个孢子/L），然后从第四天开始下降到或低于死前水平。在大量孢子形成期间，最具孢子形成能力的一只螯虾释放了约 75000-400000 个孢子/L，假设孢子均匀分布，则从一只螯虾中最多可释放约 320 万个孢子。结果证实了濒死和刚死亡的感染高贵螯虾会大量释放 A. astaci 孢子，孢子形成高峰在死后 1-3 天。在接触游动孢子后仅 3 天就出现急性螯虾死亡，证实了 PsI- 基因型的致死潜力。这里观察到的强大的孢子形成潜力可能是该基因型的关键毒力因素之一。
