Abstract：
Oocysts of the protozoan Toxoplasma gondii are found in felid feces and can be washed into coastal waters, where they persist for months, attaching to algae and accumulating in invertebrates. We used wild bivalves to assess contamination of coastal waters of the Kerguelen and Galapagos archipelagos by this zoonotic parasite. Additionally, we leveraged the contrasting situations of these archipelagos to identify some potential drivers of contamination. In the Galapagos, with a cat density reaching 142 per km2, 15.38% of the sampled oysters (Saccostrea palmula) tested positive for T. gondii by quantitative real-time PCR (qPCR) (n = 260), and positive samples were found in all eight sampling sites. In Kerguelen, with 1-3 cats per km2, 40.83% of 120 tested mussels (Mytilus edulis platensis) were positive, and positive samples were found in four out of the five sampling sites. These findings provide evidence of T. gondii contamination in the coastal waters of these archipelagos. Furthermore, T. gondii-positive bivalves were found on islands located 20 km away (Galapagos) and 5 km away (Kerguelen) from the nearest cat population, indicating that T. gondii oocysts can disperse through waterborne mechanisms over several kilometers from their initial deposition site. In the Galapagos, where runoff is infrequent and all sites are exposed to currents, the prevalence of qPCR-positive bivalves did not show significant variations between sites (p = 0.107). In Kerguelen where runoff is frequent and site exposure variable, the prevalence varied significantly (p < 0.001). The detection of T. gondii in Kerguelen mussels was significantly correlated with the site exposure to currents (odds ratio (OR) 60.2, p < 0.001) and the on-site density of giant kelp forests (OR 2.624, p < 0.001). This suggests that bivalves can be contaminated not only by oocysts transported by currents but also by consuming marine aggregates containing oocysts that tend to form in kelp forests.
摘要：
原生动物弓形虫的卵囊在粪便中发现，可以冲入沿海水域，他们坚持了几个月，附着在藻类上并在无脊椎动物中积累。我们使用野生双壳类动物来评估这种人畜共患寄生虫对Kerguelen和Galapagos群岛沿海水域的污染。此外,我们利用这些群岛的对比情况来确定一些潜在的污染驱动因素。在加拉帕戈斯,猫密度达到142/km2，15.38％的采样牡蛎（Saccostreapalmula）通过定量实时PCR（qPCR）检测为弓形虫阳性（n=260），在所有八个取样地点均发现阳性样本。在Kerguelen,每平方公里一到三只猫，120只测试的贻贝（Mytilusedulisplatensis）中有40.83%是阳性的，在五个采样点中的四个发现了阳性样本。这些发现提供了这些群岛沿海水域中弓形虫污染的证据。此外，在距离最近的猫种群20公里（加拉帕戈斯）和5公里（克格伦）的岛屿上发现了弓形虫阳性双壳类动物。这表明弓形虫卵囊可以通过水传播机制从它们的初始沉积地点分散数公里。在加拉帕戈斯,径流很少发生，所有地点都暴露在水流中，qPCR阳性双壳类的患病率在不同部位之间没有显著差异(p=0.107).在径流频繁且现场暴露可变的Kerguelen，患病率差异显著(p<0.001).克格伦贻贝中弓形虫的检测与现场暴露于水流（赔率比（OR）60.2，p<0.001）和巨型海带森林的现场密度（OR2.624，p<0.001）显着相关。这表明双壳类动物不仅会受到洋流运输的卵囊的污染，而且还会受到消耗含有在海带森林中形成的卵囊的海洋聚集体的污染。
