Zvuloni Assaf, Artzy-Randrup Yael, Stone Lewi, Kramarsky-Winter Esti, Barkan Roy, Loya Yossi
Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel.
PLoS One. 2009;4(4):e4993. doi: 10.1371/journal.pone.0004993. Epub 2009 Apr 1.
Transmission mechanisms of black-band disease (BBD) in coral reefs are poorly understood, although this disease is considered to be one of the most widespread and destructive coral infectious diseases. The major objective of this study was to assess transmission mechanisms of BBD in the field based on the spatio-temporal patterns of the disease.
METHODOLOGY/PRINCIPAL FINDINGS: 3,175 susceptible and infected corals were mapped over an area of 10x10 m in Eilat (northern Gulf of Aqaba, Red Sea) and the distribution of the disease was examined monthly throughout almost two full disease cycles (June 2006-December 2007). Spatial and spatio-temporal analyses were applied to infer the transmission pattern of the disease and to calculate key epidemiological parameters such as (basic reproduction number). We show that the prevalence of the disease is strongly associated with high water temperature. When water temperatures rise and disease prevalence increases, infected corals exhibit aggregated distributions on small spatial scales of up to 1.9 m. Additionally, newly-infected corals clearly appear in proximity to existing infected corals and in a few cases in direct contact with them. We also present and test a model of water-borne infection, indicating that the likelihood of a susceptible coral becoming infected is defined by its spatial location and by the relative spatial distribution of nearby infected corals found in the site.
CONCLUSIONS/SIGNIFICANCE: Our results provide evidence that local transmission, but not necessarily by direct contact, is likely to be an important factor in the spread of the disease over the tested spatial scale. In the absence of potential disease vectors with limited mobility (e.g., snails, fireworms) in the studied site, water-borne infection is likely to be a significant transmission mechanism of BBD. Our suggested model of water-borne transmission supports this hypothesis. The spatio-temporal analysis also points out that infected corals surviving a disease season appear to play a major role in the re-introduction of the disease to the coral community in the following season.
尽管黑带病（BBD）被认为是珊瑚礁中传播最广泛、破坏性最强的珊瑚传染病之一，但对其在珊瑚礁中的传播机制了解甚少。本研究的主要目的是基于该疾病的时空模式评估其在野外的传播机制。
方法/主要发现：在埃拉特（红海亚喀巴湾北部）10×10米的区域内对3175株易感和感染的珊瑚进行了绘图，并在近两个完整的疾病周期（2006年6月至2007年12月）内每月检查疾病的分布情况。应用空间和时空分析来推断疾病的传播模式，并计算关键的流行病学参数，如（基本繁殖数）。我们发现该疾病的患病率与水温升高密切相关。当水温升高且疾病患病率增加时，受感染的珊瑚在高达1.9米的小空间尺度上呈现聚集分布。此外，新感染的珊瑚明显出现在现有受感染珊瑚附近，在少数情况下与它们直接接触。我们还提出并测试了一种水传播感染模型，表明易感珊瑚被感染的可能性由其空间位置以及该地点附近受感染珊瑚的相对空间分布决定。
结论/意义：我们的结果提供了证据，表明局部传播（但不一定是通过直接接触）可能是该疾病在测试空间尺度上传播的一个重要因素。在所研究的地点不存在具有有限移动性的潜在疾病传播媒介（如蜗牛、多毛类蠕虫）的情况下，水传播感染可能是黑带病的一种重要传播机制。我们提出的水传播模型支持了这一假设。时空分析还指出，在一个疾病季节中存活下来的受感染珊瑚似乎在接下来的季节中将疾病重新引入珊瑚群落方面发挥了主要作用。
