School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia.
PLoS One. 2013 Dec 4;8(12):e82425. doi: 10.1371/journal.pone.0082425. eCollection 2013.
Infectious diseases can cause population declines and even extinctions. The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has caused population declines and extinctions in amphibians on most continents. In the tropics, research on the dynamics of this disease has focused on amphibian populations in mountainous areas. In most of these areas, high and low elevation sites are connected by an assemblage of streams that may transport the infectious stage of the pathogen from high to low elevations, and, also, this pathogen, which grows well at cool temperatures, may persist better in cooler water flowing from high elevations. Thus, the dynamics of disease at low elevation sites without aquatic connections to higher elevation sites, i.e., non-contiguous low elevation sites, may differ from dynamics at contiguous low elevation sites. We sampled adult common mistfrogs (Litoria rheocola) at six sites of three types: two at high (> 400 m) elevations, two at low elevations contiguous with high elevation streams, and two at low elevations non-contiguous with any high elevation site. Adults were swabbed for Bd diagnosis from June 2010 to June 2011 in each season, over a total of five sampling periods. The prevalence of Bd fluctuated seasonally and was highest in winter across all site types. Site type significantly affected seasonal patterns of prevalence of Bd. Prevalence remained well above zero throughout the year at the high elevation sites. Prevalence declined to lower levels in contiguous low sites, and reached near-zero at non-contiguous low sites. Patterns of air temperature fluctuation were very similar at both the low elevation site types, suggesting that differences in water connectivity to high sites may have affected the seasonal dynamics of Bd prevalence between contiguous and non-contiguous low elevation site types. Our results also suggest that reservoir hosts may be important in the persistence of disease at low elevations.
传染病可导致种群减少甚至灭绝。两栖类壶菌，Batrachochytrium dendrobatidis (Bd)，已导致各大洲的两栖动物种群减少和灭绝。在热带地区，对这种疾病动态的研究主要集中在山区的两栖动物种群上。在这些地区的大多数地区，高海拔和低海拔地点通过一系列溪流相连，这些溪流可能将病原体的传染性阶段从高海拔带到低海拔，并且，这种病原体在凉爽的温度下生长良好，可能在从高海拔流下来的较冷的水中更好地存活。因此，与高海拔溪流没有水生连接的低海拔地点（即不连续的低海拔地点）的疾病动态可能与连续的低海拔地点的动态不同。我们在三个地点类型的六个地点采样了成年普通雨蛙（Litoria rheocola）：两个在高海拔 (> 400 米) 地点，两个与高海拔溪流相邻的低海拔地点，两个与任何高海拔地点都不相邻的低海拔地点。从 2010 年 6 月到 2011 年 6 月，每个季节在五个采样期内对成年雨蛙进行了 Bd 诊断的拭子采样。Bd 的流行率随季节波动，在所有地点类型中冬季最高。地点类型显著影响了 Bd 的季节性流行率模式。在高海拔地点，全年的 Bd 流行率始终保持在较高水平。在相邻的低海拔地点，流行率下降到较低水平，在不相邻的低海拔地点，流行率接近零。两种低海拔地点的空气温度波动模式非常相似，这表明与高海拔地点的水连通性差异可能影响了连续和不连续低海拔地点类型的 Bd 流行率的季节性动态。我们的结果还表明，水库宿主可能在低海拔地区疾病的持续存在中很重要。
