在過去20年里,，世界各地不同地方都有關(guān)于兩棲動物種群數(shù)量下降的報道。這些事件被歸于不同原因（經(jīng)常并沒有很多證據(jù)支持）,，包括生境損失,、氣候變化和疾病等。
現(xiàn)在,，關(guān)于美國明尼蘇達州濕地中北方豹蛙（Rana pipiens）的一項案例研究表明,，農(nóng)用化學(xué)藥品的使用，再加上寄生蟲的感染,，是造成種群數(shù)量下降的一個因素,。在這項研究中，研究人員試圖找到與這種青蛙身上吸蟲幼蟲多少相關(guān)的因素,。這些寄生蟲如果很多會使青蛙身體虛弱,，引起四肢變形、腎臟損傷,、甚至死亡,。
在關(guān)于吸蟲感染的超過240種可靠的預(yù)測因素（這些因素從各種不同植物和動物物種的存在到農(nóng)用化學(xué)藥品和生境地理因素都包括在內(nèi)）中，兩個因素比較突出：“莠去津”除草劑和 “磷酸鹽”化肥,。“莠去津”和“磷酸鹽”是玉米和高粱生產(chǎn)的主要農(nóng)用化學(xué)藥品,，它們加在一起可解釋吸蟲豐度變化的74%。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 455, 1235-1239 (30 October 2008) | doi:10.1038/nature07281
Agrochemicals increase trematode infections in a declining amphibian species
Jason R. Rohr1,2, Anna M. Schotthoefer3, Thomas R. Raffel1,2, Hunter J. Carrick4, Neal Halstead1, Jason T. Hoverman5, Catherine M. Johnson6, Lucinda B. Johnson6, Camilla Lieske3, Marvin D. Piwoni7, Patrick K. Schoff6 & Val R. Beasley3
1 Biology Department, University of South Florida, Tampa, Florida 33620, USA
2 Penn State Center for Infectious Disease Dynamics, Penn State University, University Park, Pennsylvania 16802, USA
3 College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA
4 School of Forest Resources, Penn State University, University Park, Pennsylvania 16802, USA
5 Department of Forest, Wildlife and Fisheries, The University of Tennessee, Knoxville, Tennessee 37996-4563, USA
6 Natural Resources Research Institute, University of Minnesota Duluth, Duluth, Minnesota 55811, USA
7 Illinois Waste Management and Research Center, Champaign, Illinois 61820, USA
Global amphibian declines have often been attributed to disease1, 2, but ignorance of the relative importance and mode of action of potential drivers of infection has made it difficult to develop effective remediation. In a field study, here we show that the widely used herbicide, atrazine, was the best predictor (out of more than 240 plausible candidates) of the abundance of larval trematodes (parasitic flatworms) in the declining northern leopard frog Rana pipiens. The effects of atrazine were consistent across trematode taxa. The combination of atrazine and phosphate—principal agrochemicals in global corn and sorghum production—accounted for 74% of the variation in the abundance of these often debilitating larval trematodes (atrazine alone accounted for 51%). Analysis of field data supported a causal mechanism whereby both agrochemicals increase exposure and susceptibility to larval trematodes by augmenting snail intermediate hosts and suppressing amphibian immunity. A mesocosm experiment demonstrated that, relative to control tanks, atrazine tanks had immunosuppressed tadpoles, had significantly more attached algae and snails, and had tadpoles with elevated trematode loads, further supporting a causal relationship between atrazine and elevated trematode infections in amphibians. These results raise concerns about the role of atrazine and phosphate in amphibian declines, and illustrate the value of quantifying the relative importance of several possible drivers of disease risk while determining the mechanisms by which they facilitate disease emergence.
