Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
Parasit Vectors. 2013 May 7;6:139. doi: 10.1186/1756-3305-6-139.
One of the major issues concerning disease ecology and conservation is knowledge of the factors that influence the distribution of parasites and consequently disease outbreaks. This study aimed to investigate avian haemosporidian composition and the distribution of these parasites in three altitudinally separated great tit (Parus major) populations in western Switzerland over a three-year period. The objectives were to determine the lineage diversity of parasites occuring across the study populations and to investigate whether altitudinal gradients govern the distribution of haemosporidian parasites by lineage.
In this study molecular approaches (PCR and sequencing) were used to detect avian blood parasites (Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp.) in populations of adult great tits caught on their nests during three consecutive breeding seasons.
High levels of parasite prevalence (88-96%) were found across all of the study populations with no significant altitude effect. Altitude did, however, govern the distribution of parasites belonging to different genera, with Plasmodium parasites being more prevalent at lower altitudes, Leucocytozoon parasites more at high altitude and Haemoproteus parasite prevalence increasing with altitude. A total of 27 haemosporidian parasite lineages were recorded across all study sites, with diversity showing a positive correlation to altitude. Parasites belonging to lineage SGS1 (P. relictum) and PARUS4 and PARUS19 (Leucocytozoon sp.) dominated lower altitudes. SW2 (P. polare) was the second most prevalent lineage of parasite detected overall and these parasites were responsible for 68% of infections at intermediate altitude, but were only documented at this one study site.
Avian haemosporidian parasites are not homogeneously distributed across host populations, but differ by altitude. This difference is most probably brought about by environmental factors influencing vector prevalence and distribution. The high occurrence of co-infection by different genera of parasites might have pronounced effects on host fitness and should consequently be investigated more rigorously.
疾病生态学和保护学关注的一个主要问题是了解影响寄生虫分布并由此引发疾病爆发的因素。本研究旨在调查瑞士西部三个不同海拔梯度的大山雀种群中的鸟类血孢子虫组成及其寄生虫分布。研究目的是确定研究种群中寄生虫的谱系多样性，并调查海拔梯度是否通过谱系控制血孢子虫寄生虫的分布。
在这项研究中，使用分子方法（PCR 和测序）来检测在三个连续繁殖季节中在鸟巢中捕获的成年大山雀种群中的鸟类血液寄生虫（疟原虫、血孢子虫和白细胞虫）。
在所有研究种群中，寄生虫的流行率（88-96%）都很高，且没有显著的海拔效应。然而，海拔确实控制了不同属寄生虫的分布，其中疟原虫寄生虫在较低海拔更为流行，白细胞虫寄生虫在高海拔更为流行，而血孢子虫寄生虫的流行率则随着海拔的升高而增加。在所有研究地点共记录了 27 种血孢子虫寄生虫谱系，多样性与海拔呈正相关。属于谱系 SGS1（P. relictum）和 PARUS4 和 PARUS19（白细胞虫）的寄生虫主要分布在低海拔地区。SW2（P. polare）是总体上第二大流行的寄生虫谱系，这些寄生虫在中海拔地区的感染率达到 68%，但仅在一个研究地点记录到。
鸟类血孢子虫寄生虫在宿主种群中的分布不均匀，而是随海拔而异。这种差异很可能是由影响媒介物流行率和分布的环境因素引起的。不同属寄生虫的混合感染发生率很高，可能对宿主适应性产生显著影响，因此应更严格地进行研究。
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