Data from: Pythons, parasites and pests: anthropogenic impacts on Sarcocystis (Sarcocystidae) transmission in a multi-host system

Parasites are essential components of ecosystems and can be instrumental in maintaining host diversity and populations; however, their role in trophic interactions has often been overlooked. Three apicomplexan parasite species of Sarcocystis (S. singaporensis, S. zamani, and S. villivillosi) use the reticulated python as their definitive hosts and several species within the Rattus genus as intermediate hosts, and they form a system useful for studying interactions between host–parasite and predator–prey relationships, as well as anthropogenic impacts on parasite transmission. Based on predictions from a 1998 survey, which detected an inverse relationship between urban development and Sarcocystis infection in Rattus, we tested the hypothesis that Sarcocystis transmission in Singapore will decrease over time due to anthropogenic activities. Despite a large proportion of the reticulated python diet consisting of Rattus species at all sizes of pythons, Sarcocystis infection rates decreased from 1998 to 2010. Pythons found in industrial areas had lower Sarcocystis infection rates, particularly in the western industrial area of Singapore Island. Average python size also decreased, with implications that we predict may disrupt host–parasite relationships. Anthropogenic activities such as habitat modification, fragmentation, and systematic removal and translocation of pythons have negative impacts on Sarcocystis transmission in Singapore, which in turn may augment pest rat populations. Trends observed may ultimately have negative impacts on human health and biodiversity in the region.

寄生虫是生态系统不可或缺的组成部分，在维持宿主多样性与种群规模方面发挥着关键作用，但其在营养级互作中的功能却常被忽视。本研究涉及3种顶复门肉孢子虫属（Sarcocystis）寄生虫——新加坡肉孢子虫（S. singaporensis）、扎马尼肉孢子虫（S. zamani）以及维利维洛西肉孢子虫（S. villivillosi）——它们以网纹蟒作为终宿主，以家鼠属（Rattus）的多个物种作为中间宿主，该研究系统可用于探究宿主-寄生虫互作、捕食者-猎物关系，以及人为活动对寄生虫传播的影响。基于1998年一项调查的预测结论——该调查发现城市开发强度与家鼠体内肉孢子虫感染率呈负相关——我们验证了如下假设：受人为活动影响，新加坡境内的肉孢子虫传播率将随时间推移逐渐下降。尽管各体型层级的网纹蟒食谱中，家鼠物种均占据较高占比，但1998年至2010年间，肉孢子虫感染率仍呈显著下降趋势。在工业区采样的网纹蟒，其肉孢子虫感染率更低，其中以新加坡岛西部工业区的个体最为明显。网纹蟒的平均体型也出现下降，我们推测这一变化可能会打破宿主-寄生虫的互作平衡。诸如栖息地改造、生境破碎化，以及系统性捕获与迁移网纹蟒等人为活动，均对新加坡境内的肉孢子虫传播产生了负面影响，进而可能导致害鼠种群规模扩增。本次观测到的一系列变化趋势，最终可能对该地区的人类健康与生物多样性造成不利影响。