School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
Proc Biol Sci. 2013 Aug 21;280(1769):20131500. doi: 10.1098/rspb.2013.1500. Print 2013 Oct 22.
Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection. Total lipids, triacylglycerols (TAG) and polar lipids were measured in cockroaches (Blattella germanica) that were fed ad libitum, starved or infected with an endemic parasite, Gregarina blattarum. Reproductive output of an epidemic parasite, Steinernema carpocapsae, was then assessed by counting the number of infective stages emerging from these three host groups. We found both starvation and gregarine infection reduced cockroach lipids, mainly through depletion of TAG. Further, both starvation and G. blattarum infection resulted in reduced emergence of nematode transmission stages. This is, to our knowledge, the first study to demonstrate directly that host resource depletion caused by endemic infection could affect epidemic disease transmission. In view of the ubiquity of endemic infections in nature, future studies of epidemic transmission should take greater account of endemic co-infections.
在自然界中，地方性、低毒力的寄生虫感染很常见。这种感染可能会耗尽宿主的资源，进而影响其他寄生虫在混合感染时的繁殖。我们旨在确定一种流行寄生虫的繁殖能力（因此也就是其传播潜力）是否会受到地方性感染给宿主带来的能量成本的限制。我们在自由喂食、饥饿或感染了地方性寄生虫- 沙雷氏菌（Gregarina blattarum）的德国蟑螂（Blattella germanica）中测量了总脂质、三酰基甘油（TAG）和极性脂质。然后，通过统计这三种宿主群体中出现的感染性阶段的数量，评估了一种流行寄生虫-斯氏线虫（Steinernema carpocapsae）的繁殖能力。我们发现，饥饿和沙雷氏菌感染都会减少蟑螂的脂质，主要是通过耗尽 TAG。此外，饥饿和 G. blattarum 感染都会导致线虫传播阶段的减少。据我们所知，这是第一项直接证明由地方性感染引起的宿主资源枯竭会影响传染病传播的研究。鉴于地方性感染在自然界中的普遍性，未来对传染病传播的研究应该更多地考虑地方性的混合感染。
