Data from: Endemic infection reduces transmission potential of an epidemic parasite during co-infection

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.

自然环境中普遍存在低毒力的地方性寄生虫感染。此类感染可消耗宿主资源，进而影响共感染状态下其他寄生虫的繁殖能力。本研究旨在明确：地方性感染对宿主造成的能量消耗，是否会限制流行性寄生虫的繁殖能力及其传播潜能。研究对三组德国小蠊（Blattella germanica）分别开展自由采食、饥饿处理，以及感染地方性寄生虫Gregarina blattarum的操作，并测定了其体内的总脂、三酰甘油（TAG）及极性脂含量。随后，通过计数三组宿主体内释放的感染期虫体数量，评估了流行性寄生虫斯氏线虫（Steinernema carpocapsae）的繁殖产出水平。研究发现，饥饿处理与G. blattarum感染均会降低德国小蠊的脂类含量，且主要通过消耗三酰甘油实现。此外，两种处理均会导致线虫传播期虫体的释放量下降。据我们所知，本研究首次直接证实：地方性感染引发的宿主资源消耗，可对流行性疾病的传播造成影响。鉴于地方性感染在自然环境中广泛存在，未来的流行性疾病传播研究应更加重视共感染中的地方性感染因素。