Center for Infectious Disease Dynamics, Biology Department, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802, USA.
Int J Parasitol. 2009 Sep;39(11):1253-62. doi: 10.1016/j.ijpara.2009.02.025. Epub 2009 May 4.
Peromyscus leucopus populations exhibit unstable population dynamics. Mathematical models predict instability with chronic parasite infections that reduce host fecundity when the parasite distribution within the host population is close to random. We examined the role the nematode Pterygodermatites peromysci may play in influencing the dynamics of these mice. There were seven gastrointestinal worms infecting mice. Pterygodermatites peromysci was the most prevalent and varied seasonally from 12.3% in November to 36.0% in July. Prevalence was higher in adults (30.8%) than juveniles (4.6%) and there were no statistical differences in prevalence or intensity between the sexes. Overall the distribution was random; the relationship between log variance and log mean of P. peromysci intensity from 17 sites was not significantly different from unity. There were significant relationships between infection and breeding condition, suggesting parasites could be the cause of reduced female breeding. A generalized linear model found the likelihood of P. peromysci infection in adults increased with body mass, the presence of other helminths, and when hosts were in breeding condition. Likewise, the intensity of infection was positively related to co-infections and body mass. Pterygodermatites peromysci infection was associated with the presence of the oxyurid nematode Syphacia peromysci but co-infection was lower in females than males. Amongst females, co-infection was greater when breeding, particularly during lactation. The P. peromysci age-intensity relationship increased with age and rose to an asymptote as expected for a parasite with constant mortality and no acquired immunity. Overall, P. peromysci had a random distribution and was associated with reduced breeding; we discuss how these destabilizing processes may influence the dynamics of P. leucopus.
白足鼠种群表现出不稳定的种群动态。数学模型预测，当寄生虫在宿主种群中的分布接近随机时，慢性寄生虫感染会导致宿主繁殖力下降，从而导致不稳定。我们研究了线虫 Pterygodermatites peromysci 可能在影响这些老鼠动态方面所起的作用。有七种胃肠道蠕虫感染老鼠。Pterygodermatites peromysci 是最常见的寄生虫，其季节性变化从 11 月的 12.3%到 7 月的 36.0%不等。成年老鼠（30.8%）的感染率高于幼鼠（4.6%），且雌雄之间的感染率和感染强度没有统计学差异。总体而言，寄生虫的分布是随机的；从 17 个地点获得的 P. peromysci 强度的对数方差与对数均值之间的关系与 1 没有显著差异。感染与繁殖状况之间存在显著关系，这表明寄生虫可能是导致雌性繁殖减少的原因。广义线性模型发现，成年老鼠感染 P. peromysci 的可能性随着体重的增加、其他寄生虫的存在以及宿主处于繁殖状态而增加。同样，感染强度与共感染和体重呈正相关。Pterygodermatites peromysci 感染与寄生线虫 Syphacia peromysci 的存在有关，但雌性的共感染率低于雄性。在雌性中，繁殖时特别是哺乳期的共感染率更高。P. peromysci 的年龄-强度关系随着年龄的增长而增加，并随着预期的具有恒定死亡率且无获得性免疫的寄生虫的渐近线而上升。总体而言，P. peromysci 的分布是随机的，与繁殖减少有关；我们讨论了这些破坏稳定的过程如何影响白足鼠的动态。
