Sapp Sarah G H, Weinstein Sara B, McMahan Christopher S, Yabsley Michael J
* Southeastern Cooperative Wildlife Disease Study, University of Georgia, College of Veterinary Medicine, 589 DW Brooks Dr., Athens, Georgia 30602. Correspondence should be sent to:
J Parasitol. 2016 Oct;102(5):538-544. doi: 10.1645/16-57. Epub 2016 Jun 28.
Wild rodents such as Peromyscus spp. are intermediate hosts for the zoonotic ascarid Baylisascaris procyonis (raccoon roundworm), and previous studies indicate Peromyscus leucopus (white-footed mouse) likely serves an important role in parasite ecology. Natural infections have been sporadically identified in a few Peromyscus spp., but no data are available on differences in susceptibility among the many other species. We compared survival and infection dynamics of B. procyonis in 4 species ( P. leucopus , Peromyscus maniculatus [deer mouse], Peromyscus californicus [California mouse], Peromyscus polionotus [Oldfield mouse]) from regions of varying habitat types as well as B. procyonis prevalence in raccoons. Six captive-bred mice of each species were inoculated per os with 1 of 3 biologically-relevant doses of embryonated B. procyonis eggs (∼10, ∼50, or ∼500). Animals were monitored twice daily for clinical signs and behavioral abnormalities and were euthanized at the onset of neurological signs or extensive (≥20%) weight loss, or at 45 days post-infection if no disease developed. Larvae were counted in the brain via microscopic examination and in skeletal muscle and visceral organs via artificial digestion. In the high-dose group, all but 1 mouse developed severe neurologic disease and were euthanized. In the medium-dose group, survival was variable and ranged from 33-85% across species. Little to no disease was observed in the low-dose group, although 1 P. maniculatus developed disease and was euthanized. Survival analysis reveals P. leucopus had a longer time until clinical disease onset versus the other species, which did not differ significantly from each other. Interestingly, larval recovery relative to dose was nearly identical across species and doses; however, larvae were differentially distributed in skeletal muscle, visceral organs, and brain among species. These data indicate that P. leucopus may be more resilient toward severe baylisascariasis compared to the other species and that even closely-related rodents may experience differential mortality. This variation in tolerance may have ecological implications for the different species as B. procyonis intermediate hosts, although more work is needed to put these experimental findings into context.
诸如白足鼠属（Peromyscus spp.）等野生啮齿动物是兽共患蛔虫——浣熊贝蛔虫（Baylisascaris procyonis，又称浣熊蛔虫）的中间宿主，先前的研究表明白足鼠（Peromyscus leucopus）可能在寄生虫生态学中发挥重要作用。在一些白足鼠属物种中偶尔发现过自然感染情况，但对于许多其他物种之间易感性的差异尚无数据。我们比较了来自不同栖息地类型地区的4种啮齿动物（白足鼠、鹿鼠[Peromyscus maniculatus]、加利福尼亚鼠[Peromyscus californicus]、旧域鼠[Peromyscus polionotus]）感染浣熊贝蛔虫后的存活情况和感染动态，以及浣熊中浣熊贝蛔虫的感染率。每个物种的6只圈养繁殖小鼠经口接种3种与生物学相关剂量之一的感染性浣熊贝蛔虫卵（约10、约50或约500个）。每天对动物进行两次临床症状和行为异常监测，在出现神经症状或体重显著减轻（≥20%）时实施安乐死，若未发病则在感染后45天实施安乐死。通过显微镜检查计数脑中的幼虫，并通过人工消化法计数骨骼肌和内脏器官中的幼虫。在高剂量组中，除1只小鼠外，所有小鼠均出现严重神经疾病并被安乐死。在中剂量组中，不同物种的存活率各不相同，范围为33% - 85%。在低剂量组中几乎未观察到疾病，尽管有1只鹿鼠发病并被安乐死。生存分析表明，与其他物种相比，白足鼠出现临床疾病的时间更长，而其他物种之间无显著差异。有趣的是，不同物种和剂量下相对于剂量的幼虫回收率几乎相同；然而，幼虫在不同物种的骨骼肌、内脏器官和脑中的分布存在差异。这些数据表明，与其他物种相比，白足鼠可能对严重的贝蛔虫病更具抵抗力，而且即使是亲缘关系密切的啮齿动物也可能有不同的死亡率。这种耐受性的差异可能对作为浣熊贝蛔虫中间宿主的不同物种具有生态学意义，不过还需要更多研究来结合实际情况解读这些实验结果。
