Dickinson Eleanor R, Orsel Karin, Cuyler Christine, Kutz Susan J
Faculty of Veterinary Medicine, University of Calgary, 3280 University Drive, NW, Calgary, AB T2N 1N4, Canada.
Faculty of Veterinary Medicine, University of Calgary, 3280 University Drive, NW, Calgary, AB T2N 1N4, Canada.
Int J Parasitol. 2023 Apr;53(4):221-231. doi: 10.1016/j.ijpara.2023.01.001. Epub 2023 Feb 16.
Parasites can impact wildlife populations through their effects on host fitness and survival. The life history strategies of a parasite species can dictate the mechanisms and timing through which it influences the host. However, unravelling this species-specific effect is difficult as parasites generally occur as part of a broader community of co-infecting parasites. Here, we use a unique study system to explore how life histories of different abomasal nematode species may influence host fitness. We examined abomasal nematodes in two adjacent, but isolated, West Greenland caribou (Rangifer tarandus groenlandicus) populations. One herd of caribou were naturally infected with Ostertagia gruehneri, a common and dominant summer nematode of Rangifer sspp., and the other with Marshallagia marshalli (abundant; winter) and Teladorsagia boreoarcticus (less abundant; summer), allowing us to determine if these nematode species have differing effects on host fitness. Using a Partial Least Squares Path Modelling approach, we found that in the caribou infected with O. gruehneri, higher infection intensity was associated with lower body condition, and that animals with lower body condition were less likely to be pregnant. In caribou infected with M. marshalli and T. boreoarcticus, we found that only M. marshalli infection intensity was negatively related to body condition and pregnancy, but that caribou with a calf at heel were more likely to have higher infection intensities of both nematode species. The differing effects of abomasal nematode species on caribou health outcomes in these herds may be due to parasite species-specific seasonal patterns which influence both transmission dynamics and when the parasites have the greatest impact on host condition. These results highlight the importance of considering parasite life history when testing associations between parasitic infection and host fitness.
寄生虫可通过影响宿主的健康和生存来影响野生动物种群。寄生虫物种的生活史策略能够决定其影响宿主的机制和时间。然而，由于寄生虫通常作为共感染寄生虫的更广泛群落的一部分出现，因此很难阐明这种物种特异性效应。在此，我们使用一个独特的研究系统来探究不同真胃线虫物种的生活史如何影响宿主健康。我们检查了西格陵兰驯鹿（Rangifer tarandus groenlandicus）两个相邻但隔离的种群中的真胃线虫。一群驯鹿自然感染了格鲁内奥奥斯特线虫（Ostertagia gruehneri），这是驯鹿属常见且占主导地位的夏季线虫，另一群感染了马氏马歇尔线虫（Marshallagia marshalli，数量众多；冬季）和北方泰勒线虫（Teladorsagia boreoarcticus，数量较少；夏季），这使我们能够确定这些线虫物种对宿主健康的影响是否不同。使用偏最小二乘路径建模方法，我们发现，在感染格鲁内奥奥斯特线虫的驯鹿中，较高的感染强度与较低的身体状况相关，且身体状况较差的动物怀孕的可能性较小。在感染马氏马歇尔线虫和北方泰勒线虫的驯鹿中，我们发现只有马氏马歇尔线虫的感染强度与身体状况和怀孕呈负相关，但有幼崽在身边的驯鹿更有可能两种线虫的感染强度都较高。这些兽群中真胃线虫物种对驯鹿健康结果的不同影响可能是由于寄生虫物种特异性的季节性模式，这些模式既影响传播动态，也影响寄生虫对宿主状况产生最大影响的时间。这些结果凸显了在测试寄生虫感染与宿主健康之间的关联时考虑寄生虫生活史的重要性。
