University of Groningen, Arctic Centre, PO Box 716, 9700 AS Groningen, The Netherlands.
Vet Parasitol. 2013 May 1;194(1):9-15. doi: 10.1016/j.vetpar.2012.12.027. Epub 2012 Dec 20.
Toxoplasma gondii is an intracellular coccidian parasite found worldwide and is known to infect virtually all warm-blooded animals. It requires a cat (family Felidae) to complete its full life cycle. Despite the absence of wild felids on the Arctic archipelago of Svalbard, T. gondii has been found in resident predators such as the arctic fox and polar bear. It has therefore been suggested that T. gondii may enter this ecosystem via migratory birds. The objective of this study was to identify locations where goose populations may become infected with T. gondii, and to investigate the dynamics of T. gondii specific antibodies. Single blood samples of both adults and juveniles were collected from selected goose species (Anser anser, A. brachyrhynchus, Branta canadensis, B. leucopsis) at Arctic brood-rearing areas in Russia and on Svalbard, and temperate wintering grounds in the Netherlands and Denmark (migratory populations) as well as temperate brood-rearing grounds (the Netherlands, non-migratory populations). A modified agglutination test was used on serum, for detection of antibodies against T. gondii. Occasional repeated annual sampling of individual adults was performed to determine the antibody dynamics. Adults were found seropositive at all locations (Arctic and temperate, brood-rearing and wintering grounds) with low seroprevalence in brood-rearing birds on temperate grounds. As no juvenile geese were found seropositive at any brood-rearing location, but nine month old geese were found seropositive during spring migration we conclude that geese, irrespective of species and migration, encounter T. gondii infection in wintering areas. In re-sampled birds on Svalbard significant seroreversion was observed, with 42% of seropositive adults showing no detectable antibodies after 12 months, while the proportion of seroconversion was only 3%. Modelled variation of seroprevalence with field data on antibody longevity and parasite transmission suggests seroprevalence of a population within a range of 5.2-19.9%, in line with measured values. The high occurrence of seroreversion compared to the low occurrence of seroconversion hampers analysis of species- or site-specific patterns, but explains the absence of an increase in seroprevalence with age and the observed variation in antibody titre. These findings imply that even though infection rate is low, adults introduce T. gondii to the high Arctic ecosystem following infection in temperate regions.
刚地弓形虫是一种广泛存在于全球的细胞内球虫寄生虫，已知几乎可以感染所有温血动物。它需要猫科动物（猫科）来完成其完整的生命周期。尽管斯瓦尔巴群岛的北极群岛上没有野生猫科动物，但已在当地的捕食者（如北极狐和北极熊）中发现了刚地弓形虫。因此，有人认为刚地弓形虫可能通过候鸟进入这个生态系统。本研究的目的是确定鹅种群可能感染刚地弓形虫的地点，并调查刚地弓形虫特异性抗体的动态。在俄罗斯和斯瓦尔巴的北极育雏区以及荷兰和丹麦的温带越冬地（迁徙种群）以及温带育雏地（荷兰，非迁徙种群）采集了选定鹅种（鹅、短颈鹅、加拿大鹅、白额雁）的成年和幼鹅的单份血液样本，并使用改良的凝集试验检测血清中的抗刚地弓形虫抗体。对个体成年鹅进行了偶尔的年度重复采样，以确定抗体动态。在所有地点（北极和温带，育雏和越冬地）都发现成年鹅呈血清阳性，而在温带育雏地的育雏鸟类中血清阳性率较低。由于在任何育雏地点都没有发现幼鹅呈血清阳性，但在春季迁徙期间发现了 9 个月大的鹅呈血清阳性，因此我们得出结论，无论物种和迁徙如何，鹅在越冬区都遇到刚地弓形虫感染。在重新采样的斯瓦尔巴成年鹅中观察到显著的血清学逆转，42%的血清阳性成年鹅在 12 个月后没有检测到抗体，而血清转化的比例仅为 3%。基于抗体持久性和寄生虫传播的现场数据对血清阳性率的变化进行建模表明，种群的血清阳性率在 5.2-19.9%的范围内，与测量值一致。与低血清转化率相比，血清学逆转的高发生率阻碍了对特定物种或特定地点模式的分析，但解释了与年龄相关的血清阳性率增加和观察到的抗体效价变化。这些发现意味着，尽管感染率较低，但成年鹅在感染温带地区后将刚地弓形虫引入北极高生态系统。
