Miller Jaimie L, Erickson Lawrence, Fork Susanne, Roderick Constance L, Grear Daniel A, Cole Rebecca A
U.S. Geological Survey National Wildlife Health Center, Madison, WI, USA.
Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.
Int J Parasitol Parasites Wildl. 2024 Feb 17;23:100908. doi: 10.1016/j.ijppaw.2024.100908. eCollection 2024 Apr.
In the fall of 2021, California Department of Fish and Wildlife reported larval and adult California giant salamanders ( Eschscholtz, 1833) with skin lesions at multiple creeks in Santa Clara and Santa Cruz Counties, California, USA. Field signs in both stages included rough, lumpy textured skin, and larvae with tails that were disproportionately long, flat, wavy, and flaccid. Presence of large-bodied larvae suggested delayed metamorphosis, with some larvae having cloudy eyes and suspected blindness. To determine the cause of the disease, three first-of-the-year salamanders from one location were collected, euthanized with 20% benzocaine, and submitted for necropsy to the U.S. Geological Survey, National Wildlife Health Center. Upon gross examination, all salamanders were emaciated with no internal fat stores, and had multiple pinpoint to 1.5-mm diameter raised nodules in the skin over the body, including the head, gills, dorsum, ventrum, all four limbs, and the tail; one also had nodules in the oral cavity and tongue. Histologically all salamanders had multiple encysted metacercariae in the dermis, subcutis, and skeletal muscles of the head, body, and tail that were often associated with granulomatous and granulocytic inflammation and edema. A small number of encysted metacercariae or empty cysts were present in the gills with minimal inflammation, and rarely in the kidney with no associated inflammation. Morphology of live metacercariae (Trematoda: Heterophyiidae), and sequencing of the 28S rRNA gene identified a species of (Poche, 1926). Artificial digestion of a 1.65 g, decapitated, eviscerated carcass yielded 773 metacercariae, all of similar size and morphology as the live specimens. Based on these findings, the poor body condition of these salamanders was concluded to be due to heavy parasite burden. Environmental factors such as drought, increased temperature, and overcrowded conditions may be exacerbating parasite infections in these populations of salamander.
2021年秋季，美国加利福尼亚州鱼类和野生动物部报告称，在美国加利福尼亚州圣克拉拉县和圣克鲁斯县的多条溪流中发现了患有皮肤损伤的加州巨螈（Eschscholtz，1833）幼体和成体。两个阶段的野外体征包括皮肤粗糙、有肿块，幼体的尾巴异常长、扁平、呈波浪状且松弛。体型较大的幼体表明变态延迟，一些幼体眼睛浑浊且疑似失明。为了确定病因，从一个地点收集了三只当年出生的蝾螈，用20%的苯佐卡因实施安乐死，并提交给美国地质调查局国家野生动物健康中心进行尸检。经大体检查，所有蝾螈均消瘦，无体内脂肪储存，在身体包括头部、鳃、背部、腹部、四肢和尾巴的皮肤上有多个针尖至直径1.5毫米的凸起结节；其中一只在口腔和舌头也有结节。组织学检查显示，所有蝾螈在头部、身体和尾巴的真皮、皮下组织和骨骼肌中有多个包囊化的后尾蚴，这些后尾蚴常伴有肉芽肿性和粒细胞性炎症及水肿。鳃中有少量包囊化的后尾蚴或空囊，炎症轻微，肾脏中很少见，且无相关炎症。活后尾蚴（吸虫纲：异形科）的形态以及28S rRNA基因测序确定为一种（Poche，1926）。对一个1.65克、去头去内脏的尸体进行人工消化后得到773个后尾蚴，其大小和形态均与活标本相似。基于这些发现，得出结论，这些蝾螈身体状况不佳是由于寄生虫负担过重。干旱、气温升高和拥挤等环境因素可能会加剧这些蝾螈种群中的寄生虫感染。
