Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA.
Parasitol Res. 2011 Sep;109(3):581-9. doi: 10.1007/s00436-011-2289-4. Epub 2011 Feb 24.
The peritoneal cavity (PNC) and intestine of northern fur seal (Callorhinus ursinus) pups and California sea lion (Zalophus californianus) pups that died in late July and early August, 2003, on San Miguel Island, California, were examined for hookworms. Prevalence and morphometric studies were done with the hookworms in addition to molecular characterization. Based on this and previous molecular studies, hookworms from fur seals are designated as Uncinaria lucasi and the species from sea lions as Uncinaria species A. Adult hookworms were found in the PNC of 35 of 57 (61.4%) fur seal pups and of 13 of 104 (12.5%) sea lion pups. The number of hookworms located in the PNC ranged from 1 to 33 (median = 3) for the infected fur seal pups and 1 to 16 (median = 2) for the infected sea lion pups. In addition to the PNC, intestines of 43 fur seal and 32 sea lion pups were examined. All of these pups were positive for adult hookworms. The worms were counted from all but one of the sea lion pups. Numbers of these parasites in the intestine varied from 3 to 2,344 (median = 931) for the fur seal pups and 39 to 2,766 (median = 643) for the sea lion pups. Sea lion pups with peritoneal infections had higher intensity infections in the intestines than did pups without peritoneal infections, lending some support for the hypothesis that peritoneal infections result from high-intensity infections of adult worms. There was no difference in intestinal infection intensities between fur seal pups with and without peritoneal infections. Female adult hookworms in the intestines of both host species were significantly larger than males, and sea lion hookworms were larger than those in fur seals. Worms in the intestine also were larger than worms found in the PNC. Gene sequencing and (RFLP) analysis of (PCR) amplified (ITS) ribosomal DNA were used to diagnose the species of 172 hookworms recovered from the PNC and intestine of 18 C. ursinus and seven Z. californianus hosts. These molecular data revealed that U. lucasi (hookworm of C. ursinus) and Uncinaria species A (of Z. californianus) infrequently mature in the intestine of the opposite host species in California rookeries. However, there is no support from molecular data for the hypothesis that cross-infection with "the wrong" Uncinaria species is a contributing factor in these cases of host peritonitis. The major significance of this research is the unusual finding of adult hookworms in the PNC of so many dead pups. No obvious explanation for this occurrence could be determined. Further research, like in the present study, should help understand and monitor the apparent ever changing role of hookworm disease in the health of northern fur seal and California sea lion pups on SMI.
加利福尼亚圣米格尔岛于 2003 年 7 月底和 8 月初死亡的北象海豹（Callorhinus ursinus）幼崽和加州海狮（Zalophus californianus）幼崽的腹膜腔（PNC）和肠道被检查是否存在钩虫。除了分子特征描述外，还对钩虫进行了流行率和形态计量学研究。基于这一点以及之前的分子研究，海豹体内的钩虫被指定为 Uncinaria lucasi，而来自海狮的钩虫则被归类为 Uncinaria 物种 A。在 57 只北象海豹幼崽中有 35 只（61.4%）和 104 只（12.5%）海狮幼崽的 PNC 中发现了成年钩虫。在感染的北象海豹幼崽中，PNC 中钩虫的数量范围为 1 至 33（中位数=3），在感染的海狮幼崽中为 1 至 16（中位数=2）。除了 PNC，还检查了 43 只北象海豹和 32 只海狮幼崽的肠道。所有这些幼崽的肠道中都发现了成年钩虫。除了一只海狮幼崽，其余的都对这些寄生虫进行了计数。在这些北象海豹幼崽的肠道中，这些寄生虫的数量从 3 到 2344（中位数=931）不等，而在海狮幼崽中，这些寄生虫的数量从 39 到 2766（中位数=643）不等。腹膜感染的海狮幼崽的肠道感染强度高于未感染腹膜的幼崽，这在一定程度上支持了这样的假设，即腹膜感染是由成年虫高强度感染引起的。在有和没有腹膜感染的北象海豹幼崽之间，肠道感染的强度没有差异。两种宿主物种肠道内的雌性成年钩虫明显大于雄性，而海狮钩虫大于北象海豹。在肠道中发现的蠕虫也比在 PNC 中发现的蠕虫大。从 18 只 C. ursinus 和 7 只 Z. californianus 宿主的 PNC 和肠道中回收的 172 条钩虫的种系发生和（RFLP）分析（PCR）扩增（ITS）核糖体 DNA 用于诊断这些钩虫的种类。这些分子数据表明，在加利福尼亚的繁殖地，U. lucasi（C. ursinus 的钩虫）和 Uncinaria 物种 A（Z. californianus 的钩虫）很少在相反宿主物种的肠道中成熟。然而，分子数据并没有支持这样的假设，即与“错误”的 Uncinaria 物种交叉感染是导致这些宿主腹膜炎的一个因素。这项研究的主要意义是在如此多死亡幼崽的 PNC 中发现了成年钩虫，这是一个不寻常的发现。对于这种情况的发生，目前还没有明显的解释。像本研究这样的进一步研究应该有助于了解和监测钩虫病在北象海豹和加州海狮幼崽健康中不断变化的作用。
