Mao Gaohui, Guo Bingyan, Xie Shanshan, Yang Yurong
College of Veterinary Medicine, Henan Agricultural University, Zhengzhou 450000, China.
Parasite. 2025;32:48. doi: 10.1051/parasite/2025045. Epub 2025 Aug 1.
Toxoplasma gondii infects almost all warm-blooded animals, including marine mammals. Toxoplasmosis has been reported in wild and captive marine mammals in North America; however, no viable T. gondii strains have been isolated from northern fur seals. In this study, reproduction and T. gondii infection status were investigated in 10 northern fur seals (Callorhinus ursinus), from tissues collected from 2012 to 2024 in China. Toxoplasma gondii infections were determined by the modified agglutination test (MAT), PCR, immunohistochemical (IHC) staining, and isolation of the parasite by bioassay in mice. MAT was performed using placenta or tissue exudates to detect anti-T. gondii IgG antibodies. Four of the 10 seals had anti-T. gondii antibodies; Toxoplasma gondii DNA was detected by PCR in placenta tissues of two of these four animals, and T. gondii antibody positive reactions were observed in four seals by IHC. A viable T. gondii strain, TgFurSealCHn1, was isolated from placenta of one seal by bioassay in mice. In all, five seals had signs of T. gondii infection, and three of them had fetal stillbirth. One stillborn fetus had T. gondii nucleic acid detected by PCR, indicating potential vertical transmission of the parasite. Multilocus genetic typing of the TgFurSealCHn1 isolate revealed ToxoDB #5 genotype, which had demonstrated avirulence in Swiss Webster outbred mice, and the ROP18/ROP5 type was 2/2. ToxoDB #5 is the dominant genotype of wild terrestrial and marine mammals in North America. This is the first report of a viable T. gondii strain isolated from northern fur seal placenta.
刚地弓形虫感染几乎所有温血动物，包括海洋哺乳动物。北美野生和圈养海洋哺乳动物中均有弓形虫病的报道；然而，尚未从北海狗体内分离出有活力的刚地弓形虫菌株。在本研究中，对2012年至2024年在中国采集的10只北海狗（海狗属）的组织进行了繁殖情况和刚地弓形虫感染状况调查。通过改良凝集试验（MAT）、聚合酶链反应（PCR）、免疫组织化学（IHC）染色以及在小鼠体内进行生物测定来分离寄生虫，从而确定刚地弓形虫感染情况。使用胎盘或组织渗出液进行MAT以检测抗刚地弓形虫IgG抗体。10只海豹中有4只具有抗刚地弓形虫抗体；在这4只动物中的2只胎盘组织中通过PCR检测到了刚地弓形虫DNA，并且通过IHC在4只海豹中观察到了刚地弓形虫抗体阳性反应。通过在小鼠体内进行生物测定，从1只海豹的胎盘中分离出了一株有活力的刚地弓形虫菌株TgFurSealCHn1。总共有5只海豹有刚地弓形虫感染迹象，其中3只出现胎儿死产。一只死产胎儿通过PCR检测到了刚地弓形虫核酸，表明该寄生虫可能存在垂直传播。对TgFurSealCHn1分离株进行多位点基因分型显示为ToxoDB #5基因型，该基因型在瑞士韦伯斯特远交小鼠中表现为无毒力，且ROP18/ROP5类型为2/2。ToxoDB #5是北美野生陆生和海洋哺乳动物的主要基因型。这是首次从北海狗胎盘中分离出有活力的刚地弓形虫菌株的报告。
