McBride Michael P, Sims Michele A, Cooper Robert W, Nyaoke Akinyi C, Cullion Cheryl, Kiupel Matti, Frasca Salvatore, Forrester Naomi, Weaver Scott C, Weber E Scott
Buttonwood Park Zoo, 425 Hawthorn Street, New Bedford, Massachusetts 02740, USA.
J Zoo Wildl Med. 2008 Dec;39(4):631-7. doi: 10.1638/2008-0021.1.
A 31-yr-old male, captive harbor seal (Phoca vitulina) was evaluated for a 48-hr period of anorexia followed by the onset of seizures. A prolonged seizure failed to respond to anticonvulsant therapy and the animal was euthanized. At necropsy, no significant gross lesions were identified. Reverse transcriptase-polymerase chain reaction testing of brain samples was positive for eastern equine encephalitis virus (EEEV) RNA, and serum was positive for anti-EEEV antibodies by plaque reduction neutralization. Histopathologic evaluation revealed severe and multifocal encephalitis with leptomeningitis, characterized by neutrophilic infiltrates in neuropil, neuronal necrosis, satellitosis, neuronophagia, and perivascular cuffs of lymphocytes, macrophages, and neutrophils. Additionally there was moderate, multifocal, adrenal cortical necrosis. Immunohistochemical staining for EEEV demonstrated viral antigen within necrotic neurons and glial cells. Virus was isolated from frozen brain tissue, sequenced for comparison to other strains, and determined to be a typical North American strain. EEEV should be included as a possible cause of neurologic disease in harbor seals with compatible signs located in geographic regions where vector transmission of EEEV is encountered.
一只31岁的圈养港海豹（斑海豹）因厌食48小时后出现癫痫发作而接受评估。一次长时间的癫痫发作对抗惊厥治疗无反应，该动物被实施安乐死。尸检时，未发现明显的肉眼可见病变。脑样本的逆转录聚合酶链反应检测显示东部马脑炎病毒（EEEV）RNA呈阳性，血清通过蚀斑减少中和试验检测抗EEEV抗体呈阳性。组织病理学评估显示严重的多灶性脑炎伴软脑膜炎，其特征为神经纤维网中的嗜中性粒细胞浸润、神经元坏死、卫星现象、噬神经元现象以及淋巴细胞、巨噬细胞和嗜中性粒细胞的血管周围套袖。此外，还有中度的多灶性肾上腺皮质坏死。对EEEV进行免疫组织化学染色显示坏死神经元和神经胶质细胞内有病毒抗原。从冷冻脑组织中分离出病毒，进行测序以与其他毒株比较，并确定为典型的北美毒株。在EEEV通过媒介传播的地理区域，对于出现符合症状的港海豹，EEEV应被视为神经疾病的可能病因之一。
