Histopathological Observation of Canine Distemper in Raccoon Dogs

Fang XlANG，Juan CHEN，Minghe YU，Guohui WANG，Qiumei SHl*，Yanying ZHANG，Yongmei SU，Guangping GAO，Guisheng GAO，Fujin Ll，Hongxue ZHANG，Yu ZHAO

1.Changli Center for Animal Disease Prevention and Control，Changli 066600，China；

2.Key Laboratory of Preventive Veterinary Medicine of Hebei Province/Hebei Normal University of Science and Technology，Changli 066600，China；

3.Wen’an Animal Husbandry and Veterinary Bureau，Wen’an 065800，China；

4.Qilu Animal Health Products Co.，Ltd.，Ji’nan 250100，China

Histopathological Observation of Canine Distemper in Raccoon Dogs

Fang XlANG1，Juan CHEN2，Minghe YU3，Guohui WANG3，Qiumei SHl2*，Yanying ZHANG2，Yongmei SU2，Guangping GAO2，Guisheng GAO2，Fujin Ll4，Hongxue ZHANG4，Yu ZHAO2

1.Changli Center for Animal Disease Prevention and Control，Changli 066600，China；

2.Key Laboratory of Preventive Veterinary Medicine of Hebei Province/Hebei Normal University of Science and Technology，Changli 066600，China；

3.Wen’an Animal Husbandry and Veterinary Bureau，Wen’an 065800，China；

4.Qilu Animal Health Products Co.，Ltd.，Ji’nan 250100，China

In this study，histopathological changes in the heart，liver，spleen，lung，kidney and other organs of raccoon dogs died of canine distemper were observed. According to the results，the lung of infected raccoon dogs exhibited severe hemorrhage and emphysema；the liver was congested and degenerated；the spleen was enlarged；the exhibited severe hemorrhage and hyaline degeneration.Multiple organs of infected raccoon dogs were congested and hemorrhaged with tissue damage，inflammatory cell infiltration and a series of pathological changes.This study laid a solid foundation for clinical diagnosis and treatment of canine distemper in raccoon dogs.

Canine distemper；Histopathology；Raccoon dog

C anine distemper is an acute infectious disease caused by canine distemper virus［1］，which is characterized by biphasic fever，rhinitis，severe gastrointestinal disorders and respiratory tract inflammation，and even encephalitis in a few cases.Various secretions，excrements（nasal mucus，saliva，tears，pericardial fluid，pleuraleffusion，ascites and urine）， blood， cerebrospinal fluid，lymph nodes，liver，spleen，spinal cord and other organs of infected animals contain large amounts of canine distemper virus，and the virus can be excreted outward via respiratory tract secretions and urine.Healthy animals can be infected through respiratory tracts or gastrointestinal tracts by direct contact with infected animals and contaminated air or food［2-3］.Fur-bearing animals such as foxes and minks are extremely susceptible to canine distemper［4］.So far，little information is available on canine distemper in raccoon dogs.In this study，pathological changes in five raccoon dogs clinically diagnosed with canine distemper were observed；typical lesions of liver，lung，spleen，kidney and small intestine of dead raccoon dogs were collected，prepared into paraffin sections and stained with HE for histological observation，aiming at providing reference for clinical diagnosis and treatment of canine distemper in raccoon dogs.

Materials and Methods

Materials

Experimental animals From July 2014 to January 2015，the experiment was carried out with five raccoon dogs with suspected canine distemper as experimental materials in Hebei Normal University of Science and Technology.

Reagents Canine distemper virus diagnostic kit；pathologicalsectionreagents such as paraffin，70% ethanol，80%ethanol，95%ethanol，100% ethanol，xylene，hematoxylin and eosin.

Methods

Diagnosis and necropsy of raccoon dogs with typical symptoms A small amount of serum or tear，saliva and other secretions of infected raccoon dogs were collected，transferred into testtubes containing dilution buffer，and mixed evenly by stirring；several drops of sample dilution was added into sample holes of test strip with a pipette.After 10-20 min，test strips with test line and control line turning red indicated positive results，suggesting that the experimental animal could be diagnosed with canine distemper；test strips without appearance of T line indicated negative results.Raccoon dogs died of canine distemper were necropsied to observe the pathological changes.

Preparation of pathologicalsections The liver，spleen，lung，kidney and small intestine tissues of infected raccoon dogs were collected，fixed with 100 ml/L neutral buffered formalin，prepared into pathological sections in accordance with the literature［5-6］，and embedded in paraffin. The histopathological changes were observed and photographed under the microscope.

Results and Analysis

Clinical diagnosis results

The diagnosis results of five raccoon dogs with suspected canine distemper using canine distemper virus diagnostic kit were positive.

Gross necropsy results

Infected raccoon dogs were emaciated and depressed with disheveled hair，sunken eyes and gum in the eyes.Laparoscopy results indicated bloody ascites， remarkable hepatomegaly with rounded liver edge and an incision extending outward，dark red lung with bleeding points on the surface and bloody foam after extrusion，large amounts of bleeding spots and ulcer lesions on the surface of gastric mucosa，different degrees of congestion and necrosis in duodenum，small intestine and large intestine，large amounts of intestinal mucus，renal congestion，bleeding and swelling， and gallbladder filling，without any other abnormalities.

Histopathological observation results

Liver:as shown in Fig.1，the liver was congested and degenerated with amyloid substances concentrated between hepatic cord and bean shaped gap，forming reddish-brown trabes with varying thickness，and the bean shaped gap was squeezed and became smaller；there were small blisters in hepatocyte cytoplasm and vacuoles in some nuclei.

Spleen:as shown in Fig.2，extensive hemosiderin congestion points were observed；splenic lymphoid tissues were reduced with diffuse necrosis of lymphocytes；individual red pulp macrophages increased.

Duodenum:the duodenum of infected raccoon dogs exhibited surface necrosis，epithelial cell necrosis or shedding，duodenalgland atrophy，duodenal gland cell degeneration and necrosis， swelling， vacuolization；duodenal villi were shortened with surface tissue necrosis；some capillaries were congested； petechial hemorrhagewasobservedaround duodenal gland（Fig.3 and Fig.4）.

Lung:the lung of infected raccoon dogs exhibited alveolar collapse and serious alveolar hemorrhage in some regions with thickened alveolar wall and scattered lymphocytes；in addition，emphysema occurred in some alveolar regions with hyperaemia inside the bronchiole（Fig.5）.

Kidney:as shown in Fig.6 and Fig.7，the kidney hemorrhaged with hyaline degeneration； red-stained homogeneous vitreous bodies were visible.

Discussions

Currently，canine distemper has become a majorobstacle limiting large-scale breeding offur-bearing animals.The number of raccoon dogs died of canine distemper is increasing yearly.So far，canine distemper virus has become one of the major viruses infectingraccoondogs［7-10］.Inthisstudy，different lesions of the infected raccoon dog exhibited varying degrees of hemorrhage，especially the lung，liver and intestinal tract.In addition，the middle and posteriorsegments of smallintestine were dilatate with serous congestion，watery intestinal contents that were mixed with blood，and severe shedding of dark red intestinal mucosa.Funicular mesenteric lymph nodes exhibited cord swelling，congestion and hemorrhage.In some cases，the entire small intestine was congested and hemorrhaged signifi-cantly with mucosal epithelial necrosis，shedding and villousatrophy.The above lesions increase the difficulty of treatment.Therefore，several recommendations have been proposed for the prevention and treatment of canine distemper as follows.①Strengthening comprehensive prevention and control of canine distemper and prohibiting the introduction from epidemic areas. Raccoon dogs introduced from nonepidemic areas should be isolated for observed firstly，and mixed after vaccination.②Prohibiting the breeding of cats and dogs in raccoon dog farms and cutting off contact with these animals.③ Strengthening eradication of rats and all kinds of blood-sucking insects and harmful birds.④ Strengthening inoculation with inactivated or attenuated vaccines against canine distemper virus.Young raccoon dogs should be inoculated within 2-3 weeks after separation in June-July every year；adult raccoon dogs should be inoculated in December-January and June-July，respectively.Specifically，young raccoon dogs are inoculated with 2 ml of vaccines；adult raccoon dogs should be inoculated with 3 ml of vaccines；the immunization period lasts six months.

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Responsible editor：Xiaohui FAN

Responsible proofreader：Xiaoyan WU

貉犬瘟热病理组织学观察

项方1，陈娟2，于明鹤3，王国辉3，史秋梅2*，张艳英2，苏咏梅2，高光平2，高桂生2，李富金4，
张洪学4，赵宇2（1.昌黎县动物疾病预防控制中心，河北昌黎066600；2.河北省预防兽医学重点实验室，河北科技师范学院，河北昌黎066600；3.文安县畜牧兽医局 河北文安065800；4.齐鲁动物保健品有限公司，山东济
南250100）

观察了犬瘟热病死貉的心脏、肝脏、脾脏、肺脏、肾脏等器官的病理组织学。结果显示病死貉的肺脏严重出血及气肿，肝脏淤血、变性，脾脏肿大，肾脏出血、透明变性。患病貉的多器官发生充血，出血，组织破坏及炎性细胞浸润等一系列的病理变化。

犬瘟热；病理组织学；貉

河北省科技厅科技支撑计划（14826613D）；秦皇岛市农业科学研究院项目（2014-04）；秦皇岛科技局项目（201502A054）；国家级星火计划项目（2015GA620002）。

项方（1964-），男，河北昌黎人，高级兽医师，研究方向为毛皮动物疾病防治，E-mail：clxykzx@163.com。*通讯作者，教授，博士，研究方向为动物传染病防治，E-mail：shiqiumei@126.com。

2015-09-23

Supported by Science and Technology Support Program of Science and Technology Department of Hebei Province （14826613D）；Project of Qinhuangdao Academy of Agricultural Sciences （2014-04）；Project of Qinghuangdao Municipal Science and Technology Bureau（201502A054）；China Spark Program（2015GA620002）.

*Corresponding author.E-mail:shiqiumei@126.com

Received:September 23，2015 Accepted:November 15，2015

修回日期 2015-11-15