犊弓首蛔虫 Toxocara vitulorum 动医 07 （ 2 ）班 王晶 吕嘉敏 卢沛兰

Introduction Kingdom Animalia （动物界） Phylum Nemathelminthes （线形动物门） Class Secernentea （尾感器纲） Order Ascaridata （蛔目） Family Toxocaridae （弓首科） Genus Toxocara （弓首属） Scientific classification

Host: cattle and buffalo Site: small intestine （小肠）

Morphology Size: large The largest intestinal parasite of cattle

Shape : it has a cylindrical( 圆柱状 ) form ， tapering at either end( 两端尖 ), and the body is covered by a colorless, somewhat translucent( 半透明的 ), layer, the cuticle ( 角皮 ).

11 ～ 26cm 14 ～ 30cm

70~80 μm ｘ 60 ～ 66 μm Egg( 卵 )

Life cycle Adult nematodes develop only in the small intestines （小肠） of young calves under 6 months of age. The eggs do not hatch in the environment, but larvae in the eggs develop to the infective second stage larvae （ L2 ）. Direct Life Cycle( 直接型生活史 )

Egg Infective egg (with L2) L2 在母牛小肠 孵化 适宜的温度、湿度 移行 至肝、肺、肾等 发育成 L3 L4 移行至子宫胎牛吞入体内 犊牛小肠 Adult 经粪便排出 进入胎盘羊水液 Transmission from mother to fetus ( 胎儿 ) across the placenta （胎盘）

Egg L3 进入小肠 乳腺 乳汁 Adult Infective egg (with L2) 移行 适宜的温度、湿度 L2 在母牛小肠 孵化 L4 Transmission by the milk of the dam 至肝、肺等 发育成 L3 移行

In some parts of the world calves may become infected ingesting infective eggs from the environment ， for example, in the southern part of Africa.

Egg 适宜的温度和湿度 肝脏 L3 门静脉 心 肺动脉 细支气管、 支气管、气管 肺泡 进入口腔 小肠 Adult 经粪便排出 咽部 Infective egg (with L2) L2 在犊牛小肠 孵化 Ingestion of infective eggs 后腔静脉肝静脉 肺 L4

Epidemiology cattle and buffalo Bos ( 牛属 ) calves seem to be less susceptible than Bubalus ( 水牛属 ) calves Toxocara vitulorum is found mostly in tropical and subtropical climates worldwide

Calves can be infected both transplacentally （经胎盘地） before birth and via milk after birth, while they may also become infected ingesting infective eggs from the environment.

Transmission through milk is the major route of infection of calves in Southeast Asia. But studies in the southern part of Africa have indicated that the ingestion of infective eggs from the environment is the most common route of infection there.

Larvae develop into adults in the small intestines of young calves, and then begin shedding eggs in the feces contaminating the environment and other animals.

The thick-walled eggs are very resistant to adverse climatic and environmental conditions. At temperatures between 20 and 30ºC they can remain infective for a long period of time (several years).

Prevalence of Toxocara vitulorum in beef cattle in North Central Florida (Davila ， et al 2010) Calf agePrevalence <3 months 29/165 = 17.6% 3 – 4 months5/113= 0.4% 5 – 6 months1/108 = 0.9% 7 – 9 months0/47 = 0%

The prevalence( 感染率 ) in most countries is between 5 and 50% and has been influenced by animal species, sex and seasonal variations. Prevalence can reach 100%, when uncontrolled in the field, since each female worm can lay up to eggs per day.

Lesions punctate hemorrhage 点状出血 eosinophilia 嗜酸性粒细胞增多 hemorrhage 出血 ulcer 溃疡 intestinal obstruction 肠阻塞 intestinal perforation 肠穿孔

Signs enteritis 肠炎 emaciation 消瘦 lethargy 嗜睡 fever, couch, dyspnea( 呼吸困难 ) a stink smell likes acetone( 丙酮 ) diarrhea 腹泻 stomachache 腹痛 exhaustion 衰竭 intestinal obstruction 肠阻塞 intestinal perforation 肠穿孔

Diagnosis Epidemiological analysis 流行病学分析 history of disease ( 病史 ) 、 age 、 feeding and management practices （饲养管理方式）、 season of occurrence （发病季节）、 climate, etc. Clinical signs 临床症状 Faecal examination: by flotation method Post-mortem examination( 死后剖检 ) Diagnosis for treatment ( 治疗性诊断 )

Control The principle of control is to prevent the parasites from having an effect on the calves and from contaminating the environment with eggs.

anthelmintics( 驱虫药 ) 盐酸左旋咪唑 Levamisole 8mg/kg po/im 丙硫苯咪唑 Albendazole 10~15mg/kg po 伊维菌素 Lvermectin 0.3mg/kg sc/po symptomatic treatment 对症治疗 1 、 Treatment 治疗

2 、 prevention 预防 preventative deworming 预防性驱虫 Eliminating the immature parasites before they can harm the calves and start egg production ； Calves under 20 days of age Sanitation 卫生 e.g. Harmless disposal of feces 粪便无害化处理 isolated feeding 隔离饲养

It is advised that all calves under 6 months of age should be used anthelmintics( 驱虫药 ) in endemic area.

References [1] 李国清. 兽医寄生虫学 ( 双语版 ). 北京 : 中国农业大学出版 社,2006 [2] 朱兴全. 兽医专业英语. 北京 : 中国农业出版社,2003 [3] 肖院先, 尹正发, 陈德寿, 等. 杂交水牛犊新蛔虫病的防治 [J]. 中国牛业科学,2009,35(1) ： 95—96 [4] 刘东军. 犊新蛔虫病的诊断和防治措施 [J]. 中国奶 牛,2009,(4) ： [5] 童泽恩, 徐 刚, 吴丽英, 等. 犊新蛔虫病的诊断与治疗 [J]. 中 国兽医寄生虫病,2005,13(3). [6] 张天伟, 岁丰军. 犊牛弓首蛔虫病的诊断与控制 [J]. 河南农 业科学,2004,(9) ： [7]G.Davila,M.Irisk,E.C.Greiner.2010.Toxocara vitulorum in beef calves in North Central Florida.Veterinary Parasitology. 168(3-4),

[8]M. Mahieu, M. Naves Incidence of Toxocara vitulorum in Creole calves of Guadeloupe.Tropical animal health and production.40(4), [9] J. Hansen, B. Perry. The epidemiology, diagnosis and control of helminth parasites of ruminants. the International Laboratory for Research on Animal Diseases, [10] J.A.Roberts. The life cycle of Toxocara vitulorum in Asian buffalo(Bubalus bubalis), International journal for parasitology.(1990)20(7), [11] Fabio R.B, Sebastião R.F, Jackson V.A, Juliana M.A, André R.S, Rogério O.C, Artur K.C, Leandro G.F. Trop Anim Health Prod (2010) 42:309–314 [12]Muhammad, A.R., Zafar, I., Abdul, J., Muhammad, Y., 2007.Point prevalence of gastrointestinal helminthiasis in ruminants in southern Punjab, Pakistan. Journal of Helminthology, 81, 323–328. References