摘要昆明地区马肉孢子虫包囊的自然感染率为78%。光镜下。包囊呈梭形，具有锥状和棍棒状的突起。透射电镜下突起内的微管在顶端松散排列，向下延伸集结成束，斜伸入基质层，有的和母细胞的膜相连。用含有包囊的马肉实验感染2只犬、2只猫，感染后犬粪中发现孢子囊和卵囊。潜伏期为13～14天。剖检，2只犬的小肠固有层中均查到孢子囊和卵囊。猫粪中一直未检到孢子囊和卵囊，剖检亦未发现。表明马肉孢子虫的终末宿主是犬，不是猫。我们认为马体内的肉孢子虫仅有一种，鉴定为柏氏肉孢子虫(Sarcocystis bertrami)。本文是国内马肉孢子虫的首次报告。

PREVALENCE,CYST WALL ULTRASTRUCTURES AND EXPERIMENTAL

DIFINITIVE HOST INFECTIONS OF SARCOCYSTIS FROM HORSES

Hu Junjie

(Department of Biology,Yunnan University,Kumming,650091)

Zuo Yangxian

(Department of Biology,Yunnan University,Kumming,650091)

AbstractThe prevalence of sarcosporidiosis in horses from Kunming was 76.7%.Light microscropy re-vealed that the intramuscular cysis were shuttle-shaped.The cyst wall was formed by cone-or clubshaped protrusions.Electvo-microscopy showed that in the core of the protrusion there were bundles of microtubules which penetrated diagonally into the ground substance along the longitudinal axis of the protrusion and sometimes reached the interior border of the ground substance.Two dogs that had been fed on musculature containins Sarcocysts of naturally infected horse shed sporulated oocysts and sporocysts in feces 13 to 14 day. later In histologic sections of canine small intestien,the oocysts and sporocysts were located in the lamina porpia near the tips of the vfilli.Two cats fed on similar musculature containing sarcocysts did nof shed sporulated oocysts and sporocysts,ond there were no oocysts and sporocysts in cat small intestine.under histo logical examinations. So the dog is the final host of Sarcocystis of the horse.Based on this study and the literature,we suqqest that only one species named Sarcocystis bertrami exists in horses in Kunming.

Key wordsHorse SarcocystisPrevalenceUltrastructureExperimental infectivity

在欧洲、亚洲、美洲等地均有关于马肉孢子虫的报道。迄今共报道了有3种寄生于马肌肉中的肉孢子虫：柏氏肉孢子虫(Sarcocystis bertrami)、马犬肉孢子虫(Sarcocystis equicanis)、法氏肉孢子虫(Sarcocysitis fayeri)。关于各个种之间的关系及种名的有效性存在着不同的观点。此外，近年来还在北美马的脑和脊索神经细胞中发现神经肉孢子虫(Sarcocystis neurora)，其终末宿主尚不明。我国尚无马肉孢子虫的研究报道。因此，本研究在理论上和实践上具有一定意义。

1材料与方法

1.1自然感染率调查及光镜观察包囊

分部位剪取昆明市郊屠宰的马肉，带回实验室。剔除脂肪和结缔组织，顺肌纤维方向将肌肉剪成铅笔芯粗细的小条，有规则地置放在载玻片，每张玻片可放5～10条，用另一张载玻片盖上，缓缓轻压，使肌肉变薄变扁，低倍镜下检查肉孢子虫包囊。查到包囊后，记下位置，取去上面一张载玻片，将包囊剥离出来，移入另一张载玻片上，滴加0.85%的生理盐水，加盖玻片，高倍镜或油镜下观察包囊形态、测量和初步鉴定。刺破包囊可观察和测量溢出的缓殖子和母细胞。统计马各部位肌肉的肉孢子虫自然感染率。

1.2透射电镜材料制备

选包囊较多的一小块马肌肉，以2.5%戊二醛(0.1mol/L pH=7.3的磷酸缓冲液配制)预固定2h,1%锇酸后固定2h，经脱水包埋后作超薄切片，以醋酸双氧铀和柠檬酸铅染色，自然干燥，透射电镜观察。

1.3实验感染

1.实验动物犬(Canis familiaris)4只，猫(Felis catus)4只：购自昆明市郊农贸市场，刚断奶，约40日龄。犬和猫实验感染前均经连续5次粪检(每天检查一次)，检查肉孢子虫孢子囊和卵囊，证实没有自然感染的肉孢子虫卵囊和孢子囊。

2.实验感染从自然感染的马肉中分离包囊，包含有大小两型包囊，经口感染2只犬和2只猫(约200包囊/只)，另2只犬、2只猫留作对照。自感染后第5天起，每天收集犬、猫粪便，以37%ZnSO₄漂浮法涂片镜检。15～20天后剖杀动物，取其小肠粘膜固有层涂片镜检。

2结果

2.1马肉孢子虫自然感染率调查结果

本研究共对50头马进行了肌肉检查，在39头马的肌肉中发现了肉孢子虫包囊，自然感染率为78%。食道肌、颈部肌、颌肌、舌肌、背肌、肋间肌、膈肌、前腿肌、后腿肌、臀肌、尾肌等12个部位肌肉中均检查到肉孢子虫包囊。常见的寄生部位是食道肌(60.0%)、前腿肌(41.6%)和后腿肌(38.4%)。心肌不被寄生。

2.2包囊在光镜下的观察结果

马体内发现两型包囊，两型包囊均呈乳白色，长梭形，具有倾斜指状突起，突起末端伸入肌细胞质。Ⅰ型包囊较小，大小为1 175～7 375μm×25～125μm,平均2 541μm×71.1 μm(n=30)。突起长2.5～5.3μm(含基质层厚度)，平均长3.7μm(n=20)。缓殖子香蕉形，大小为14.5～17.0μm×2.1～4.5μm,平均15.0μm×3.9μm(n=20)(图Ⅱ-1)。Ⅱ型包囊较大，大小为1 250～8 325μm×100～325μm，平均4 907μm×241μm(n=24)。突起稍短，突起长1.8～3.0μm(含基质层厚度)，平均2.4μm(n=18)。缓殖子香蕉形，大小为15.1～20.5μm×3.8～5.5μm，平均16.3μm×4.2μm(n=20)(图版Ⅱ-2)。

1自然感染的马的柏氏肉孢子虫(Sarcocystis bertrami)Ⅰ型包囊,包囊壁上有长指状突起(×500);

2自然感染的马的柏氏肉孢子虫(Sarcocystis bertrami)Ⅱ型包囊,包囊壁上有短指状突起(×600);

3马体内具有长指状突起的Ⅰ型包囊的纵切面.突起内有微管(MT)和嗜锇颗粒(OS),

微管在突起顶部和中部比较分散,在基部和基质层(GS)集结成束,斜伸入基质层,

有时甚至达到基质层的内壁(×13000);

4马体内具有短指状突起的Ⅰ型包囊的纵切面.突起内有微管(MT)和嗜锇颗粒(OS),

微管在突起顶部和中部比较分散,在基部和基质层(GS)集结成束,斜伸入基质层,

有时甚至达到基质层的内壁(×26000);

5感染的柏氏肉孢子虫(Sarcocystis bertrami)14天后,犬粪中的肉孢子虫孢子囊(×1200);

6感染的柏氏肉孢子虫(Sarcocystis bertrami)14天后,犬小肠固有层中的肉孢子虫虫卵囊(×1200);

1 Sarcocysts from naturally infected horse.Sarcocystis bertrami cyst surrounded by a cyst wall with long protrusions(×1500)2.Sarcocystis bertrami cyst surrounded by a cyst wall with short protrusins (×600).3 TEM micrographs of the cyst wall with long protrusions.Longitudinal section through villar protrusion with large osmiophilic granules(OS) and microtubules(MT)in the core.The bundle of microtubules which penetrated diagonally into the ground substance (GS)along the longitudinal axis of the villar protrusion and sometimes reached the interior border of the ground substance was generally loosely organized within the middle and distal parts of the villar protrusions,and tightly packed within the proximal part of the protrusions and the ground substance of the cyst wall (×1300).4 TEM micrographs of the cyst wall with long protrusions.Note osmiophilic granules(OS),microtubules(MT) adn round substance(GS)(×26000).5 Sarcocystis bertrami Sporocysts from the feces of a dong 14 days after feeding horse muscles(×1200).6 Sarcocystis bertrami Sporuiated ocysts from the small intestine of a dog 14 days after feeding h