Cysticercosis & Sarcocystosis

السلام عليكــم ورحمـة الله وبركاتــة ،،

Cysticercosis

Bovine cysticercosis is caused by Cysticercus bovis, which is the cystic form of the human tapeworm Taenia saginata.

Life cycle :

Cysticercus bovis is the larval stage of Taenia saginata. Taenia saginata may grow from 3 – 7 m in length and lives in the intestine of man. It consists of a suckered head called scolex which is attached to the intestine. It also consist of a neck and hundreds of proglotid segments. Mature proglotids are filled with eggs. The proglotids break off and are excreted in the faeces where they fragment and release the ova. Cattle become infected by grazing on ground and by the digestion of foodstuff contaminated with human faeces. The oncosphere liberated in the intestine from the egg penetrates the intestinal wall and through the lymphatics and blood stream reaches the skeletal muscles and heart. In the muscles the oncosphere develops into the intermediate or cysticercus stage containing a scolex. The sites of predilection are the masseter muscles, tongue, heart and diaphragm. In some countries in Africa the cysticerci appear to show uniform distribution in the musculature. If ingested by man, the final or definite host, the scolex attaches itself to the intestinal wall and tapeworms then develop and mature (Fig. 90).

Transmission : Infection in man occurs following consumption of raw or undercooked beef containing viable cisticerci. Cattle become infected by ingestion of feedstuff containing ova passed from infected humans. Cattle raised on free range become often infected through contamination of grazing with human faeces. Infected farm workers may contaminate hay, silage, other feeds or sewage effluent. Intrauterine infection of a bovine fetus was also recorded.

Antemortem findings :

Heavy infestation in cattle may show:

Muscle stiffness
Rarely fever

Postmortem findings :

Small white lesions (cysticerci 2 – 3 weeks after infection) in muscle tissue
Clear transparent bladders 5 × 10 mm (infective cysticerci, 12 – 15 weeks after infection, Fig. 91)
Opaque and pearl like (over 15 weeks of infection)
Degeneration, caseation and calcification (after 12 months or more after infection)
Degenerative myocarditis

Fig. 90: Life Cycle of Taenia saginata

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 934 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Judgement :

Carcass and viscera of an infested animal should be differentiated with those with "heavy" infestation and those with "light" infestation. Carcass and viscera of heavily infested animals are condemned and those with light infestation should be treated either by boiling or freezing. The extent of "heavy infestation" is prescribed by the controlling authority. An animal is commonly considered heavily infected, if lesions are discovered in two of the usual inspection sites including the masseter muscles, tongue, oesophagus, heart, diaphragm or exposed musculature and in two sites during incisions into the shoulder and into the rounds. Generalized infection according to Canadian regulations means 2 or 3 cysts found on each cut into the muscles of mastication, heart, diaphragm and its pillars, and also if 2 or 3 cysts are found in muscles exposed during dressing procedures. In moderate or light infestation consisting of a small number of dead or degenerated cysticerci, the carcass is held depending on the existing country regulations for approximately 10 days at - 10° C.

Differential diagnosis:

Hypoderma species (migration to heart), nerve sheath tumour, eosinophilic myositis, abscess and granuloma caused by injections

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 418 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Fig. 91: Caseous cysticercus. Numerous clear transparent cysts on the heart surface. 0.6 mm in diameter in the heart muscle.

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Sarcocystosis (Sarcosporidiosis)

Sarcocystosis is caused by the various species of the protozoan genus Sarcocystis. This is one of the most common parasitic conditions in domestic food animals and a high percentage of cattle in various parts of the world are infested with these parasites which are usually host specific. In cattle three species have been recognized. They are listed in Table 1. Cattle are the intermediate hosts of Sarcocystis spp. All Sarcocystis spp. in the intermediate hosts, the food animals, are characterised by the formation of cysts in the muscles.

Table 1: Sarcocystis spp. in Cattle

SpeciesDistributionDefinitive
Host/sSize of cystPathogenicityS. cruziWorld-wideDog, coyote, red fox, racoon and wolfMicroscopic, less than 0.5mm long.Most pathogenic species in cattle it can cause fever, anaemia, abortion neurologic signs and even death.S. hirsutaProbably world-wideCatMacroscopic, up to 8mm long and 1mm wide, fusiform in shapeMildly pathogenicS. hominisEuropeHumans and some primatesMicroscopicMildly pathogenic to cattle

Life cycle:

All Sarcocystis species require two hosts and a pre-predator cycle to complete their life-cycle. A herbivore, the prey, and a carnivore or omnivore, the predator are involved Sexual development occur in the predator which is therefore a definitive host, and a******ual development occurs in the prey which is the intermediate host.

Two species, one in cattle (S. hominis) and one in pigs (S. suihominis) use humans as definitive hosts and therefore these infections in animals are zoonoses (Fig. 105). Generally speaking dog transmitted Sarcocystis are pathogenic and whereas cat transmitted ones are not.

The most important species in cattle is S. cruzi which has world-wide distribution and uses the dog as the definitive host. ******ual development takes place in the dog after which infective sporocysts are passed in the faeces. The details of development in cattle are illustrated in Fig. 106.

The buffalo is the intermediate host for two species: S. levinei which forms microscopic cysts and uses the dog as the definitive host, and S. fusiformis which forms macroscopic spindle or globular shaped cysts measuring 3.2cm × 8 mm and uses the cat as the definitive host. S. fusiformis cysts are seen in the oesophagus and the skeletal musculature and is common parasite of the waterbuffalo in many parts of the world.

Transmission :

Cattle acquire infection by ingesting sporocysts contaminating feed, pasture or water. After several generations of a******ual reproduction by schizogony they form cysts in muscles. S. cruzi, the most pathogenic species for cattle forms microscopic cysts. The definitive host, including humans acquire the infection when they eat bovine tissues containing the viable Sarcocystis cysts. The data provided below are for S. cruzi infestations, unless specified otherwise.

Fig. 105: Life cycle of Sarcocystis hominis (cattle) and Sarcocystis suihominis (pigs) in final host (man) (Courtesy G.J. Jackson, Division of Microbiology, US FDA, Washington D.C., USA)

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 949 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Fig. 106: Life cycle of Sarococystis cruzi in the bovine and canine (prey-predator cycle)

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 919 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Antemortem findings :

Incubation period 5 - 11 weeks
Fever
Loss of appetite
Excessive salivation
Anaemia
Abortion
Loss of hair especially at the tip of the tail

Postmortem findings:

The cysts are microscopic and therefore are not detected on routine postmortem inspection. They cause little tissue reaction.
In some cases the cysts may be associated with eosinophilic myositis (Fig. 107).
A histological section of bovine muscle affected with eosinophilic myositis showing massive accumulation of eosinophiles and two microcysts of S. cruzi (Fig. 108).
S. hirsuta cysts may be seen as fusiform objects 8 mm × 1 mm in the oesophagus, diaphragm and skeletal muscles of older animals especially bulls.
Macroscopic cysts of S. fusiformis in the skeletal muscle of buffalo (Fig. 109).

Judgement:

Judgement should be made on macroscopic presence of cysts. In heavy and widespread infestations with the visible cysts the whole carcass is condemned. In lighter infestations those parts of the carcass which are not affected are passed for human consumption. Microscopic examination of muscle may show as much as 70 % infestation in animals worldwide.

Differential diagnosis:

Cysticercosis, toxoplasmosis, neurofibromatosis, eosinophilic myositis

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 413 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Fig. 107: Sarcocystosis. Eosinophilic myositis.

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 410 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Fig. 108: Histological section showing accumulation of eosinophiles and two microcysts of S. Cruzi. There is no tissue reaction.

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] تم تقليل : 85% من الحجم الأصلي للصورة[ 600 x 408 ] - إضغط هنا لعرض الصورة بحجمها الأصلي
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Fig. 109: S. Fusiformis in the skeletal musculature of buffalo

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