Wormy world Symposium

Taenia saginata/ Taenia solium

Restate the basic concepts of parasitologyDefine of the various terms related to basic parasitologyDiscuss briefly the life cycle and pathogenesis of medically important parasitesApply the knowledge of the life cycle to the principles of laboratory diagnosis 

Learning outcomes:

What is parasitology?Parasitology is the study of parasites, their hosts, and the relationship between them.

What is medical parasitology?Medical parasitology is the subject which deals with the parasites that infect humans, the diseases caused by them, clinical picture and the response generated by humans against them. It is also concerned with the various methods of their diagnosis, treatment and finally their prevention and control.

1. Morphology - important in laboratory diagnosis which helps to identify the different stages of development.

2. Geographical distribution – Easy escape of the parasite from the host Environmental conditions favoring survival

outside the body of the host The presence of an appropriate vector or

intermediate host

Basic Concepts of Parasitology

Common phase

Route a parasite

follows inside the body

Route a parasite follows

outside the body

3. Life cycle of a parasite

Symptoms, pathology and

diagnosis

Epidemiology, prevention and

control

4. Host parasite relationshipCarrier state - a perfect host parasite relationship where tissue destruction by a parasite is balanced with the host’s tissue repair.

Disease state - this is due to an imperfect host parasite relationship where the parasite dominates the upper hand.

Parasite destruction – occurs when the host takes the upper hand.

5. Laboratory diagnosisBlood –malaria

Stool –Amoebiasis

Urine – urinary Schistosomiasis

Sputum –amoebic abscess of lung or in the case of amoebic liver abscess bursting into the lungs, the trophozoites of E. histolytica are detected in the sputum.

Biopsy material - spleen punctures in cases of kala-azar, muscle biopsy in cases of Cysticercosis, and Chagas’ disease.

Urethral or vaginal discharge – for Trichomonas vaginalis

6.Prevention and control

Reduction of the source of infection

Good personal hygiene

Sanitary control of drinking

water and food

Proper waste

disposal

Avoidance of

unprotected sexual

practices

Any organism that depends on another organism, i.e. the host, for food, shelter, or some other benefit and which receives these benefits in such a way that the host experiences detrimental effects as a consequence.

The parasites included in medical parasitology are protozoa, helminthes and some arthropods.

Parasite

Ectoparasite

• a parasitic organism that lives on the outer surface of its host

• e.g. lice, ticks, mites etc.

Endoparasite

• parasites that live inside the body of their host

• e.g. Entamoeba histolytica

Obligate parasite

• This parasite is completely dependent on the host during a segment or all of its life cycle

• e.g. Plasmodium spp.

Facultativ

e parasit

e

• an organism that exhibits both parasitic and non-parasitic modes of living and hence does not absolutely depend on the parasitic way of life, but is capable of adapting to it if placed on a host

• E.g. Naegleria fowleri

Erratic parasit

e

• is one that wanders in to an organ in which it is not usually found

• E.g. Entamoeba histolytica in the liver or lung of humans.

Definitive host – a host that harbors a parasite in the adult stage or where the parasite undergoes a sexual method of reproduction.

Intermediate host - harbors the larval stages of the parasite or an asexual cycle of development takes place. In some cases, larval development is completed in two different intermediate hosts, referred to as first and second intermediate hosts.

Oncosphere- the larva of the tapeworm contained within the external embryonic envelope and armed with six hooks

Scolex- the attachment organ of a tapeworm , generally considered the anterior or cephalic end

Proglottids- one of the segments making up the body of a tapeworm

Extrinsic incubation period-The interval between the acquisition of an infectious agent by a vector and the vector's ability to transmit the agent to other susceptible vertebrate hosts.

 Taenia saginata  is a beef tapeworm.

Taenia solium is a pork tapeworm.

Taenia saginata and Taenia solium

Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata or Taenia solium. Humans are the only definitive hosts for T. saginata and T. solium. Eggs or gravid proglottids are passed with feces ; the eggs can survive for days to months in the environment. Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids . In the animal's intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci.A cysticercus can survive for several years in the animal.

Humans become infected by ingesting raw or undercooked infected meat .

In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex  and reside in the small intestine .Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium.

The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day). 

T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids. The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces. T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.

TaeniasisPassage of proglottids in stoolMild irritation at site of attachmentEpigastric painWeaknessWeight lossLoss of appetitePruritisObstruction in intestine ,bile duct and appendix because proglottids are actively motile

Taenia saginataPathogenesis

Mild ,non-specific abdominal complaintsProglottids are not as motile as T.saginata so organ obstruction is less likelyCysticercus cellulosae involving any organ or tissues(common subcutaneous tissues and muscle)Autoinfection by finger contamination with eggs from perianal skin or faeces Neurocysticercosis- Cysticercosis of the brain

Taenia soliumPathogenesis

Taeniasis

Confirmative diagnosis of taeniasis is made by finding gravid proglottides or egg in stool Direct fecal smear Brine floatation technique Cellophane-tape technique

Visualization of Taenia eggs-has poor sensitivity and difficult to differentiate from T.saginataCoproantigen detection ELISA-95% sensitivity and 99% specificity

CysticercosisBiopsy of subcutaneous nodules, X-ray, CT scan or MRI are used for the diagnosis of brain type and ophthalmoscope examination is used for ocular form

Immunological test are for reference only

Diagnosis

Treatment for cysticercosis

Surgical removal is required for ocular and superficial cysticercosisPraziquantal may be used to treat brain cysticercosis but it should be taken in a hospital

Prevention

Health educationAvoid eating raw porkAvoid pigs eating human stoolSanitary inspection of slaughter and sanitary disposal of night soil

Thanks