Taenia Species (3rd Stage) PDF

Taenia species (3rd stage) Microbiology Department Dr.Ban Anas Medicine College University of Basrah Objectives Learning 1-Studying Taenia spp and main differences among them 2–Studying Morphology, biology, distribution life cycle , p...

Taenia species (3rd stage) Microbiology Department Dr.Ban Anas Medicine College University of Basrah Objectives Learning 1-Studying Taenia spp and main differences among them 2–Studying Morphology, biology, distribution life cycle , pathogenesis,diagnosis, treatment and control for these species. Cyclophyllidean Cestodes Taenia species  Taenia saginata (Beef tapeworm)  Taenia solium (Pork tapeworm) Morphology The differences in morphology between the two species can be summarized in following table: T.saginata T. solium Adult stage The adult worm is opalescent white in color, ribbon-like, dorsoventrally flattened and segmented. It consists of head (scolex), neck and strobila (immature, mature and gravid segment) length 5- 10 meters 2-3 meters Scolex bearing 4 hemispherical bearing 4 hemispherical suckers but It suckers. (no rostellum or contains a fleshy rostellum and double hooklets so it's called the crown (row)of well-defined hooks unarmed tapeworm) Neck long and narrow short and half as thick as the head The 1000-2000 segments Less than 1000 segments strobila The 15 - 20 uterine branches 7 -13 uterine branches on each side of the gravid on each side of the uterus. uterus segment Eggs Eggs of both species are indistinguishable. It is consists of a hexacanth embryo which is surrounded by radial striations embryophore. 1  Taenia species (3rd stage) Larva Cysticercus is the larval stage of Taenia spp It contains a muscular organ with bladder like sac. Scientific Cysticercus bovis Cysticercus cellulosae name of larva Content contains a single contains a single invaginated scolex with invaginated scolex hooks Natural muscles of mastication It can develop in various organs of pig as habitat ,cardiac muscles, well as in man diaphragm and tongue of infected cattle. Note: from the neck region that new segments, or proglottids, differentiate. Life cycle (T.saginata and T. solium) Definitive host: Humans are the definitive hosts and harbor the adult worm. Intermediate host: Cattle (cow or buffalo) for T.saginata and pigs for T.solium are the intermediate host and harbor the larval stage of the worm. (Note:in case of T.solium ,the human may be intermediate host). Infective stage: Cysticercus (larval stage) is the infective stage to man, while eggs are infective to human in case of T.solium only. 1. Infection with Taenia spp. occurs following the ingestion of raw or undercooked beef (T. saginata) or pork (T. solium) contaminated with a cysticercus larva. 2. Scolex attachment to the intestinal mucosa occurs after the larva emerges in the small intestine, in which maturation into an adult worm occurs. 3. The resulting adult multiplies, producing numerous eggs, some of which may be passed into the feces. 4. These eggs are then consumed by the proper animal species (cow or pig) in which the oncosphere hatches. 5. The oncosphere then migrates via the blood to the animal tissue and converts into the infective cysticercus larval stage. Note :In T. solium life cycle. Humans can become infected with cysticerci from ingestion of eggs (or possibly occasionally by retrain infection of gravid proglottides). 2 Taenia species (3rd stage) 3 Taenia species (3rd stage) 4  Taenia species (3rd stage) Epidemiology and Geographical Distribution T. saginata infection is and occurs in almost all countries where cattle breeding areas and beef is eaten raw or undercooked.. Taenia solium infection has a cosmopolitan distribution in countries where pork is eaten raw or undercooked. However, it is reported less from the Muslim countries (as pork eating is not allowed). Natural Habitat The adult worms of T. saginata and T. solium reside in the small intestine (jejunum and ileum) of humans, where as the larva of T. solium (cysticercus cellulosae) reside and form cystic lesions in the muscle, brain and eyes. Pathogenesis and Clinical features  Asymptomatic: Most people who become infected with Taenia spp. typically remain asymptomatic.  Taeniasis: Beef or Pork Tapeworm Infection:Nondescript symptoms, such as diarrhea, abdominal pain, change in appetite, and slight weight loss. In additon, symptoms including dizziness, vomiting, and nausea may also develop.  Cysticercosis:Clinical spectra of the disease depend upon the localization of the cyst. Though it is discovered from any site of the body but the common sites are central nervous system(CNS),subcutaneous tissue, skeletal muscle and eyes. 1- Subcutaneous cysticercosis: It is frequently asymptomatic but may manifest as palpable nodules. 2- Muscular cysticercosis: Manifest as muscular pain, weakness or pseudo hypertrophy. 3- Ocular cysticercosis: Can involve eye lids, conjunctiva and sclera. Common symptoms like proptosis, diplopia, loss of vision and slow growing nodule with focal inflammation 4- Neurocysticercosis (NCC): is the most common form of cysticercosis and accounts for 60–90% cases of cysticercosis which included: A:Asymptomatic neurocysticerosis (NCC):Sometimes NCC remains in the brain without causing any apparent symptoms. B:Manifestations: Seizure , late onset epilepsy,hydrocephalus ,increased intracranial pressure and hypertension presented as headache,vomiting and vertigo,Chronic meningitis and dementia. 5  Taenia species (3rd stage) Laboratory diagnosis A.Diagnosis of Taeniasis 1. Microscopic examination: Detection of characteristic eggs, gravid proglottids of Taenia in faeces.Species identification cannot be made from shape of eggs since the eggs of T.saginata and T. solium look alike but eggs of T. saginata are acid fast. 2. Molecular diagnosis: These technique are used to detect and differentiate between T. saginata and T. solium such as PCR on faecal sample. 3. Serodiagnosis: Specific antibodies to adult stage antigen in serum can be demonstrated by ELISA, indirect immunofluorescence test and indirect hemagglutination (IHA) test B.Diagnosis of Cysticercosis 1. Histopathology Definitive diagnosis of cysticercosis is by biopsy of the lesion and its microscopic examination to show the invaginated scolex with suckers and hooks. 2. Serodiagnosis Antibody & Antigen detection: in serum or cerebrospinal fluid (CSF). 3. Radiodiagnosis CT scan and MRI Treatment 1. Intestinal taeniasis Praziquantel is the drug of choice. 2. Cysticercosis Excision is the best method, where the cysts are accessible. For cerebral Cysticercosis , praziquantel and albendazole may be administered. Corticosteroids may be given along with praziquantel or albendazole to reduce the inflammatory reactions caused by the dead cysticerci. Prevention and control 1. Proper cooking of beef and pork. 2. Proper sanitation. 3. Personal hygiene mainly to prevent autoinfection with T.solium eggs 4. Avoid eating raw vegetables grown in polluted soil to prevent from acquiring Cysticercosis. 6