Pathogen Safety Data Sheets: Infectious Substances – Taenia saginata
PATHOGEN SAFETY DATA SHEET - INFECTIOUS SUBSTANCES
SECTION I - INFECTIOUS AGENT
NAME: Taenia saginata
Adult Worm: Mature worms are found only in humans. Mature worms are 4 to 8 meters in length with 1,000 to 2,000 proglottids. The scolex has 4 suckers and the rostellum has no hooks. The gravid proglottids measure 18-20 mm by 5-7 mm with a genital pore. The mature proglottids have two lobe ovaries and vaginal sphincters and will break away form the worm and migrate actively out of the anus of the host.
Cysticercus: The larval stage of the T. saginata is also known as Cysticercus bovis Footnote 3. Cysticerci are unhooked scolex in fluid filled bladders. These are found in the tissues of the intermediate hosts and are 4-6 mm by 7-10 mm. They have pearl like appearance.
Egg: Eggs are found in the feces of the infected hosts. Eggs are spherical with a diameter of 30-40 μm. They have a thin yellow-brown radiated shell and contain a 6 hooked embryo (oncosphere).
SECTION II - HAZARD IDENTIFICATION
PATHOGENICITY/TOXICITY: Adult Taenia saginata can live up to 30 to 40 years in the small intestine of its human host Footnote 3. Most humans who carry an adult tapeworm are asymptomatic Footnote 1, Footnote 3-Footnote 6. Patients may intermittently pass proglottids either with their stool (T. solium) or spontaneously (T. saginata), and may either notice the segment in the toilet bowel or may feel the spontaneous movement of proglottids through the anus. There may be associated nonspecific GI symptoms, including nausea, anorexia, or epigastric pain. Anxiety, headache, dizziness, and urticaria can also occur.
Symptoms are rare but may include obstruction, diarrhea, abdominal pain, weight loss and discomfort.
EPIDEMIOLOGY: Worldwide Footnote 1, Footnote 3, Footnote 7-Footnote 9. It has increased prevalence in Sub-Saharan Africa Footnote 8, Central and South America, Asia and some European countries Footnote 2. High prevalence is associated with the habit of heating raw or undercooked beef Footnote 8. In Ethiopia, 2.2-3.2% of cattle are infected with larval stage of T. saginata, although the reported rates of infection in humans vary widely.
HOST RANGE: Humans are the definitive host Footnote 1, Footnote 2, Footnote 8, Footnote 10, Footnote 11. Cattle are the most common intermediate host. Other host include reindeer, llamas, antelope, wildebeest, giraffes, lemurs, gazelle, camels, and sheep Footnote 12.
INFECTIOUS DOSE: Unknown
MODE OF TRANSMISSION: The intermediate host will contract T. saginata by ingesting the eggs Footnote 2, Footnote 11. The eggs develop into the infective cysticercus in the tissues of the infected intermediate host. Humans contract T. saginata by ingesting the cysticercus from the infected flesh of raw or undercooked beef.
INCUBATION PERIOD: After ingestion of contaminated meat it takes 2 to 3 months for the tapeworm to develop Footnote 2. Development for egg into infectious cysticercus in the intermediate host occurs in 3 months Footnote 3.
COMMUNICABILITY: The eggs that are shed from the human host are not infectious to humans Footnote 1. Eggs are infectious to intermediary hosts, who develop the infectious cysticercus Footnote 1, Footnote 2, Footnote 11. Human cysticercosis (neurocysticercosis), is caused by T. solium, not T. saginata, via ingestion of T. solium eggs Footnote 4.
SECTION III - DISSEMINATION
RESERVOIR: Humans and cattle Footnote 1, Footnote 2. Other animals may also serve as reservoir, including reindeer, llamas, antelope, wildebeest, giraffes, lemurs, gazelle, camels, and sheep Footnote 12.
ZOONOSIS: Taenia saginata infection is a “true zoonosis” in which man is the mandatory definitive host who disseminates the infection to bovine intermediate hosts. Humans contract the beef tapeworm by ingestion of raw or undercooked meat of infected intermediate host Footnote 1-Footnote 3, Footnote 11, Footnote 13. The most common source is cattle.
VECTORS: None. Diphteran flies may be responsible for the dispersion of eggs in the environment Footnote 14.
SECTION IV - STABILITY AND VIABILITY
PHYSICAL INACTIVATION: Cooking (heating to 60ºC) or freezing (-10ºC for at least 10 days) meat will inactivate the cysticerci Footnote 11. Eggs are fully inactivated at 55ºC after few hours in aerobic conditions Footnote 17.
SURVIVAL OUTSIDE HOST: Eggs can survive 5 ½ to 9 ½ months in soil and for an unreported time in treated sewage Footnote 8. Eggs can survive winter on pasture and in fresh, brackish and salt water Footnote 11. Cysticerci can remain viable for 639 days in infected tissues of the intermediary host Footnote 18.
SECTION V – FIRST AID / MEDICAL
SURVEILLANCE: Monitor for symptoms. Can be diagnosed by looking for eggs in feces and the active migration of the gravid proglottids out of the anus Footnote 1, Footnote 2. Identification is done by examination of the proglottids based on the morphology of the uterus. The uterus is injected with India ink for visualization of the branching. Other identification methods include PCR of species-specific sequences of mitochondrial DNA, detection of coproantigens and enzyme linked immunoabsorbent assays for the detection of serum antigens Footnote 19.
FIRST AID/TREATMENT: Infestation of T. saginata can be treated with praziquantel and niclosamide, although the latter is a poorly absorbed, narrow-spectrum anthelmintic that is no longer commercially available in some countries Footnote 1-Footnote 3, Footnote 10, Footnote 19, Footnote 20.
IMMUNISATION: No immunisation for humans. Experimental vaccines for infection in livestock are under development Footnote 10.
SECTION VI - LABORATORY HAZARDS
LABORATORY-ACQUIRED INFECTIONS: None reported to date.
SOURCES/SPECIMENS: Eggs are found in faeces, sewage, feed, and water Footnote 11. Cysticerci are found in the cardiac and skeletal muscles of the intermediate hosts.
PRIMARY HAZARDS: Ingestions of infective cysticerci Footnote 1.
SPECIAL HAZARDS: Eggs are similar to the infectious eggs of T. solium and T. muliceps Footnote 1. During the identification process caution should be taken until a definitive identification as non-infectious T. saginata has been confirmed.
SECTION VII – EXPOSURE CONTROLS / PERSONAL PROTECTION
RISK GROUP CLASSIFICATION: Risk Group 2.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes. Footnote 21.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC) Footnote 21. Additional precautions should be considered with work involving animals or large scale activities. Cysticercosis is a reportable disease under the Health of Animals Regulations Footnote 22. All cases must be reported.
SECTION VIII – HANDLING AND STORAGE
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled.
SECTION IX - REGULATORY AND OTHER INFORMATION
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011
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