GI Cestodes and Trematodes Flashcards
Cestodes
***Tapeworms*** Segmented bodies Hermaphroditic Absorb nutrients Segments house mature eggs as they advance toward end of worm Can be 20 to 40 feet long
Three Basic Structures of Adult Cestodes (Tapeworms)
1) Scolex: rounded head of the worm, usually armed with HOOKS and/or SUCKERS
2) Neck: the area from which new body segments are generated
3) Body (Strobila): a long segmented structure
What are individual segments of the Strobilia (i.e. Body) called?
Proglottids
Cestodes (Humans as Definitive vs. Intermediate Host)
1) Definitive Host: Adult tapeworms residing in the GI tract (Small intestine)
- Taenia saginata (Beef tapeworm)
- Taenia solium (Pig tapeworm)
- Diphyllobothrium latum (Fish tapeworm)
2) Intermediate Host: Larval stages present in various tissues (e.g. liver, brain, eye, etc.)
- Echinococcus granulosus (Dog tapeworm)
- Taenia solium (Pig tapeworm)
Beef Tapeworm - Taenia saginata (Life Cycle)
Infected human passes eggs/proglottids in their feces, cattle graze on the area that is contaminated with human waste
We eat meat medium rare and get this
Beef Tapeworm - Taenia saginata (Transmission)
Ingestion of undercooked beef containing encysted larvae (Cysticerci)
-Humans are generally infected with a single adult worm (Can reach 10-30 ft in length and live up to 25 years)
Beef Tapeworm - Taenia saginata (Symptomatology)
Generally Asymptomatic
-Mild abdominal pain/feeling of fullness
Beef Tapeworm - Taenia saginata (Diagnosis, Control/Prevention)
Diagnosis:
-Identification of proglottids or eggs passed by infected material
Control/Prevention:
- Prevent cattle from becoming infected (eliminated their contact with human feces)
- Prevent human infection by cooking meat thoroughly
Pork Tapeworm - Taenia solium (Transmission)
Ingestion of UNDERCOOKED PORK containing CYSTS results in intestinal disease
-Ingestion of embryonated eggs results in extra-intestinal disease (Cysticercosis)
Pork Tapeworm - Taenia solium (Intestinal Disease)
Similar to Beef Tapeworm
Generally Asymptomatic
-Mild abdominal pain/feeling of fullness
Pork Tapeworm - Taenia solium (Extra-Intestinal Disease)
- Ingested eggs hatch in intestine and release infectious larvae, which enter the circulation and travel to various body sites where they encyst (ONCHOSPHERE form penetrates intestine)
- Cysticercus creates a space-filling lesion and induces localized inflammation
- Location and size determines pathology (striated muscle, heart, brain, eyes)
- NEUROCYSTICERCOSIS = Severe complication. Seizure and neurological defects. (Approximately 2000 cases of neurocysticercosis in the U.S. annually)
Pork Tapeworm - Taenia solium (Diagnosis and Prevention/Control)
Diagnosis:
- Intestinal infection (PROGLOTTIDS or eggs in stool via O and P test)
- Extra-intestinal: CT scan, MRI, serology
Prevention/Control:
- Keep pigs away from human feces
- Cook pork thoroughly
Fish Tapeworm - Diphyllobothrium latum (Characteristics)
- LARGEST TAPEWORM infectin man (30 to 40 ft)*
- Infected fish can be found in freshwater lakes in Minnesota, Michigan, Florida, and California
Fish Tapeworm - Diphyllobothrium latum (Transmission)
Ingestion of raw or undercooked fish containing infectious larvae
Fish Tapeworm - Diphyllobothrium latum (Symptomatology)
Asymptomatic or mild
- Transient nausea, abdominal pain, diarrhea, etc.
- Infection with multiple worms can lead to intestinal obstruction
- 2% of patients develop MACROCYTIC ANEMIA (VITAMIN B12 DEFICIENCY)
Fish Tapeworm - Diphyllobothrium latum (Diagnosis, Control/Prevention)
Diagnosis:
-Eggs in stool
Control/Prevention:
- Limit exposure of fish to human feces
- Cook fish adequately
Dog Tapeworm - Echinococcus granulosus (Characteristics)
- Humans are an accidental host
- Acquired through exposure to DOG FECES (ingestion of eggs)
- Disease occurs where LIVESTOCK are raised in association with DOGS
Dog Tapeworm - Echinococcus granulosus (Disease)
- Ingested eggs hatch in the intestine, release larvae which travel via the BLOODSTREAM to multiple body sites. In the tissue, larvae secrete a HYALINE MEMBRANE. Over time, a FLUID-FILLED CYST (HYDATID CYST): frequently form in the liver, lung, brain, and bone marrow
- Ruptured cysts release large amount of NITROGEN and can induce ANAPHYLACTIC RESPONSE
Dog Tapeworm - Echinococcus granulosus (Diagnosis)
-Presence of cyst and history consistent with exposure
Pink circles in picture; must be careful not to break them open when removing from the body
Trematodes
Flukes
Humans are the DEFINITIVE host
Freshwater snails serve as intermediate hosts
Larval forms release from snails encyst on fish, shellfish, or vegetation and are acquired by ingestion
Intestinal Flukes - Fasciolopsis buski (Life Cycle)
Leech-shaped appearance
Hermaphroditic
-Get eggs into environment via feces, get into water, larvae hatch open, infect snails, develop in SNAILS, released from snails and swim in the water, attach to VEGETATION and are mainly associated with WATER CHESTNUTS
~3 months from ingestion to egg production
Intestinal Flukes - Fasciolopsis buski (Characteristics)
NOT VERY COMMON IN THE U.S.
-Common in China, Southeast Asia, and India
Reservoirs = Pigs, dogs, and rabbits
Intestinal Flukes - Fasciolopsis buski (Disease)
- Humans acquire infection by ingesting freshwater aquatic plants with encysted CERCARIAE attached
- In the small intestine, the cercariae encyst, attach to the columnar epithelium and mature to egg-laying adults (HERMAPHRODITIC)
Intestinal Flukes - Fasciolopsis buski (Light vs Heavy Infection)
Light Infection (single worm): -Focal inflammation, intermittent diarrhea
Heavy Infection (multiple worms) -Continuous diarrhea, intestinal hemorrhage, ulceration, abscess formation
