Worm Parasites Pt. II : Cestodes/Trematodes/nematodes Flashcards
Taenia solium vs. saginata morphology
solium = pork, saginata = beef
T. Saginata – no scolex hooks, more uterine branches in proglottid
T. Solium – hooklets in circle in scolex and fewer uterine branches,
Taenia solium/saginata morphology
Cestode
Cestodes (flatworms with scolex – head for sucking and proglottids – infectious segments containing eggs)
Taenia solium/saginata pathogenesis life cycle
Ingestion of gravid proglottid by pig or cattle (water, food, etc) –> Release of eggs into intestine –> enter into circulation –> seeding of muscle forms larval cyst –> Human infection by the consumption of raw/under cooked meat –> attachment to intestine by scolex –> establish residency –> Fecal-Oral trasnmission —> If humans ingest the gravid proglottid (eggs) the infection will disseminate and form cysts –> Blindness, Neurocysticercosis, encephalitis
Taenia solium/saginata diagnosis
Stool sample w/ gravid proglottid uterus w/ >1000 eggs
Epidemiology Taenia solium/saginata
Worldwide, esp in areas of poverty with poor sanitation where humans in close contact w/ pigs or ingestion of raw beef. Rare in Muslim countries.
Human consumption of cysts from infected carrier (i.e., meat); carrier acquires from infected food/water (think feces)
1 cause of New onset adult seizures in the developing world
Parasitic infections
Remember most flatworms and flukes are treated with
praziquantel
Taenia solium vs. saginata clinical presentation
T. Solium:
In T. solium, disease depends on whether eat undercooked pork (tapeworm symptoms) or food/water contaminated by feces (containing ovum) of infected human (neurocysticercosis)
Larval disease –> Neurocysticercosis (CNS calcifications, dilated ventricles, hydrocephalus) –> headaches/adult-onset seizures, aseptic meningitis, blindness (ventricles dilate –> ICP↑ –> papilledema)
T. saginata
Usually asymptomatic, can cause GI upset, weight loss, dizziness, headaches, bowel obstruction, allergy against worm Ags
Treatment of Taenia solium/saginata
Praziquantel or albendazole
Treatment is controversial for neurocysticercosis b/c cysts will often die on own;
albendazole (often with steroids to avoid acute encephalitis) for 5-100 lesions (b/c larval form);
surgical removal when ventricles involved
Medical name for fish tapeworm
Diphyllobothrium latum
Diphyllobothrium latum properties
Cestode
Scolex w/ 2 ventral sucking apparatuses (bothria) to attach to bowel wall, flat/wide proglottids
Oval/operculated egg (lid-like opening at 1 end and knob at other end)
Diphyllobothrium latum clinical presentation
Macrocytic anemia (high MCV) from B12 deficiency
Can also have diarrhea, abdominal pain, vomiting, weight loss, fatigue, constipation and discomfort)
Diphyllobothrium latum diagnosis
Eggs/proglottids in feces
Diphyllobothrium latum epidemiology
Consumption of raw fish
Diphyllobothrium latum treatment
Praziquantel
Scientific name for dog tapeworm
Echinococcus granulosus
Echinococcus granulosus properties
Cestode
Larvae hatch –> penetrate small intestine –> bloodstream –> organs (liver, lungs, brain)
Echinococcus granulosus clinical presentation
Pulmonary – pulmonary densities, cough, vomica (salty taste in mouth w/ cough = rupture of hydatid cyst with spillage of scolices, leading to metastatic spread of daughter cysts)
Hepatic Echinococcosis w/ hydatid cyst
- Active cyst wall consisting of single cell germinal layer and thicker gelatinous laminar layer (budding of germinal layer = daughter cysts)
- Pericyst (reactive fibrous layer) around cyst
- Expansion may rupture into biliary tree, erode through diaphragm into pleural cavity, rupture into peritoneum –> can cause anaphylaxis from parasitic Ag release
Echinococcus granulosus diagnosis
Water lily appearance on imaging (CT/MRI)
Echinococcus granulosus epidemiology
Ingestion of feces contaminated with eggs (cycles between sheep & dogs)
Endemic in regions where dogs (primary) in contact with sheep, elk, caribou (intermediate). Mediterranean, Middle East, SA, Greece, Italy, Turkey, esp. sheep farmers
Echinococcus granulosus treatment
puncture, aspiration, injection, and reaspiration (PAIR) tx in liver (prevent spilling of hydatic sand); surgical excision in lung or albendazole for unresectable
Echinococcus granulosus transmission
Humans become infected when they swallow eggs in contaminated food.
In which animals?
- T. solium
- T. saginata
- D. latum
- E. granulosus
- T. solium –> pork.
- T. saginata –> cattle.
- D. latum –> fish.
- E. granulosus –> sheep and dogs.
Schistosome properties
Nonsegmented parasites, life-cycle must pass through snail, operculated eggs. Male and Female schistosomes!!!
Trematode
List of schistosomes
(S. mansoni, S. hematobium, S. japonicum, S.mekongi)
life cycle of schistosomes
Cercariae (larvae) penetrate intact skin in water –> venous plexuses of GI tract, bladder –> circulation –> live in mesenteric venules and bladder –> mature, lay eggs –> usually end in stool
Clinical Schistosomiasis
Manifestations depend on region, but are mainly based on inflammatory rxn to cellular infiltrates of egg
S. Mansoni clinical presentations
S. Mansoni – mainly liver (brisk inflammatory rxn, chronic liver scarring, granulomatous response, “pipestem fibrosis”); can also migrate to lungs or spinal cord
S. Hematobium clinical presentations
S. Hematobium – mature in the GU venous plexuses instead of portal circulation –> hematuria –> bladder wall scarring, obstruction, bladder cancer
Avian schistosoma clinical presentation
intensely pruritic dermatitis (“swimmer’s itch”), remain in skin only, cannot develop into adult worms in human host
Schistosoma transmission
Fresh water sources (playing in water) and contact w/ cercariae form tropics
Geography
S. mansoni
S. hematobium
avian schistosoma
S. mansoni esp. in Africa/Brazil;
S. hematobium in Africa;
avian schistosoma in Canada/northern water
Treatment schistomas
Praziquantel, snail control!!!!!!!!!!!!
schistosomes pathogenesis
The eggs themselves do not damage the body. Rather it is the cellular infiltration resultant from the immune response that causes the pathology classically associated with schistosomiasis.
Opistorchis (Clonorchis) sinensis properties
Trematode
Chinese liver fluke, operculated egg, hermaphroditic
Opistorchis (Clonorchis) sinensis clinical presentation
RUQ pain, cholecystitis
Penetrates intestinal wall –> bile ducts –> chronic biliary tract inflammation –> higher risk of cholangiocarcinoma (bile duct cancer)
Opistorchis (Clonorchis) sinensis diagnosis
Eggs in gallbladder
Opistorchis (Clonorchis) sinensis transmission
Eating raw fresh water fish
Opistorchis (Clonorchis) sinensis treatment
Praziquantel
Fasciola hepatica properties
Trematode
Nonsegmented parasites, life-cycle must pass through snail, hermaphroditic, operculated eggs
Fasciola hepatica life-cycle
Cercariae leave snail, attach to aquatic vegetation –> humans ingest raw watercress –> penetrate intestinal wall and liver (Glisson’s) capsule –> liver, bile ducts
Fasciola hepatica clinical
RUQ pain, fever, chills, diarrhea, gallstones, liver abscesses (usually symptomatic)
Fasciola hepatica diagnosis
High WBCs, eosinophils
Fasciola hepatica transmission
Ingestion of raw watercress
Fasciola Hepatica treatment
Fasciola is the one trematode not treated with praziquantel.
Treatment: Veterinary formulation of triclabendazole
Paragonimus westermani properties
Trematode
Lung fluke: ingestion –> excyst in stomach –> penetrates intestinal wall, diaphragm, then pleural cavity –> cysts
Paragonimus westermani clinical presentation
Cystic cavities in lung (mimic TB), migrating larval worms can also invade spinal cord/brain
Paragonimus westermani diagnosis
Eosinophilia
Eggs in Lung Tissue biopsy
Paragonimus westermani transmission/epidemiology
Fecal-oral ingestion of raw infected shellfish in East Asia (some in Central America)
Trichinella spiralis properties
nematode
Spiral shaped larvae
Trichinella spiralis pathogenesis
Ingestion of undercooked meat –> larvae penetrate bowel –> migrate to skeletal muscle –> inflammation
Trichinella spiralis clinical
Myalgia, preorbital edema, fever
Trichinella spiralis diagnosis
Muscle biopsy, serology, Eosinophilia + elevated CPK
Trichinella spiralis epidemiology
Hunters eating game meat (deer, boar, etc)
Found in NA, SA, Europe, East Asia
Trichinella spiralis treatment
Mebendazole and Steroids
*use steroids with treatment because cysts rupture causes a release of more antigen and an increase in symptoms. Steroids act as an immune suppressor to blunt symptoms.
List of Cestodes
Taenia Solium
Taenia Saginata
Diphyllobothrium Latum (fish tapeworm)
Echinococcus Granulosa (dog tapeworm)
List of Trematodes
Schistosomas: S. mansoni, S. hematobium, S. japonicum, S.mekongi
Opistorchis (Cinorchis) Sinensis
Fasciola Hepatica
Paragonimus westermani
List of nematode
Trichinella spiralis
