Worm Parasites Pt. II : Cestodes/Trematodes/nematodes

Question 1

Taenia solium vs. saginata morphology

Answer 1

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,

Question 2

Taenia solium/saginata morphology

Answer 2

Cestode

Cestodes (flatworms with scolex – head for sucking and proglottids – infectious segments containing eggs)

Question 3

Taenia solium/saginata pathogenesis life cycle

Answer 3

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

Question 4

Taenia solium/saginata diagnosis

Answer 4

Stool sample w/ gravid proglottid uterus w/ >1000 eggs

Question 5

Epidemiology Taenia solium/saginata

Answer 5

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)

Question 6

1 cause of New onset adult seizures in the developing world

Answer 6

Parasitic infections

Question 7

Remember most flatworms and flukes are treated with

Answer 7

praziquantel

Question 8

Taenia solium vs. saginata clinical presentation

Answer 8

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

Question 9

Treatment of Taenia solium/saginata

Answer 9

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

Question 10

Medical name for fish tapeworm

Answer 10

Diphyllobothrium latum

Question 11

Diphyllobothrium latum properties

Answer 11

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)

Question 12

Diphyllobothrium latum clinical presentation

Answer 12

Macrocytic anemia (high MCV) from B12 deficiency

Can also have diarrhea, abdominal pain, vomiting, weight loss, fatigue, constipation and discomfort)

Question 13

Diphyllobothrium latum diagnosis

Answer 13

Eggs/proglottids in feces

Question 14

Diphyllobothrium latum epidemiology

Answer 14

Consumption of raw fish

Question 15

Diphyllobothrium latum treatment

Answer 15

Praziquantel

Question 16

Scientific name for dog tapeworm

Answer 16

Echinococcus granulosus

Question 17

Echinococcus granulosus properties

Answer 17

Cestode

Larvae hatch –> penetrate small intestine –> bloodstream –> organs (liver, lungs, brain)

Question 18

Echinococcus granulosus clinical presentation

Answer 18

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

Question 19

Echinococcus granulosus diagnosis

Answer 19

Water lily appearance on imaging (CT/MRI)

Question 20

Echinococcus granulosus epidemiology

Answer 20

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

Question 21

Echinococcus granulosus treatment

Answer 21

puncture, aspiration, injection, and reaspiration (PAIR) tx in liver (prevent spilling of hydatic sand); surgical excision in lung or albendazole for unresectable

Question 22

Echinococcus granulosus transmission

Answer 22

Humans become infected when they swallow eggs in contaminated food.

Question 23

In which animals?

1. T. solium
2. T. saginata
3. D. latum
4. E. granulosus

Answer 23

1. T. solium –> pork.
2. T. saginata –> cattle.
3. D. latum –> fish.
4. E. granulosus –> sheep and dogs.

Question 24

Schistosome properties

Answer 24

Nonsegmented parasites, life-cycle must pass through snail, operculated eggs. Male and Female schistosomes!!!

Trematode

Question 25

List of schistosomes

Answer 25

(S. mansoni, **S. hematobium**, S. japonicum, S.mekongi)

Question 26

life cycle of schistosomes

Answer 26

**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

Question 27

Clinical Schistosomiasis

Answer 27

Manifestations depend on region, but are **mainly based on inflammatory rxn to cellular infiltrates** of egg

Question 28

S. Mansoni clinical presentations

Answer 28

S. Mansoni – mainly **liver** (brisk inflammatory rxn, chronic liver scarring, granulomatous response, **"pipestem fibrosis"**); can also migrate to lungs or spinal cord

Question 29

S. Hematobium clinical presentations

Answer 29

S. Hematobium – mature in the GU venous plexuses instead of portal circulation --\> hematuria --\> **bladder wall scarring, obstruction, bladder cancer**

Question 30

Avian schistosoma clinical presentation

Answer 30

intensely pruritic dermatitis **("swimmer's itch")**, **remain in skin only**, cannot develop into adult worms in human host

Question 31

Schistosoma transmission

Answer 31

**Fresh water sources (playing in water)** and contact w/ cercariae form tropics

Question 32

Geography S. mansoni S. hematobium avian schistosoma

Answer 32

S. mansoni esp. in Africa/Brazil; S. hematobium in Africa; avian schistosoma in Canada/northern water

Question 33

Treatment schistomas

Answer 33

Praziquantel, snail control!!!!!!!!!!!!

Question 34

schistosomes pathogenesis

Answer 34

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.

Question 35

Opistorchis (Clonorchis) sinensis properties

Answer 35

Trematode **Chinese liver fluke,** operculated egg, **hermaphroditic**

Question 36

Opistorchis (Clonorchis) sinensis clinical presentation

Answer 36

RUQ pain, **cholecystitis** Penetrates intestinal wall --\> bile ducts --\> **chronic biliary tract inflammation** --\> **higher risk of cholangiocarcinoma** (bile duct cancer)

Question 37

Opistorchis (Clonorchis) sinensis diagnosis

Answer 37

Eggs in gallbladder

Question 38

Opistorchis (Clonorchis) sinensis transmission

Answer 38

Eating raw fresh water fish

Question 39

Opistorchis (Clonorchis) sinensis treatment

Answer 39

Praziquantel

Question 40

Fasciola hepatica properties

Answer 40

Trematode ## Footnote Nonsegmented parasites, **life-cycle must pass through snail**, **hermaphroditic**, operculated eggs

Question 41

Fasciola hepatica life-cycle

Answer 41

Cercariae leave snail, **attach to aquatic vegetation** --\> **humans ingest raw watercress** --\> penetrate intestinal wall and liver (Glisson’s) capsule --\> **liver, bile ducts**

Question 42

Fasciola hepatica clinical

Answer 42

RUQ pain, fever, chills, diarrhea, gallstones, **liver abscesses (usually symptomatic)**

Question 43

Fasciola hepatica diagnosis

Answer 43

High WBCs, eosinophils

Question 44

Fasciola hepatica transmission

Answer 44

Ingestion of raw watercress

Question 45

Fasciola Hepatica treatment

Answer 45

Fasciola is the one trematode not treated with praziquantel. Treatment: Veterinary formulation of triclabendazole

Question 46

Paragonimus westermani properties

Answer 46

Trematode ## Footnote Lung fluke: ingestion --\> excyst in stomach --\> penetrates intestinal wall, diaphragm, then **pleural cavity --\> cysts**

Question 47

Paragonimus westermani clinical presentation

Answer 47

**Cystic cavities in lung (mimic TB)**, migrating larval worms can also invade spinal cord/brain

Question 48

Paragonimus westermani diagnosis

Answer 48

Eosinophilia Eggs in Lung Tissue biopsy

Question 49

Paragonimus westermani transmission/epidemiology

Answer 49

Fecal-oral ingestion of **raw infected shellfish** in East Asia (some in Central America)

Question 50

Trichinella spiralis properties

Answer 50

nematode ## Footnote Spiral shaped larvae

Question 51

Trichinella spiralis pathogenesis

Answer 51

Ingestion of undercooked meat --\> larvae penetrate bowel --\> migrate to skeletal muscle --\> inflammation

Question 52

Trichinella spiralis clinical

Answer 52

**Myalgia**, preorbital edema, fever

Question 53

Trichinella spiralis diagnosis

Answer 53

Muscle biopsy, serology, **Eosinophilia + elevated CPK**

Question 54

Trichinella spiralis epidemiology

Answer 54

**Hunters eating game meat (deer, boar, etc)** Found in NA, SA, Europe, East Asia

Question 55

Trichinella spiralis treatment

Answer 55

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.

Question 56

List of Cestodes

Answer 56

Taenia Solium Taenia Saginata Diphyllobothrium Latum (fish tapeworm) Echinococcus Granulosa (dog tapeworm)

Question 57

List of Trematodes

Answer 57

Schistosomas: **S. mansoni**, **S. hematobium**, S. japonicum, S.mekongi Opistorchis (Cinorchis) Sinensis Fasciola Hepatica Paragonimus westermani

Question 58

List of nematode

Answer 58

Trichinella spiralis