Nematodes, Cestodes and Trematodes Flashcards

Question 1

Q

Name 5 species of clinically significant Cestodes

Answer

A

Taenia saginata - beef tapeworm
Taenia solium - pork tapeworm
Diphyllobothrium latum - broad/fish tapeworm
Hymenolepsis nana - dwarf tapeworm
Echinococcus spp. - hydatid

Question 2

Q

What are Helminths?

Answer

A

‘parasitic worms’
2 phyla
1. Platyhelminthes - flatworms
  1. Cestodes - tapeworms
    1. Cyclophylidea ‘Land’
      1. Taenidae: T**aenia, Echinococcus
      2. Hymenolepidae: Hymenolepsis
    2. Pseudophyllidea ‘Water’
      1. Diphyllobothridae: Diphylobothrium
  2. Trematotodes - flukes
2. Nematodes - roundworms

Question 3

Q

What is the Generalised Tapeworm Lifecycle?

Answer

A

Adults ⇒ definitive hosts
Eggs ⇒ external environment
Juveniles ⇒ Intermediate host
- Hymenolepsis nana ⇒ humans
- Taenia saginata ⇒ cattle
- Taenia solium ⇒ pigs
- Diphylobothrum latum ⇒ copepods, fish
- Hymenolepsis nana ⇒ larvae of cereal meal worms or fleas (rodent reservoir)
- Hymenolepsis diminula ⇒ fleas or flour beatles
- Diphylobothrum caninum ⇒ dog or human flea (Ctenocephalides canis or C. felis)

Question 4

Q

Name 4 species of clinically significant Trematodes.

Etymology

Answer

A

Fasciola hepatica - the liver fluke
Paragonimus westermani - the lung fluke
Opisthorchis sinensis - Chinese liver fluke (aka Clonorchis sinensis
Schistosoma mansoni, S. japonicum, S. haematobium - schistosome or bilharzia flukes

Etymology: old English word for Flounder

Question 5

Q

5 species of Clin. significant Nematodes.

What is the etymology?

Answer

A

Strongyloides stercoralis - threadworm
Necator americanus & Ancylostoma duodenale - the Hookworms
Ascaris lumbricoides - the Large Roundworm of Man
Tricuris trichuria - the Whipworm
Enterobius vermicularis - the pinworm
Toxocara canis & toxocara cati - Visceral and ocular larva migrans

From Greek “nema” or thread

Question 6

Q

What is this?

Life cycle?

Symptoms?

Answer

A

Ascaris
largest of intestinal soil-transmitted helminths
adults live in intestine, eggs passed in feces and contaminate environment, water and food
Ascariasis caused by ingeting eggs on soiled hands or consuming fruit or veg that have not been washed or peeled
eggs hatch into larva in small intesting, penetrate intestinal wall and migrate through blood and lungs where they may cause symptoms
if coughed up and swallowed they return to gut to mature and reproduce

Question 7

Q

What are these?

Answer

A

left to right
- Necator americanus or Cyclostoma duodenalis (hookworm) egg
- tricuriasis (whipworm) egg
- fertile ascaris egg

Question 8

Q

What is this?

Describe it.

Answer

A

fertile Ascaris egg
oval shape, about 60µm long
brownish colour
thick shell covered by a rough coat stained brown by bile in gut

Question 9

Q

What is this?

Describe it?

Describe it and what triggers it to dev

Answer

A

infective Ascaris egg
oval, thick wall, contains visible larvum
as the fertile egg leaves host, reduction in temperature, oxygen and moisture levels trigger ovum to develop into this infective stage
takes 20-40 days to do so
if ingested in contaminated food, will hatch in intestine and person will become infected

Question 10

Q

What is this?

Describe.

Answer

A

infertile Ascaris egg
less common in feces than fertile eggs
egg is longer an narrower than fertile ege, as large as 75-90µm long
usually very dark in colour with flattened ends

Question 11

Q

What is this?

Where is it found?

Life cycle?

Answer

A

adult pinworm (Enterobius)
worldwide distribution, commonly affects children
female deposits eggs on perianal skin during night, and within a few hours of being laid they contain infected larvae (embryonated eggs)
child scratches and autoinoculates self, eggs travel to intestin and hatch
sometimes larvae hatch on perinal skin and migrate back to the intestine and mature

Question 12

Q

What is this?

Describe.

Life Cycle

How diagnosed?

Answer

A

Enterobius eggs
oval in shape, colourless, with clear shell
about 55 µm long
eggs laid on perianal skin, eggs become infective within few hours, itching causes host to scratch and then reinfects self by swallowing fertile egss, which hatch in the intestine
best collected from perianal skin at night “sellotape method” or “Graham swab”, eggs visible under microscope

Question 13

Q

What is this?

Life Cycle?

Clinical disease?

Complications?

Answer

A

trichuris (whipworm)
round worm of humans found in warm moist climate and poor sanitation
may occur in cecum, ileum, appendix and colon of humans
ingestion of infective eggs in contaminated food/fingers
light infections may cause few symptoms
young children severe infections may cause chronic diarrhea, ulceration with blood and mucous passed in stool
fe deficiency, wt loss
prolapse rectum

Question 14

Q

What is this?

What other symptoms may occur?

Answer

A

prolapsed rectum in child
caused by whipworm (Trichuris)
fe def anemia, wt loss

Question 15

Q

What is this?

Describe it.

Life Cycle.

How long does egg take to become infective.

Answer

A

trichuris egg (whipworm)
egg barrel-shaped, 50 µm long with clear mucoid plug at either end
when passed in feces egg contains undeveloped ovum
after about 3 weeks in soil becomes embryonated (infective)
infective egg ingested from contaminated food or fingers, larvae hatch and develop in small intestine
adult worms bore into wall of the large intestine and embed in anterior part of mucosa
secretes digestive fluid into tissues of intestinal wall, liquefying surface, which is then taken up by the worm

Question 16

Q

What is this?

Describe it?

Size, distinctive characteristics.

Answer

A

Trichuris (whipworm) egg.

egg barrel-shaped, 50 µm long with clear mucoid plug at either end

Question 17

Q

What is this?

Answer

A

hookworm (Ancylostoma duodenale or Necator americanus)
adult parasites live in small intestine, sucking and ingesting blood through intestinal wall
male worms 8-9 mm, females 11-12 mm, heads of both males and females are bent dorsally giving “fishing hook appearance”

Question 18

Q

What is this?

Geographic distribution?

Life Cycle?

Disease?

Answer

A

Ancylostoma duodenale
hookworm
worldwide in areas with moist warm climate
this species predominant in Middle East, Africa, Southern Europe
transdermal entry via hair follicles, also ingested orally ⇒ Wakana syndrome
preferred site upper small intestine, but in very heavy infections may extend as far as lower ileum
hookworm mouthparts of adult penetrate blood vessels, nourish by sucking blood
cause chronic anemia, blood loss
differentiate from N. americanus by teeth in buccal cavity. N. americanus has flat cutting plate

Question 19

Q

What is this?

Geographical distribution?

How distinguished from similar parasite?

Answer

A

Necator americanus
hookworm
this species predominates in America and Australia
distinguished by flat cutting plates in N. americanus vs teeth in A. duodenale

Question 20

Q

What is this?

FOBT?

Answer

A

adult hookworm, either Necator americanus or Ancylostoma duodenale
teeth embedded in small intestine wall
FOBT usually positive

Question 21

Q

What is this?

Life Cycle

Answer

A

Hookwoorm eggs
Ancylostoma duodenale and Necator americanus are indistinguishable
Size: 57-76 µm, oval or ellipsoidal shape
thin shell
eggs passed into stool, hatch into rhabditiform larvae, which take about a week to develop into infective stage
larvae penetrate skin usually of foot, travel through venous circulation through lungs up to trachea then swallowed, travel to small intestine, attach and mature into adults after feeding on blood
female hookworms produce up to 30,000 eggs per day

Question 22

Q

What is this?

Characteristic features?

Answer

A

hookworm larvae
long buccal cavity at anterior end, which differentiates them from Strongyloides larvae
no notch at the tail end

Question 23

Q

What is this?

sex?

Morphology? Identification

Life Cycle?

Answer

A

Adults of Strongyloides stercoralis may be found in human host or soil
in human host no parasitic males
parasitic females are long and slender, measuring 2-3 mm
in human host, female lays eggs in intestinal mucosa, larvae hatch almost immediately to only larvae are found in feces
larvae similar to first stage Hookworm larve but have shorter mouth cavity and are found in freshly passed feces (hookworm larvae are found in stale faeces)

Question 24

Q

What is this?

What do the arrows indicate.

Answer

A

female Strongyloides sterocralis larva passed in fresh species
Red arrow indicates short (compared to hookworm larva) cavity and rhabditiform esophagus
also differentiated by notch at tail end (not shown here)

Question 25

Q

What are the specific clinical features/syndromes associated with ascariasis?

Larval migration?

Adult gastrointestinal parasitism?

General features?

Answer

A

larval migration⇒verminous pneumonia
adult GI parasitism⇒
- lactose intolerance
- vitamin A malabsorption
- intestinal obstruction
- hepatopancreatic ascariasis
General
- impaired growth
- impaired physical fitness
- impaired cognition
- reductions in school attendance and performance

Question 26

Q

What are the specific clinical features/syndromes associated with trichuriasis?

Common name?

Larval migration?

Adult gastrointestinal parasitism?

General features?

Answer

A

whipworm
lm: none
adult GI parasitism:
- colitis
- trichuris dysentery syndrome
- rectal prolapse

Question 27

Q

What are the specific clinical features/syndromes associated with hookworm

parasite name?

Larval migration?

Adult gastrointestinal parasitism?

General features?

Answer

A

Ancylostoma duodenalis
Necator americanis
lm:
- ground itch
- cough
- Wakana disease: when A. duodenale transmitted orally, characterized by nausea, vomiting, pharyngeal irritation, cough, hoarseness, dyspnea
adult gi parasitism
- intestinal blood loss
- fe def anemia
- protein malnutrition

Question 28

Q

Describe the lifecycle of Ascariasi lumbricoides.

Answer

A

infection via fecal-oral transmission
embryonated eggs swallowed, first stage larvae (L1) hatch, moult into L2 then penetrate intestinal mucosa and migrate to pulmonary circulation
L3 migrate across alveolar wall, ascend tracheobronchial tree to larynx, then to small intestine
Adult female A. lumbricoides produce thousands of eggs daily that pass into stool
Egg production occurs 2-3 months after infection and worms can live for several years
Eggs remain viable in warm moist soil for years

Question 29

Q

Describe Trichuris trichuria lifecycle.

Answer

A

embryonated eggs ingested via food or hands, hatch into larvae that moult in small intestine
larvae develop into adult worms in cecum and ascending colon
female worms lay thousands of eggs daily for several years
eggs pass into stool, embryonate over 2-4 weeks in warm, moist soil
survive for months

Question 30

Q

Describe hookworm lifecycle.

Which species?

Answer

A

Ancyclostoma duodenal and Necator americanus larvae free living in soil
infect people by penetrating skin, usually feet
larvae migrate to pulmonary capillaries, penetrate alveolare wall, migrate to larynx and are swallowed
larvae moult and develop into mature worms in small intestine over 1-2 months
can survive for months (A. duodenalis) or years (N. americanus)
female worm releases thousands of eggs daily into stool
after 5-10 days hatch in warm, moist, sandy soil or feces
Rhabditiform larvae (L1) become infective after moulting to L2 & L3 larvae that survive for several weeks
A. duodenalis can also be ingested orally and can cause Wakana syndrome (nausea, vomiting, pharyngeal irritation, cough, hoarseness, dyspnea)
Zoonotic ancylostoma species can also infect people, causing cutaneous larva migrans (as well as possibly causing pathology similar to a. duodenalis or necator americanus in some people)

Question 31

Q

What is Wakana syndrome and how does it occur.

Answer

A

hookworm Ancyclostoma duodenalis can also be ingested orally instead of penetrating skin resulting in Wakana syndrome (nausea, vomiting, pharyngeal irritation, cough, hoarseness, dyspnea)

Question 32

Q

What causes cutaneous larva migrans?

Answer

A

infection by zoonotic ancyclostoma species
eg dog or cat hookworm

Question 33

Q

Strongyloides stercoralis lifecycle.

Answer

A

complex lifecycle, may take multiple routes including complete lifecycle outside human host
filariform larvae inject human host orally or percutaneously
skin, esp feet ⇒ pulmonary capillaries to alveoli, then larynx to small intestine
oral ingestion same route after penetrating intestinal mucosa to lungs etc.
female adults penetrate gut wall, lodging in duodenal & jejunal lamina propria, laying up to 50 eggs daily
eggs hatch within gut wall, rhabditiform larvae migrate to lumen and are passed with stol
larvae might penetrate colonic wall or perianal skin to enter a newy cycle or disseminate to other organs
autoinfection may last decades without repeated external exposure

Question 34

Q

Describe possible clinical presentations with S. stercoralis.

Answer

A

commonly assymptomatic in otherwise healthy
pulmonary migration of larvae ⇒ eosinophilic pneumonia with cough, dyspnea, wheezing, hemoptysis
- in hyperinfection pneumonia may be severe, fatal
chronic strongyloidiasis: asthenia, anorexia, nause, abd pain, diarrhea, abdominal tenderness
larva currens common in chronic infection, serpiginous urticaria, typically over abdomen, torso, buttocks, groin
- lesions last a few days
rarely reactive arthritis
in immunosupressed strongyloides hyperinfection syndrome leading to pulmonary or intestinal failure
- disseminated strongyloidiasis to any organ in immune suppressed

Question 35

Q

How many eggs will a femal ascaris worm produce per day?

Answer

A

200,000 sticky resistant eggs/day

Question 36

Q

Ascaris: how many infections per year?

how many deaths?

Answer

A

1 billion infections

20,000 deaths

Question 37

Q

What kinds of disease can ascaris larvae produce?

Answer

A

A: pneumonitis
- seasonal fever, cough, hemoptysis, bronchospasm
- Dx: Eosinophilia, larvae in sputum, lobular consolidation
B: ectopic e.g. brain
C: allergy

Question 38

Q

What are possible effects of ascaris adult worms?

Answer

A

GI
- intestinal obstruction, also volvulus, intussusception, gangrene, perforation, rectal prolapse
- malnutrition, stunting, developmental
- lactose intolerance
- vit A deficiency
- bile duct migration: biliary coli, stones, liver abscess (2⁰ bacterial), pancreatic duct, ascending cholangitis
- migration to mouth, nose or anus during fever

Question 39

Q

Eosinophilia means …?

Answer

A

Worms

predominantly nematodes (roundworms) and trematodes (flukes).
non-invasive tapeworms (cestodes) dont usually cause it
- except Hymenolepsis nana
Invasive tapeworms do. i.e. hydatid disease, but often not until rupture

Question 40

Q

Ascaris treatment?

What about intestinal obstruction?

Answer

A

mebendazole 100 mg bid x 3 days or
albendazole 400 mg one dose
deal with the obstruction first, hydratin, ng suction acutely, then deworm
may require laparotomy

Question 41

Q

What aspects of worm population dynamics limit success of mass deworming programs?

Answer

A

heavy infections concentrated in few individuals
worm “crowding” reduces egg output
treatment rarely removes all worms
surviving worm population compensates by producing mor eggs/worm
worm prevalence in human population may diminish acutely but rises rapidly to baseline within a year

Question 42

Q

Summary of worm treatments:

First and alternative for

Ascaris

trichuris

hookworm

strongyloides

Answer

A

For Ascaris and hookworm, first line treatments are
- albendazole 400 mg single dose or
- mebendazole 500 mg single dose or
- mebendazole 100 mg bid for 3 days
Trichuris needs longer courses:
- albendazole 400 mg od x 3 days or
- mebendazole 500 mg od x 3 days or
- mebendazole 100 mg bid for 3 days
- ivermectin 200 µgm/kg daily x 3 d
Strongyloides needs Ivermectin 200µgm/kg daily x 2 d
- with long high doses of albendazole as alternatives
Of the four, only hookworm cannot be treated with ivermectin
This poses a problem for mass deworming campaigns that would then have to include both albendazole and ivermectin in order to target all 4 STH

Question 43

Q

What are the early clinical features of hookworm disease?

Answer

A

ground itch: unusual
- itch, edema, erythema, papulo-vesicular eruptions lasting 1-2 wks
pulmonary sx: unusual
- cough (“foxhole cough” 1st WW), mucoid sputum, wheezing
Initial intestinal sx
- abd pain, diarrhea, steatorrhea
Initial eosinophilia

Question 44

Q

What is this and what is it caused by?

Answer

A

cutaneous larva migrans
cat or dog hookworm larvae

Question 45

Q

What are the chronic clinical effects of hookworm?

Answer

A

chronic gi nutritional defects
- protein loss
- anemia esp if child has borderline iron intake/stores

Question 46

Q

What distinguishes hookworm from trichuriasis and ascariasis in terms of worm burden distribution and age.

Answer

A

hookworm burden increases with age, in contrast with ascaris lumbricoides and trichuris trichiuria, whic are most intense in childhood.

Question 47

Q

How does skin pallor associated with hookworm respond to deworming.

Answer

A

skin pallor associated with hookworm disease due to fe deficiency, which recovers quickly after deworming
Pallor due to hypoproteinemia is slower to recover

Question 48

Q

Treatment of hookworm anemia

Answer

A

oral iron eg Ferrous sulfate 200 mg tid x 3 months after hgb normal
folic acid 5 mg daily at least 1 month
vit c if not present in diet
deworm with albendazole or mebendazole
nb NOT ivermectin

Question 49

Q

What is this?

Outline diagnosis and treatment

Answer

A

barrel shaped eggs in faeces
proctoscopy shows worms in heavy infections
treat with mebendazole or albendazole (or thiabendazole) - only moderately effective so REPEAT
oral iron, hydration

Question 50

Q

What are these and how are the species distinguished?

How many suckers?

Answer

A

Taenia saginatum (left) - beef tapeworm
Taenia soleum (right) - pork tapeworm
- 13-30 primary lateral uterine branches on T. saginatum; 7-13 on T. soleum
- scolex on both have 4 suckers, but T. soleum has hooks, T. saginatum does not
Eggs from both are identical

Question 51

Q

What are these and how are they distinguished from other species?

Answer

A

Taenia species ova
- T. saginatum and T. soleum eggs indistinguishable
- eggs round, 33 -43 µm with thick radially striated dark brown wall
- inside each shell an embryonated oncosphere with 3 pairs of hooks
- egg in figure C still has primary membrane (yolk sac) that surrounds eggs in uterine branches
distinguish T. saginatum and T. soleum by presence of hooks on scolex of latter

Question 52

Q

What are these?

Distinguishing features?

Answer

A

Diphyllobothrium latum ova
egg pale yellow-brown and oval shape
65-70 µm
operculum at one end can be hard to see
egg contains mass of granulated yolk cells surrounding undeveloped ovum
eggs mature and hatch in freshwater and after 1-2 wks hatch to release ciliated coracidium stage

Question 53

Q

What are these?

How is the diagnosis made?

How long are the eggs infective in the environment?

What are the intermediate hosts?

What are the definitive hosts?

Answer

A

Eggs of H. nana in an unstained wet mount. Note the presence of hooks in the central oncosphere and polar filaments within the space between the oncosphere and outer shell.

Diagnosis is by identifying the distinctive eggs in faeces: eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment.

When eggs are ingested by an arthropod intermediate host (beetles and fleas may serve as intermediate hosts) they develop into cysticercoids, which can infect humans or rodents upon ingestion and develop into adults in the small intestine

Question 54

Q

What is this?

Answer

A

Hydatid Sand

Question 55

Q

What is this?

Answer

A

Hydatid Cyst Cross Section

Question 56

Q

Name the four main clinically significant species of tissue flukes and their 2nd intermediate hosts.

Question 57

Q

Praziquantel dosing (fix this card)

Answer

A

tabs 600 mg, can be broken in 1/4 or have

child dose is 15 mg/kg

use height scale

Question 58

Q

Describe the lifecycle of Necator americanus.

What are the clinical features of acute infection and the consequences of that infection.

Answer

A

eggs are passed in the soil and embryonate there, hatching into larvae
larvae “quest” on grass or pass through skin from ground, migrate through heart and lungs, coming out through trachea then descending into GI tract
In some areas, oral ingestion of cysts is very common⇒Wakana syndrome
larvae mature into adults after passing down GI tract to duodenum, anchor there and small intestine consuming blood
Syndromes:
- ground itch
- cough
- Wakana disease: when larvae are transmitted orrally, they produce nausea, vomiting, pharyngel irritation, cough, hoarseness, dyspnea
Adult GI parasitism in small intestine leads to
- intestinal blood loss
- fe def anemia
- protein malnutrition

Question 59

Q

What is the best initial treatment of a patient with high Loa loa microfilaraemia?

Answer

A

Albendazole
Treatment of individuals with high Loa loa microfilaraemia is associated with a risk of encephalopahty if ivermectin or DEC is used. Albendazole administration for 3 weeks initially reduces the microfilarial load and the risk of encephalopathy. Doxycycline is used in other filarial worms that carry Wolbachia, but this does not apply to Loa loa. Praziquantel is used in other parasitic infections, eg schistosomiasis, taeniasis.

Question 60

Q

How can the differentiation of adult Taenia species in humans most accurately be achieved?

Answer

A

By examining the scolex
The eggs of Taenia solium and T. saginata are identical in morphology and can’t be distinguished. Both may appear in faeces. Microscopy of mature proglottids can indicate species, as T. saginata proglottids have more uterine branches than those of T. solium (12-30 vs. 7-13), but since this is variable it is not very accurate. The scolices (heads) of T. saginata and T. solium are different: T. solium has hooks and suckers, whereas T. saginata has only suckers.

Question 61

Q

A soldier returning from a five year posting in Sierra Leone has suspected onchocerciasis. What, seen on microscopy, would help to confirm diagnosis?

Answer

A

skin microfilariae without a sheath
Onchocerca volvulus microfilariae are found in the skin or eye, not blood. They are unsheathed. Sheathed microfilariae found in blood are W. bancrofti, B. malayi and L. loa. Unsheathed microfilariae found in blood are Mansonella ozzardi, M. perstans.

Question 62

Q

A 19 year old student who has returned to Liverpool after a gap year building a school in Cameron visited his GP complaining that two days previously his left eye became very painful and when he looked in a mirror he saw a worm wandering across his eyeball. What is the most likely source of infection?

Answer

A

A bite of Chrysops silacea
This is a clinical description of Loa loa infection. L. loa is transmitted by the bite of Chrysops flies (also known as deerflies, mangrove flies). The flies introduce larvae onto the skin during feeding. Larvae then penetrate into the bite wound and develop as adults in the subcutaneous tissue. Adult worms produce microfilariae with diurnal periodicity.
Culex mosquitoes are the main vector of filariae (W. bancrofti); Mansonia may transmit viral infections (Rift Valley fever); Simulium damnosum is the black fly responsible for transmitting onchocerca; Mseocyclops copepods transmit Guinea worm (Dracunculiasis).

Question 63

Q

Indoor residual spraying programmes are carried out to control malaria in parts of Africa. The burden of which disease might also be reduced by the same programme?

Answer

A

Lymphatic filariasis
Indoor residual spraying reduces the abundance of indoor biting Anopheles mosquitoes that carry the malaria parasite. In most parts of Africa, lymphatic filariasis is tramsitted by the same Anopheles mosquitoes that transmit malaria. Targeting indoor biting mosquitoes, through IRS will also reduce the burden of LF.

Question 64

Q

What is an intermediate host for a parasite?
For what disease(s) are humans an intermediate host?
What is a definite host?
For Taenia saginata, what role does the human play and what role other species of mammal?
Taenia soleum?
Echinococcus?

Answer

A

an organism that supports the immature or non-reproductive forms of a parasite.
malaria, trypanosomiasis
The defninite host of a parasite is defined as that hosting the adult stage. Intermediate hosts would host other, non adult, parasite stages.
Taenia saginata is widely known as the beef tapeworm, but is really a human tapeworm, since humans are the definitive host. Taenia solium is also a human tapeworm, with intermediate stages in the pig. Dog tapeworms are the Echinococcus species, with intermediate stages in sheep (or humans, as hydatid disease).

Answer 64

A

Paragonimus westermani
Crustaceans, such as crabs or crayfish are second intermediate hosts for Paragonimus.
The first intermediate hosts are snails. Humans become infected by eating undercooked crustaceans harbouring parasite metacercariae.

Answer 65

A

Snails are the intermediate host
humans (and monkeys, which provide a reservoir) for S. hematobium and S. mansoni are the definitive hosts

pair of adults inhabit parts of the venous system of the human host including the terminal venules of the bowel wall in the case of S. mansoni and japonicum; and of the bladder in the case of S. hematobium.
the eggs migrate to the lumen of the bowel or bladder and are released into the environment
in water they hatch to release a miracidium larva, which penetrates the snail intermediate host and multiply to produce mother, then daughter sporocysts that break out of the snail
as cercariae and penetrate human skin, which migrate into the venules, where male and female forms unite and copulate and release eggs and so on …

Answer 66

A

S. mansoni lives in inferior mesenteric veins
S. japonicum and S. mekongi live in superior mesenteric veins.
S. hematobium almost exclusively in venous plexus draining urinary bladder.
S. japonicum also go to choroid plexus, venues around spinal column and other ectopic locations

Answer 67

A

S. japonicum: important reservoirs water buffalo, cattle, pigs
S. mansoni also has reservoir in monkeys and baboons, but plays no sig role in human disease.
S. hematobium: single mini-epidemic in white-water rafters traced back to monkey

Answer 68

A

S. mansoni intermediate host Biomphalaria snails.
S. hematobium, intermediate host snail Bulinus.
S. japonicum east Asia, eradicated from Japan. Intermediate host snail Oncomelania.
(Lymnea plays a role in transmission of Liver fluke)

Answer 69

A

Bulinus - S. hematobium
Biomphalaria - S. mansoni
Oncomelania - S. japonicum
Lymnea - Fasciola hepaticum (liver fluke)

Answer 70

A

S. mansoni egg, note lateral spine
size 150 x 60µm

Answer 71

A

When the female worm applies her ventral sucker to the endothelial surface, eggs pass through the birth pore located above the ventral sucker, encounter endothelial cells and penetrate into the surrounding connec- tive tissue. The larvae, in the eggs, secrete lytic enzymes facilitating this process. Eggs collect in the sub-mucosa (Fig. 33.7) before lysing their way into the lumen of the small intestine, or, in the case of S. haematobium, the lumen of the bladder.
When adult females raise their ventral suckers, eggs inadvertently escape into the circulation, which carries them to the liver via the portal circulation. Nearly 50% of all S. mansoni eggs produced end up in the liver, a dead end for the life cycle. Eggs that reach the lumen of the small intestine are included in the fecal mass. Eggs of S. haematobium must traverse the wall of the bladder (Fig. 33.8) before exiting the host in the urine. In both cases, the egg’s penchant for penetrating tissues causes the infected individual significant pathological consequences.

Answer 72

A

S. japonicum egg (S. mekongi similar)
85x60µm

Answer 73

A

S. hematobium egg - note terminal spine
155x55µm

Answer 74

A

Biomphalaria glabrata, major intermediate snail host for S. mansoni

Answer 75

A

cercaria (of S. mansoni)
about 8 hrs before utilizing glycogen stores (Parasitic Diseases). Beeching says cercariae survive for about 2 days in fresh water.
miracidium
Cercariae are highly motile, fork-tailed, non-ciliated organisms barely visible to the human eye (200–500 µm long).
Cercariae (L-2 or stage-2 larvae) are released each day from infected snails in accordance with a circadian rhythm. Their release is triggered by light and temperature, which act as external cues (zeitgebers).
They are especially attracted to shadows, to any water disturbance and, significantly, to the chemicals on human skin.
Top part breaks off once penetrates skin, leaving tail behind and becomes schistosomulum.

Answer 76

A

occurs primarily in heavy acute infections with S. mansoni and S. japonicum (Sj>Sm>Sh due to # of eggs and immunogenicity)
The symptoms are often dramatic and appear approximately 2-10 weeks after initial exposure, when adult worm pairs begin releasing their eggs in the tissues.
Some investigators believe that Katayama fever resembles some of the manifestations of serum sickness: passive production of IgG to first round of egg production
There is also a clinical resemblance to typhoid fever.
Patients experience hepatosplenomegaly and lymphadenopathy as well as an impressive eosinophilia. The affected individual is frequently febrile and has flu-like symptoms, including cough and headache. At this stage of the illness, schistosome eggs may not yet have appeared in the feces.
serology might be positive now, but may need to repeat
diff diagnosis:
- strongyloides stercoralis, trichuris trichuria, capillaris phillipensis - examine stool for eggs of these parasites, though schistosoma eggs my not be seen this early
- typhoid fever
- malaria

Answer 77

A

S. mansoni and S. japonicum
heavy investations lead to chronic abd pain, sometimes bloody diarrhea, anemia, growth stunting - partly reversible by specific antihelminthic treatment
“pipestem portal fibrosis” with relatively prolonged preservation of liver fx until late
portal hypertension with hepatosplenomegaly, then development of collateral circulation around liver
this leads to eggs from portal circulation being deposited in lungs, inflammatory response leading to pulmonary hypertension, cor pulmonale
longstanding infections of all 3 species can lead to deposition of immune complexes in renal basement membrane, nephrotic syndrome
S. hematobium leads to extensive GU inflammation and damage, increased susceptibility to HIV
hydronephrosis, hydroureter, bladder ca
female genital schistosomiasis
note Schistosomes in peri-intestinal venules can harbor non-typhoid salmonella, associated with increased risk of non-typhoid salmonellosis
rarely S. japonicum and S. hematobium eggs find their way to cns leading to myelitis, encephalopathy

Answer 78

A

eggs in stool or urine
urine collection best around noon (10am to 2 pm)
concentration methods for stool and urine
Kato-Katz method for quantification
rectal snip for egg identification, “flame cells” eggs containing live miracidia
PCR
serology +ve 6-12 wks after acute infection, +ve before eggs can be seen in stool or urine
role of US, inc bedside US

Answer 79

A

Katayama fever treated initially with short course steroids then delayed treatment to allow larvae to mature before treating with praziquantel (active against adults not larvae)
- treat again with 2nd dose 4-6 wks later
Chronic disease also treated with Praziquantel
- monitor for cns disease - may need steroids
- may reverse hep fibrosis in kids (Symmer’s fibrosis)
  *

Answer 80

A

hepatic periportal fibrosis due to chronic schistosomiasis
leads to portal hypertension, associated hepatosplenomegaly etc.

Answer 81

A

calcified bladder pathognomonic of S. hematobium infection

Answer 82

A

edema around schistosoma eggs in left hemisphere
pml, toxo, tb, lymphoma, glioma

Answer 83

A

A ‘schistosomulum’ is the name given to a cercaria once it has penetrated the skin and lost its tail. It is technically a third stage larva (L-3). After remaining in the skin for several days in search of a post-capillary venule, schistosomula pass to the lungs. S. mansonischistosomula are regarded as slower migrants than others, e.g. S. japonicum. Schistosomula do not multiply in the body.

Answer 84

A

Cercariae pierce unbroken skin but probably prefer to enter via abrasions and hair follicles. As schistosomula they first travel to the lungs and thence in the general circulation to the liver, which they reach in 8–10 days. Here they develop into adults (10 mm long) in 1–3 months. They now couple in an intrahepatic portal vein with the longer slender female lying in the ventral groove of the male. From here the paired worms relocate against the blood flow to the inferior mesenteric veins (S. mansoni, S. japonicum) or the vesical plexus (S. haematobium).

In both cases they induce inflammation and fibrosis so that partial or complete obstruction eventually occurs.

Both sexes are actively motile and appear to mate for life Worm pairs can live from 4–20 years. Males appear to be able to actively compete for paired females by pulling them away from their partners, thus effecting a change of mate.

Eggs are continually being produced with production varying from 300 (S. haematobium) to 3000 (S. mansoni) per day.

After cercarial penetration it takes about 4 weeks for the eggs of S. mansoni to appear in the faeces. In the case of S. haematobium it takes about 12 weeks before eggs appear in the urine. This has important implications for diagnosis and treatment (see below).

The major symptoms of the disease are due to an inflammatory response by the body to circulating egg antigen, and to intact eggs that recirculate to the liver, and to eggs that are in the process of being expelled with the faeces or urine.

Answer 85

A

dwarf tapeworm, classified as a parasite of minor medical importance
occurs worldwide, esp among young children
infections usually assymptomatic but abd pain, nausea, vomiting, pruritis ani and diarrhea - sometimes with blood found in heavy infections
headache, dizziness, sleep and behavioural disturbances rel frequent, rare convulsions
autoinfection common in children, occ in immunosuppressed, rare in adults
humans definitive host
It is the only cestode that does not require an intermediate host to develop into its infective stage. A common intermediate host, however, is the grain bettle.

Answer 86

A

praziquantel 1 dose (10–20 mg/kg)
albendazole & niclosamide are alternatives

Answer 87

A

Before therapy is planned, proper characterisation of the specific type and brain involvement of neurocysticercosis is important.42 Therapeutic approaches might include symptomatic therapy, antiparasitic treatment, or surgery (lesion resection or shunt placement), and often more than one of these options are needed)
Generally consider whether cysts still viable or calcified - no point in treating dead cysts
location: parencymal vs meningeal or intraventricular
size of lesion: intraventricular racemose i.e. growing like cluster of a florette, need more aggressive aproach
treat with AED’s, pretreat with steroids
for multiple active lesions, esp with edema treat with albendazole or praziquentel for 2 weeks.
solitary lesions may do as well with short course - 3 days of albendazole or 1 day of praziquantel
1 paper suggesting combined P & A x 10 days for few lesions

Answer 88

A

a cyst containing larval forms of Echinococcus granulosus or dog tapeworm causes most disease in humans.
associated with dog, sheep or cattle contact
Infections with Echinococcus multilocularis less common but lesions less capsular and more invasive
Hydatid cysts gradually enlarge in liver, each cyst consisting of a mother cyst and daughter cysts. Eventually may become painful or become secondarily infected, or involve the biliary tree.
Rupture or leakage can lead to intense allergic reaction or anaphylaxis, or if involving biliary tree, colic, jaundice or ascending cholangitis.
Lung cysts usually assymptomatic until they rupture and may be incidental finding, giving characteristic “water-lily” finding on xray.

Answer 89

A

KEY POINTS

Eosinophilia is an elevation in the total number of bloodstream eosinophils, can be transient or sustained, and can exist in milder versus more significant levels.

Sustained and significant eosinophilia in the 1500 cells/µL or above range, without clear cause, should prompt evaluation.

Processes known to cause modest eosinophilia include allergic disease, parasitic disease, drug allergy, and mastocytosis.

More significant eosinophilia is often caused by drug allergy, aspirin exacerbated respiratory disease, sustained and significant atopic dermatitis, and some parasitic disorders.

If no apparent cause of the eosinophilia is known and levels above 1500 cells/µL exist for greater than 1 month, an exhaustive search guided by clinical presentation should ensue.

Box 1: Causes of allergy associated eosinophilia

Mild degree of eosinophilia

Allergic rhinitis

Asthma

Atopic dermatitis

Eosinophilic esophagitis

Drug allergy

Moderate to severe degree of eosinophilia

Chronic sinusitis (especially polypoid and aspirin-exacerbated respiratory disease)

Allergic bronchopulmonary aspergillosis

Chronic eosinophilic pneumonia

Drug allergy (drug rash with eosinophilia and systemic symptoms [DRESS] syndrome)

Box 2: Commonly implicated pharmaceuticals in drug rash with eosinophilia and systemic symptoms (DRESS) syndrome

Antibiotics: Penicillins, cephalosporins, dapsone, sulfa-based antibiotics

Xanthine oxidase inhibitor: Allopurinol

Antiepileptics: Carbamazepine, phenytoin, lamotrigine, valproic acid

Antiretrovirals: Nevirapine, efavirenz

Nonsteroidal antiinflammatory drugs: Ibuprofen

Box 3: Select parasitic infections that cause eosinophilia

Helminthic infections

Nematodes

Angiostrongyliasis costaricensis

Ascariasis

Hookworm infection

Strongyloidiasis

Trichinellosis

Visceral larva migrans

Gnathostomiasis

Cysticercosis

Echinococcosis

Filariases

Tropical pulmonary eosinophilia

Loiasis

Onchocerciasis

Flukes

Schistosomiasis

Fascioliasis

Clonorchiasis

Paragonimiasis

Fasciolopsiasis

Protozoan infections

Isospora belli

Dientamoeba fragilis

Sarcocystis

Fungal Infections: histo, aspergillus, crypto, blasto

Box 4: Eosinophilia associated with connective tissue, rheumatologic, and autoimmune disease

Eosinophilic fasciitis

Eosinophilic granulomatosis with polyangiitis (Churg-Strauss vasculitis)

Dermatomyositis

Severe rheumatoid arthritis

Progressive systemic sclerosis

Sjögren syndrome

Thromboangiitis obliterans with eosinophilia of the temporal arteries

Granulomatosis with polyangiitis (Wegener syndrome)

Systemic lupus erythematosus

Behçet syndrome

IgG4-related disease

Inflammatory bowel disease

Sarcoidosis

Bullous pemphigoid

Dermatitis herpetiformis (celiac disease)

Box 5: Primary eosinophilias

Idiopathic hypereosinophilic syndrome: sustained peripheral eosinophilia at greater than 1500 cells/µL with associated end-organ damage.

Lymphoproliferative hypereosinophilic syndrome: sustained peripheral eosinophilia at greater than 1500 cell/µL, often associated with rash, aberrant T-cell immunophenotypic profile, often steroid responsive.

Myeloproliferative hypereosinophilic syndrome: sustained peripheral eosinophilia at greater than 1500 cell/µL, often features of splenomegaly, heart related complications, and thrombosis. Can have associated FIP1L1-PDGFRA and other mutations and are often steroid resistant. Patients can be considered to have a diagnosis of chronic eosinophilic leukemia.

Episodic eosinophilia associated with angioedema (G syndrome): cyclical fevers, swelling, hives, pruritus, marked eosinophilia, and IgM elevation. Aberrant T-cell phenotypes often associated.

Box 6: Malignancy-associated eosinophilia

Blood-related neoplasms

Acute or chronic eosinophilic leukemia

Lymphoma (T cell and Hodgkin)

Chronic myelomonocytic leukemia

Solid organ–associated neoplasms

Adenocarcinomas of the gastrointestinal tract (gastric, colorectal)

Lung cancer

Squamous epithelium related cancers (cervix, vagina, penis, skin, nasopharynx, bladder)

Thyroid cancer

Box 7: Entities that can be associated with eosinophilia

Rejection of a transplanted solid organ

Graft-versus-host disease after hematopoietic stem cell transplantation

Kimura disease and epithelioid hemangioma

Eosinophilia-myalgia syndrome/toxic oil syndrome

Adrenal insufficiency

Irritation of serosal surfaces

Cholesterol embolus

Answer 90

A

Echinococcus granulosus or dog tapeworm causes 90% of Hydatid Disease in humans, the remainder being caused by Echinococcus multilocularis.
It is 5.5 mm long
The zoonotic cycle for E. granulosus involves dogs as the definitive host, sheep or other ungulates as intermediate hosts. Humans are accidental intermediate hosts through accidental ingestion of eggs in dog feces through direct contact with domestic dogs, or through ingestion of contaminated groundberries such as cloudberries (Asia, Arctic).
The ingested eggs hatch as oncospheres in the small intestine and penetrate the mucosa and enter the blood stream, most travelling via the portal circulation to the liver, where the oncospheres develop into encysted larvae. Unless the human gets eaten be a dog or wolf it is a dead end cycle for the tapeworm.
Indigenous peoples of the Canadian Arctic, especially the Inuit, are infected with a north- ern variant, E. granulosus var. canadensis, acquired in a sylvatic cycle involving moose and caribou (cervids), wolves, and sled dogs.
Alveolar Hydatid Disease is caused by E. multilocularis, in which humans become infected by swallowing eggs passed by foxes and other Canidae**, mainly by eating contaminated wild ground fruits such as bilberries, lingonberries and cloudberries, widely eaten in Northern Europe, Canada and highland China.

Answer 91

A

Dog tapeworm oocyst

Dipylidium caninum

Answer 92

A

Hydatid cyst characteristic calcified rim of mother cyst

Answer 93

A

2 different diseases with overlapping geographical prevalences

• Cystic hydatid (E granulosus) benign unless large or rupture

– Treat with albendazole and surgery or PAIR

• Alveolar hydatid (E multilocularis) like a malignancy in liver

– Surgery and prolonged albendazole or palliative treatment alone

Answer 94

A

Alveolar Echinococcus (E. multilocularis)

• TypicallyRUQpain,hepatomegaly/jaundice and palpable mass

• Complications:
– local invasion
– metastatic lesions in 2%

Untreated,70-90%ofpatientsdiewithin10 yrs of presentation
70-90%10yrsurvivalpossiblewithearly diagnosis and treatment

Answer 95

A

Tapeworm species causing Disease in humans
- Echinococcus granulosus
  - Cystic hydatid or echinococcosis (CE)
- E. multilocularis
  - Alveolar hydatid or echinococcosis (AE)
- Taenia solium
  - Cysticercosis

Answer 96

A

Embryonated Echinococcus eggs (Iodine stain)

Answer 97

A

The water-lily sign is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily.

It is classically described on plain radiographs (mainly chest X-ray) when the collapsed membranes are calcified but may be seen on ultrasound, CT or MRI.

Answer 98

A

Summary of CE management

nb. Praziquantel good for tx of intestinal tapeworm in dogs and humans, but albendazole or albendazole + praziquantel needed for tx cysts
Calcified inactive asymptomatic: observe – Other asymptomatic ? “watch and wait”
Symptomatic or large cysts:
- Albendazole for 3 month
- Assess response by ultrasound
- Surgery for non response or where follow-up difficult
single, simple cysts
- PAIR After albendazole/praziquantel
- Possible roles for endoscopic surgery

Answer 99

A

PAIR for treatment of echinococcal cysts
- Puncture under ultrasound control
- Aspiration of cyst
- Injection hypertonic saline 20% or EtOH 95%
- Reaspirate after 20 minutes
Patients undergoing surgery or PAIR should receive pre-op albendazole (for 1 – 3 months) +/- praziquantel

Answer 100

A

longterm albendazole

Answer 101

A

Operculated egg, with knob, yellow-brown ~70 μm
2–10mlongadult

Bothria – sucking grooves

Segments ‘wider than long’

Definitive Host: Human swallows plerocercoid larva, which attach to small intestine and grow, producing proglottids, shed proglottids and eggs in stool
(Reservoir Host: Bears)
In water, eggs hatch into coracidium (aquatic larvum) that is ingested by
- 1st Intermediate host: copepod
  - procercoid larvum develops here and is taken up by
- 2nd intermediate host
  1. fish, where plerocercoid larvum develops, which is eaten by
Definitive or reservoir host and so on …
Disease: Fish Tapeworm

Answer 102

A

mainly by scolex
both have 4 suckers, but only T. soleum has hooks
can also tell by examining proglottid microscopically but less reliable. T. saginatum proglottid has approximately twice as many uterine branches
15-32 vs 7-13

Answer 103

A

prepatent period. : the period between infection with a parasite and the demonstration of the parasite in the body especially as determined by the recovery of an infective form (as oocysts or eggs) from the blood or feces.
D. latum or fish tapeworm PPP is 2-8 wks

Answer 104

A

Definitive Host: Human swallows plerocercoid larva, which attach to small intestine and grows, producing proglottids, shed proglottids and eggs in stool
(Reservoir Host: Bears)
In water, eggs hatch into coracidium (aquatic larvum) that is ingested by
- 1st Intermediate host: copepod
  - procercoid larvum develops here and is taken up by
- 2nd intermediate host

fish, where plerocercoid larvum develops, which is eaten by

Definitive or reservoir host and so on …

Answer 105

A

Echinococcus adult and egg

Answer 106

A

Scolex.
Rostellum: a knob-like protrusion at the extreme anterior end of a tapeworm, as an extension of the tegument. It is globular, spiny structure when it protrudes, and a circular hollow pit when retracted. It is structurally composed of a number of concentric rows of hooks.
4 suckers + hooks
by size of proglottids: smaller overall and each segment much wider than long
scolex: taenia also have 4 suckers, t. soleum has hooks, but only h. nana has rostellum

Answer 107

A

The first symptoms of trichinellosis are gastrointestinal, usually occurring 1-2 days after a person consumes raw or undercooked meat from a Trichinella-infected animal. These symptoms include:

Nausea

Diarrhea

Vomiting

Abdominal pain

The classic trichinellosis symptoms often occur within 2 weeks after eating contaminated meat, and can last up to 8 weeks:
- Muscle pain

Fever

Swelling of the face, particularly the eyes

Weakness or fatigue

Headache

Chills

Itchy skin or rash

Cough

Diarrhea

Constipation

Symptoms may range from very mild to severe and relate to the number of infectious worms consumed in the meat. Many mild cases of trichinellosis are never specifically diagnosed because they are assumed to be the flu or other common illnesses. Furthermore, many people with Trichinella infection do not experience any symptoms at all.

If the infection is heavy, persons may have trouble coordinating movements, and have heart and breathing problems. Although rare, death can occur in severe cases. For mild to moderate infections, most symptoms go away within a few months.

Answer 108

A

one definitive host is man, others in domestic cycle are pigs and rodents: in sylvatic cycle bears, rodents, wild boars act as definitive host
there are no intermediate hosts
the disease was widespread in 40’s but has been controlled through improved animal husbandry of pigs; still foci of disease in China, Thailand and other parts of Asia where pork is still eaten raw.
the worm is not shed via eggs in stool, but passed from one host to another through eating raw or undercooked meat containing nurse cells containing larvae. Capsule is digested by pepsin in stomach, releasing larvae, which mature in intestine, copulate and release a fresh round of larvae which penetrate intestinal mucosa and disseminate via blood stream throughout body causing acute febrile illness 2-8 weeks after ingestion of affected meat associated with fever, diarrhea, abd pain, headache, periorbital edema, occasionally fatal causing death.
recovery and development of immunity prevents further reproduction of larvae and expulsion of adults. Larvae which have made it to skeletal muscle penetrate it and take over cellular metabolism to develop protective coat, angiogenesis about larvum to create host-parasite nurse cell that may last decades. Unless the body is consumed raw by another carnivore this is a dead end for the parasite.

Answer 109

A

Hydatid disease is a zoonosis in which the adult tapeworms (E. granulosus) infest the gut of dogs and other canid hosts such as jackals. The adult is small, only 2-7mm in length and consists of 3 proglottids, an immature one, a mature one and a gravid one full of eggs.

Eggs pass out in the faeces and may be ingested by herbivorous animals such as cows, sheep, horses and goats. Once ingested hooked embryos develop in the duodenum, penetrate the mucosa, and become dispersed throughout the body via the circulation.

As a result, larval cysts (‘hydatid cysts’) form in various tissues with the majority favouring the liver. These cysts contain ‘protoscolices’ or early forms of the head of a new tapeworm. These develop into adult worms when ingested by a dog or similar host.

The condition is perpetuated when animals, especially dogs, ingest contaminated offal with the development of huge numbers of adult worms in the small intestine.

Humans are an incidental host and become infected by the accidental ingestion of eggs from contaminated food or close proximity to infected animals. Turkana in northern Kenya has one of the highest incidences of hydatid disease in the world. Here dogs and man live very closely together and quite often the locals employ ‘nurse dogs’, facilitating echinococcal spread.

Each egg contains an oncosphere, which is liberated in the herbivore intestine, penetrates the gut wall, and travels to distant organs, particularly to the liver and lungs. Ultimately, over the years, the oncosphere (larva) becomes encysted in a typical hydatid cyst. Humans become the secondary host if they ingest eggs due to contamination of food or fingers by dog faeces and ultimately develop cysts in major organs (70% in liver, 20% in lung, 10% elsewhere).

Beware of poorly husbanded sheep rearing areas.

Four echinococcal species cause disease in man, E. granulosus, E. multilocularis, E. oligarthrusand E. vogeli.

E. granulosus is by far the most common.

E. multilocularis is less common but the most virulent. Foxes are the usual primary host for E. multilocularis infections. Rodents are the secondary hosts for the intermediate cyst stages. See Q4 below.

E. vogeli is found mainly in the southern parts of South America and is the rarest form.

A fifth type, E. granulosis, is a tiny dog tapeworm for which it is theoretically possible that humans can act as intermediate hosts with the development of ‘hydatid’ disease.

Answer 110

A

The oncosphere usually reaches the liver of man about 3 hours after ingestion of eggs.

Hydatid cysts grow slowly and it is rare to diagnose one before adulthood, unless it happens to be in the cranium, when pressure symptoms appear early even with a small cyst.

The cyst wall consists of an inner nucleated germinal layer and outer laminated one. Brood capsules protrude inwards from the germinal layer. These contain fluid and inwardly projecting protoscolices. When the brood capsules break off to float free in the hydatid cyst they constitute classical ‘hydatid sand’.

If an animal, e.g. a dog, eats a carcass that contains hydatid cysts, then the ingested protoscolices evaginate in the dog’s intestine and mature into adult tapeworms. Thus the cycle is completed.

In humans both sexes are equally affected.

Answer 111

A

We acquire infection by swallowing the eggs of E. multilocularis. These eggs are excreted by infected foxes and can contaminate wild ground fruits, wild and cultivated berries and common vegetables to which the expanding fox population has access.

In humans, the cysts are located almost entirely in the liver, in contrast to E. granulosus cysts (liver 75%, lungs 15%, rest of body 10%). They also differ significantly by having daughter cysts that bud outwards instead of inwards. This means a greater invasion into the surrounding local tissues with occasional metastasis to other tissues, notably the lung.

A patient with a liver mass due to E. multilocularis presents as if they have cancer, either primary hepatocellular carcinoma or metastastic spread from other organs. Untreated E. multilocularisdisease carries a very high mortality.

Answer 112

A

Bulimus snail
intermediate host for S. mansoni

Answer 113

A

Schistosoma haematobium
- causes urogenital schistosomiasis
- throughout Africa, parts of Arabia, Near East, Madagascar & Mauritius
- snail Bulinus
S. mansoni
- bowel and liver primarily
- Africa, Madagascar
- exported by slave trade to parts of South America, Caribbean and Arabia where permissive snail intermediate hosts found
- snail Biomphalaria
S. japonicum
- bowel and liver primarily
- China, Phillippines and Sulawesi (now eliminated from Japan)
- small focus on Mekong river caused by related S. mekongi
- snail Oncomelania
S. intercalatum and sister species S. guineensis minor species confined to West africa.
- inhabits veins of lower bowel and produc terminal-spined eggs

Answer 114

A

cercarial dermatitis
cercarial penetration of skin and entering capillaries
acutely in human schistosomal infection, also dead end manifestation of infection by avian schistosome’s (swimmers’ itch).
serology will be negative

Answer 115

A

causes significant stunting
chronic anemia of
- fe deficiency and
- chronic disease through interfering with hepcidin
related cognitive impairment
reversible through treatment

Answer 116

A

polyposis
inflammation bowel wall
strictures
bleeding, overt or occult
may screen with FOB, Calprotectin tests
periportal fibrosis with relative preservation of liver fx until late, portal hypertension
S. japonicum has sl different pattern of fibrosis with normal parenchyma surrounded by “building blocks” of fibrosis, prob related to diff pattern of egg deposition
should not usually have ascites or evidence of liver failure, so if you see this, consider comorbidities, eg. alcohol, chronic hepatitis
once portal hypertension develops, can get egg deposition in lungs due to egg deposits through portosystemic collaterals ⇒ pulmonary hypertension
17% of children under 10 in Lake Albert Uganda had some degree of liver fibrosis
nb can also get spillover of S. eggs into systemic circulation with S. hematobium

Answer 117

A

Hepcidin is a protein that in humans is encoded by the HAMP gene. Hepcidin is a key regulator of the entry of iron into the circulation in mammals.[4]

In states in which the hepcidin level is abnormally high such as inflammation, serum iron falls due to iron trapping within macrophages and liver cells and decreased gut iron absorption. This typically leads to anemia due to an inadequate amount of serum iron being available for developing red cells.

Answer 118

A

vaginal discharge
bloody discharge
genital itching
dyspaerunia
infertility/subfertility
pelvic pain during or after intercourse
4-fold increase in HIV transmission

Answer 119

A

for all, larval stages are ingested as meta-cercariae/cysts
adult worms in liver, lungs or gut
eggs released harmlessly into lumen of gi tract (unlike schistosomiasis in which eggs are the main component causing harm)

Answer 120

A

Opisthorchis viverrini egg, but it could just as well be Clonorchis sinensis egg as the two are almost identical (also Opisthorcois felineus)
Natural definitive hosts include dogs & cats and lifecycles are much the same
In this case man is the definitive host

embryonated eggs pass from feces into water
eggs are ingested by snail
free-swimming cercariae penetrate and encyst in skin or flesh of fresh water fish
metacercariae in fish are ingested by human host (or other fish eating mammal)
excyst in duodenum & ascend the biliary tract, where they mature to become
egg producing adults

Answer 121

A

Fresh-water crabs like this one were implicated in a Paragonimus outbreak in January of 2007. Specialty dishes in which shellfish are consumed raw or prepared only in vinegar, brine, or wine without cooking play a key role in the transmission of paragonimiasis. Raw crabs or crayfish are also used in traditional medicine practices in Korea, Japan, and some parts of Africa.
Several species of Paragonimus cause most infections;
the most important is P. westermani, which occurs primarily in Asia including China, the Philippines, Japan, Vietnam, South Korea, Taiwan, and Thailand.
P. africanus causes infection in Africa, and
P. mexicanus in Central and South America.
Although rare, human paragonimiasis from P. kellicotti has been acquired in the United States, with multiple cases from the Midwest. Several cases have been associated with ingestion of uncooked crawfish during river raft float trips in Missouri

Answer 122

A

Paragonimiasis
1. The eggs are excreted unembryonated in the sputum, or alternately they are swallowed and passed with stool .
2. In the external environment, the eggs become embryonated , and
3. miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues .
4. Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail.
5. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host .
6. Human infection with P. westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite .
7. The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5 to 12 mm by 4 to 6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycles is not achieved, because the eggs laid cannot exit these sites. Time from infection to oviposition is 65 to 90 days.

Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P. westermani.

Answer 123

A

Infection with Paragonimus spp. can result in an acute syndrome with cough, abdominal pain, discomfort, and low-grade fever that may occur 2 to 15 days after infection. Persons with light infections may have no symptoms. Symptoms of long-term infection may mimic bronchitis or tuberculosis, with coughing up of blood-tinged sputum.
Human paragonimiasis is acquired through ingestion of raw or undercooked crabs or crayfish, and is usually a lung infection. After ingestion, metacercariae excyst in the small intestine and release larvae that penetrate the duodenal wall and enter the peritoneal cavity. The larvae migrate for approximately 1 week, then penetrate the diaphragm, enter the pleural cavity, and migrate directly through lung tissue to reach the bronchi. There they form cystic cavities and develop into adult worms in 5-6 weeks. The adult parasites are reddish brown and ovoid, measuring 7.5-12 mm by 4-6 mm. Adult worms induce an inflammatory response in the lungs, generating a fibrous cyst that contains a purulent, bloody effusion and eggs released by the flukes which are passed into the environment via expectoration, or may be swallowed and passed with feces.
Eosinophilia, wide range of CXR findings
acid fast stain for TB smear destroys eggs in sputum
occ CNS infection, can migrate anywhere
occ skin nodules
Treatment: praziquantel

Answer 124

A

usually fasciola hepatica
occasionally fasciola gigantica
beware, not fasciola buski, which has similar eggs, but is an intestinal fluke and is treated differently - with Praziquantel, which does not work for fasciolopsis.
Fasciolopsis is treated with Triclabendazole.

Answer 125

A

Fasciola hepatica egg
Definitive host human (or sheep or cow)
Snail is the intermediate host

immature Fasciola eggs are discharged in biliary ducts and in stool
Eggs become embryonated in water and
Invade suitable snail intermediate host, including genera Galba, Fossaria, and Pseudosuccinea.
Undergoes several developmental stages in snail (sporocysts, rediae and cercariae)
Cercaria released from snail
encyst as metacercariae on aquatic plants, esp watercress, where they are ingested by humans, cattle or sheep (or possibly by drinking unfiltered water)
After ingestion the metacercariae excyst in duodenum and
migrate through the intestinal wall, the peritoneal cavity and the liver parenchyma into the biliary ducts where they develop into adult flukes.

In humans maturation from metacercariae into adult flukes takes 3-4 months. Adult flukes reside in biliary ducts of mammalian host.

Answer 126

A

liver fluke
fasciola parasites do not multiply in people so parasite load depends on inoculum
acute and chronic phases may be symptomatic or not. non-specific clinical features of both phases include
- fever, maybe intermittent
- malaise
- abd pain: ruq, epigastrium or more diffuse/generalized
- anorexia, n, v, d, altered bowel habit, wt lossAcute phase
- hepatomegaly, jaundice
- eosinophilia, esp in acute phase
- anemia, esp in kids
- transaminitis
acute phase lasts 2-4 months
chronic pahse begins when immature larvae reach bile ducts, mature and start producing eggs
comps: cholangitis, biliary obstruction
cholecystitis, gallstones
pancreatitis, cirrhosis
ectopic infection possible
Diagnosis: serology may be usefel before egg production begins, or if low level or sporadic egg production, or ectopic infection
Treatment: triclabendazole or possible nitazoxanide, NOT PRAZIQUANTEL

Answer 127

A

Treatment is Triclabendazole 10 mg/kg in single dose (double dose in case of treatment failure)
Treat all confirmed cases; in endemic areas treat all suspect cases.
Preventive chemotherapy: in areas where cases of fascioliasis appear to be clustered treat all school-age children or all residents q 12 months

Answer 128

A

Praziquantel 25 mg/kg tid for 2-3 days
- treat all confirmed cases, or in endemic area, all suspect cases
Preventive treatment
- in districts where prevalence > 20% treat all residents q 12 months
- <20% treat q 24 mo or treat only those reporting habit of eating raw fish q 12 months
(Also some evidence that new Chinese drug tribendimidine may provide an alternative)

Answer 129

A

Individual case managemet: confirmed cases or suspect in endemic areas
- Triclabendazole 2 x 10 mg/kg in the same day or
- Praziquantel 25 mg/kd tid x 3 days
Preventive Chemo in places where cases appear clustered
- Triclabendazole 20 mg/kg in single dose

Answer 130

A

West Africa: limited to Cameroon & Nigeria
China, East and South East Asia
Ecuador, Peru
Def Host: Human
1st Intermediate: Freshwater Snail
2nd Intermediate: Freshwater Crab or Crayfish

Answer 131

A

Albendazole
- 400 mg single dose
  - Roundworm/Ascaris, Hookworm/N.americanus, Pinworm/Enterobius
- 400 mg daily x 3 days
  - Whipworm/Trichuris
- 400 mg bid x 3 days
  - Threadworm/Strongyloides
- Prolonged course +/- Surgery: Echinococcus
Ivermectin: Ascaris, Enterobius, Strongyloides, Filaria
Praziquantel: Schistosomiasis, Paragonomiasis, Clonorchis
Triclabendazole: Fasciolopsis
Metronidazole: Entameba, Giardia
Nitazoxanide most of the above, v broad spectrum
Co-trimoxazole: Isospora belli

Answer 132

A

Both are conditions in which humans are the accidental host of an animal parasitic worm.
Visceral larva migrans is caused by the larvae of animal (usually dog or cat) species of Toxocara Canis or cati. The larva penetrates the intestine and wanders about causing inflammation, usually in the lungs, or liver, sometimes in the eye or csf
Cutaneous larva migrans is caused by zoonotic species of Ancylostoma or hookworm. Here the L2 larva penetrates the skin but is only able to proceed a short while before dying, usually causing local inflammation and itching and leaving a serpentiginous rash.

Answer 133

A

Hyperinfection acute or chronic

• Abdo

Weight loss, malabsorption, blood in stool, protein loss, abdo distension

• Chest

As above, also Gram neg sepsis, ARDS/pneumonitis, often post op in ICU

• Skin

Petechial/purpuric rashes, DIC rash
• Eosinophilia absence = poor prognosis

Answer 134

A

(a) Human African Trypanosomiasis (HAT)
(b) Neurocysticercosis (tapeworm)
(c) Neuroschistosomiasis
(d) Angiostrongylus cantonensis
(e) Toxoplasmosis

The correct answer is (a). Any of these conditions may cause stupor/coma. Swollen neck glands (Winterbottom’s sign) are found in African trypanosomiasis and suggest that trypanosomes enter the brain via the lymphatic system. Different stages of coma are seen in this disease from very mild daytime sleepiness to deep coma. HAT (‘sleeping sickness’) is transmitted by the tsetse fly. It occurs in equatorial regions of Africa, notably just north of Lake Victoria.

Humans are the definitive host and ultimate reservoir for pig tapeworm (Taenia solium, Taenia asiatica) and for cattle tapeworm (Taenia saginata). This means that adult tapeworms only develop and produce their eggs in human intestine. One way of acquiring tapeworm infestation (taeniasis) is to ingest eggs via faecally contaminated food or water or via the faeco-oral route. Mostly however infection occurs after eating raw or undercooked ‘measly’ pork or beef that contains encysted tapeworm larvae (cysticerci). In this case the ingested cysts invaginate the mucosa of the small intestine, mature into adults, and, after about 12 weeks, gravid females produce up to 50 000 eggs per day, which are shed in the stool. Adult tapeworms can remain in situ for many years.

When pigs or cattle eat contaminated material it is usual that some eggs turn into oncospheres in the stomach and duodenum, cross the intestinal membrane, and are carried via the vascular system to different parts of the body, where they form larval cysts (cysticerci) 1–2 cm in size.

In the case of man a similar cysticercosis occurs only when oncospheres of T. solium are released. This causes little or no trouble when cysts form in areas such as muscle or subcutaneous tissues, but it can be very serious when they develop in the CNS. Cysts in the CNS may be asymptomatic or cause focal or general neurological symptoms. In many countries neurocysticercosis is by far the commonest cause of seizures.

In short, neurocysticercosis represents an aberrant cystic larval stage of Taenia solium in man in which eggs released in the upper small intestine invade the body and develop into cysts in the CNS (autoinfection).

Neuroschistosomiasis occurs when pairs of adult worms, particularly of S. japonicum, lodge in the CNS instead of in the mesenteric or vesical plexuses. The ensuing granuloma can then produce symptoms if it presses on important structures.

Angiostrongylus cantonensis (rat lung worm) is a parasitic nematode found in the Far East. It is a zoonosis that affects rodents. Humans contract it by eating food (snails, slugs, molluscs) infected with 3rd stage larvae. It is the commonest cause of eosinophilic meningitis.

Answer 135

A

rat or dwarf tapeworm
Hymenolepis nana, the dwarf tapeworm, occurs worldwide, principally among children. Most infections are asymptomatic, but heavy infections may cause abdominal pain, nausea, vomiting, pruritus ani and diarrhea, sometimes containing blood. Headache, dizziness, sleep and behavior disturbances are frequent. Convulsions have also been reported. Autoinfection is common.

Hymenolepis diminuta, the rat tapeworm, may affect humans who ingest the intermediate host, usually a weevil, flea or cockroach. Most infections are asymptomatic and of short duration.

Dipylidium caninum infection may occur in humans, usually young infants, following accidental ingestion of a flea, the intermediate host of this cestode whose usual host is a dog or other carnivore. Most infections are asymptomatic. Some children experience abdominal pain, diarrhea, pruritus ani and urticaria.

Diagnosis and treatment

Diagnosis is usually made by identification of characteristic eggs or proglottids in feces. There may be a variable eosinophilia, minimal in cases of T. saginata and often reaching 5–10% in hymenolepiasis.

Praziquantel is the drug of choice for all of the above intestinal cestode infections. A single oral dose of 10 mg/kg is usually effective. H. nana requires 25 mg/kg as a single dose.

Answer 136

A

Ascaris: 800 mill
Trichuris: 440 million
Hookworm: 460 million
Strongyloides:100 million

Answer 137

A

migrating larvae from toxocara, parasitic roundworms of dogs and cats
larva ingested in contaminated soil or food and released in intesting
prolonged migration through tissues causing pneumonitis, fever, abd pain, myalgia, lymphadenopathy, hepatosplenomegaly, sleep and behavioural disturbances, focal or generalized convulsions
eosinophilia, hypergammaglobulinemia elevated titres of blood group isohemagglutanins.
serological dx with ELISA
tx albendazole or mebendazole

Answer 138

A

it is caused by the migration of helminth larvae through the lungs with the production of eosinophilia and a pneumonic infiltrate. Classically it is ascribed to the passage of Ascaris larvae 7-14 days after egg ingestion.
hookworm and strongyloides larva may also cause a mild eosinophilia on transiting the lungs but it is lessed marked.

Answer 139

A

Ancylostoma duodenale has teeth
Necator americanus does not

Answer 140

A

praziquantel
triclabendazole
triclabendazole or praziquantel but according to CDC former is simpler, fewer doses hence compliance better