0121100930 0122101030 - Mfm Ii - Cestodes & Nematodes (Kunigelis)

Front 1

What are the scolex, neck and strobila portions of a tapeworm?

Back 1

scolex - head
neck - new segments are added here
strobila - reproductive system is located here

Front 2

What are the main anatomical points of the scolex of a tapeworm?

Back 2

may contain:
multiple acetabulem
hooks
bothria - pits or grooves
bothridia - muscular projections that physically hold onto host

Front 3

What are the main anatomical points of the strobila of a tapeworm?

Back 3

linear series of reproductive organs (hermaphroditic) each referred to proglottid
can be
monozoic - one set of proglottid
polyzoic - multiple sets of proglottids

Front 4

What is strobilation?

Back 4

the process of new proglottids that arise at the anterior end of the strobila

Front 5

What are the three types of proglottids?

Back 5

immature - immature reproductive organs
mature - mature reproductive organs
gravid - shelled-embryo containing proglottids

Front 6

What types of copulation can occur with tapeworms?

Back 6

inter-proglottid
intra-proglottid
inter-worm

Front 7

What is the significance of Hymeolepis proglottids?

Back 7

proglottids shed and disintegrate en route through intestines of host (humans) and the only thing left in feces

Front 8

What is the significance of Teania & Dipylidium proglottids?

Back 8

proglottids shed, but remain intact in feces

Front 9

What is the significance of Diphyllobothrium proglottids?

Back 9

Proglottids are retained and eggs are released from proglottids

Front 10

Where are the hosts of tapeworms?

Back 10

EVERY VERTEBRATE CLASS

Front 11

What two diseases arise from infection of Taenia solium?

Back 11

Taeniasis - adult tapeworm infection
Cysticercosis - larvae infection in flesh to be consumed and infected

Front 12

What are the definitive and intermediate hosts of Taenia solium?

Back 12

definitive - human
intermediate - pig

Front 13

How are humans infected with Taenia solium?

Back 13

1) eating undercooked pork of which contains cysticerci (larval stage of adult tapeworm)
2) cysticerci developed in humans by consuming eggs accidentally from human feces

Front 14

Where is Taenia solium usually found, geographically?

Back 14

Latin America, Africa, India, SE Asia, China, Slavic countries

Front 15

What is the structure of a Taenia solium scolex?

Back 15

4 acetabula
crowned rostellum (hooked ring around primary oral sucker)

Front 16

What is the lifecycle of the adult Taenia solium (and Taenia saginata for that matter)?

Back 16

Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata or Taenia solium.  Humans are the only definitive hosts for T. saginata and T. solium. 
Eggs or gravid proglottids are passed with feces 1; the eggs can survive for days to months in the environment. 
Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids 2. 
In the animal's intestine, the oncospheres hatch 3, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. 
A cysticercus can survive for several years in the animal.  Humans become infected by ingesting raw or undercooked infected meat 4. 
In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. 
The adult tapeworms attach to the small intestine by their scolex 5 and reside in the small intestine 6. 
Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium. 
The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day). 
T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids. 
The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces.  T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.

(pic)

Front 17

What are mild symptoms of a T. solium infection?

Back 17

asymptomatic
hunger pains
abdominal discomfort
chronic indigestion
increased WBC

Front 18

What is tx for T. solium?

Back 18

Praziquantel (veterinary use, but also used in humans) - preferred
Niclosamide (human use, but regulated by the CDC)

Front 19

Cysticercosis

Back 19

egg ingestion that causes Cysticerci infection of Taenia solium in the muscles of the host

Front 20

What is the path of infection for cysticercosis?

Back 20

1) Humans ingests eggs present in human feces (contaminated hands, eating utensils, oral sex)
2) Eggs hatch in SI (stimulated by bile salts)
3) Oncosphere penetrates wall of the SI, gaining entrance into systemic circulation via the hepatic portal vein.
4) Cysticerci (<10 mm max dia at maturity) prefers subcutaneous tissues:
Between muscle bundles
Eye
Brain

Front 21

How long does it take to get cysticercosis from ingestion of an egg?

Back 21

~ 2 months

Front 22

What do cysticercus look like?

Back 22

semitransparent, opalescent white
elongate oval shaped
0.6 - 1.8 cm
bladder filled w/ fluid
aka bladder worms

Front 23

What are cysticercosis symptoms?

Back 23

CNS symptoms
eye symptoms
atrophy and pain when contracting infected muscle

Front 24

What does the cyst of a cysticercosis do when the cysticercus is killed by an immune response?

Back 24

The cyst calcifies and makes a calcified cyst, which is where "crunchy pork" comes from.

Front 25

What is the portion of the lifecycle of a Taenia solium that causes Cysticercosis?

Back 25

Cysticercosis is an infection of both humans and pigs with the larval stages of the parasitic cestode, Taenia solium. 
This infection is caused by ingestion of eggs shed in the feces of a human tapeworm carrier 1. 
Pigs and humans become infected by ingesting eggs or gravid proglottids 2, 7. 
Humans are infected either by ingestion of food contaminated with feces, or by autoinfection. 
In the latter case, a human infected with adult T. solium can ingest eggs produced by that tapeworm, either through fecal contamination or, possibly, from proglottids carried into the stomach by reverse peristalsis. 
Once eggs are ingested, oncospheres hatch in the intestine 3, 8 invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into  cysticerci 9. 
In humans, cysts can cause serious sequellae if they localize in the brain, resulting in neurocysticercosis. 
The parasite life cycle is completed, resulting in human tapeworm infection, when humans ingest undercooked pork containing cysticerci 4. 
Cysts evaginate and attach to the small intestine by their scolex 5. 
Adult tapeworms develop, (up to 2 to 7 m in length and produce less than 1000 proglottids, each with approximately 50,000 eggs) and reside in the small intestine for years 6.

Front 26

what is nematode related ecdysis?

Back 26

epidermal cuticle is shed four times to reach the adult morphology. cuticle shedding is called ecdysis

Front 27

What is special about nematode sexuality?

Back 27

sexually dimorphic and (smaller) males have paired copulatory spicules that bite into female vagina during mating

Front 28

What are the two morphological forms of nematodes that are infectious?

Back 28

filariform - infectious larvae
rhiabditiform - free-living stage

Front 29

What species of nematode are relevant to human infection?

Back 29

Ascaris lumbricoides - largest nematode worm, found in areas of poor sanitation

Front 30

*Where are Ascaris lumbricoides found geographically?

Back 30

temperate and tropical areas - rural areas of SE United States*

Front 31

How long does it take for Ascaris lumbricoides to undergo a complete lifecycle?

Back 31

4 mos

Front 32

What is the lifecycle of an Ascaris lumbricoides?

Back 32

Adult worms 1live in the lumen of the small intestine. 
A female may produce approximately 200,000 eggs per day, which are passed with the feces 2. 
Unfertilized eggs may be ingested but are not infective.  
Fertile eggs embryonate and become infective after 18 days to several weeks 3, depending on the environmental conditions (optimum: moist, warm, shaded soil). 
After infective eggs are swallowed 4, the larvae hatch 5, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs 6.  
The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed 7.  
Upon reaching the small intestine, they develop into adult worms 1.  
Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female.  Adult worms can live 1 to 2 years.

(pic)

Front 33

What are Ascaris lumbricoides infection symptoms?

Back 33

alveolar destruction -> asthma, pneumonia
hepatopancreatiatits
loose stools (similar to loose stools)
fever
malaise
abdominal distension
tenderness
vomiting
alveolar hemorrhage

Front 34

Tx for Ascaris lumbricoides

Back 34

Mebendazole for all roundworms stimulates worm migration

Endoscopy if necessary

Front 35

What does Wuchereria bancrofti cause?

Back 35

elephantiasis

Front 36

Where are Wuchereria bancrofti geographically found?

Back 36

tropics and subtropics

Front 37

What is special about Wuchereria bancrofti infectious third-stage filarial larvae?

Back 37

These are the infectious stage of W. bacncrofti delivered by mosquitoes to a human in a bloodmeal

Front 38

What are the hosts for Wuchereria bancrofti?

Back 38

intermediate - Culcine or Anopheline mosquito
definitive - human

Front 39

What is the lifecycle of the Wuchereria bancrofti?

Back 39

Different species of mosquitoes are vectors of W. bancrofti filariasis depending on geographical distribution. 
During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound 1. 
They develop in adults that commonly reside in the lymphatics 2. 
The female worms measure 80 to 100 mm in length and 0.24 to 0.30 mm in diameter, while the males measure about 40 mm by .1 mm. 
Adults produce microfilariae measuring 244 to 296 μm by 7.5 to 10 μm, which are sheathed and have nocturnal periodicity, except the South Pacific microfilariae which have the absence of marked periodicity. 
The microfilariae migrate into lymph and blood channels moving actively through lymph and blood 3. 
A mosquito ingests the microfilariae during a blood meal 4. 
After ingestion, the microfilariae lose their sheaths and some of them work their way through the wall of the proventriculus and cardiac portion of the mosquito's midgut and reach the thoracic muscles 5. 
There the microfilariae develop into first-stage larvae 6 and subsequently into third-stage infective larvae 7. 
The third-stage infective larvae migrate through the hemocoel to the mosquito's prosbocis 8 and can infect another human when the mosquito takes a blood meal 1.

(pic)

Front 40

How long will microfilariae wait to be picked up by an appropriate mosquito intermediate host?

Back 40

1 - 1.5 years is possible

Front 41

What symptoms are present with W. bancrofti infection?

Back 41

1) filarial/elephantoid fever begins with chill -> elevated temp for 1-2 days followed by 2-5 day fever resolution
2) lymphangititis (lymph vessel blockage and subsequent edema)
3) secondary to (2) edematous sites damage blood vessels and then keritanize so they remain enlarged
4) cough, wheezing
5) weight loss
6) lymphadenopathy

Front 42

induration

Back 42

woody hardening of lymphangititis compromised external tissue in order to resist further stretching - elephantiasis

Front 43

What is a secondary complication to elephantiasis limbs?

Back 43

bacterial and fungal infections

Front 44

What demographic of people are the most susceptible to W. bancrofti infection?

Back 44

human males

Front 45

Tx of W bancrofti?

Back 45

1) Hetrazan (DEC trade name) with an unknown mechanism
2) Mectizan
3) surgical

Front 46

What disease does Trichinella spiralis cause?

Back 46

Trichinosis aka Trichinellosis

Front 47

What are the routes of infection of Trichinella spiralis?

Back 47

many carnivores and omnivores get T. spiralis from eating raw or undercooked pork (Trichinellosis) or eating eggs results in encysted larvae in human muscles (Trichinosis)

Front 48

What are the two general phases of the T. spiralis lifecycle?

Back 48

1) Enteral phase - occurs in intestine and is generally transitory
2) Parenteral phase - occurs outside of intestine and is marked by larval migration and excystment

Front 49

What are the two general subcycles of the T. spiralis lifecycle?

Back 49

1) sylvatic cycle - no human involvement
2) domestic cycle - occurs with human intervention by feeding pigs raw infected scraps, human infection by ingestion of undercooked pork and bear meat

Front 50

What is the relative infection rate of T. spiralis in the U.S. compared to the rest of the world?

Back 50

U.S. is 3x more infected than the rest of the world.

Front 51

What is the complete lifecycle of the T. spiralis?

Back 51

Trichinellosis is acquired by ingesting meat containing cysts (encysted larvae) 1 of Trichinella. 
After exposure to gastric acid and pepsin, the larvae are released 2 from the cysts and invade the small bowel mucosa where they develop into adult worms 3 (female 2.2 mm in length, males 1.2 mm; life span in the small bowel: 4 weeks). 
After 1 week, the females release larvae 4 that migrate to the striated muscles where they encyst 5.  Trichinella pseudospiralis, however, does not encyst. 
Encystment is completed in 4 to 5 weeks and the encysted larvae may remain viable for several years.  Ingestion of the encysted larvae perpetuates the cycle. 
Rats and rodents are primarily responsible for maintaining the endemicity of this infection. 
Carnivorous/omnivorous animals, such as pigs or bears, feed on infected rodents or meat from other animals. 
Different animal hosts are implicated in the life cycle of the different species of Trichinella. 
Humans are accidentally infected when eating improperly processed meat of these carnivorous animals (or eating food contaminated with such meat).

(pic)

Front 52

What are the specific steps of the Enteral Phase of the T. spiralis lifecycle?

Back 52

1) Ingestion of infected raw or undercooked meat that contains the 1st stage larvae in skeletal muscle (1mm X 35 um)
2) Parasite freed of host tissue by digestive chemicals
3) Larvae penetrates several columnar epithelial cells lining the microvilli of the SI
= intramulticellular parasite
4) Molts 4X in 28 hrs
5) Adult molt occurs 30 hrs post infection in SI
6) Female sheds 1st stage larvae (80 X 7 um) 5-6 days post-infection
7) Newborn have a stylet to penetrate SI wall to enter a blood vessel or lacteal in microvilli

Front 53

What are the specific steps of the Parenteral Phase of the T. spiralis lifecycle?

Back 53

1) 1st stage larvae enter general circulation to become distributed throughout the body
2) Larvae uses esophageal stylet to burrow through tissues until skeletal muscle is found
3) Muscle cell converted to nurse cell over 9 d period
4) By day 12 the nurse cell is providing nutrition and removing waste
5) Larva-nurse cell complex is mature (max growth) by day 20 post infection
6) Viable for years: any species of mammal can be a reservoir for infection
7) Transmission by carnivores and scavengers

Front 54

What are the symptoms associated with T. spiralis infection?

Back 54

it is proportional to the number of larvae penetrating muscle cells
fever
eiosinophilia
/\ IgE
muscle inflammation
circumorbital edema (swelling around eyelides)
CNS symptoms
diarrhea (5 - 15 times a day)

Front 55

What is the differential symptom for T. spiralis, trichinosis infections?

Back 55

circumorbital edema

(pic)

Front 56

How can T. spiralis be killed?

Back 56

freezing 20 days @ -15C
quickfreeze 24h @ -37C
heat up to 140F (microwaves won't do it)

Front 57

Tx for T. spiralis infections?

Back 57

corticosteroids for inflammation
Mebendazole for best prognosis with all nematodes
Albendazole is better tolerated