Cestoda (tapeworms) Flashcards
Why are tapeworms considered a mostly “perfect” parasite?
Literally have no digestive system, little nervous system. Live off of the host entirely
What major challenge do cestodes face in their environment?
Staying in place despite Peristaltic movement of the gut.
The outermost part of the female reproductive tract in the Cestodes is referred to as
Ovijector
When a cestode proglottid is full of eggs it is referred to as ____
Gravid
Cestodes range in size from ____ to ____
a few mm to several meters
What is a “sparganum”? Do they always cause symptoms?
Migrating larvae of tapeworms that can infect many types of tissues, usually with a granuloma forming around them. They often develop without ever affecting the host, but may enter key areas such as the brain
How can sparganosis be treated?
With praziquantel or surgery, but often use of praziquantel kills them, resulting in more inflammation which can be harmful if the sparganum is in the brain
How does D. latum differ from most other tapeworms? What other defining traits do they have?
Have grooves rather than hooks or suckers, and the genital pores, testes, and vitellaria are in the center of the proglottid (medial). Their eggs are very definitive with a small bump near the operculum.
What happens once a D. latum egg hatches?
Free swimming oncosphere or coracidium must reach water to complete development. Enters copepod and develops in the haemocoel as procercoid.
What conditions do D. latum tapeworm infections cause?
Lack of vitamin B12 and anemia
What is it called when a person has a genetic predisoposition to lack of vitamin B12
Avitaminosis
Name/briefly describe the parts of the tapeworm head
Scolex - Head
Rostellum - Top of scolex, may be withdrawn
Hooks - for attaching to host (around rostellum)
Suckers - on every side of scolex
Each section of a tapeworm is referred to as a ____
proglottid
What types of structures may be present on a tapeworm scolex to aid in attachment?
Suckers, grooves, hooks, spines, tentacles, or combinations of those
Where are new proglottids grown on the cestodes?
posterior end of scolex near strobila
The parenchyma from one proglottid to the next is _____
continuous
Why is the integumentary system of tapeworms so important? Is it divided in any way?
IT is important because it serves as the primary surface for nutrient intake. It is not divided into true segments but instead stretches across the whole organism.
What type of muscle is found in tapeworms?
Circular
If a tapeworm proglottid detaches when mature, it is referred to as ____. When it detaches when spent/senile it is referred to as ____ or _____. When it detaches while eggs are maturing it is referred to as ____.
Apolysis.
Anapolysis or pseudapolysis.
Hyperapolysis
IF the posterior margin of one proglottid overlaps the anterior of the next, the tapeworm is referred to as _____
Craspedote
The tapeworm larval stage in which the scolex is everted into a sac is referred to as ____
Cysticercus
Briefly describe the basic features of the life cycle of a tapeworm
- Egg hatches into a larval form called the oncosphere.
- Oncosphere hatches either before or after ingestion by first host.
- Larva becomes juvenil metacestode
- Adult forms
Which stage(s) in the tapeworm life cycle have many potential configurations based on genus/species? Describe stage(s)
Procercoid stage, which occurs in an arthropod intermediate host.
AND
Plerocercoid stage, which occurs after first intermediate host (arthropod) is consumed by second intermediate (usually a fish)
_______ contains all the really important tape worms from the standpoint of human health
Taeniidae
The causative agent of hydatid cysts is ____
Echinococcus granulosus
What is the composition of hydatid cysts and how do they form?
Inner portion of the cyst is a part of the juvenile but the outer part is made from the host. The inner portion is separated from the outer host, preventing host immune response (which may send host into shock). Cysts are full of protoscolices (hundreds to thousands) that can cause infection if burst open (each one can form a new cyst)
Describe the life cycle of Echinococcus spp.
- Eggs are passed from definitive (canine) host in feces.
- Eggs are ingested by an intermediate host (likely a warm blooded vertebrate).
- Larva hatches in small intestine, penetrates lining and enters blood stream.
- Larva usually enters liver, but can enter any organ
- Larva develops into a hydatid cyst
- Protoscolex attaches to host intestien and develops into tapeworm
How large can hydatid cysts grow?
Golf ball size is common, basketball size is possible
How are humans a dead end host for Echinococcus granulosus?
Dogs don’t often eat us, sooo…
What is one of the problems with surgical hydatid cyst removal?
IF cyst bursts open, each tiny protoscolex can become a new cyst. Also, hydatid fluid may cause massive anaphylactic shock
What are some of the general features of the tapeworm order Pseudophyllidea
- Scolex has 2 longitudinal bothria
- Genital pores medial or lateral
- Vitellaria are folliculated and scattered throughout proglottid
- Life cycles involve crustacean 1st intermediate hosts and fish second intermediate hosts
The largest member of the order Pseudophyllidea is Hexagonoporus physeteris. How long is it and what is the host?
30m long, host is a sperm whale
What is the most common human tapeworm infection?
How is it acquired? What is the first sign?
Diphyllobothrium. Acquired by eating raw/undercooked fish. The first sign is expelling proglottids from anus.
What is “sparganosis”?
Caused when humans ingest tapeworm at the procercoid stage by drinking copepod infected water or eating undercooked infected second intermediate hosts (ex. mammals, reptiles, amphibians). The “spargana” (metacestode stage) can migrate anywhere in the body and begin growing to be up to 15 cm. Can go undiagnosed if it occurs in deep muscle, but many organs will have obvious symptoms. Can cause blindness in the eye.
