Cestodes (Flatworms)

Question 1

Features of Cestodes

Answer 1

• Flat body and no alimentary canal
• Nutrients absorbed through tegument
• Scolex (head) is holdfast organ
• Strobila (body) with proglottids
• Hermaphroditic
• Indirect life cycle

Question 2

Two orders of Cestodes

Answer 2

• Cyclophyllidea: 1 IH, Organs of attachment with scolex and suckers, Egg contains an oncosphere
• Pseudophyllidea: 2 IH, Organs of attachment with scolex and bothria, Egg contains an oncosphere with cilia for motility

Question 3

Dipylidium caninum

Answer 3

• Common name: flea tapeworm, double-pore tapeworm, cucumber tapeworm, “dog tapeworm”
• FH: Dogs, coats, zoonotic (children)
• IH: Flea, Louse
• PPP: 3wk
• SOI: Small intestine (ingestion of flea/louse with cysticercoid)
• Signs: Non-pathogenic, Discomfort from segments, Excessive grooming
• Diagnosis: Segments in bedding, Adhesive/Scotch tape swab
• Treatment: Praziquantel, Insecticide (IH)

Question 4

Choanotaenia spp.

Raillietina spp.

Answer 4

• FH: Domestic/wild fowl
• IH: Arthropods
• SOI: Small intestine
• Signs: Pathogenic in large numbers (Choanotaenia); Chronic infection causes reduced growth, emaciation, weakness, and heavy infection causes nodular tapeworm disease (Raillietina)
• Diagnosis: Necropsy is best, Section adult worms, Fecal exam not very good (intermittent shedding and don’t float well)

Question 5

Anoplocephala perfoliata

Anoplocephala magna

Answer 5

• FH: Horses
• IH: Oribatid (“forage”) mites with cysticercoids
• PPP: 1-2mo
• SOI: Adult A. perfoliata in cecum, ileocecal valve; A. magna in small intestine
• Signs: A. perfoliata- Ulceration, Partial occlusion of ileocecal valve, intususception of ileum and cecum; A. magna- less pathogenic
• Diagnosis: Centrifugation and flotation, sedimentation, Antigen ELISA
• Treatment: Praziquantel

Question 6

Moniezia spp.

Answer 6

• Common Name: “milk tapeworm”, double-pored ruminant tapeworm, sheep tapeworm
• FH: sheep, goats, cattle, other ruminants
• IH: oribatid mites
• PPP: 1-2mo
• Signs: Relatively unpathogenic, Mild unthriftiness and GI problems in lambs/kids, Presence in feces of ill animal may mask true cause of illness
• Diagnosis: Proglottids in feces or protruding from anus, Fecal exam
• Treatment: Albendazole (scolex can return), Praziquantel or Niclosamide (off label)

Question 7

Taenia spp.

Answer 7

• FH: Dogs (T. pisiformis, T. crassiceps, T. hydatigena), Cats (T. taeniaeformis), Humans (T. saginata, T. solium)
• Larva: all cysticercus except for T. taeniaeformis (strobilocercus)
• PPP: 70-84d (T. saginata), 35-84d (T. solium)
• SOI: Small intestine

Question 8

Taenia saginata

Answer 8

• Common name: Beef tapeworm, Pearly beef
• FH: Human
• IH: Cattle
• SOI: Small intestine (FH), Striated muscle (IH)
• Signs: Discomfort with passing segments (FH), None except rare cysticerci in heart (IH)
• Diagnosis (Cattle): Meat inspection, Serology (Ag or Ab)
• Treatment: Praziquantel (expensive), Sewage treatment, Vaccine, Cook/freeze meat, Hygiene

Question 9

Taenia solium

Answer 9

• Common name: Pork tapeworm, Pearly/measly pork
• FH: Humans
• IH: Pigs, Humans
• SOI: Small intestine (FH); Muscles, Eye, CNS, Subcutaneous tissue (IH)
• Signs: None (Pigs), Taeniosis causes some intestinal discomfort, Neurocysticercosis causes seizures (epilepsy), headaches, hydrocephalus, blindness, dementia and death
• Diagnosis: Serology/PCR (FH and IH), Lingual exam (Pigs), CT/MRI, Biopsy, Fecal exam
• Oxfendazole (Pigs), Praziquantel/Albendazole (Humans), Pig vaccine and husbandry, Meat inspection, Hygiene/sanitation

Question 10

Echinococcus granulosus

Answer 10

• Common name for larval infections: hydatid disease/hydatids, cystic echinococcosis(CE)
• FH: Dogs, wild canids, cats
• IH: Livestock (especially sheep), Humans
• Dog/Sheep cycle most important
• SOI: Small intestine (FH); Hydatid in liver, lungs, bones, brain and other organs (IH)
• Signs: Non-pathogenic (adults in dogs and hydatids in livestock), Pathogenic (hydatids in humans)
• Diagnosis: Eggs same as Taenia spp., Examine livestock organs, Ultrasound (Humans), Purgation or coproantigen test (Dogs)
• Treatment: Praziquantel every 6wk and fecal disposal, Prevent carcass feeding/access, Hygiene

Question 11

Echinococcus multilocularis

Answer 11

• Common name: Alveolar echinococcosis (AE) in humans, Echinococcosis (Dogs)
• FH: Dogs, Wild canids (Foxes), Cats (poor hosts) -Found only in northern hemisphere
• SOI: Small intestine (FH), Hydatids in liver with metastases to other organs (IH)
• Signs: Alveolar echinococcosis and death (IH)
• Treatment: Praziquantel (Adults), Longterm anthelmintics with or without surgery (Humans)

Question 12

Diphyllobothrium latum

Answer 12

-Common name: Fish or Broad Tapeworm
-FH: Humans, Fish-eating mammals (dogs, cats, bears)
Intermediate hosts: Copepod crustacean infected with procercoid (1st), Freshwater fish infected with plerocercoid (2nd)
-SOI: Small intestine (Adults), Muscles and viscera of fish (Larva)
-Signs: Typically non-pathogenic, Abdominal discomfort, Weight loss, Diarrhea, Anemia (Vitamin B12 deficiency), Intestinal obstruction, Gall bladder disease
-Diagnosis: Eggs/proglottids in feces
-Treatment: Praziquantel or Niclosamide (Adults), Avoid raw/undercooked fish, Prevent defecation in/near freshwater sources

Question 13

Spirometra spp.

Answer 13

• Common name: Zipperworm, Parganosis (Humans)
• Final hosts: Dogs, cats, lynxes, bobcats, raccoons
• IH: Crustacean (1st); Fish, reptiles, amphibians, birds, rodents, humans (2nd)
• PH: Humans
• PPP: 2-4wk
• SOI: Small intestine (FH), Larva in IH
• Signs: Plerocercoids (spargana) spread throughout human body
• Diagnosis: Eggs in feces, Differentiate from Trematode eggs
• Treatment: Praziquantel or Niclosamide (FH), Surgical removal (Humans), Avoid contaminated water and food, Avoid poultices from frog or water snake meat