Cestodes: Intro Flashcards
(24 cards)
General info
2 orders: Cyclophyllidea & Pseudophyllidea
- flatworms
- no alimentary canal (intestinal tract)
- nutrients absorbed through tegument (skin)
- scolex (head) is the holdfast organ
- strobila (body) with proglottid segments
- hermaphroditic: each proglottid is sexually independent and matures as it moves distal to scolex –> genital pore on proglottid is where eggs exit (can have single or double)
- indirect life cycle
- site of infection for adults: small intestine (few exceptions)–> adults are not usually pathogenic unless there is a heavy infection
- larval stage is pathogenic, different larval stages (cysticercoid, cyysticercus, strobilocercus, hydatid cyst)
- some zoonotic
- General rule: NOT all but MOST are never pathogenic in animals, only pathogenic in humans
Larval stage in IH: different larval stages
Cysticercoid: evaginated scolex, small, solid cyst found in small arthropod IHs
Strobilocercus: scolex connected to fluid filled cyst by asexual proglottid chain, only in T. taeniaeformis (cats)
Cysticercus: fluid filled invaginated scolex, up to size of a pea found in mammal IHs
Hydatid cyst: fluid filled cyst in liver/lungs growing 5-50cm. Endogenous: (E. granulosus/canadensis) or exogenous: (Alveolar; E. multilocularis) budding of brood capsules
Cestode eggs
- intermittent egg laying (may not always see in feces!!), need to do another dx method along w fecal
- liberated by disintegration of proglottid or shed thru a genital pore on proglottid
Cyclophyllidea: thin shell, contains oncosphere (hexacanth embryo). embryo has 6 hooklets. oncosphere=1st stage larva. embryophore= oncosphere surrounded by thick, dark, striated shell
Pseudophyllidea: oval, light brown, thick shell, operculate, coracidium= ciliated oncosphere (to move in water)
Dipylidium caninum
Common tapeworm, Cucumber tapeworm, Flea tapeworm, double pore tapeworm, dog tapeworm
Host: dogs, cats, humans (esp children/ppl who sleep w their animals, humans infected ONLY by ingestion of flea)
IH: flea, louse
PPP: 21 days
Larval stage: cysticercoid (evaginated scolex)
ID: fresh segment like cucumber seed in bedding/around anal region, dried segments like grain of rice in bedding, double genital pores on proglottid; mobile proglottids= can detach and move out of anus. Egg packets (25-30 eggs per packet), can see hooklets in egg, thin shelled.
Adults up to 50cm long
**synchronous development of tapeworm and flea/louse=FH infected by INGESTION of flea/louse w/ cysticercoid
Path: adults non pathogenic, segments may cause some discomfort
CS: excessive grooming/biting at anal area; flea problem or fleas in area
Dx: check bedding for segments, adhesive tape swab of perianal region; fecal float (eggs not always seen)
Tx: treat FH w praziquantel (no residual activity so reinfection is possible)…Tx IH and ENVIRONMENT w insecticide to get rid of fleas
-zoonotic
Flea the scene when you see him using dip packets
Choanotaenia spp. & Raillietina spp.
Fowl cestodes
Hosts: domestic and wild fowl
IH: arthropods (ants, beetles, houseflies)
PPP: 2-3 weeks
ID adults: 10-25cm, in SI, eggs pass in feces, ingested by IH and develop into cysticercoids, FH ingests IH, cysticercoids develop into adult in SI
ID eggs: round to oval, hexacanth oncosphere
ID larvae: cysticercoid, evaginated scolex
Path/CS:
-Choanotaenia spp: non-pathogenic unless lg #, can cause wt loss
-Raillietina spp: chronic infections= reduced growth, emaciation, weakness, decreased egg production,; heavy infection: “nodular tapeworm dz” from intestinal granulomas (immune rxns)
-affects absorptive capacity
Dx: necropsy, fecal float (not ideal), morphological exam of adult worms needed to ID spp.
Tx: screen poultry houses to prevent entry of IH
Headbangers on the rail nod their heads
Cho no!
Family Anoplocephalidae
Equine cestodes: A. perfoliata, A. magna
Ruminant cestodes: Moniezia spp.
- oribatid mite found in bedding, on pasture and hay, makes it hard to control
- no seasonality
- eggs contain oncosphere surrounded by pyriform apparatus (pear shaped)
- cysticercoid larvae
Anoplocephala perfoliata & A. magna
Equine cestodes
Host: equine
IH: oribatid (forage) mite
PPP: 1-2 mo
ID:
-A. perfoliata (more common): white, smaller (4cm), short/broad segments, no hooks. rounded scolex with lappet behind each of the 4 suckers
-A. magna (less pathogenic): white, larger (80cm), no lappets
ID larvae: cysticercoid
ID eggs: triangular/trapezoid shape, contain embryo surrounded by pyriform apparatus (pear shaped)
Site of infection:
-A. perfoliata: ileum and cecum (EXCEPTION); ileocecal valve
-A. magna: SI
-mites found in hay, straw, grass; no seasonality
Path/CS: A. perfoliata: ulcerations and ill health, locallize near ileocecal valve–> partial occlusion of valve, intussusception of terminal ileum and cecum possible (can cause death of intestinal wall)
Dx: centrifugation and floatation, sedimentation, ELISA antigen
Tx: praziquantel pasta
Moniezia spp.
Milk tapeworm, double pored ruminant tapeworm, sheep tapeworm
Hosts: ruminants
ID: oribatid mites
PPP: 1-2 mo
ID adults: 2m or longer, unarmed scolex w suckers, short broad proglottids w double genital pores
ID eggs: triangular/trapezoidal
M. expansa: sheep and goats; triangular shaped eggs
M. benedeni: cattle; cube shaped eggs
Path/CS: unpathogenic, heavy infection=mild unthriftiness &GI probs ESP IN YOUNG LAMBS AND GOATS (may overshadow other causes of ill health/incidental findings in adults- will not be cause of death)
Dx: proglottids in feces or protruding from anus esp in small ruminants; Mcmaster (may see)
Tx: albendazole approved (scolex may remain after tx), praziquantel or niclosamide off label (no praziquantel formulation for ruminants); weanling tx
-NO SEASONALITY
Taenia spp.
IH: mammals
PPP: 6-12 wks
ID eggs: all similar, hexacanth embryo/hooklet, thick striated wall
ID larvae: most cysticercus (T. taeniaeformis: strobilocercus)
Site of infection: adults: SI, non pathogenic. Larvae: varies
Eggs can persist in the environment for years
Tx: praziquantel to FH for adult worms; praziquantel & albendazole for larval infections of T. solium (and Echinococcus spp. of humans)
Taenia pisiformis
Host: dogs and foxes
IH: rabbit
PPP: 8 wks
ID adults: up to 2m, armed scolex (hooklets on scolex above suckers), single genital pore
ID larvae: cysticercus
Larvae: in liver and peritoneum
Proglottids initially moving around when first passed in feces
Rabbits piss everywhere
Taenia crassiceps
Host: dogs and foxes IH: small rodents, humans PPP: 6-9 weeks ID adults: up to 17 cm (smallest Taenia) ID larvae: cysticercus Larvae: in abdominal cavity, eye ZOONOTIC; found only in northern hemisphere: SQ infections in immunocomp ppl, VISCERAL OCULAR MIGRANS
Need my glasses to see ratatouille sitting up north on the guys head
Taenia hydatigena
Host: dogs and foxes IH: livestock, mainly sheep PPP: 7-8 weeks ID adults: up to 5 m long ID larvae: cysticercus Larvae: in peritoneal cavity Large "bladder like" cysticerci attached to omentum or liver Can also be found in wild ruminants, deer, etc as IH=hunters find these when they skin the animal on site
Taenia taeniaeformis
Host: cat IH: small rodents PPP: 5-6 wks (40d) ID adults: up tp 70 cm long ID larvae: strobilocercus Larvae: in liver Prevention: don't let rodents eat cat poop or keep cats from eating IH
Tom and Jerry formed a dynamic duo
Taenia saginata
Beef tapeworm, pearly beef
Host: humans
IH: cattle
PPP: 10-12 weeks
ID adults: 5-15m long, unarmed scolex (suckers no hooks)
ID larvae: cysticercus
Larvae: striated/cardiac muscle
ZOONOSIS
Proglottids VERY motile and can move out of anus- will notice wiggly proglottid on leg
Path/CS: FH: non pathogenic, discomfort/inflammation when passing proglottid out of anus
IH: none, except heavy infections w cysticerci in heart, cysticerci in muscle eventually die and calcify, look like a pearl
Dx: (cattle) mean inspection (may not catch w low infection); serology Ag or Ab test (premortem)
Tx: praziquantel highly effective ($$ for Lg animals), educate, sewage tx, vax not available
**cook meat thoroughly, freeze meat, hygine and sanitation–> don’t let ppl shit out in the open!
Break the life cycle
Taenia solium
Pork tapeworm, pearly/measly pork
Host: humans
IH: pigs, humans (dogs)
ZOONOSIS
PPP: 5-12 wks
ID adults: 3-5m long, scolex has 4 suckers and double row of 30 hooks
ID larvae: cysticercus, muscle, brain (CNS), SQ tissue, eye
Distribution: endemic in pig raising/pork consuming areas; associated with poverty(where people defecate out in the open); spread by people/pig movement (immigration, international travel and trade)
Dx: lingual exam in pigs, serology/PCR, imaging (CT, MRI) humans, biopsy and SQ nodules, fecal exam (not the best, intermittent egg release)
Tx: anthelmintics (oxfendazole-pigs, praziquantel/albendazole- humans), pig vaccine, pig husbandry, meat inspection, hygiene and sanitation, education
Pig got your tongue
Taenia solium life cycle
- person usually only has 1 worm (solium); proglottids are NOT motile and only get released during defecation–> spread through open defecation, eggs spread easily and contaminate soil and water supply
- release more than 50,000 eggs per day
- pigs eat human feces with eggs, eggs hatch and larvae penetrate gut wall
- migrate throughout body and encyst in muscle; pigs will wait for human to run to bushes to defecate and eat it as a treat
Taenia solium path/CS
Dz in humans:
FH: Taeniosis (adult tapeworm infection) –> intestinal discomfort, happens when humans eat raw/undercooked pork infected with cysticercus
IH: Neurocysticercosis (NCC)- larval infection in brain–> seizures (epilepsy), headaches, hydrocephalus, blindness, dementia, death
-when humans ingest the egg or through auto-infection
-cysts can camouflage themselves to not be detected by immune system
-until they start to die can cause immune rxns and have seizures= more than 1000 Dx of NCC/ yr
-most common preventable cause of epilepsy- CDC neglected parasite infection initiative
-must be from a human tapeworm carrier* no pigs involved
Pigs: no CS
Echinococcus granulosus
Host: dogs and wild canids
IH: livestock (sheep!), humans
Zoonosis: dog-sheep cycle most imp, dingo-wallaby cycle (sylvatic)
PPP: 6 wks
ID adults: small, <6mm, few proglottids (3-6)
ID larvae: hydatid cyst- endogenous budding of brood capsules each containing many scolicies
ID eggs: indistinguishable from Taenia spp.
Larval infections: hydatid dz
Adult infections (dogs): echinococcosis
Larvae: in liver, lungs, bones, brain, other organs
Eggs: viable in the environment for 2 yrs, distal proglottid full of eggs, one egg can have 1000s of worms
Path: adults nonpathogenic in dogs, hydatids non pathogenic in livestock, hydatids pathogenic in humans*=massive cysts on lungs/liver in humans, need sx removal
-dogs can have eggs in hair and feces can contaminate food and water very easily - infects humans easily
Tx: praziquantel q6wks, disposal of feces!, don’t feed uncooked livestock organs to dogs, limited access to livestock carcasses, wash hands when handling dogs, sheep vax, dog vax
Echinococcus canadensis
Hosts: wild canids (coyote, wolf)
IH: wild cervids (elk, deer, moose) and humans
N. America and Canada
-some strains in N. America have been reclassified as E. canadensis
-Everything else same as granulosus–> PCR to differ the 2
ZOONOTIC
canadians have moose
Echinococcus multilocularis
Alveolar echinococcosis (AE)- common name in humans
Echinococcosis- dz in canids
Hosts: dogs (cats are poor hosts)
IH: rodents, lagomorphs, humans, dogs
-Found in northern hemisphere
ID adults: <6mm
ID larvae: alveolar hydatid cyst- exogenous budding infiltrates surrounding tissue, grows large and cancerous
Larvae: liver and metastasis to other organs in IH
Tx: Adult: praziquantel; Larvae- long term anthelmintics/sx, high morbidity
Zoonotic- cysts can be fatal in humans, high mortality from larval stages, cancerous
multilocularis-metastasize
Order Pseudophyllidea
- 2 intermediate hosts: 1. copepod crustacean; procercoid, 2. plerocercoid (spargana)
- organs of attachment w scolex and bothria= pinching mechanism
- egg contains oncosphere with cilia for motility- hatch in water
- Eggs: brown and operculate
- Coracidium= ciliated oncosphere
- Operculum= lip or covering on egg
- Dibothriocephalus latus
- Spirometra spp (^ both in family Diphylobothriidae)
Dibothriocephalus latus
Fish or broad tapeworm
Host: humans, fish eating mammals (dogs, cats, bears)
IH: 1. copepod crustacean infected w procercoid, 2. freshwater fish infected with plercercoid
PPP: 5-6 wks
ID adults: scolex w/ bothria, up to 12 m long, square shaped proglottids (strobila may have >3000 proglottids), proglottids release up to 1 mil eggs/day (massive environmental contamination)
ID eggs: look like trematode eggs, will eventually develop cilia to hatch in water, operculated egg w small knob at opposite end of operculum
Life cycle: operculum opens when egg hits the water, develops in water to a coracidium, ingested by 1st IH (crustacean), procercoid develops in 1st IH, ingested by 2nd IH to form plerocercoids, FH ingests infected 2nd IH and adult tapeworms develop
Larval stages: in muscles and viscera of fish
Path/CS: mostly asymptomatic, may cause abdominal discomfort, wt loss, v/d. Macrocytic anemia bc uptake of vit B12 from intestine (depletion), possible intestinal obstruction or gallbladder dz (bc worm is so long)
Dx: eggs/proglottids in feces
Tx: cestocidals tx adults, avoid consuming raw/undercooked fish or feeding fish products to domestic animals, do not allow humans, dogs, or cats to defecate near bodies of freshwater
Zoonotic
Lotus flower opens in the water
Spirometra spp.
Zipperworm
Hosts: dogs, cats, raccoons
IH: 1. copepod crustacean, 2. fish, reptiles, amphibians, birds, rodents, humans
PH: humans
PPP: 2-4 wks
ID adults: <2m long, scolex w bothria, central genital pore and repro organs, proglottids shed in groups
Larvae: 1st IH body cavity filled w procercoids, 2nd IH plerocercoids in muscles and viscera of 2nd IH
Path/CS: non pathogenic in dogs/cats; plerocercoids (spargana) cause human sparganosis (plerocercoids or procercoids migrate around in SQ tissue–> SQ tissue, breast, eye, urinary tract, pleural cavity, abdominal viscera, CNS
Dx: eggs in feces, differ from trematode eggs
Tx: cestocide for FH, sx removal of spargana from humans
Prevention: avoid contaminated water and feeding products derived from IH to domestic animals (unless thoroughly cooked; avoid poulticies using frog or water snake meat)
Spirometra spp. dz in humans
- sparganosis from eating 1st or 2nd IH
- humans can become 2nd IH if ingest infected copepods
- humans can become PH from ingesting plerocercoids (spargana) in 2nd IH or from use of frog or water snake meat for poultices applied to wounds or black eye (humans taking place of FH but they can’t be infected with adults so they become PH instead
- spargana migrate through the body
