Parasitic Worms

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Parasitic Worms

• Pathogenic Human Helminthes and Arthropods

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Characteristics

• Multicellular
• Well developed organ systems
• Reproductive
• Dioecious
• Hermaphrodite
• Worldwide
• Tropical, subtropical
• Survival of eggs
• Survival of larval stages
• Less developed
• Sanitation
• Intermediate host survival

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Life Cycle

• Host
• Definitive
• Intermediate
• Cycle
• Egg ? ingestion
• Larvae ?ingestion, penetration, migration
• Infectious stage ? intermediate host
• Adult?reproduces

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Overview of Generic Life Cycle
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Helminth Types

• Platyhelminths
• Flatworms
• Flukes
• Trematodes
• Flat, leaf shaped
• Suckers
• Named for location
• Tapeworms
• Cestodes
• Long body
• Scolex
• Proglottid

• Nematoda
• Roundworms
• Cylindrical body
• Cuticle
• Dioecious
• Roundworms
• Hookworms
• Pinworms
• Whipworms
• Strongyles
• Filaria

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Host Susceptibility
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Pathogenesis

• Direct Damage
• Blockage
• Worm size
• Worm migration
• granulomas
• Pressure
• Tissue
• Necrosis
• Migration
• Turnover

• Indirect Damage
• Host response
• Inflammation
• Hypersensitivity
• Mucosal changes

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PLATYHELMINTHS

• Flat body
• Hermaphrodites
• Parasitic
• Trematodes
• Cestodes

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FLUKES (Trematodes)

• Schistostomiasis
• Fascioliasis
• Intestinal Fluke
• Chinese Liver Fluke
• Lung Fluke

• Life Cycle
• Eggs
• Miracidia
• Intermediate host
• Cercariae
• Second intermediate host
• Metacercariae
• Definitive host
• Adult fluke

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Fluke Anatomy and Life Cycle
Miracidia
Adult Fluke
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Liver Flukes

• Fasciola hepatica
• Typical life cycle
• Snail intermediate host
• Humans exposed to metacercaria by eating
  watercress
• Intestine ? Liver ? Bile Ducts ? eggs in feces

• Chinese Liver Fluke
• Typical life cycle
• Snail intermediate host
• Humans exposed to metacercaria by eating
  undercooked fish
• Intestine ? Liver ? Bile ducts? eggs in feces

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Flukes Fasciola sp.
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Flukes of other Organs Lungs

• Paragonimus westermani
• Eggs coughed and swallowed, passed in feces that
  contaminate water
• Cercaria in snails
• Metacercaria in crabs
• Humans eat crabmeat
• Adult flukes migrate from GI? Blood ? Lungs
• Signs Coughing

Egg
Adult Fluke
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Flukes of other Organs Urine

• Schistostoma
• Eggs in urine, feces
• Miracidia in snails
• Cercaria in snails
• Penetrate skin
• Schistosomulae in liver
• Adults migrate to urinary system
• Signs damage to liver, and urinary bladder

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Flukes

• DX
• Eggs in feces
• TX
• Antihelmenics
• Prevention
• Thoroughly cook meats
• Cook vegetables

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TAPEWORMS (Cestodes)
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Life Cycle of Tapeworms

• Eggs in proglottids passed in stool
• Larval phase in Intermediate host
• Intestine ? blood ? Skeletal muscle and other
  tissue ? cysts
• Acquire by eating raw meat with cysts
• Cysts ? adult worms in intestines

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Tapeworm Anatomy
Scolex with hooks
Adult Tape worm
Proglottids
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Taenia tapeworms

• Taenia saginata (beef)
• Taenia solium (pork)
• Symptoms
• Abdominal discomfort
• Diagnosis
• Worm segments
• Eggs in stool
• Treatment
• Antihelminics
• Prevention
• Cook meat

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Taenia species
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Dipylidium canium

• Dog / cat tapeworm
• Zoonotic
• Intermediate host
• Flea
• Children
• Ingest
• acquire

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Hydatid Disease

• Echinococcus granulosus
• Eggs ingested by herbivores
• Embryos from eggs go to various sites to develop
  cysts
• Ingestion of cysts or eggs
• Humans intermediate host
• Cyst
• Damage due to size
• Anaphylactic shock

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Ecchinococcus
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Tapeworm Summary

• DX
• Worm segments
• Eggs in stool
• TX
• Antihelmenthics
• Prevention
• Hygiene
• Inspect meat

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Tapeworms
Taenia eggs
Ecchinococcus
Diplidium canium
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NEMATODES

• Roundworms
• Cyclindrical body
• Dioecious
• Cuticle

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Filaria Worms
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FILARIASIS

• Elephantitis
• Wuchereia bancrofti
• Mosquito
• Lymphatics
• Microfilaria in blood
• Adults in LN
• Blockage
• Swelling

• Loaisis
• Onchocerca volvulus
• Biting flies
• CT
• Microfilaria in blood
• Adults in conjunctiva
• Inflammation
• swelling

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Fliaria Summary

• DX
• Id microfilaria in blood
• TX
• Diethylcarbamazine
• Prevention
• Control of intermediate hosts

Wuchereia bancrofti
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ASCARIASIS
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Roundworms

• Ascaris lumbriocoides
• Fecal contaminated food
• Eggs ingested
• Larvae released and migrate
• GI ? lymph/blood ? lung alveoli ? coughed ?
  swallowed
• Adults mature in upper GI (stomach and SI)

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Roundworms (Ascarids)

• Symptoms
• Asymptomatic
• Respiratory
• GI
• DX
• Eggs in stool
• Adults in vomitus
• TX
• Prevention
• Sanitation
• Cook food

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Toxocariasis

• Toxacaris canis, T. cati
• Eggs in environment
• Fecal ? oral
• Larvae hatch in GI ? Blood ? Liver ? Lung ? any
  tissue
• aka Visceral Larval Migrans
• Zoonosis

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Toxocariasis

• Symptoms
• Resp cough, fever, wheezing
• Organomegaly
• Skin rash
• Eye inflammation
• DX
• Blood work
• Biopsy
• Eggs in stool
• TX
• Prevention
• Hygiene
• Deworm animals

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Ancylostomaisis
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Hookworms

• Ancylostoma, Necator
• Eggs in feces hatch
• Larvae mature in soil and penetrate skin
• Skin ? Lymphatic ?Blood ? Lungs ?coughed
  swallowed
• Adults develop in SI by attaching mouth parts to
  lining ? blood meals

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Hookworms

• Symptoms
• Skin rash, pruritic
• Resp
• GI pain
• Anemia
• DX
• Eggs / larvae in stool
• TX
• Prevention
• Limit soil exposure

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Trichuriasis
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Whipworms

• Trichuris trichura
• Eggs in soil, ingestion of contaminated food
• Larve hatch in SI, migrate to cecum
• Larvae mature to adult stage

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Whipworm

• Symptoms
• GI pain, diarrhea, bleeding, anemia, rectal
  prolapse
• DX
• Eggs in stool
• Colonoscopy to view adults
• TX Antihelminthics
• Prevention
• Sanitation
• Wash vegetables

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Pinworms

• Enterobiasis vermicularis
• Eggs _at_ perineum
• Fecal-oral
• Eggs hatch ? Lower GI to mature
• Female moves to perineal region to deposit eggs
  in sticky substance
• HUMANS ONLY !!

DX GI itching, eggs Worms in colon TX
Anthelminthics Prevetion Hygiene
Wash clothing
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Trichinosis
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Trichinosis

• Trichinella spiralis
• Larvae in skeletal m.
• Exposure by eating uncooked meat
• Cyst ? larvae?adult in intestine mature and
  release larvae
• Larvae gt migrate using blood/lymph ? penetrate
  muscles to form cysts

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Trichinosis

• Symptoms
• Asymptomatic
• GI cramps, diarrhea
• Muscle stiffness, pain, soreness
• Skin rash
• Eyelid swelling, pain, injected sclera
• DX symptomatic
• TX
• Prevention
• Cook
• Freeze

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Strongyloidiasis

• Strongyloides stercoralis
• Eggs hatch in SI mucosal glands
• Larvae passed in stool
• Exposure larvae migrate through skin
• Skin ? Lungs ? coughed and swallowed ? Intestines
• Larvae mature to adult stage

Larva
Adult
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Guinea Worm Disease

• Drancunculus
• Larvae in water
• Crustacean (IH)
• Humans ingest uncooked meat
• Larvae released ? skin ? Adult in blister like
  lesion
• Larvae produced and released with water

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Drancunculus removal
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Other Parasites
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Arthropod Parasites

• Scabies
• Sarcoptes scabeii
• Mite
• Burrows into skin
• Lays eggs
• Intense pruritis
• Direct contact
• Zoonosis
• TX insecticides

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Arthropod Parasites

• Pediculosis
• Human Lice
• Head
• Body
• Direct contact
• Blood meal
• Eggs (nits) laid at base of hair shaft
• Pruritis
• TX Insecticides

Pediculus humanus
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Human Lice
Nits on hair
Pediculus humanus
crabs
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Antihelminthics

• Praziquantel
• Albendazole, Mebendazole
• Diethylcarbamazine
• Pyrantel pamoate
• Metronidizole
• Insecticides
• Pyrethrin
• Permethrin

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Questions?