ZOONOTIC HELMINTHIASIS

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ZOONOTIC HELMINTHIASIS

• Helminth parasitic worm (Greek)
• Platyhelminthes (flukes, tapeworms)
• Nematodes- (roundworms) literally means
  thread-like
• Pathogenic helminths are some of most common
  parasites
• Worlwide distribution

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ZOONOTIC HELMINTHIASIS

• Toxocariasis (visceral/ocular larval migrans)
• Toxocara canis, T. cati
• Meningoencephalitis
• Balysascaris procyonis
• Trichinosis
• Trichinella spiralis
• Taeniasis
• Taenia soleum, T. saginata
• Hydatid disease
• Echinococcus granulosus, E. multilocularis

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NEMATODES

• Interspecies associations
• Criteria
• loss/gain from association
• degree of dependence of one or both species on
  the other
• Types
• symbiosis generic term for living together
• commensalism least obligatory mutually
  beneficial benefit greater than for those
  without it transport, camouflage, cleaning
• mutualism more intimate, essential to both
  more physiologically dependent
• parasitism- dependency on host benefit at
  expense of host

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NEMATODES

• Host
• The non-parasitic member of relationship
• Types
• Paratenic (transport) no further development
• Definitive host in which parasite reaches
  maturity both growth and reproduction occur
  within host
• Intermediate all other hosts necessary for
  development other than definitive growth, but
  not reproduction occur within host

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NEMATODES

• Life cycle
• 6 stages molt (shed cuticle) between each

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NEMATODES

• Life cycle
• Reproduction
• Amphimictic (sexual)
• Parthenogenetic (from eggs without fertilization)
• Hermaphroditic (possess both male and female
  organs or reproduction)
• Oviparous eggs hatch after laid
• Ovoviviparous eggs hatch within uterus, live
  young expelled
• Types of life cycle
• Direct- intermediate host not required
• Indirect intermediate host required

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TRICHINOSIS

• Agent
• Trichinella spiralis - intestinal nematode of
  many wild and domestic carnivores and omnivores
• T. nativa - Arctic bears
• T. pseudospiralis - mammals and birds
• T. nelsoni - African predators and scavengers
• T. britovi - carnivores in Europe, Western Asia
• Other names for disease
• trichinellosis
• trichiniasis

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Larva in cyst from muscle
Larva from Alaskan bear
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TRICHINOSIS

• Agent

Larva in cyst from muscle
Larva from Alaskan bear
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TRICHINOSIS

• Life cycle
• larva released from ingested cyst
• invade mucosa of small intestine where they
  develop into adults
• after 4 weeks (life span in intestine), females
  release larva that migrate to striated muscle
• encystment complete in 4-5 weeks
• note T. pseudospiralis does not encyst
• may remain viable for several years

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TRICHINOSIS

• Epidemiology
• Reservoir
• swine, dogs, cats, rodents, many wild animals,
  especially bears, boars, marine mammals, and
  large felids
• Occurrence
• worldwide, most common in Europe and US
• age adjusted incidence rate ? 2

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TRICHINOSIS

• Epidemiology
• Transmission
• ingestion of raw or undercooked meat
• pork and pork products
• bear meat
• marine mammal meat
• hamburger adulterated with pork

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TRICHINOSIS

• Clinical features
• Incubation period
• generally 8-14 days up to 45 days
• Symptoms
• from inapparent to highly fatal
• myalgia
• edema - periorbital and facial edema
• conjunctivitis
• fever
• eosinophilia
• gastrointestinal - diarrhea, pain, vomiting

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TRICHINOSIS

• Clinical features
• Life threatening symptoms
• myocarditis
• CNS involvement
• pneumonitis

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TRICHINOSIS

• Diagnosis
• Serology
• EIA
• ES (excretory-secretory) products - TLS-1 surface
  antigens conserved in all species, can be used
  for detection in animals or humans
• Ab levels not present until 3-5 weeks post
  infection - IgM, IgG, IgE peak in 2-3 months
• IgG most sensitive
• used for routine screening
• Bentonite flocculation
• Muscle biopsy
• Microscopic examination

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TRICHINOSIS

• Diagnosis detection of larvae in muscle

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TRICHINOSIS

• Treatment
• Anthelmintics
• mebendazole (Vermox)
• only effective against intestinal stages, not
  encysted stage
• Corticosteriods
• decrease severity of symptoms during muscle
  invasion phase

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TRICHINOSIS

• Prevention
• Proper cooking of pork and pork products and meat
  from wild animals
• internal temperature should reach 160ºF (71ºC)
• Irradiation of food effective
• low level gamma - sterilization
• higher levels - effectively kills trichinae
• Freezing will inactivate larvae of T. spiralis
  but not of T. nativa (arctic strains)