Parasitology Ascarids

  1. Nematodes (Roundworms) Characteristics
    • *Sensory organs (amphids) around head
    • Unsegmented
    • Bilaterally symmetrical
    • Elongated
    • Tapered at both ends
    • Digestive tract is usually complete
    • *most important to distinguish them
  2. Nematode Life Cycle Generalizations
    Five states: one-cell--> morula--> vermiform embryo (pre-first state larvae)--> First State--> Second State--> Third State (usually infective state)--> Fourth State--> Fifth State (adult)-->
  3. Nematode Bursate
    Posterior end of the male end. Baseball like structure that is used to clasp onto the females
  4. Nematode Non-bursate
    Male does not have a bursate but does usually have a curved end which helps the male grab onto the female
  5. Spicules
    On the end of the male worms that open up the females in order for sperm to be injected in
  6. Ascarids Morphology
    • "Roundworms"
    • Thick bodies
    • Adults large, white
    • They have three lips
  7. Ascarids Life Cycle Characteristics
    • Females pass HUGE numbers of eggs
    • Eggs are remarkably resistant to environmental degradation
    • Infect young, immunologically naive animals
  8. Pathogenesis of Ascarids Migrating Larvae (normal path)
    • Liver or kidney- scarring, hemorrhagic tract, "milk spots"
    • Lung- antigenic pulmonary edema, 2-3 day old pups can die, nasal discharge in foals
  9. Pathogenesis of Ascarids Adult Worms
    migrate from small intestine to stomach (causing vomiting)

    Large numbers in intestine (mucoid diarrhea, pot-belly, contributes to malnutrition, painful, rough hair coat, fail to thrive)

    May block bile duct
  10. Pathogenesis of Ascarids Aberrant Larval Migration
    • Visceral larva migrans (VLM)
    • Ocular larva migrans (OLM)
    • CNS disease common
    • Hepatomegaly, eosinophilia
  11. Diagnosis of Ascarids
    • Adults
    • Characteristic eggs on fecal float if patent
    • Presumptive if within prepatent period (Clinical signs, gross apperance, age)
    • Transtracheal aspirate in foal with respiratory disease due to ascarids
  12. Ascaris suum (host, site of infection, distribution)
    • Intestinal large roundworm
    • Host: pigs
    • Site of infection: Adults in small intestines
    • Distribution: Common, pigs raised outdoors
  13. Ascaris suum Life Cycle and Transmission Patterns
    • Ingestion of infetive eggs (3rd State Larvae)
    • Paratenic hosts: earthworms and dung beetles
    • No transplacental or transmammary
    • Prepatent period= 6-8 weeks

    Hatches in stomach--> liver--> lungs--> swallowed--> Stomach
  14. Ascaris suum Pathogenesis due to migrating juveniles
    Mechanical destruction of tissue- early infection (initial focal hemorrhages, respiratory distress)

    Hypersensitivity (hyperemia, edema, eosinophilic infiltrates)

    Fibrosis (milk spot lesions)
  15. Ascaris suum Parthogenesis Clinical signs due to adults
    • Interference with proper nutrition and growth
    • Diarrhea
    • Occasional occlusion or perforation
    • Subclinical effects- reduce growth rate
  16. Ascaris suum Diagnosis
    • Patent infection: eggs in flotations, adults at necropsy
    • During prepatent Period: respiratory signs in young pigs, feeder pigs 2 to 5 months
  17. Ascaris suum Eggs
    50-70 by 40-60 in size, thick pitted outer wall, golden brown
  18. Parascaris equorum/ P. univalens (host, site of infection, distribution)
    • Large intestinal roundworm or horse roundworm
    • Host: equine species, horses and donkeys
    • Site of infection: adults in small intestine, juveniles migrate extensively
    • Distribution: common throughout the world
  19. Parascaris equorum Life Cycle
    • Similar to A. suum (Hatches in small intestine--> liver--> lungs--> swallowed--> small intestine)
    • Prepatent period: 10 weeks
    • Prenatal infections are not known to occur
    • Ingestion of infective eggs primary route
  20. Parascaris equorum pathogenesis migrating juveniles
    • Respiratory distress and nasal discharge in foals
    • Similar to the for A. suum
  21. Parascaris equorum pathogenesis adult worms
    • moderate enteritis, colic
    • subnormal growth
    • dull hair coat
  22. Parascaris equorum diagnosis
    Patent infections: eggs in flotations, adults at necropsy

    • Prepatent infections: caughing and greyis-white nasal discharge in foal up to 6 months
    • Endoscopy reveals frothy mucous in upper air passages
  23. Toxocara canis (host, site of infection, distribution)
    • Host: canines
    • Site of infection: adult in small intestines, juveniles migrate extensively
    • Distribution: throughout the world, very common
    • Have cervical alae (wings) on head
  24. Toxocara canis Life Cycle (Very important)
    Puppy less than 5 weeks old ingests egg
    L3 hatch in small intestines--> goes to liver--> lungs to aveoli--> goes to trachea to get swallowed--> stomach--> small intestine
  25. Toxocara canis Life Cycle (Very important) Transplacental
    • Primary way that puppy becomes infected: Arrested larvae in the dams tissue-->Transplacental migration of L3 to fetal liver --> neonatal pup lungs (until puppy is born)--> lungs to aveoli--> goes to trachea to get swallowed--> stomach--> small intestine
    • So efficient you can assume every puppy born is infected
  26. Toxocara canis Life Cycle (Very important) Mammary Glands transmission
    • migration of L3s to mammary glands--> L3s ingested by sucking pups--> swallowed--> stomach--> small intestine
    • (Rare)
  27. Toxocara canis Life Cycle (Very important) Paratenic Host
    paratenic host ingests egg--> somatic migration L3 into tissue--> dog eats host and larvae released--> develops into an adult in intestines
  28. Toxocara canis Pathogenesis migrating juveniles
    • Respiratory disease: 2-3 day old pups, transplacental transmission
    • Heavy infection of worms in small intestine: nursing and weaned pups, pot-bellied pups, tender abdomens often due to bloating, pups will frequently whimper and cry
  29. Toxocara canis adult dogs
    • Less susceptible:
    • intestinal infection is rare in adult dogs but 5% of dogs 7 years of age in shelters were infected
    • Puppies spontaneously purge intestinal infections as they mature and develop immunity to T. canis
  30. Toxocara cati (Host, Site of infection, Distribution)
    • Large round worm of cats
    • Host: Feline
    • Site of Infection: adults in small intestine, juveniles migrate extensively
    • Distribution: common throughout the world
  31. Toxocara cati Life Cycle
    Transmission: ingestion of infective eggs, no prenatal infections, transmammary infections (maybe), ingestion of paratenic hosts important, prepatent period is 2 months
  32. Toxocara cati pathogenesis and disease
    • respiratory signs in newborn kittens are absent
    • nursing kittens may obtain heavy infections from transmammary transmissions
    • clinical signs may include: abdominal distension and distress, chronic ill thrift
  33. Toxascaris leonina (host, site of infection, distribution)
    • Roundworm
    • Host: dogs, cats, foxes other wild carnivores
    • Site of infection: small intestines
    • Distribution: worldwide, uncommon in domestic dogs and cats, very common in wild carnivores
  34. Toxascaris leonina Life Cycle
    • transmission: eggs embryonate in approximately 1 week
    • may use mice as paratenic hosts
    • does not require somatic migration like Toxocara canis
    • no transplacental nor transmammary transmission
    • Prepatent period: 2-2.5 months
  35. Toxascaris leonina pathogenesis
    • not considered as pathogenic as Toxocara canis
    • minor clinical significance, however, infected animals may be potbellied and unthrifty
  36. Toxocara vitulorum (host, site of infection, distribution)
    • Host: cattle
    • Site of infection: small intestines for adults, VLM in calves this is non-pathogenic
    • Distribution: world wide but rare in US
  37. Baylisascaris spp. (hosts and importance)
    • Hosts: wildlife, carnivores and omnivores
    • Raccoon= Baylisascaris procyonis
    • Importance: can also infect dogs, public health implications because of the close association of raccoon and humans
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Parasitology Ascarids