Chapter 35 Chewing Lice and Sucking Lice - PowerPoint PPT Presentation


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Chapter 35 Chewing Lice and Sucking Lice


The family Pthiridae includes the human pubic or crab louse in the genus Pthirus ... It frequents the pubic hairs and perianal regions of man, but may wonder to ... – PowerPoint PPT presentation

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Title: Chapter 35 Chewing Lice and Sucking Lice

Chapter 35 Chewing Lice and Sucking Lice
  • General Information
  • Lice fall into one of two orders Mallophaga -
    chewing lice, with chewing mouthparts Anoplura -
    sucking lice, with sucking mouthparts
  • Members of both orders are wingless and
    dorsoventrally flattened
  • Eyes are reduced or absent
  • Tarsal claws are often enlarged, an adaptation
    to allow them to cling to hair and feathers of
    their hosts

  • Life Cycle
  • Eggs are cemented to the feathers or hairs of
    their hosts
  • Hemimetabolous development the young are
    similar to the adults except for size and
    development of the genitalia there are 3 nymphal
  • Members of these orders are highly adapted to a
    parasitic lifestyle they have no free living
    stages and die very quickly in the absence of the

  • Order Mallophaga Biting Lice or Chewing Lice
  • Head is slightly broader than the prothorax
    mouthparts are primitive, resembling those of the
    primitive free-living forms
  • Three suborders are recognized Amblycera,
    Ischnocera, and Rhynchopthirina

Trichodectes canis
  • Order Mallophaga cont.
  • The Amblycera are the most generalized and least
    host specific their antennae are composed of 4
    joints and lie in a ventrolateral groove on each
    side of the head and may not project beyond the
    sides of the head amblyceran parasites of
    mammals include Gyropus ovalis and Gliricola
    porcelli of guinea pigs and Heterodoxus spiniger
    on dogs

Gliricola porcelli from Guinea pigs
  • Order Mallophaga cont.
  • The Ischnocera are the most specialized their
    antennae are filiform in nature and composed of
    3-5 joints well known pests of cats, dogs and
    domestic cattle, horses, mules, etc.
  • e.g., Bovicola bovis on cattle Trichodectes
    canis is a common parasite of dogs and serves as
    the intermediate host of Diplydium caninum

Trichodectes canis
  • O. Anoplura Sucking Lice
  • All are parasitic of mammals possess piercing
    mouthparts small fused thorax antennae are
    visible and composed of 5 joints second and
    third pair of legs are often the largest and are
    broad and flattened
  • Head narrower than the remainder of the body
  • The family Pediculidae includes the human head
    louse and the body louse, both in the genus
  • The family Pthiridae includes the human pubic or
    crab louse in the genus Pthirus

  • Pediculus humanus
  • Occurs in 2 forms the body louse, P. humanus
    humanus (P. h. corporis) and the head louse P.
    h. capitis
  • Head lice are smaller than body lice body lice
    are seldom if ever found in the head, but head
    lice may be found on the body head lice are
    adapted to clinging to hairs, but body lice find
    refuge in clothing
  • Head lice and body lice can interbreed and
    produce fertile offspring
  • Females can lay from 150-300 eggs (nits) during
    their lives eggs are either cemented to clothing
    (body lice) or to hair (head lice)

  • Pediculus humanus cont.
  • Body lice can be transmitted from one person to
    another through contact, clothing or bedding
    head lice usually transmitted through physical
  • Infestations with lice usually are not life
    threatening, unless the lice carry some sort of
    disease organisms (e.g., it is a major vector for
    relapsing fever, epidemic typhus and trench
  • The lice normally cause red papules and cause
    severe itching which can lead to dermatitis and
    secondary infection years of infection can lead
    to darkened, thickened skin a condition known as
    vagabonds disease

  • Phthirus pubis
  • Possesses a wide thorax that constitutes most of
    the body, and the coxae are far apart at the
    margins of the thorax
  • It frequents the pubic hairs and perianal
    regions of man, but may wonder to other parts of
    the body, including the head

  • Phthirus pubis cont.
  • It is smaller and much broader than the other
    human lice, and its legs have the appearance of
    being attached to the edge of the flattened body
  • The forelegs are slender with long, fine claws
    the middle and hindlegs are thick, with thick
  • Transmission is often from person to person by
    close personal contact