Chapter 35 Chewing Lice and Sucking Lice

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Chapter 35 Chewing Lice and Sucking Lice
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• 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

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• 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
  instars

• 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
  host

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• 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
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• 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
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• 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
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• 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
  Pediculus
• The family Pthiridae includes the human pubic or
  crab louse in the genus Pthirus

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• 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)

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• Pediculus humanus cont.
• Body lice can be transmitted from one person to
  another through contact, clothing or bedding
  head lice usually transmitted through physical
  contact
• 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
  fever)
• 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

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• 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

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• 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
  claws
• Transmission is often from person to person by
  close personal contact