1. Chapter 35 Chewing Lice and Sucking Lice

2. 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

3. 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

4. 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

5. Gliricola porcelli from Guinea pigs
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

6. 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

7. 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

8. 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 eggs (nits) during their lives; eggs are either cemented to clothing (body lice) or to hair (head lice)

9. 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 vagabond’s disease

10. 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

11. Transmission is often from person to person by close personal contact
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