LICE

Question 1

Meaning of Phthiraptera

Answer 1

Wingless lice

Question 2

Spend entire life on ?

Answer 2

host (highly host-specific: some prefer anatomical regions)

Question 3

Morphology
-body division?
-how many pairs of jointed legs?
-have wing or not?
-body flatted in what way?
-Sensory organ characteristics?

Answer 3

• Segmented body is divided into head, thorax and abdomen
• 3 pairs
• No wings
• Sensory organ is not well-developed, has short antennae and eyes is vestigial or absent

Question 4

Differences between sucking lice (anoplura) and chewing lice (mallophaga)

Answer 4

Anoplura has head that is narrower than the thorax and is elongated while chewing lice has large head that is wider than the thorax and is rounded.

Placental mammals are the host for anoplura while birds and mammals are the host for Mallophaga.

Adult of anoplura is 0.5 to 8 mm in length while mallophaga is 2-3 mm in length

Question 5

Mouthpart of anoplura is ?

Answer 5

higly modified
- composed of 3 stylets which form a set of fine cutting structures

Question 6

Mouthpart of mallophaga is

Answer 6

mandibulate
- feed on feather, skin and hair
- some feed on blood

Question 7

Differences of the claw between anoplura and mallophaga

Answer 7

anoplura has crab-like claws on the tarsus. The claw will clings to hair of the host. The diameter of the claw is associated with the diameter of the host’s hair shaft which proves the host specificity

Mallophaga typically have 2 claws on each of the tarsus for those that feed on birds; those that feed on mammal only have just 1 claw

Question 8

Examples of anoplura

Answer 8

Haematopinus
- Host: horses, cattle, pigs

Linognathus
- Host: dogs, cattle, sheep, goats

Question 9

Examples of mallophaga

Answer 9

Trichodectes (dogs)
Felicola (Cats)
Bovicola (Horse, cattle, sheep)
Menopon (poultry)

Question 10

Transmission through

Answer 10

close contact

Question 11

Factors getting infected

Answer 11

Stressed animals, poor husbandry and poor individual health

Question 12

Life stages occur at?

Answer 12

On the host

Question 13

Life cycle?

Answer 13

• Completed within 3 to 4 weeks.
  1. Louse eggs (nits) glued to hairs [pale, translucent, and suboval]
  2. Hatch into (3) nymphal stages [smaller but resemble adults in habits and appearance]
• Adult is visible to naked ye
• One adult female may lay 50 to 100 eggs in its life
• Not able to survive off host for more than 2 days

Question 14

Diagnosis of lice infestation?

Answer 14

1. History, clinical sign
2. Observation
   - lice on the skin
   - nits on the hairs
   - part hair to see skin
3. Comb test (-+/-)
4. Acetate tape strips (cannot do this test in mite infestation)
   - DDx : dermatophilosis, other parasites

Question 15

Indirect effects of lice infestation

Answer 15

1. Vectors
   - Typhus and relapsing fever in humans
   - Pox virus in pigs (mechanical vector)
   - Anaplasmosis in cattle
2. Intermediate host
   - Dipylidium caninum
3. Secondary bacterial infection, hairball due to excessive grooming

Question 16

Direct effects

1. Heavy infestations

Answer 16

Causes pruritus, alopecia and self-wounding
Direct damage, depends on density of lice.
Small number considered as normal flora in most animals in our country

Question 17

Direct effect

Answer 17

Poor body condition leads to increased lice population.
Causes rough/pulled haircoar or wool in dogs/cats whith heavy coat prone to infestation (felicola, trichodectes).

Question 18

Direct effect 3 & 4

Answer 18

1. Sucking lice - anaemia
2. Louse infestation may be indicative of other problems (chronic disease, malnutrition)

Question 19

Direct effect 5

Answer 19

Reduced vigour and weight loss
In birds, may cause severe irritations -leads to feather damage, restless and cessation of feeding (menopon)

Question 20

Host epidemiology

Answer 20

Malnourished animal - prone to heavy infestation
Free range animals
Stress factor
Management factor
Long hair coat
Immunity & underlying disease

Question 21

Agent epidemiology

Answer 21

• 200 to 300 eggs glued to hair
• 2-3 weeks life cycle completed
• very intimate relationship with host (cant live without host)

Question 22

Environment epidemiology

Answer 22

Heavy infectation in winter and early sping, also during rainseason

Question 23

Treatment and control

Answer 23

Treat
Environmental control
Stress factor
- Shearing neede - depend on climate
- Treatmetnt of meat and dairy animals - withdrawal period
- Husbandry issues - need to tackle
- Decontamination of animal equipment

Question 24

Pediculosis

Answer 24

Easily killed by a variety of treatments

Dogs and cats
= insectidal
= bedding and grooming equipment should be disinfected

Livestock
= topical or systemic insecticides
= ivermectin, moxidectin, doramectin
= imidacloprid for sheep (less common)
= Bedding & grooming equipment should be disinfected

Question 25

Immunitity consequences

Answer 25

It is expressed through
Reduction in nos and engorgement rate
Reduced fecundity
Reduced egg survival

Mechanism?
- Neutrophils, eosinophils and lympocytes at infestation sites
- Vasoconstriction, epidermal thickening