LICE Flashcards
Meaning of Phthiraptera
Wingless lice
Spend entire life on ?
host (highly host-specific: some prefer anatomical regions)
Morphology
-body division?
-how many pairs of jointed legs?
-have wing or not?
-body flatted in what way?
-Sensory organ characteristics?
- 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
Differences between sucking lice (anoplura) and chewing lice (mallophaga)
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
Mouthpart of anoplura is ?
higly modified
- composed of 3 stylets which form a set of fine cutting structures
Mouthpart of mallophaga is
mandibulate
- feed on feather, skin and hair
- some feed on blood
Differences of the claw between anoplura and mallophaga
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
Examples of anoplura
Haematopinus
- Host: horses, cattle, pigs
Linognathus
- Host: dogs, cattle, sheep, goats
Examples of mallophaga
Trichodectes (dogs)
Felicola (Cats)
Bovicola (Horse, cattle, sheep)
Menopon (poultry)
Transmission through
close contact
Factors getting infected
Stressed animals, poor husbandry and poor individual health
Life stages occur at?
On the host
Life cycle?
- 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
Diagnosis of lice infestation?
- History, clinical sign
- Observation
- lice on the skin
- nits on the hairs
- part hair to see skin - Comb test (-+/-)
- Acetate tape strips (cannot do this test in mite infestation)
- DDx : dermatophilosis, other parasites
Indirect effects of lice infestation
- Vectors
- Typhus and relapsing fever in humans
- Pox virus in pigs (mechanical vector)
- Anaplasmosis in cattle - Intermediate host
- Dipylidium caninum - Secondary bacterial infection, hairball due to excessive grooming
Direct effects
- Heavy infestations
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
Direct effect
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).
Direct effect 3 & 4
- Sucking lice - anaemia
- Louse infestation may be indicative of other problems (chronic disease, malnutrition)
Direct effect 5
Reduced vigour and weight loss
In birds, may cause severe irritations -leads to feather damage, restless and cessation of feeding (menopon)
Host epidemiology
Malnourished animal - prone to heavy infestation
Free range animals
Stress factor
Management factor
Long hair coat
Immunity & underlying disease
Agent epidemiology
- 200 to 300 eggs glued to hair
- 2-3 weeks life cycle completed
- very intimate relationship with host (cant live without host)
Environment epidemiology
Heavy infectation in winter and early sping, also during rainseason
Treatment and control
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
Pediculosis
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
Immunitity consequences
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
