LICE Flashcards
what are the 2 different types of lice
chewing lice - mallophaga
blood sucking - anoplura
what do chewing lice feed on?
skin debris - things found on the skin readily available such as subcutaenous secretions and dried blood etc
what are chewing lice identified by?
wide heads - large musculature in the feeding apparatus to allow them to feed on the skin debris
example of chewing lice?
bovicula
what are blood sucking lice
suck on blood
how long are blood sucking lice
05-8mm long as adults
what part of the blood sucking lice is specialised?
mouthparts
what do lice lack of in their development?
they lack a pupae stage (incomplete metamorphosis)
what happens in the nymph stage of lice?
they are a small additon of an adult
the live and feed in the same way
is the lice entire lifecycle spent on the host?
yes
what is the lifecycle of the lice
male/female reproduce
lay eggs on hairs
eggs hatch > nymphs 2-3 months
egg to egg - 3-4 weeks -> short life
do lice have a high degree of host specifity?
yes they only go on hosts that a closely related
sheep lice may go onto goats
sheep lice wont go onto horse
how are lice spread?
direct contact
closely penned together = horizontal tranmission
close contact - mother to offspring = vertical transmission
do lice have a reduced lifespan off host?
yes they do, they can live off them but not very long
transmission can be done through alternative routes known as phoresy
what time of year do lice thrive?
winter time - due to animals huddling to stay warm
in sheep predicted 400-4000 between the winter months
what time of year do lice prefer in the uk
january - april
what affect do lice have on hosts?
irritation
scratching
excessive grooming
what happens when animals get a loss of condition?
poor weight gain
decrease in milk yield
anaemia
2 degree bacterial infection - wound opening due to excessive scratching
how are lice unique?
have continuous attatchement
inject biologically active diverse components saliva
modulate host defence - prevent itching, pain and haemostasis
what is the common response in lice?
infestation induced down regulation of Th1 cytokines
upregulation of Th2 cytokines
what is the lice first line of defence to reduce its awareness to the host body?
secrete kinases and lipcalines
they target histamine and bradykinine to mediate pain and itch response
what are other factd about lice immune response
- Generally Th2
- Th1 mediated through Th2 components
o Lymphocytes - Proposed for infestation
o Local type 1 hypersensitiity response - Balance
o Tick modulation – induce changes of skin immune effectors
o Ability to respond to tick borne pathogens - K cells encountered as serrated MP penetrate
o Supressed by tick saliva - Tick saliva antigens trapped by skin Dendritic cells
o Antigens drive cd4+ lumphocute differentiation to Th2 effector lymphocyte - Suppression of natural killer cells
o Reduces the defence against microbes
