LICE

Question 1

what are the 2 different types of lice

Answer 1

chewing lice - mallophaga
blood sucking - anoplura

Question 2

what do chewing lice feed on?

Answer 2

skin debris - things found on the skin readily available such as subcutaenous secretions and dried blood etc

Question 3

what are chewing lice identified by?

Answer 3

wide heads - large musculature in the feeding apparatus to allow them to feed on the skin debris

Question 4

example of chewing lice?

Answer 4

bovicula

Question 5

what are blood sucking lice

Answer 5

suck on blood

Question 6

how long are blood sucking lice

Answer 6

05-8mm long as adults

Question 7

what part of the blood sucking lice is specialised?

Answer 7

mouthparts

Question 8

what do lice lack of in their development?

Answer 8

they lack a pupae stage (incomplete metamorphosis)

Question 9

what happens in the nymph stage of lice?

Answer 9

they are a small additon of an adult
the live and feed in the same way

Question 10

is the lice entire lifecycle spent on the host?

Answer 10

yes

Question 11

what is the lifecycle of the lice

Answer 11

male/female reproduce
lay eggs on hairs
eggs hatch > nymphs 2-3 months
egg to egg - 3-4 weeks -> short life

Question 12

do lice have a high degree of host specifity?

Answer 12

yes they only go on hosts that a closely related
sheep lice may go onto goats
sheep lice wont go onto horse

Question 13

how are lice spread?

Answer 13

direct contact
closely penned together = horizontal tranmission
close contact - mother to offspring = vertical transmission

Question 14

do lice have a reduced lifespan off host?

Answer 14

yes they do, they can live off them but not very long
transmission can be done through alternative routes known as phoresy

Question 15

what time of year do lice thrive?

Answer 15

winter time - due to animals huddling to stay warm
in sheep predicted 400-4000 between the winter months

Question 16

what time of year do lice prefer in the uk

Answer 16

january - april

Question 17

what affect do lice have on hosts?

Answer 17

irritation
scratching
excessive grooming

Question 18

what happens when animals get a loss of condition?

Answer 18

poor weight gain
decrease in milk yield
anaemia
2 degree bacterial infection - wound opening due to excessive scratching

Question 19

how are lice unique?

Answer 19

have continuous attatchement
inject biologically active diverse components saliva
modulate host defence - prevent itching, pain and haemostasis

Question 20

what is the common response in lice?

Answer 20

infestation induced down regulation of Th1 cytokines
upregulation of Th2 cytokines

Question 21

what is the lice first line of defence to reduce its awareness to the host body?

Answer 21

secrete kinases and lipcalines
they target histamine and bradykinine to mediate pain and itch response

Question 22

what are other factd about lice immune response

Answer 22

• 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