25: Lice

Question 1

What is the only louse that isn’t host-specific?

Answer 1

Bovicola in sheep and goats

Question 2

What is the only louse that isn’t permanent?

Answer 2

The human body louse

Question 3

What are the two methods by which lice can be transmitted?

Answer 3

Mother to young, or direct contact

Question 4

Why does louse population increase in winter?

Answer 4

Like warm and dark

Question 5

Why does lice population decrease with age?

Answer 5

Protective immunity

Question 6

What do adult lice look like?

Answer 6

Have head, thorax, abdomen, 3 pairs of legs, DV flattened, wingless

Question 7

How long is the lice life cycle?

Answer 7

3-4 weeks

Question 8

How long does the louse egg take to hatch?

Answer 8

One week

Question 9

Where are louse eggs found?

Answer 9

Single and cemented to the hair

Question 10

Which part of the egg does the nymph hatch from?

Answer 10

From the operculum (this differentiates them from other parasites)

Question 11

What do nymphs look like?

Answer 11

Like the adult, but are sexually immature

Question 12

What are the two groups of lice?

Answer 12

Chewing/biting (mallophaga, with broad blunt head) and sucking (siphunculata, with narrow pointed head)

Question 13

Why do you need to know if the louse is chewing or sucking?

Answer 13

Because some drugs act systemically and are ingested by the sucking lice but won’t affect the chewing louse

Question 14

What type of reaction do sucking lice cause?

Answer 14

Antigenic saliva with enzymes and anti-coagulants so more excoriation and more type I/IV hypersensitivity

Question 15

What type of reaction do chewing lice cause?

Answer 15

Chronic, exfoliatory, dandruff

Question 16

What colour do sucking lice go when fed?

Answer 16

Blue (usually brown)

Question 17

What are some clinical signs of lice?

Answer 17

Immediate and delayed hypersensitivity, pruritis, licking, sucking, biting, alopecia, wool damage, tags of wool, secondary infections, exfoliative dermatitis, anaemia

Question 18

Which type of cattle mainly get mixed lice infections?

Answer 18

Housed cattle in winter

Question 19

What degree of production loss can lice infections in housed cattle cause?

Answer 19

10%

Question 20

Why did lice infection in sheep used to be rare?

Answer 20

Because of sheep scab dipping

Question 21

After introducing infected sheep, how long until clinical signs occur?

Answer 21

Tags and rash by 6 weeks

Question 22

After introducing infected sheep, how long until all are infected?

Answer 22

6 months

Question 23

How do you tell the difference between sheep scab and lice in sheep?

Answer 23

Scab is rapid whereas lice is slow, lice has poor BCS and sheep scab is good, in scab they are pruritic with scabs and wool pulled out whereas with lice the skin is irritated, damaged and scaly.

Question 24

What are the only type of lice pigs get?

Answer 24

Sucking

Question 25

What can happen in debilitated animals?

Answer 25

Large numbers can build up and there may be marked hypersensitivity

Question 26

What kind of lice do birds get?

Answer 26

Chewing