Found only on the body and in clothing,
the body louse lays its eggs in the seams of underclothing
and similar sheltered places. It is somewhat hardier than the
head and at 23°C it can live for 4 days without access to blood.
The best conditions for the spread of these lice are when humans
are living close together in primitive conditions. They do
not thrive amongst people who maintain a good standard of hygiene
with frequent washing and changing of clothes. Body lice are
important as vectors of typhus fever, trench fever and louse
borne relapsing fever. In populations where these diseases
do not occur, the only effect of louse bites is the resultant
annoying irritation.
The head louse, which looks the same as the body louse, attaches
its eggs firmly to hairs close to the scalp. The eggs are extremely
tenacious and can only be removed by using a fine comb and
much effort. Even frequent washing of the hair may not be sufficient
to remove them. The empty egg shells remain on the hair and
move outward as it grows. Under a lens they can be distinguished
from unhatched eggs because they are more transparent and the
lid is missing. As already mentioned, lice
require a blood meal twice a day, and at ordinary room temperatures
a head louse can only survive a couple of days when not living
on a human. Head lice do not transmit diseases. They can be
controlled by special preparations, but these do not kill the
eggs, so treatment needs to be repeated several times at intervals
of 4 - 5 days. |
Parasites
of Man 
