145
According to one of the researchers, the degree to which the louse tracks human his-
tory is amazing. At the same time, it was apparent that two genetically distinct lineages
of P. humanus appeared about 1.18 million years ago. One subspecies is now distributed
worldwide and infects either the head or the body, whereas the other only inhabits the
New World and only lives on scalps. This means that the two subspecies must have
diverged at about the same time. Lice thought to have been living on Homo erectus must
have migrated to H. sapiens at some point before H. erectus became extinct some 30,000
years ago.8
Anatomy
Like most other insects, lice have three main body parts: a head, a thorax and an abdomen,
and similar to other insects, lice have six legs (three on each side). The legs originate from
the thorax. The louse’s legs are specially shaped for gripping the host animal’s fur, hair or
feathers. In the case of many sucking lice species, the legs are gripping claws exceptionally
large in size, compared to the size of the louse’s body, and very strong.9
The adult head louse is 2–3 mm long, and is usually tan to grayish white. The female
lives three to four weeks and, once mature, can lay up to 10 eggs per day. These tiny eggs
are firmly attached to the base of the victim’s hair shaft within approximately 4 mm of the
scalp with a glue-like substance produced by the louse. The eggs are incubated by body
heat and typically hatch in 8–9 days. Once it hatches, a nymph leaves the shell casing and
passes through three stages during the next 9–12 days to reach the adult stage. The female
louse can mate and begin to lay viable eggs approximately 1.5 days after becoming an
adult. The louse feeds by injecting small amounts of saliva with vasodilatory and antico-
agulation properties and sucking tiny amounts of blood from the scalp every few hours.10
Body lice are similar in appearance to head lice. Females are usually larger than males
and can lay up to eight eggs per day. Adult lice can live up to 30 days on a person’s body.
To live, adult lice need to feed on blood several times a day. Without blood meals from a
host, the louse will die within 1–2 days.
Transmission
Head lice transmission occurs mainly through direct head-to-head contact and is com-
mon within households. It is also thought to occur through the sharing of combs, hair
brushes or hats, although supporting evidence is lacking.11 Adult lice can survive up to 55
hours without a host, but probably become nonviable because of dehydration long before
death.12,13 Lice cannot jump or fly they crawl. Pets are not vectors.
Body lice live and lay eggs on clothing and only move to the skin to feed, which
occurs several times daily. The louse resides close to the skin to maintain its body temper-
ature. Lice are spread most commonly by close person-to-person contact, but are generally
limited to persons who live under conditions of crowding and poor hygiene.14 In the most
severe cases, up to 30,000 body lice have been reported on one individual.15
Epidemic typhus, as with other Rickettsial diseases, is transmitted to man by insects.
The body louse becomes infected with typhus by biting an infected person who has the dis-
ease and then carrying the infection from one human being to another. The louse takes up
the Rickettsia with infected blood and the organisms multiply in the cells lining the stom-
ach and intestinal walls, and finally appear in large numbers in the feces. It takes about six
days for the louse to become infectious. The louse is a relatively recent host of Rickettsia
and even more susceptible than man. The louse will sicken and die within two weeks.16
Epidemic Typhus
One of the earliest decisive typhus epidemics occurred when the army of Maximilian II
of Germany was preparing 80,000 men to face Sultan Soliman in Hungary. In a camp at
To a Louse, Typhus and More
According to one of the researchers, the degree to which the louse tracks human his-
tory is amazing. At the same time, it was apparent that two genetically distinct lineages
of P. humanus appeared about 1.18 million years ago. One subspecies is now distributed
worldwide and infects either the head or the body, whereas the other only inhabits the
New World and only lives on scalps. This means that the two subspecies must have
diverged at about the same time. Lice thought to have been living on Homo erectus must
have migrated to H. sapiens at some point before H. erectus became extinct some 30,000
years ago.8
Anatomy
Like most other insects, lice have three main body parts: a head, a thorax and an abdomen,
and similar to other insects, lice have six legs (three on each side). The legs originate from
the thorax. The louse’s legs are specially shaped for gripping the host animal’s fur, hair or
feathers. In the case of many sucking lice species, the legs are gripping claws exceptionally
large in size, compared to the size of the louse’s body, and very strong.9
The adult head louse is 2–3 mm long, and is usually tan to grayish white. The female
lives three to four weeks and, once mature, can lay up to 10 eggs per day. These tiny eggs
are firmly attached to the base of the victim’s hair shaft within approximately 4 mm of the
scalp with a glue-like substance produced by the louse. The eggs are incubated by body
heat and typically hatch in 8–9 days. Once it hatches, a nymph leaves the shell casing and
passes through three stages during the next 9–12 days to reach the adult stage. The female
louse can mate and begin to lay viable eggs approximately 1.5 days after becoming an
adult. The louse feeds by injecting small amounts of saliva with vasodilatory and antico-
agulation properties and sucking tiny amounts of blood from the scalp every few hours.10
Body lice are similar in appearance to head lice. Females are usually larger than males
and can lay up to eight eggs per day. Adult lice can live up to 30 days on a person’s body.
To live, adult lice need to feed on blood several times a day. Without blood meals from a
host, the louse will die within 1–2 days.
Transmission
Head lice transmission occurs mainly through direct head-to-head contact and is com-
mon within households. It is also thought to occur through the sharing of combs, hair
brushes or hats, although supporting evidence is lacking.11 Adult lice can survive up to 55
hours without a host, but probably become nonviable because of dehydration long before
death.12,13 Lice cannot jump or fly they crawl. Pets are not vectors.
Body lice live and lay eggs on clothing and only move to the skin to feed, which
occurs several times daily. The louse resides close to the skin to maintain its body temper-
ature. Lice are spread most commonly by close person-to-person contact, but are generally
limited to persons who live under conditions of crowding and poor hygiene.14 In the most
severe cases, up to 30,000 body lice have been reported on one individual.15
Epidemic typhus, as with other Rickettsial diseases, is transmitted to man by insects.
The body louse becomes infected with typhus by biting an infected person who has the dis-
ease and then carrying the infection from one human being to another. The louse takes up
the Rickettsia with infected blood and the organisms multiply in the cells lining the stom-
ach and intestinal walls, and finally appear in large numbers in the feces. It takes about six
days for the louse to become infectious. The louse is a relatively recent host of Rickettsia
and even more susceptible than man. The louse will sicken and die within two weeks.16
Epidemic Typhus
One of the earliest decisive typhus epidemics occurred when the army of Maximilian II
of Germany was preparing 80,000 men to face Sultan Soliman in Hungary. In a camp at
To a Louse, Typhus and More