The best preventive measure against lice is strict personal cleanliness. Clothes should be frequently changed, and as frequently washed. The hair should be kept cropped short, especially at the sides and back of the head, and in the tropics it is very advisable to shave all hairy parts of the body.

Space does not permit a full account of how to deal with verminous persons and verminous clothing, but it may be said that the only reliable methods of destroying lice are by hot air, steam, boiling water, or hydrocyanic acid gas. At the same time it should be noted that the heads of those infested with head lice should be thoroughly combed and treated with paraffin, petrol, or white precipitate ointment, and then well washed with carbolic soap. The nits may be loosened by treatment with warm vinegar or acetic acid. In the case of body lice possibly the most satisfactory grease for application to the underclothing is one composed of crude unwhizzed naphthalene from the coke oven, four parts, and soft soap, one part. It is important that the proper type of naphthalene be used.

A useful palliative method is the ironing of clothing, especially along the seams, with heavy hot irons.

Fleas.—Bubonic plague is known to be transmitted by fleas, and it is possible that they play a part in the transmission of that form of leishmaniasis which is known as kala-azar (see [p. 202]). Fleas dislike powdered naphthalene and pyrethrum powder, and either of these may be applied to the clothes to ward them off.

A note on the troublesome Chigger flea or Jigger will be found under “Skin Diseases” (see [p. 228]).

Bed-Bugs.—The traveller sleeping in hotels or inns abroad is very apt to be attacked by bed-bugs, which harbour in wooden beds and bedding, crevices in walls, floors and ceilings, and other places which are dark and sheltered. Fortunately, so far as is known, the bed-bug does not carry any disease, but its bites are annoying, and its presence is a sign of insanitary conditions. It is difficult to protect oneself against bed-bugs without instituting a campaign against their hiding-places and breeding-places, but a skin ointment like vermijelli is useful, and powdered naphthalene or Keating’s powder may deter the insects to some extent.

Note.—Keating’s powder, which contains pyrethrum, is slow in its effects, and therefore, if possible, should be shaken over the sleeping bag or blankets some hours before bedtime. If not, the pests will struggle through it and find renewed vigour on the sleeper. It is best in very bad quarters to rub the powder on the skin as well as to dust it over the bed. It will not kill a full-grown bug under an hour, but it is extraordinarily effective with fleas. It is important to obtain a good pyrethrum powder, as such preparations are frequently adulterated.

The Itch Insect is the cause of the skin disease known as scabies. It is a mite, the female of which burrows under the skin to lay her eggs. The favourite site for her operations is between the fingers, but other parts of the body may be affected, and the rash produced may assume various forms, so that it is well in the case of any skin eruption in the tropics to remember the possibility of scabies.

Treatment.—Its effective treatment is by no means easy, and would take much too long to detail here. All that can be said is that the skin should be washed well with soap and hot water, and that thereafter a liberal quantity of sulphur ointment should be thoroughly rubbed into the skin twice daily for three days. On the fourth day recourse should be had again to soap and hot water, if possible in the form of a hot bath. Meanwhile, clothing and bedding should be boiled or destroyed.

Ticks.—The most important tick from the traveller’s point of view, at least, in Africa, is the species responsible for the transmission of tick fever (see [p. 242]). It would seem that the fowl tick may occasionally attack man, and some believe that it may spread the infection of certain kinds of relapsing fever (see [p. 218]). The larval stages of certain ticks are often very troublesome in many parts of the world, owing to their habit of burrowing into the skin of persons coming into contact with them.