One of the diseases which may be produced by the bites of insects is a form of fever, conveyed by the bite of a tick, which is common in many parts of Africa. This produces a series of symptoms which are similar to those found in the disease known as relapsing fever, which has been known to occur even in the United Kingdom, and which used to be called “famine fever” (_see_ p. 218). _Cause._—The cause is a corkscrew-shaped organism found in the blood, and its vector is the tick above mentioned, which in its adult state and unfed is roughly about the length of a finger-nail, that is, four-tenths of an inch. It is of a greenish brown colour, and is covered by a leathery integument, which looks as if it was spotted all over and which is grooved in several places. When the tick is gorged, these grooves disappear. A gorged female tick may be well over half an inch in length, and very nearly of an equal breadth. The tick lives in native houses and in rest houses, especially along caravan routes. At night it sallies forth in search of blood, but during the day it conceals itself in cracks and corners in the walls and floors, and sometimes in cracks in native wooden bedsteads. Its bite is painful, but the infection takes place not through the bite, but as a result of the infected excreta of the tick contaminating the tick bite. One tick is sufficient to cause infection. _Symptoms._—The chief symptoms are those of a severe attack of fever, ushered in by a shivering fit and acute symptoms such as are usually found in cases of fever, for example, pains in the back and limbs, rapid pulse, and sometimes severe vomiting and diarrhœa, frontal headache, and painful bloodshot eyes are rather characteristic. The fever, which is of the relapsing type, generally keeps up for about a week, after which there may be an interval without fever for a few days, to be followed later on by another attack of fever. There are usually several relapses. As many as eleven have been noted. _Prophylaxis._—Avoid sleeping in native huts and rest houses which have been occupied by natives. Do not sleep on the ground or on wooden native bedsteads. If the latter have to be used, their legs should be smoothed to prevent ticks from climbing up them. In badly infested places, it is well to employ a hammock. A mosquito-net is useful, as it excludes the ticks; and it is well to make use of a night-light, which also keeps them away. Packs and blankets should be periodically inspected to see that they do not harbour ticks. If one has to camp on an infected area, the ground should be fired and the floors of huts dug up and thereafter removed and buried or treated with fire, care being taken that the ticks do not escape during the process. Wandering ticks can be kept away from a tent to some extent by digging round it a trench and filling it with wood ashes.