Tunga penetrans (the sand flea, jigger flea, chigoe, chique) is the cause, the female being adapted for an intracutaneous permanent attachment to the host (human, pig, poultry and other animals). As with other fleas, the larvae are free living, dusty or sandy soil being best for T. penetrans. Adults are also free living at first, when copulation occurs. The fertilized female then finds a suitable host and tries to penetrate crevices in the skin, such as cracks in the soles of the feet (Figure), between the toes and especially around the toenails. Any part of the human anatomy can be affected. By means of the mouthparts, the female Tunga becomes firmly attached and soon swells to the size and shape of a small white pea. Somehow, the host skin envelops the jigger, which lies below the stratum corneum but above the stratum granulosum, leaving only the posterior spiracles exposed to the air. Only when the jigger is almost mature and distended, after 8-12 days, does the infection begin to irritate. Severe inflammation and ulceration ensues, so that scratching helps to expel large numbers of white eggs from the jigger.
Jigger seldom attacks the leg above the dorsum of the foot, but no part of the body escapes (especially when sleeping on the soil). The soles, the skin between the toes and that of the roots of the nails are favorite situations. Usually only one or two jiggers are found at a time, but occasionally they are present in hundreds (see photos), the little pits left after extraction or expulsion being sometimes so closely set that parts of the surface may look like a honeycomb. During her gestation the jigger causes a considerable amount of irritation. Pus may form around her distended abdomen, which now raises the integument into a pea-like elevation. After the eggs have been laid, the skin ulcerates and the jigger is expelled, leaving a small sore which may become seriously infected or lead to tetanus. Ulceration is common and may follow removal of the jigger or natural extrusion of the egg sac. The ulcer commences as a tiny pit and, as it extends, the sloping edge may develop into a septic ulcer. It remains more or less circular in outline, except under the nail or nail margin, where the outline is more irregular and a pocket of pus forms underneath.