Tungiasis is a dermatosis causes by Tunga, mostly Tunga penetrans.
Tunga penetrans is also known chigoe flea or sand flea. Adult sand fleas are about 1mm in size, but pregnant female sand fleas can be 5 - 8 mm in size.
The eggs of sand fleas are oval and large, and the larvae are relatively thick and short and grow in organic-rich soils. Under optimal temperature, the larvae develop into pupae in about 10 - 14 days. The pupal stage is 10 - 14 days. Sand fleas take about 3 weeks to develop from eggs to adults. Before finding the host, the sand fleas are very active and good at jumping, up to 10cm in height. After burrowing into the skin of the host, the tarsal and tibial segments of the feet are atrophied and absorbed by the host tissue. Male sand fleas do not invade the skin, and they die after copulation prior to female sand fleas invade the host.
Signs and Symptoms
Sand fleas pierce the host's skin with their sharp horn of the frontal margin and burrow into the subcutaneous tissue. The head and body of the female sand fleas are fully in the skin. After copulation, there are numerous eggs in the uterus of the female sand fleas. The intersegmental membrane in the front of the third abdominal segment is relatively loose, so that the abdomen of pregnant fleas is enlarged, resembling peas, resulting in nodules of the invasion sites. The host's soles, toes, and fingers are common parasitic sites. There are strong skin reactions around the fleas. The lesion is pale initially, with black spots in the center. Patients are gradually sore and difficulty walking. When there are numerous parasites, patients can be lame. When secondary bacterial infections occur, there may be painful ulcers, gangrene, tetanus, and even death. After the female fleas lay eggs, the flea body can shrink, the lesion can heal, and the flea body can fall off from the scab.
Figure 1 tungiasis
Tunga caecigena and Tunga callida pierce the skin with the sharp horn of the frontal margin and burrow into the subcutaneous tissue. Except for leaving a small hole in the skin for copulation, oviposition, breath, and excretion, the body is completely in the subcutaneous tissue, forming pea sized, round cysts.
The sticktight flea adults insert deeply their mouthpart into the skin of the host and suck blood continuously for several days to weeks. The daily amount of blood sucked by a sticktight flea is dozens of times its body weight. There are often local ulcers, and the skin may turn black. Adult fleas often mate while feeding. The female fleas lay their eggs in the ulcers, and the larvae crawl out and fall to the ground after hatching.
If there are typical clinical presentations and fleas found in the skin lesions, the disease can be diagnosed.
The sand fleas in the skin can be removed with a sterile needle or sharp blade. The nodules can be excised with sterile scissors, and the contents in the nodules should be fully cleaned. Topical iodine tincture is appropriate. If there are lymphadenitis or abscesses, antibiotics can be administered.