Tunga penetrans (chigoe flea or jigger) is a parasitic arthropod found in most tropical and sub-tropical climates, not to be confused with the larval form of Trombiculidae (called chiggers) found in more temperate climates. It is native to Central and South America, and has been inadvertently introduced by humans to sub-Saharan Africa. At 1 mm long, T. penetrans is the smallest known flea. Breeding females burrow into exposed skin on the feet of mammals and remain there for two weeks while developing eggs, during which time they swell dramatically, sometimes causing intense irritation (a condition called tungiasis). After this point, the skin lesion looks like a 5- to 10-mm blister with a central black dot, which are the flea’s exposed hind legs, respiratory spiracles and reproductive organs.
If the flea is left within the skin, dangerous complications can occur including secondary infections, loss of nails, and toe deformation. These seem to be commonplace especially where heavy infestations combine with unsanitary conditions and poverty.
The parasitic flea lives in soil and sand, and feeds intermittently on warm-blooded hosts, such as humans and cattle. Males leave the host after a blood meal like other fleas, but the female flea burrows head-first into the host’s skin, leaving the caudal tip of its abdomen visible through an orifice in a skin lesion. This orifice allows the flea to defecate while feeding on blood vessels from which it gets its oxygen as well. It lives in the cutaneous and subcutaneous dermal layer. Over the next two weeks, its abdomen swells with up to several hundred to a thousand eggs, which it releases through the caudal orifice to fall to the ground when ready to hatch. The flea then dies and is often the cause of infection as the body rots under thick scales its body chemistry created to protect it. The eggs mature into adult fleas within three to four weeks and the process begins anew.
Since the fleas spend most of their time on the ground, tungiasis lesions are usually on the feet; however, like most fleas they are capable of jumping up 20 cm, and lesions may occur on any part of the body, favoring regions of soft skin such as between the toes. During the first day or two of infection, the host may feel an itching or irritation which then passes as the area around the flea calluses and becomes insensitive. As the flea’s abdomen swells with eggs later in the cycle, the pressure from the swelling may press neighbouring nerves or blood vessels. Depending on the exact site, this can cause sensations ranging from mild irritation to serious discomfort.
In addition to T. penetrans, the genus Tunga includes over a dozen species, which infect various specific mammals in South America.