Тұңғыа паразиті: сипаттамасы және таралуы

Species of flea

Tunga penetrans is a species of flea also known as the jigger, jigger flea, chigoe, chigo, chigoe flea, chigo flea, nigua, niknik, sand flea, or burrowing flea. It is a parasitic insect found in most tropical and sub tropical climates. In its parasitic phase it has significant impact on its hosts, which include humans and certain other mammalian species. A parasitical infestation of T. penetrans is called tungiasis. Jiggers are often confused with chiggers, a type of mite. Jiggers are native to Central and South America, and have been introduced to sub Saharan Africa. Synonyms for Tunga penetrans include Sarcopsylla penetrans, Pulex penetrates, and many others.

T. penetrans is most recognizable in its parasite phase. While embedded under the stratum corneum layer of the skin, it may reach up to 1 cm across. During the first day or two of infestation, 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.

The colloquial name jigger may be confused with chigger, a parasitical mite. However, the jigger is a type of flea (Order Siphonaptera). The chigger is a minute arachnid. Mites penetrate the skin and feed on skin cells that are broken down through an enzyme they secrete from their mouth, but they will then leave the host. The adult and the larval forms both feed on other animals. This is not the case with T. penetrans, as only the adults feed on mammals, and the mature female remains in the host for the rest of her life.

Tunga penetrans is unusual for the 13 known species of the genus Tunga. First, it has a wide distribution: some 88 countries, in the Caribbean, Central and South America, tropical (sub Saharan) Africa, and India. Second, it can infest a wide variety of hosts: at least 26 different species in over 5 different orders of mammals. In contrast, most of the 13 species of Tungidae are only in the Western hemisphere, and each only targets 1 2 specific warm blooded hosts. Seven tunga species infest only rodents. Two dedicate themselves to armadillos, one to sloths, and another prefers only cattle. Only one, Tunga trimamillata, has also been found infesting humans as well as cows, but only in Ecuador and Peru. Host species for T. penetrans' samples were taken from the top of the soil (to a maximum depth of 1 cm). The presence of T. penetrans in a soil sample was unaffected by soil temperature, air temperature or air humidity. No life stages of T. penetrans were found in any outdoor sample. There is an observable drop in infestations during the wet season. After hatching, the flea will progress through two instar phases. This is unique in that most fleas go through three. Over the course of that development, the flea will first decrease in size from its just hatched size of 1.5 mm to 1.15 mm (first instar) before growing to 2.9 mm (second instar). About six to eight days after hatching, the larva pupates and builds a cocoon around itself. Because it lives mostly on and below the surface of sand, sand is used to stabilize the cocoon and help to promote its development. An environmental disturbance such as rain or a lack of sand have been shown to decrease incidence, most likely due to decreasing the environmental factors (i. e., sand) on which the flea depends for overall growth. Barring any disturbances to the cocoon, an adult flea will emerge from the puparium after 9–15 days. In dividing the natural history of the disease, the Fortaleza Classification formally describes the last part of the female flea's life cycle where it burrows into its host's skin, expels eggs, and dies. Stage 1 is characterized by the penetration of the skin by the female chigoe flea. Running along the body, the female uses its posterior legs to push its body upward by an angle between 45 and 90 degrees. Penetration then starts, beginning with the proboscis going through the epidermis. In 3b, the chitin exoskeleton of tergites 2 and 3 increase in thickness and gives the structure the look of a mini caldera. Egg release is common in substage 3b, as are fecal coils. The eggs tend to stick to the skin. Lingering effects may include loss of toenails and toe deformation. These seem to be commonplace especially where heavy infestations combine with unsanitary conditions and poverty. The first European description was published in 1526 by Gonzalo Fernández de Oviedo y Valdés, where he discussed the skin infection and its symptoms on crew members from Columbus's Santa Maria after they were shipwrecked on Haiti. Through ship routes and further expeditions, the chigoe flea was spread to the rest of the world, particularly to the rest of Latin America and Africa. The spread to greater Africa occurred throughout the 17th and 19th centuries, specifically in 1873 when the infected crewmen of the Thomas Mitchell's ship introduced it into Angola, having sailed from Brazil.

There are no drugs currently available with proven effectiveness. Surgical extraction still remains the treatment of choice in patients with a low parasite load, such as tourists returning from endemic areas. The only approach to reduce tungiasis associated morbidity in heavily affected individuals is the application of a repellent to prevent the penetration of sand fleas.