|
|
The female Dracunculus worm emerges through the skin of its human host one to two years after infection. Often, persons with emergent worms enter sources of drinking water and unwittingly allow the worm to release larvae into the water. These larvae are ingested by microscopic fresh-water copepods ("water fleas", especially of the genus Cyclops). Inside the copepods, the larvae develop into the infective stage in 10–14 days. In turn, humans may then become infected by drinking water containing infected copepods.
Once inside the body, the stomach acid digests the water flea, but not the guinea worm larvae sheltered inside. These larvae find their way to the small intestine, and then pass into the body cavity. During the next 10–14 months, the female copulates with a male guinea worm. The small male (1.2–2.9 centimeters long) dies and is absorbed into the larger female. The female develops into its full length of 60–100 centimeters (2‑3 feet) long and a narrow width similar to that of a cooked spaghetti noodle. Having mated, the adult female is packed with thousands of tiny larvae. The worm migrates to the area of the body from which it will emerge, which, in more than 90% of all cases, is on one of the lower limbs.
A blister develops on the skin at the site where the worm will emerge. This blister causes a very painful burning sensation, and, within 24 to 72 hours of its appearance, will rupture, exposing one end of the emergent worm. To relieve the burning sensation, infected persons often immerse the affected limb in water. When the guinea worm blister, which shortly becomes an ulcer or open sore, is submerged in water, the adult female releases a milky white liquid, containing hundreds of thousands of guinea worm larvae, into the water. Over the next several days, the female worm is capable of releasing more larvae whenever it comes in contact with water. These larvae contaminate the water supply and are eaten by copepods, thereby repeating the lifecycle of the disease, as described
Treatment
Infected individuals usually wind the emergent worm around a small stick; however, they dare only pull out a few centimeters of worm each day, lest the worm break. If the worm breaks, the individual will experience a painful and serious reaction that may include anaphylaxis. Without surgical intervention, the process of removing the worm usually takes weeks or months.
No medication is available to end or prevent infection. However, sometimes the worm can be surgically removed before an ulcer forms. Analgesics, such as aspirin or ibuprofen, can help reduce swelling; antibiotic ointment can help prevent secondary infections. Mebendazole is effective in killing the worm.
According to the Carter Center, the incidence of GWD has dropped from an estimated 3.5 million cases worldwide in 1986 to only 16,026 reported cases in 2004.
Dracunculiasis now occurs only in 12 countries in sub-Saharan Africa. Transmission of the disease is most common in very remote rural villages and in areas visited by nomadic groups. In the 2nd century BC, the Greek writer Agatharchides described this affliction as being endemic amongst certain nomads in what is now Sudan and along the Red Sea (fragments preserved in Photius, Bibliotheca Cod. 250.59, 453b; and Plutarch, Quaestiones Convivales 8.9.16).
In 2004 the three most endemic countries—i.e. Ghana, Sudan, and Nigeria—reported 7,275; 7,266; and 495 cases of GWD respectively. Other endemic countries reporting cases of GWD in 2004 were: Benin (3 cases), Burkina Faso (60 cases), Côte d'Ivoire (21 cases), Ethiopia (17 cases), Mali (357 cases), Mauritania (13 cases), Niger (293 cases), and Togo (278 cases). Kenya (7 cases) and Uganda (4 cases) reported incidences imported from Sudan.
Asia is now free of the disease. Transmission of GWD no longer occurs in several African countries, including Kenya, Senegal, Cameroon, Chad, and Central African Republic. No locally acquired cases of disease have been reported in these countries in the last year or more. The World Health Organization has certified 168 countries free of transmission of Dracunculiasis, including four formerly endemic countries: Pakistan (in 1996), India (1996), and in Senegal and Yemen (in 2004).
Because GWD can only be transmitted via drinking contaminated water, educating people to follow these simple control measures can completely prevent illness and eliminate transmission of the disease:
Cymothoa exigua is a parasitic crustacean of the family Cymothoidae. This parasite attaches itself at the base of the spotted rosesnapper fish's tongue with the claws on its front three pairs of legs, and extracts blood from the tongue of its host fish. As the parasite grows, less and less blood is able to reach the tongue, and eventually the organ atrophies from lack of blood. The parasite then replaces the fish's tongue with its own body, by attaching to the muscles of the tongue stub. The fish is able to use the parasite just like a normal tongue, except that it has to share its food with the parasite. It appears that the parasite does not cause any other damage to the host fish. Once C. exigua replaces the tongue, it supplements its diet with food particles, thereby relieving strain on the host's circulatory system. This is the only known case of a parasite functionally replacing a host organ.
A stage play involving this phenomenon has been written and performed. The play focuses on a dream that playwright Tennessee Williams has, in which his tongue is consumed by a parasite and he loses the ability to speak. The play's author is the American playwright R. J. Tsarov, and the play first premiered at the annual Tennessee Williams Festival in New Orleans in March 2003.
There are many species of Cymothoa, but only C. exigua is known to consume and replace its host's tongue.
A fish parasitised by what could be Cymothoa exigua was recently discovered in the United Kingdom, leading to speculation that the parasite's range may be expanding. The animal in question will be put on display in the Horniman Museum
The Clonorchis sinensis is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile. These animals, which are believed to be the third most prevalent worm parasite in the world, are endemic to Japan, China, Taiwan, and Southeast Asia, currently infecting an estimated 30,000,000 humans.
The egg of a Clonorchis sinensis (commonly: Human Liver Fluke), which contains the miracidium that develops into the adult form, floats in freshwater until it is eaten by a snail.
Once inside of the snail body, the miracidium hatches from the egg, and parasitically grows inside of the snail. The miracidium develops into a sporocyst, which in turn house the asexual reproduction of redia, the next stage. The redia themselves house the asexual reproduction of free-swimming cercaria. This system of asexual reproduction allows for an exponential multiplication of cercaria individuals from one miracidium. This aids the Clonorchis in reproduction, because it enables the miracidium to captilatize on one chance occasion of passively being eaten by a snail before the egg dies.
Once the redia mature, having grown inside the snail body until this point, they actively bore out of the snail body into the freshwater environment. There, instead of waiting to be consumed by a host (as is the case in their egg stage), they seek out a fish. Boring their way into the fish's body, they again become parasites of their new hosts.
Once inside of the fish muscle, the cercaria create a protective metacercarial cyst with which to encapsulate their bodies. This protective cyst proves useful when the fish muscle is consumed by a human. The acid-resistant cyst enables the metacercaria avoid being digested by the human gastric acids, and allows the metacercaria to reach the small intestine unharmed. Reaching the small intestines, the metacercaria navigate toward the human liver, which becomes its final habitat. Clonorchis feed on human bile created by the liver. In the human liver, the mature Clonorchis reaches its stage of sexual reproduction. The hemaphroditic adults produce eggs every 1 - 30 seconds, resulting in the rapid multiplication of inhabitants in the liver.
Dwelling in the bile ducts, Clonorchis induces an inflammatory reaction, epithelial hyperplasia and sometimes even adenocarcinoma of the bile ducts (cholangiocarcinoma), the incidence of which is high in fluke-infested areas. One adverse effect of Clonorchis is the possibility for the adult metacercaria to consume all bile created in the liver, which would inhibit the host human from digesting, especially fats. Another possibility is the overcrowding of the common bile duct. The adults deposit vast amounts of eggs into the common bile duct, which poses the risk of the common bile duct and neighboring gall bladder exploding within the human body.
In biology, Cestoda is the class of parasitic flatworms, called cestodes or tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals as juveniles.
In a tapeworm infection, adult worms absorb food predigested by the host, so the worms have no need for a digestive tract or a mouth. Large tapeworms are made almost entirely of reproductive structures with a small "head" for attachment. Symptoms vary widely, depending on the species causing the infection.
Symptoms may include upper abdominal discomfort, diarrhea, and loss of appetite. However, infestations are usually asymptomatic. Worm segments or eggs may be found in the stool of an infected person. Tapeworms can grow 15 to 30 feet (10 meters) in length.[1] The largest tapeworms grow up to 100 feet (30 meters)[citation needed]. Most tapeworms enter humans through an infected flea, the same way they enter pets. Tapeworms harm their host by stealing vital nutrients, causing malnutrition and, if left untreated, can cause intestinal blockages.
There are two subclasses in class Cestoda, the Cestodaria and the Eucestoda. By far the most common and widespread are the Eucestoda, with only a few species of unusual worms in subclass Cestodaria. The cyclophyllideans are the most important to humans because they infect people and livestock. Two important tapeworms are the pork tapeworm, Taenia solium, and the beef tapeworms, T. saginata. Different types of tapeworms have radically different larval stages (see their specific articles).
The candirú or canero (Vandellia cirrhosa) or toothpick fish is a freshwater fish in the group commonly called the catfish. It is found in the Amazon River and has a reputation among the natives as the most feared fish in its waters, even over the piranha. The species has been known to grow to a size of 6 inches in length and is eel shaped and translucent, making it almost impossible to see in the water. The candiru is a parasite. It swims into the gill cavities of other fish, erects a spine to hold itself in place, and feeds on the blood in the gills, earning it a nickname as the "vampire fish of Brazil".
It is feared by the natives because it is attracted to urine or blood, and if the bather is nude it will swim into an orifice (the anus or vagina, or even in the case of smaller specimens the penis—and deep into the urethra). It then erects its spine and begins to feed on the blood and body tissue just as it would from the gills of a fish. The candirú is then almost impossible to remove except through surgery. As the fish locates its host by following the water flow from the gills to its source, urinating while bathing increases the chance of a candiru homing in on a human urethra.
A traditional cure involves the use of two plants, the Xagua plant (Genipa americana) and the Buitach apple which are inserted (or their extract in the case of tight spaces) into the affected area. These two plants together will kill and then dissolve the fish. More often, infection causes shock and death in the victim before the candirú can be removed. Though there have been documented candirú attacks on humans, there is no evidence the fish can survive once inside a human. It was recently sought after by Nick Baker a wildlife specialist on British TV in a series about the world's strangest animals.
Acarapis woodi is a mite that is an internal parasite of honey bees. It lives and reproduces in the tracheal tubes of the bees. The mites pierce the tracheal tube walls with their mouthparts and feed on the haemolymph of the bees. The mites are very small, generally under 175 micrometres[1], and can only be seen and identified under a microscope.