Gnathostomiasis
Encyclopedia
Gnathostomiasis is the human
infection
by the nematode
(roundworm) Gnathostoma spinigerum
and/or Gnathostoma hispidum
, which infects vertebrate
s.
when inspecting the stomach of a young tiger that had died at London Zoo
from a ruptured aorta. However it was not until 1889 that the first human case was described by Levison when he found the gnathostoma larva in an infested Thai woman. This delay in identification of the parasite in humans is due to the fact that humans are not a definitive host for this parasite making infection from this parasite rare. Gnathostomiasis infection is rare because the parasite must be digested when it has reached its third larvae stage, providing only a short time frame in which the parasite is capable of infecting humans. It is uncommon for the larvae to penetrate the skin of individuals exposed to contaminated food or water without ingestion.
, which is type of worm (more specifically a type of nematode
). The most common cause in Asia is G. spinigerum, and the most common cause in the Americas is G. binucleatum. Three other species, G. hispidium, G. doloresi, and G. nipponicum are found only in Japan. There is one unconfirmed report of G. malaysiae causing disease in humans.
, insufficiently cooked definitive hosts such as fresh water fish
, poultry
, or frog
s.
In Thailand and Vietnam, the most important cause appears to be consumption of undercooked Asian swamp eels (Monopterus albus
, also called Fluta alba) which transmit G. spinigerum. Monopterus albus
is an invasive species in North America, but no Gnathostoma has yet been identified in the US.
is the minute crustacean
s of the genus Cyclops
. These crustaceans are then ingested by a second intermediate host, such as frogs.
for gnathostomiasis include cat
s, dog
s, tigers, leopard
s, lion
s, mink
, opossums, raccoon
s, poultry, frogs, freshwater fish, snake
s or bird
s.
for gnathostomiasis is 3–4 weeks when the larvae begin to migrate through the subcutaneous tissue of the body.
are oval and have a mucoid plug at one end.
and in about a week hatch in water to develop into first stage larva. Larvae are then ingested by minute copepods of the genus Cyclops. Once entering the copepod
, the larvae penetrate the gastric wall of their intermediate host and begin to develop into second-stage and even early third-stage larvae. The copepods are then ingested by a second intermediate host such as fish, frogs, or snakes. Within this second intermediate or definitive host the larva repeat a similar pattern of penetrating the gastric wall, but then continue to migrate to muscular tissue and develop into advanced third-stage larvae. These larvae then encyst within the musculature of the new host. If the cyst
containing flesh of these hosts is ingested by a definitive host, such as dogs, and cats, the cysts are ingested and the larvae escape the cysts and penetrate the gastric wall. These released larvae travel to the connective tissue
and muscle as observed before and after 4 weeks they return to the gastric wall as adults. Here they form a tumor
and continue to mature into adults for the next 6–8 months. Worms mate
and females begin to excrete fertilized eggs with feces 8–12 months after ingestion of cysts.
, vomiting
, and loss of appetite resulting from migration of larvae through intestinal wall to the abdominal cavity
will appear in the patient. Migration in the subcutaneous tissues (under the skin
) causes intermittent, migratory, pain
ful, pruritic swellings (cutaneous larva migrans). Patches of edema appear after the above symptoms clear and are usually found on the abdomen
. These lesions vary in size and can be accompanied by pruritus, rash
, and stabbing pain. Swellings may last for 1 to 4 weeks in a given area and then reappear in a different location. Migration to other tissues (visceral larva migrans), can result in cough
, hematuria
, ocular (eye
) involvement, meningitis
, encephalitis
and eosinophilia
. Eosinophilic myeloencephalitis may also result from invasion of the central nervous system
by the larvae.
of gnathostomiasis is possible (with microscopy
) after removal of the worm.
The primary form of diagnosis of gnathostomiasis is the identification of larva in the tissue. Serological testing such as enzyme-linked immunosorbent assay (ELISA) or the Western blot
are also reliable but may not be easily accessible in endemic
areas.
CT scanning or MRI can be used to help identify a soft tissue worm and when looking at CNS disease it can be used to reveal the presence of the worm. The presence of haemorrhagic tracks on gradient-echo T2-weighted MRI is characteristic and possibly diagnostic. Urinalysis
can also be used to identify the presence of hematuria
or the worm, but it is not a very reliable diagnostic
tool.
or treatment with albendazole
or ivermectin is recommended.
The most prescribed treatment for gnathostomiasis is surgical removal of the larvae but this is only effective when the worms are located in an accessible location. In addition to surgical excision, albendazole and ivermectin have been noted in their ability to eliminate the parasite. Albendazole is recommended to be administered at 400 mg daily for 21 days as an adjunct to surgical excision, while ivermectin is better tolerated as a single dose. Ivermectin can also serve as a replacement for those that can’t handle albendazole 200 ug/kg p.o. as a single dose. However, ivermectin has been shown to be less effective then albendazole.
, Mexico
, India
and parts of South Africa
. Originally believed to be confined to Asia, in the 1970s gnathostomiasis was discovered in Mexico, and found in Australia in 2011. Even though it is endemic in areas of Southeast Asia
and Latin America
, it is an uncommon disease. However, researchers have noticed recently an increase in incidence. This disease is most common in both Thailand
and Japan
, but in Thailand it is responsible for most of the observed parasitic CNS infection. It has long been recognised in China, but reports have only recently appeared in the English literature.
The dish ceviche is native to Peru
and a favorite of Mexico. It consists of onion
, cubed fish, lime
or lemon
juice and Andean spices including salt
and chili
. The ingredients are mixed together and they are allowed to marinate several hours before being served at room temperature. Then in endemic areas in Southeast Asia there are traditional dishes associated with these areas that also include raw uncooked fish, such as koipla in Thailand, koi ga in Vietnam, sashimi and sushi in Japan.
Acknowledging these cultural traditions, individuals in these cultural can be educated on methods of adapting their food preparation activities in order to remove the larvae without greatly altering these traditional dishes. For instance, meat should be marinated in vinegar
for six hours or in soy sauce
for 12 hours in order to successfully kill the larvae. In areas with reliable electricity, meat can be frozen at -20 degrees Celsius for 3–5 days to achieve the same results of killing the larvae present.
Human
Humans are the only living species in the Homo genus...
infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
by the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
(roundworm) Gnathostoma spinigerum
Gnathostoma spinigerum
Gnathostoma spinigerum is a parasitic nematode that causes gnathostomiasis in humans, also known as its clinical manifestations are creeping eruption, larva migrans, Yangtze edema, Choko-Fuschu Tua chid and wandering swelling. Gnathostomiasis in animals can be serious, and even fatal...
and/or Gnathostoma hispidum
Gnathostoma hispidum
Gnathostoma hispidum is a nematode that infects many vertebrate animals including humans. Infection of Gnathostoma hispidum, like many species of Gnathostoma causes the disease gnathostomiasis due to the migration of immature worms in the tissues.- Life cyle :In the natural definitive host , the...
, which infects vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s.
Synonyms
The following are commonly used terms when referring to gnathostomiasis- Gnathostoma
- LarvaLarvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
migrans profundus - NodularNodule (medicine)For use of the term nodule in dermatology, see Nodule In medicine, a nodule refers to a relatively hard, roughly spherical abnormal structure....
migratory eosinophilic panniculitis - Physaloptera
- Spiruroid larva migrans
- Wandering swelling
- Yangtze edemaEdemaEdema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
Background
The first case of Gnathostoma was identified by Sir Richard OwenRichard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
when inspecting the stomach of a young tiger that had died at London Zoo
London Zoo
London Zoo is the world's oldest scientific zoo. It was opened in London on 27 April 1828, and was originally intended to be used as a collection for scientific study. It was eventually opened to the public in 1847...
from a ruptured aorta. However it was not until 1889 that the first human case was described by Levison when he found the gnathostoma larva in an infested Thai woman. This delay in identification of the parasite in humans is due to the fact that humans are not a definitive host for this parasite making infection from this parasite rare. Gnathostomiasis infection is rare because the parasite must be digested when it has reached its third larvae stage, providing only a short time frame in which the parasite is capable of infecting humans. It is uncommon for the larvae to penetrate the skin of individuals exposed to contaminated food or water without ingestion.
Causes
Human gnathostomiasis is infection by the migrating third-stage larvae of any of five species of GnathostomaGnathostoma
Not to be confused with Gnathostomata , a Vertebrate Superclass.Gnathostoma is a genus of parasitic nematodes. The species Gnathostoma spinigerum and Gnathostoma hispidum can cause gnathostomiasis.-Species:...
, which is type of worm (more specifically a type of nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
). The most common cause in Asia is G. spinigerum, and the most common cause in the Americas is G. binucleatum. Three other species, G. hispidium, G. doloresi, and G. nipponicum are found only in Japan. There is one unconfirmed report of G. malaysiae causing disease in humans.
Transmission
Gnathostomiasis is transmitted by the ingestion of rawRaw
Raw is a term referring to food that has not been cooked.RAW or raw may refer to:-Technology:* Raw audio format, a file type used to represent sound as pulse-code modulation data...
, insufficiently cooked definitive hosts such as fresh water fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
, or frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s.
In Thailand and Vietnam, the most important cause appears to be consumption of undercooked Asian swamp eels (Monopterus albus
Monopterus albus
Monopterus albus is an important air-breathing commercial species of fish in the Synbranchidae family...
, also called Fluta alba) which transmit G. spinigerum. Monopterus albus
Monopterus albus
Monopterus albus is an important air-breathing commercial species of fish in the Synbranchidae family...
is an invasive species in North America, but no Gnathostoma has yet been identified in the US.
Intermediate host
The primary intermediate hostIntermediate host
A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, humans are the primary host, while the tsetse fly is the secondary host...
is the minute crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s of the genus Cyclops
Cyclops (genus)
Cyclops is one of the most common genera of freshwater copepods, comprising over 400 species . The name Cyclops comes from the Cyclops of Greek mythology which shares the quality of having a single large eye, which may be either red or black in Cyclops.Cyclops individuals may range from...
. These crustaceans are then ingested by a second intermediate host, such as frogs.
Definitive host
The definitive hostsHost (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
for gnathostomiasis include cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, tigers, leopard
Leopard
The leopard , Panthera pardus, is a member of the Felidae family and the smallest of the four "big cats" in the genus Panthera, the other three being the tiger, lion, and jaguar. The leopard was once distributed across eastern and southern Asia and Africa, from Siberia to South Africa, but its...
s, lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s, mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
, opossums, raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
s, poultry, frogs, freshwater fish, snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s or bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s.
Incubation period
The incubation periodIncubation period
Incubation period is the time elapsed between exposure to a pathogenic organism, a chemical or radiation, and when symptoms and signs are first apparent...
for gnathostomiasis is 3–4 weeks when the larvae begin to migrate through the subcutaneous tissue of the body.
Morphology
The adult parasite is reddish-brown in color and has a globular cephalic dome that is separated from the rest of the body by constriction. The posterior portion of the nematode is smooth while the anterior half is covered with fine leaf-like spines. The head is round and contains 4 to 8 transverse rows of hooklets that are protected by a pair of fleshy lips . The males are shorter than the females, 11 millimetre compared to 25 millimetre respectively. EggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are oval and have a mucoid plug at one end.
Life cycle in definitive hosts
Adult worms are found in a tumor located in the gastric wall of the definitive hosts and release eggs into the host’s digestive tract. The eggs are then released with fecesFeces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
and in about a week hatch in water to develop into first stage larva. Larvae are then ingested by minute copepods of the genus Cyclops. Once entering the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
, the larvae penetrate the gastric wall of their intermediate host and begin to develop into second-stage and even early third-stage larvae. The copepods are then ingested by a second intermediate host such as fish, frogs, or snakes. Within this second intermediate or definitive host the larva repeat a similar pattern of penetrating the gastric wall, but then continue to migrate to muscular tissue and develop into advanced third-stage larvae. These larvae then encyst within the musculature of the new host. If the cyst
Cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...
containing flesh of these hosts is ingested by a definitive host, such as dogs, and cats, the cysts are ingested and the larvae escape the cysts and penetrate the gastric wall. These released larvae travel to the connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
and muscle as observed before and after 4 weeks they return to the gastric wall as adults. Here they form a tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
and continue to mature into adults for the next 6–8 months. Worms mate
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
and females begin to excrete fertilized eggs with feces 8–12 months after ingestion of cysts.
Life cycle in humans
Infection of humans by gnathostomiasis is accidental because humans are not one of the definitive hosts of the parasite and do not allow the parasite to complete its life cycle. Infection in humans follows ingestion of raw, insufficiently cooked infected intermediate hosts. The ingested third stage larva migrates from the gastric wall and its migration results in the symptoms associated with infection by gnathostomiasis. The third stage larvae don't return to the gastric wall preventing it from maturing into adult worms, leaving the life cycle incomplete. Instead the larvae continue to migrate unpredictably unable to develop into adults, so eggs are seldom found in diagnostic tests. This also means the number of worms present in humans is a reflection of the number of third stage larvae ingested.Symptoms
A few days after ingestion epigastric pain, feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, and loss of appetite resulting from migration of larvae through intestinal wall to the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
will appear in the patient. Migration in the subcutaneous tissues (under the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
) causes intermittent, migratory, pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
ful, pruritic swellings (cutaneous larva migrans). Patches of edema appear after the above symptoms clear and are usually found on the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. These lesions vary in size and can be accompanied by pruritus, rash
Rash
A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
, and stabbing pain. Swellings may last for 1 to 4 weeks in a given area and then reappear in a different location. Migration to other tissues (visceral larva migrans), can result in cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
, hematuria
Hematuria
In medicine, hematuria, or haematuria, is the presence of red blood cells in the urine. It may be idiopathic and/or benign, or it can be a sign that there is a kidney stone or a tumor in the urinary tract , ranging from trivial to lethal...
, ocular (eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
) involvement, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
and eosinophilia
Eosinophilia
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 0.45×109/L . A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia. Several causes are known, with the most common being...
. Eosinophilic myeloencephalitis may also result from invasion of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
by the larvae.
Diagnosis
DiagnosisMedical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
of gnathostomiasis is possible (with microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
) after removal of the worm.
The primary form of diagnosis of gnathostomiasis is the identification of larva in the tissue. Serological testing such as enzyme-linked immunosorbent assay (ELISA) or the Western blot
Western blot
The western blot is a widely used analytical technique used to detect specific proteins in the given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide...
are also reliable but may not be easily accessible in endemic
Endemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
areas.
CT scanning or MRI can be used to help identify a soft tissue worm and when looking at CNS disease it can be used to reveal the presence of the worm. The presence of haemorrhagic tracks on gradient-echo T2-weighted MRI is characteristic and possibly diagnostic. Urinalysis
Urinalysis
A urinalysis , also known as Routine and Microscopy , is an array of tests performed on urine, and one of the most common methods of medical diagnosis...
can also be used to identify the presence of hematuria
Hematuria
In medicine, hematuria, or haematuria, is the presence of red blood cells in the urine. It may be idiopathic and/or benign, or it can be a sign that there is a kidney stone or a tumor in the urinary tract , ranging from trivial to lethal...
or the worm, but it is not a very reliable diagnostic
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
tool.
Treatment
Surgical removalSurgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
or treatment with albendazole
Albendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
or ivermectin is recommended.
The most prescribed treatment for gnathostomiasis is surgical removal of the larvae but this is only effective when the worms are located in an accessible location. In addition to surgical excision, albendazole and ivermectin have been noted in their ability to eliminate the parasite. Albendazole is recommended to be administered at 400 mg daily for 21 days as an adjunct to surgical excision, while ivermectin is better tolerated as a single dose. Ivermectin can also serve as a replacement for those that can’t handle albendazole 200 ug/kg p.o. as a single dose. However, ivermectin has been shown to be less effective then albendazole.
Epidemiology
Endemic areas include AsiaAsia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and parts of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Originally believed to be confined to Asia, in the 1970s gnathostomiasis was discovered in Mexico, and found in Australia in 2011. Even though it is endemic in areas of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
and Latin America
Latin America
Latin America is a region of the Americas where Romance languages – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...
, it is an uncommon disease. However, researchers have noticed recently an increase in incidence. This disease is most common in both Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, but in Thailand it is responsible for most of the observed parasitic CNS infection. It has long been recognised in China, but reports have only recently appeared in the English literature.
Public health and prevention strategies
The best strategies for preventing accidental infection of humans is to educate those living in endemic areas to only consume fully cooked meat. The inability of the parasite to complete its life cycle within humans means that transmission can easily be contained by adequate preparation of meat from intermediate hosts. This is especially useful because of the difficulty and lack of feasibility inherent in eliminating all intermediate hosts of gnathostomiasis. So instead, individuals in endemic areas should avoid eating raw and undercooked meat in endemic areas, but this may be difficult in these areas. This is due to preference for dishes containing raw fish in these endemic areas.The dish ceviche is native to Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
and a favorite of Mexico. It consists of onion
Onion
The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
, cubed fish, lime
Lime (fruit)
Lime is a term referring to a number of different citrus fruits, both species and hybrids, which are typically round, green to yellow in color, 3–6 cm in diameter, and containing sour and acidic pulp. Limes are a good source of vitamin C. Limes are often used to accent the flavors of foods and...
or lemon
Lemon
The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking...
juice and Andean spices including salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
and chili
Chili pepper
Chili pepper is the fruit of plants from the genus Capsicum, members of the nightshade family, Solanaceae. The term in British English and in Australia, New Zealand, India, Malaysia and other Asian countries is just chilli without pepper.Chili peppers originated in the Americas...
. The ingredients are mixed together and they are allowed to marinate several hours before being served at room temperature. Then in endemic areas in Southeast Asia there are traditional dishes associated with these areas that also include raw uncooked fish, such as koipla in Thailand, koi ga in Vietnam, sashimi and sushi in Japan.
Acknowledging these cultural traditions, individuals in these cultural can be educated on methods of adapting their food preparation activities in order to remove the larvae without greatly altering these traditional dishes. For instance, meat should be marinated in vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...
for six hours or in soy sauce
Soy sauce
Soy sauce is a condiment produced by fermenting soybeans with Aspergillus oryzae or Aspergillus sojae molds, along with water and salt...
for 12 hours in order to successfully kill the larvae. In areas with reliable electricity, meat can be frozen at -20 degrees Celsius for 3–5 days to achieve the same results of killing the larvae present.
External links
- Gnathostomiasis at CDCCenters for Disease Control and PreventionThe Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
- Gnathostomiasis at eMedicineEMedicineeMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely, two medical doctors. The website is searchable by keyword and consists of approximately 6,800 articles, each of which is associated with one of 62 clinical subspecialty textbooks...
- Endemic Areas at Google MapsGoogle MapsGoogle Maps is a web mapping service application and technology provided by Google, free , that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API...