Gnathostomiasis

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Gnathostomiasis
Other namesGnathostoma, Larva migrans profundus, Nodular migratory eosinophilic panniculitis, Spiruroid larva migrans, Wandering swelling, Yangtze edema[1]
SpecialtyInfectious diseases, helminthology Edit this on Wikidata

Gnathostomiasis, also known as larva migrans profundus,[2]: 436  is the human infection caused by the nematode Gnathostoma spinigerum and/or Gnathostoma hispidum, which infects vertebrates.

Symptoms and signs

A few days after ingestion epigastric pain,

pruritus, rash, and stabbing pain. Swellings may last for 1 to 4 weeks in a given area and then reappear in a different location.[3] Migration to other tissues causes visceral larva migrans and can result in cough, hematuria, ocular involvement,[4] meningitis, encephalitis and eosinophilia. Eosinophilic myeloencephalitis may also result from invasion of the central nervous system by the larvae.[1]

Causes

Human gnathostomiasis is infection by the migrating third-stage larvae of any of five species of Gnathostoma. The most common cause in Asia is G. spinigerum, and the most common cause in the Americas is G. binucleatum. G. hispidium and G. doloresi occur in East and Southeast Asia; the former has also been found in Eastern Europe. G. nipponicum occurs only in Japan and China.[5][6][7] There is one unconfirmed report of G. malaysiae causing disease in humans.[8]

Transmission

Life-cycle of Gnathostoma

Gnathostomiasis is transmitted by the ingestion of raw or insufficiently cooked definitive hosts such as fresh water fish, poultry, or frogs.[citation needed]

In Thailand and Vietnam, the most common cause appears to be consumption of undercooked Asian swamp eels (

Monopterus albus, also called Fluta alba) which transmit G. spinigerum.[9][10][11][12] Monopterus albus is an invasive species in North America, but no Gnathostoma infections in humans have yet been conclusively identified in the US.[13]

Hosts

Intermediate host

The primary

Cyclops.[14] These crustaceans are then ingested by a second intermediate host, such as frogs.[citation needed
]

Definitive host

The definitive hosts for gnathostomiasis include cats, dogs, tigers, leopards, lions, mink, opossums, raccoons, poultry, frogs, freshwater fish, snakes or birds.[1]

Incubation period

The incubation period for gnathostomiasis is 3–4 weeks when the larvae begin to migrate through the subcutaneous tissue of the body.[15]

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.

Eggs are oval and have a mucoid plug at one end.[15]

Life cycle

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

fertilized eggs with feces 8–12 months after ingestion of cysts.[14] They are passed out in the feces and eaten by another fish.[citation needed
]

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 or insufficiently cooked infected intermediate hosts.[14] The ingested third stage larva migrates from the gastric wall and its migration results in the symptoms associated with infection by gnathostomiasis.[3] 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.[1] This also means the number of worms present in humans is a reflection of the number of third stage larvae ingested.[citation needed]

Diagnosis

Diagnosis 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.

enzyme-linked immunosorbent assay (ELISA) or the Western blot are also reliable but may not be easily accessible in endemic areas.[1]

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.[3] The presence of haemorrhagic tracks on gradient-echo T2-weighted MRI is characteristic and possibly diagnostic.[6]

Prevention

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.[citation needed]

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, goi ca song in Vietnam, sashimi and sushi in Japan.[16]

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.[14]

Treatment

Surgical removal 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.[1] In addition to surgical excision, albendazole and ivermectin have been noted in their ability to eliminate the parasite.[3] 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.[1] Ivermectin can also serve as a replacement for those that can't handle albendazole 200 ug/kg p.o. as a single dose.[1] However, ivermectin has been shown to be less effective than albendazole.[19]

Epidemiology

Endemic areas include Asia, Mexico, India and parts of South Africa.[3] Originally believed to be confined to Asia, in the 1970s gnathostomiasis was discovered in Mexico,[3] and found in Australia in 2011.[20][21] 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.[14] It has long been recognised in China, but reports have only recently appeared in the English literature.[22]

History

The first case of Gnathostoma infection was identified by Sir

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.[14]

See also

References

External links