Human gnathostomosis in Spain: first report in humans

Abstract

Gnathostomosis has been known since 1836, when the parasite was discovered in the stomach of a tiger in London Zoo. Today it is considered an important food-borne parasitic zoonosis, endemic mainly in Asian countries where some people prefer to eat raw fish, amphibians or reptiles. In its mammal definitive host the adults are located in the stomach wall, even in granulomes. The eggs leave the definitive host with the faeces and develop further in an aquatic environment. Larva 1, mobile, is ingested by a copepod, in which it evolves to immature larva 3. The larvae become infectious for mammals in a second intermediary non-specific host, which ingest the copepod. These may be a number of crustaceans, cold-blooded vertebrates, birds or mammals. The infective larva can pass from one host to another within different food chains of the biotope in question. Maturation to the adult stages takes place only in the definitive specific hosts (canids and felids in G. spinigerum). It is a slow process of some 6.5 months in duration. This is due to a migration followed by the infectious larval stage, which involves: perforation of the gastric wall, entry into the liver, migration to muscles and connective tissues, and, again, perforation of the gastric wall from the outside in order to reach its final destination. This internal migration often leads to ectopic locations, especially in uncommon hosts, such as humans, where Gnathostoma larvae are not able to reach sexual maturity. The most dangerous locations are the brain and spinal cord, while others include the eye, lung, pleura, urinary tract and intestine (Oriel and Ash, 1994). In some patients with eosinophilic myeloencephalitis, G. spinigerum has been found in the eyes, suggesting a possible migration via the optic nerve. External gnathostomosis usually comes from the therapeutic application of reptile or amphibian flesh or the manipulation of raw meat. Most human cases, both external (cutaneous migration) and internal (visceral migration), have been diagnosed in Thailand and Japan, or in * Corresponding author. Present address: Departamento de Parasitologia, Facultad de Ciencias, Universidad de Granada, E-18071, Granada, Spain. Tel.: +34-58-243263; fax: +34-58243174. E-mail address: cmascaro@goliat.ugr.es (C. Mascaro).