Angiostrongyliasis is caused by species of the nematode genus Angiostrongylus Kamensky, 1905. About 14 species of this genus infect animals (rodents and carnivores), but only two infect humans, and these are A. cantonensis (Chen, 1935) Dougherty, 1946 and A. costaricensis Morera and Cespedes, 1971. In the early 1960s, it was discovered that the rat lungworm A. cantonensis is the primary agent causing human eosinophilic meningitis or eosinophilic meningoencephalitis in many islands of the Pacific and in several countries of Southeast Asia, In 1971, A. costaricensis from rats was described as a new species responsible for a clinicopathological disease in Costa Rica observed mainly in children and characterized by the formation of granulomas with heavy eosinophilic infiltration in the abdominal cavity. The lesions are, in most cases, localized in the appendix, but some are found to extend to the terminal portion of the ileum, cecum, the first part of the ascending colon, and the regional lymph nodes. The adult worms are present in the arteries and the embryonated eggs in the tissues. Like most members of the superfamily Metastrongyloidea, these nematodes require a mollusc for the development of the first stage larva which is discharged in the feces of the mammalian host.