On the Biology of Gnathostoma spinigerum

Abstract

Abstract

Gnathostoma spinigerum, the main causative agent of human gnathostomosis, is actually a nematode parasite of carnivores. The life cycle of the worm essentially involves 3 hosts: a definitive host, the first intermediate host and the second intermediate host. In Thailand, the natural definitive hosts of G. spinigerum are normally cats and dogs. Four species of cyclops serve experimentally as the first intermediate host. Forty-eight species of vertebrates serve naturally as the second intermediate (and/or paratenic) hosts. Among these animals, fish, especially swamp eels, have been found to be the best second intermediate/paratenic hosts of G. spinigerum on the basis of having the highest prevalence rate and the greatest infection intensity. Swamp eels have also been found to harbor at least 4 species of Gnathostoma.

This paper reviews G. spinigerum natural definitive hosts; natural second intermediate hosts and paratenic hosts; the record numbers of G. spinigerum larvae in second intermediate/paratenic hosts; tissue distribution of the larvae in naturally infected swamp eels; experimental first intermediate hosts; experimental primary infection in vertebrate hosts; experimental secondary infection in vertebrate hosts; experimental infection in cats and dogs; infectivity of the larvae in mice; and the effects of temperature, chemicals, radiation and some native Thai foods upon the viability of the larvae.

Keywords : Gnathostoma spinigerum, gnathostomosis, biology, early third-stage larvae, advanced third-stage larvae, hosts