Gnathostomiasis in Africa – Is Gnathostoma spinigerum Spreading?

Posted by Rosemary Drisdelle Aug 20, 2009

Gnathostomiasis is not for the squeamish. A recent report (Herman, Wall, Tulleken et al, 2009) describes a man with an immature Gnathostoma spinigerum larva that traveled from his groin up across his rib cage, around (or through) to his back after a possible detour down his right leg, over his shoulder and up his neck. After wandering about inside his face, the larva exited through the skin below his nose. Awful as this sounds, it wasn’t the larva’s behavior that was unusual, it was the fact that the man got it in Botswana. This is a parasite of Southeast Asia and Japan. Only a handful of human cases have been reported in Africa since 1994—in Zambia and Tanzania.

Has G. spinigerum spread to Africa, and if so, how did it do so? The adult worms live in the stomachs of carnivores and are usually acquired—by both carnivores and people—by eating raw fish, or other raw animal flesh. Many animals are paratenic hosts including… birds.

Nothing moves about the planet as famously as birds. Jonathan Elphick’s Atlas of Bird Migration (Firefly Books, 2007) confirms that some birds, notably birds of prey do migrate through Southeast Asia to the region of Africa that includes Tanzania, Zambia, and Botswana. And birds of prey eat fish, invertebrates, and small mammals. It makes sense that a migratory bird might bring G. spinigerum to southern Africa, fall prey to a carnivore there and start up a focus of the parasite. It has probably happened multiple times, but sporadically, and not often enough to establish the parasite permanently—or perhaps it is permanently established. If human cases in Africa increase, we will know.

This raises the question of why we don’t see sporadic cases in other regions that receive migrating birds from Southest Asia and Japan. One must remember that we are only likely to see human cases where people habitually eat raw fish and other animal flesh.

Read the Report of Recent Cases Acquired in Botswana:

"Gnathostomisasis Acquired by British Tourists in Botswana." Herman, Joanna S., Emma C. Wall, Christoffer van Tulleken et al. Emerging Infectious Diseases 2009; 15(4): 594-597.