al host, but 11 other species of rodents have also
been found with natural infections.  The coatimundi (Nasua
narica) in Costa Rica, marmosets (Saguinus mystax) of the
Peruvian Amazon, and the domestic dog also have been found with
natural infections.  It is probable that this epidemiological
panorama is different in South America due to the variety of
species of rodents and mollusks that exist there.

     Since the parasite is capable of adapting to a large number
of intermediate and final hosts, the differences in existing
species in distant places in the Hemisphere should not be the
reason that very marked differences exist with respect to
prevalences in the environment; neither is there a special
biological condition that would cause more cases to be observed
per year in Costa Rica than in the rest of America.  In 1991,
through last 31 October, we had verified 513 cases in our
laboratory in examining 1,758 sera that had been sent us because
in those patients there was some reason