Naturally acquired antibodies to tetanus toxin in humans and animals from the galápagos islands.

A serologic survey using a highly sensitive enzyme-linked immunosorbent assay confirmed the anticipated finding of naturally acquired antibodies to tetanus toxin both in humans and animals on the Galápagos Islands. In 57 inhabitants (mean age, 31.3 years) who had not been vaccinated against tetanus, antibody to tetanus toxin was detected in the blood in varying titers (geometric mean [reciprocal] titer [GMT], 0.015 international units [IU]/ml). In one individual the titer of antibody was greater than 12.5 IU/ml. Two individuals who had never been vaccinated against tetanus but who had reported having had clinical tetanus had titers of antibody to tetanus toxin of 0.02 IU/ml and 0.3 IU/ml, respectively. All nine of the animals studied showed antibody to tetanus toxin (GMT, 0.028 IU/ml).